Space

The Copernicus Complex by Caleb Scharf

drorzel — Thu, 16 Oct 2014 06:52:20 +0000

The Copernicus Complex by Caleb Scharf

I enjoyed Caleb Scharf's previous book, Gravity's Engines a good deal, so I was happy to get email from a publicist offering me his latest. I'm a little afraid that my extreme distraction of late hasn't really treated it fairly, but then again, the fact that I finished it at all in my current state of frazzlement may be the best testament I can offer to its quality. This is a sweeping survey of what we've learned about our place in the universe over the last five hundred years or so.

Now, a grandiose description like that often portends a bunch of wifty philosophizing that poses grand questions but doesn't answer any. Happily, Scharf's book is largely free of that-- it's not that he actually has concrete answers for questions about the origin of life in the universe, but he resists the worst sort of speculation, and grounds everything in solid modern science.

In fact, if anything, it's a bit anti-philosophical, starting with the title. Scharf spends a good deal of time arguing against more extreme versions of the Copernican principle, the idea that the Earth isn't special. This is one of those meta-scientific ideas, like Occam's Razor, that are perfectly sensible in a simple form, but are sometimes stretched well beyond their natural domain, as if they were built into the very structure of the universe.

The mis-application of the Copernican principle that Scharf argues against is the idea that the Earth has to be perfectly mediocre, unexceptional in every regard. You'll sometimes hear this trotted out in arguments that there must be bazillions of inhabited planets out there, just like Earth, and therefore we need to spend more on the favored space exploration schemes of whoever's talking. Scharf dismantles this line of thinking with a clear and thorough survey of modern astronomy, showing that the Earth is, in fact, special. Our Sun isn't an average star, but a type that's a little bit unusual. Our solar system, with rather circular and relatively stable orbits, looks unusual when compared to the many exoplanet systems that have been discovered-- we don't even have any examples of the most common planet types we've seen around other stars. And Earth itself is a little unusual, with our large Moon stabilizing the rotation axis. Given what we now know about astronomy, there are lots of ways in which the Earth is, in fact, special.

At the same time, though, he's careful not to go too far the other way, into asserting that our uniqueness indicates that life is exceedingly improbable and therefore rare. After all, as he points out, everything is unique in some sense. If you flip a fair coin twenty times, writing down the sequence of heads and tails, the resulting string will be literally one in a million (1,048,576, if you want to get pedantic). But that's true of absolutely any string of coin-flips-- they're all unique. Similarly, any life-bearing world out there will have a large number of features that make it unique, and would allow alien bloggers to hold forth about the improbability of such a combination occurring elsewhere. Just as the improbability of a particular string of coin-flips doesn't tell you all that much about the general operation of flipping coins, the contingent factors associated with our particular brand of life don't tell us all that much about life in general.

The main weakness of the book isn't a weakness of the book itself, but the underlying science. Scharf goes through as much detail as he can about what we can say about the conditions for life and the possibility of life elsewhere, but it's necessarily an incomplete picture. We don't yet have enough information to make many sensible statements about what's really going on with life in the universe, and that constrains what he can do with this book. But he does muster a good argument that we're really close to having enough information to address these questions in a concrete manner, thanks to ongoing developments in exoplanet searches and robotic probes and all that sort of thing. It's a fun time to be in science.

This is, in many ways, a book that's pitched just right for me. It engages in speculation about some fun subjects, but it's appropriately constrained speculation, with Scharf looking askance at the more excessive sorts of speculation in a manner I find very congenial. If you're an enthusiastic follower of the wilder sort of Fermi paradox/ anthropic principle/ "rare Earth" stuff that's out there (or an "Ancient Aliens" theorist, for that matter), you won't find much to like. But if you want a compact and engaging survey of what we actually know about the possibilities involved with life in the universe, this is an excellent read.

drorzel Thu, 10/16/2014 - 02:52

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Impossible Thruster Probably Impossible

drorzel — Mon, 04 Aug 2014 07:11:03 +0000

Impossible Thruster Probably Impossible

I've gotten a few queries about this "Impossible space drive" thing that has space enthusiasts all a-twitter. This supposedly generates thrust through the interaction of an RF cavity with a "quantum vacuum virtual plasma," which is certainly a collection of four words that turn up in physics papers. An experiment at a NASA lab has apparently tested a couple of these gadgets, and claimed to see thrust being produced. Which has a lot of people booking tickets on the Mars mission that this supposedly enables.

Most physicists I know have reacted to this with some linear combination of "heavy sigh" and "eye roll." The proposed mechanism doesn't really make any sense, and more importantly, even in the free abstract for their conference talk they state that both the configuration of the device that was supposed to produce thrust and the "null" version that was not supposed to produce thrust gave basically the same result. As Tom notes, this is mind-boggling, and John Baez goes into more detail, including a link to the paper.

The paper itself is kind of a strange read, like it was put together by a committee containing a mix of responsible, hard-headed engineers and wild-eyed enthusiasts. The experimental procedure and results sections are very sober and pretty clear that this is not a meaningful test of anything, but then there's a whole section planning missions to Mars with scaled-up versions of the technology. Which sort of suggests that this was a test run by some career engineers at the insistence of an enthusiast who's highly-placed enough to make them do tests and write up stuff that they find kind of dubious. But that's just speculation on my part.

The only thing I have to add to this discussion is a quick mention of why this is likely to have gone wrong. The core technique described in the report is a "torsion pendulum." This is a technique for measuring tiny forces that dates back to the days of the singularly odd Henry Cavendish, and is still one of the principal techniques for measuring the force of gravity. The basic idea is to hang your test system from a thin wire, balanced at one end of a barbell-like arm, then do something that makes the barbell twist. The amount of twist in the wire will then tell you how much force was produced.

The basic technique has a long and distinguished history. It's also notoriously finnicky, which is why there's still a lot of uncertainty and debate about gravity measurements. From stuff quoted by Baez, this seems to be the first use of the NASA lab's torsion pendulum apparatus, which is not terribly promising. There are zillions of ways this could go wrong, and you're not going to account for all of them the first time out of the gate.

To give you an idea of what's involved, one of the very best groups in the world at doing this sort of measurement is the "Eöt-Wash Group" at the University of Washington, whose short-range tests of Newton's inverse-square law provide the extremely shiny photograph in the "featured image" up at the top of this post. I've seen numerous talks by these guys, who are awesome, and in many of them they show a photograph of the lab, which contains a big shiny vacuum chamber and set of magnetic shield at one side of the room, and a knee-high stack of lead bricks right in the middle of the floor. That's not because some grad student got tired before getting all the lead back to the storage room-- the pile is placed very deliberately to counter the gravitational attraction of a large hill behind the physics building there.

That's the level of perturbation you need to account for when you're doing these sorts of experiments right. Now, the Eöt-Wash crew are looking for much smaller forces than the rocket scientists in Houston, and Houston is pretty flat, anyway, so they may not need to worry about carefully placing lead bricks. But there are dozens of tiny perturbations that are really hard to sort out-- the report specifically mentions vibrations caused by waves in the ocean a few miles away, and if they're seeing that, they're going to be bothered by a lot of other stuff. This isn't something you're going to sort out in the roughly one week of testing that they actually did.

So, yeah, don't go booking yourself a ticket to Mars because of this story. It's almost certainly an experimental error of some sort, most likely a thermal air current due to uneven heating. Which is a failure mode with a long and distinguished history-- Cavendish himself noted in 1798 that an experimenter standing near the case could drive air currents that would deflect the pendulum, so he put the entire apparatus in a shed, and took his readings with a telescope. And in his final set of data, he found that he needed to account for the difference in heating and cooling rates between his metal test masses and the wood and glass of the case.

The good news is that there's enough sober and practical content in the report to suggest that somebody there will eventually do this right. At which time the effect will probably disappear-- it's already a few orders of magnitude smaller than an earlier claim, according to the space.com story linked above. Removing air currents as an issue (which they can do, but didn't because they were using cheap RF amplifiers that couldn't handle vacuum) will probably wipe it out completely.

So, don't go booking tickets to Mars. But do go look at the Eöt-Wash experiment, because they're awesome, and check out the Physics Today story on measurements of "big G", because it's fascinating.

(Also, my forthcoming book has a big section on Cavendish. But that's not out until December...)

drorzel Mon, 08/04/2014 - 03:11

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The thing that baffles me most, here, is the breathless acceptance in some quarters _even though the null device generated thrust!!_ Is this not strongly suggestive that the thrust was produced by the outgassing of bullshit or some other similar mechanism?

And the thing I find most boggling, rather than baffling, is that NASA apparently couldn't be arsed to find a better grade of capacitor for their RF amplifiers. They're NASA, for Chrissakes, they do actually know how to make vacuum hardened equipment. I know, I've done it for them, and sat through the exceedingly painful design reviews.

My last assignment with the Air Force was with a group charged with attempting to forecast the social & political world landscape 20-25 years out and making technology investment recommendations. I'm not a physicist (my PhD is in computer science), but my BS was in EE so I could at least mouth-out the words. Everyone else's degrees were in the humanities, so it was up to me to throw cold water on the what-if fairy from time to time. At one point I was asked to look at the EmDrive based on the limited literature available at the time. My verbal report was along the lines of (cutting out the elimination of possible explanations for its apparent performance) "I can find no theoretical basis for this device to work as claimed. If it does work, as the Boeing video appears to show, then facts always trump theory. At the risk of sounding like Lord Kelvin, I'm more inclined to believe that the facts are wrong than that the theory is wrong -- without more information we can't really make that determination. I recommend that we don't include this in the 2035 toolbox. As I've said before, Blue Horizons loses credibility if we include anticipated technologies that violate our current understanding of physics."

Interesting. A close friend who's smarter than I am, sent me a link to the abstract, but didn't comment on it. What struck me was that the two test devices each appeared to produce an effect, and this was interpreted as supporting the hypothesis. I took that on face value, "after all, NASA," and also took the opportunity to speculate about electric propulsion in space.

Now it turns out there are good reasons for skepticism, so I'll re-file this under "reported effect may disappear with further testing."

To reason backward from the conclusion, I would say that if both test devices produced identical or very similar results, that by itself should be good cause for skepticism. Reason being, even if both devices produce an effect, the difference in construction should produce a difference in the degree of effect. Embarrassing to admit not seeing that when I read the abstract, but potentially useful as a lesson for avoiding that particular type of mistake again.

Even if the device did work, they talked about getting energy from solar panels,. Did they forget how liitle solar power they'd get on an intertsellar trip as the ship left the vicinity of the sun(inverse square).

I should note that it's not too hard to retcon the "null" thruster also producing thrust-- the design was apparently a modification of one end that's different from some previous unit that supposedly produced thrust, and was supposed to be a big improvement. If you (want to) believe the result, it's easy to write that off as "well, the theory that suggested this as an improvement needs more work."

I agree with the general consensus, though, that this is vastly more likely to be a signature of some garbage thermal effect than New Physics in action. I can see, though, how somebody who believed in the validity of the underlying mechanism might be able to rationalize reporting thrust from both units as not completely idiotic. (And thus, they won't be convinced by "the null unit showed the same effect" as a counter-argument...)

If you look at the report, too, the number of trials is ridiculously low-- it's something like five tests of each unit in one orientation, and only one in the other. Another easy rationalization would be that there will turn out to be some difference between the two, once the statistics get better.

http://en.wikipedia.org/wiki/Ionocraft

Said "drive" was never NASA-tested in hard vacuum. When Mythbusters evacuated the ionodrive, it flopped. Make a little aluminum foil swastika with a dimple at its center of mass. Balance it on an upright nail point. Connect to a Tesla coil. Wheee! It spins in vacuum, too, via cold cathode emission. Radiometer, etc. In all cases it is reaction thrust.

Linear momentum is conserved by the homogeneity of the vacuum plus Noether's theorems. Immersed in a gravitational potential, vacuum is not homogeneous. Vacuum loopholes are not exploitable as reductions to practice. arXiv:1103.5222, 1107.2886, /gr-qc/0205059 are reaction thrust. arXiv:1402.5022, 1107.5938 close, but no cigar in vacuum.

Angular momentum non-conservation may have Milgrom acceleration shaping spiral galaxies. 1.2×10^(-10) m/s^2 is a very slow way to travel.

Reminds me of the coherent neutrino detector proposed at U of MD 30 years ago. Similar experimental procedures with similar problems of isolating all outside influences. Congress earmarked funding to support this over and over. Each agency in turn tried to kill it but it kept turning up elsewhere. This in spite of a theoretical calculation by Freeman Dyson showing that if a coherent neutrino detector were possible it would require integration times longer than the age of the universe.

Note that this appears to be the same group at NASA that got some press recently for working on warp drive engines and actually displaying a "mockup" of a proposed starship! Doesn't NASA see that this kind of thing is embarrassing?

This group at NASA clearly has some issues, as Lee points out. When I saw a headline about this, I knew before reading the article that it was going to be from that group. My real problem with all this is, when pathological work makes a big press splash, it makes the public less able to discern good work from bad. It pains me.

Doesn’t NASA see that this kind of thing is embarrassing?

More relevant question: Does anybody at NASA who is in a position to do anything about this see that this kind of thing is embarrassing?

If the research group in question has a powerful enough patron in the bureaucracy, or on Capitol Hill, they can get quite silly indeed before anybody feels they have enough political cover to take action. That goes for any bureaucracy: if the people supplying the money want it to happen, it will happen.

I had no idea Sonny White moved into propulsion after grad school (I knew him tangentially from classes). Working with whistlers and Venus lightning is an enigmatic choice for an Masters-level mechanical engineer to choose, not to mention doing a physics PhD to begin with.

Doug, despite being on Sonny White's committee, I suspect you don't remember his defense (the title page says 2008)? In general would you agree that this is pretty far from Venus lightning and whistler work? I'm not seeing a way to tie this to plasmas (though admittedly after several years in industry, I've largely forgotten plasma physics).

agm@11: I do plasma physics for a living, and I have never encountered anybody doing quantum plasma physics, as these guys claim to be doing. That isn't to say there is legitimate work out there, but most of the applications of plasma physics are in either classical or relativistic settings. The part about using RF to excite this alleged quantum plasma may (or may not--I haven't read the paper) have something to do with whistlers, and whistlers are frequently generated by lightning, but the relationship is tenuous at best.

Some years ago there was some theoretical and experimental work on a mini-magnetosphere propulsion system. I knew the theory guy on that project. I haven't heard anything about it in years, so I suspect that the results didn't justify further work in that direction. But even if that is the case, at least that project rose to the level of being wrong, which this quantum plasma system seems not to have achieved yet.

G@3: “after all, NASA,”

NASA is not above doing/announcing bone-headed scientific "discoveries". Take the "arsenic life" debacle, which was done by a NASA research fellow and announced at a NASA press conference. That was another situation where people who were excited about the implications of the discovery announced their results, and people with experience in the field immediately came forward to say "this violates everything we currently understand about how these sorts of systems work - we strongly suspect that you have some sort of experimental error." At least for the arsenic life paper, that turned out to be the case, where they saw arsenic in DNA because they didn't wash off the loose stuff well enough. Time will tell if this result also suffers from inadequate experimental proceedure.

agm, I do remember Sonny. I think that all of his "Mach effect warp drive" and "EM Drive" stuff is very far (in multiple ways) from the (completely reasonable, but perhaps unglamorous) thesis topic of lightning on Venus.

Srsly? It's called the "cannae drive"? Did no Scotsmen see this at any point?

Google points me to an article in Forbes which explicitly claims that the name comes from Scotty's line, "You cannae change the laws of physics," and not from the ancient Roman town of Cannae as I had initially assumed. The theory guy on this thing is presumably from Italy, the country in which Cannae is located (but I don't know if he's from that part of Italy).

Force produced with a load resistor placed in palce of the test article was 9uN (vs. 49uN with the test article). If the effect is due to heat, then the force produced with the resistor should be larger, as the resistor dissipates all of received RF energy as heat. Further, air circulation for the "slotted" test article will be different then for the "unslotted" test article, so produced force should be different -- but both test articles produced the same force.

As for the sea waves and the shape of local gravity fields. The former can be treated as random disturbance, so after doing several measurements the effect will average out. (There were 4 measurements done for one test article and 5 for the other). The latter is not a factor, because it is constant -- and there is a graph in the paper showing the displacement value while switching the RF source on and off -- the displacement clearly increases when the RF source is on.

A force that would register as thrust needs to be in a particular direction, which implies some uneven heating. producing air currents that yield a consistent force. That's way more likely with a complicated shape like their tapered RF cavity than a simple 50-ohm dummy load, which is probably more symmetrical (it didn't specify the form of the dummy load, that I recall). My impression was that the slots or lack thereof were on an interior surface of the cavity, and thus unlikely to have a big effect on the air circulation. I didn't look all that carefully at the schematics, though.

This also generated a comment from xkcd

http://xkcd.com/1404/

Be sure to hover your cursor over the cartoon and read the second punch line.

This “Impossible Drive” is not the first such claim of unconventional physics leading to propulsive, or force, effects. One that caught my attention years ago was the so-called “Impulse Gravity Generator” of Evgeny Podkletnov in 2001. Podkletnov claimed to have observed 1000 g impulses emanating from YBCO superconductors subjected to 2 million volt discharges. But these impulses only lasted for about 1/10,000ths of a second. Understandably no professional physicists took this claim at face value.

But a few years later a group at the Austrian Research Center (ARC) subjected a niobium ring to 7.33 g’s acceleration, yielding 100 micro-g’s signal. Out of curiosity I did a back of the envelope calculation of how many g’s acceleration a free electron would experience if subjected to the conditions in Podkletnov’s experiment. It turned out the yield of signal versus electron acceleration between Podkletnov’s experiment and the ARC team’s experiment were not proportional, but differed by a factor which was close to the ratio of electron/proton mass. This was kind of a curious result, showing that if one substituted the proton’s mass for the electron’s mass, that there is a very close linearity between applied acceleration and signal yield, between the two experiments.

The fly in the ointment is that the protons are bound tightly within the nuclei at the superconductor’s lattice sites, so they are not independent masses. Nonetheless, I was sufficiently curious to run experiments of my own, similar to Podkletnov’s, but on a much smaller scale. Only recently with a little electronic wizardry have I been able to isolate the acoustic ‘pop’ from the high voltage discharge through the superconductor, from the hoped-for acceleration signal. At one time I thought I saw something, but that was before I isolated the acoustic signal, although oddly it didn’t show up when the superconductor rose above the critical temperature.

My hope is a lab, that routinely works with liquid helium, will allow me to shock pieces of niobium, which has 10 times the cooper pair density with high voltage discharges, and see what shows up. Here is my website describing the experiments: http://starflight1.freeyellow.com

Son of Interstellar Laser Communications

drorzel — Thu, 03 Jul 2014 07:13:55 +0000

Son of Interstellar Laser Communications

I didn't plan to do a follow-up to yesterday's post about the optics of sending messages with lasers, but then I starting idly thinking about detection, prompted in part by a bunch of conversations with my summer students about single-photon detectors. which led to scribbling on the back of an envelope, which led to Googling, and suddenly, I have a follow-up post.

So: as we said yesterday, if you want to send messages over a distance of ten light years, a relatively efficient way to do this might be to send them via lasers. This results in the light being spread over a pretty big area, though-- the best you can do at a distance of 11 light-years is a spot around 160,000m radius-- so how easy would that be to detect?

Well, we have the ability to detect single photons, so a good way to think about this would be to ask how many photons from that laser spot we could expect to collect with a telescope. The number of photons per second sent out by a laser will be equal to the laser power in watts divided by the energy per photon (a watt is one joule per second, remember). The photon energy depends on the wavelength, and yesterday's estimates used a wavelength of 400nm, at the short end of the visible spectrum, which corresponds to around 5x10^-19 joules per photon. So a one-watt laser would be sending out 2x10¹⁸ photons per second.

Yesterday, we said that the smallest spot you could hope to make at the far end is 1.6x10⁵ meters in radius, so we need to spread those photons over that area, which works out to about 24,000,000 photons per square meter per second. If you were looking at that with a telescope having a mirror with a 10-meter radius, you'd expect to see something just under eight billion photons per second. That's a pretty substantial rate, something you would easily be able to detect even without going to fancy single-photon counters.

Of course, it's not quite as simple as just detecting those eight billion photons per second, because your communications laser is going to be coming from a region very close to your home star, so you'll need to pick it out from that background. which is where we have to turn to Google, which turned up this discussion at CosmoQuest giving two different values: a very bright star produces something like two million photons per second per square centimeter, and a very dim one about 0.2 photons per millisecond per square centimeter. Doing a bit of multiplication gets us a total photon flux for our imaginary telescope of somewhere between 6x10⁸ and 6x10¹² photons per second, depending on the magnitude of the star the signal is coming from. At the low end, that would make our 1W laser clearly detectable; at the high end, not so much.

But then, it's not as bad as it might seem, because a laser by definition is concentrated in a very narrow band of wavelengths, while the flux from a star is spread out in a black-body sort of spectrum. So if you were to focus on a very narrow region in the right range of wavelengths, the laser photons might very well stand out even against the background of light from the star. This will also depend somewhat on the character of the star-- a violet laser would be more clearly detectable coming from the neighborhood of a reddish star. I've had enough mucking around with weird astronomical unit conversions, though, so I'm not going to try to figure out the details-- call it extra-credit homework, which you can send to Rhett for grading.

Of course, that's the optimum case, where you're getting the smallest possible spot size at your distant target by launching your signal from a mirror with a radius of 100,000m, the size of a biggish asteroid. That might not be completely ludicrous for a civilization capable of launching an interstellar probe in the first place, but it's not going to work for the probe itself. So what would the return signal look like, assuming you used the 10-m-radius detection mirror to send the return signal?

Well, from yesterday's post, a 10m launch mirror gives you a beam at the far end with a radius of 1.3x10⁹m. that's a factor of 8000 or so bigger than you would get with the asteroid-scale mirror, which corresponds to an increase in the beam area by a factor of 66,000,000. Which means a 10m telescope back on Earth would pick up just 114 photons/s from a space probe equipped with a 1W laser at 400nm. That's... more challenging. You might try using the same asteroid-scale mirror as a telescope to pick up the return signal, which would boost your laser photon counts back up to the same level as before. But, of course, that's going to boost the photon rate from the background star by that same factor of 66,000,000, so it doesn't actually help. If you wanted your laser flux to match the total background light from a dim star, you'd need to use a five megawatt laser to send the signal, which is a bit tricky. But I suppose you could run it off the magic compact fusion reactor you're using to power your relativistic space probe in the first place...

So, anyway, there's another blog post on the feasibility of using lasers to send messages between the stars. There are, of course, a lot of factors left out of this, chiefly the fact that I assumed perfect Gaussian beams for this (which you're probably not going to get) and that I've ignored any effects of stuff along the beam line. Even interstellar space isn't perfectly empty, and over the span of 11 light years, you might need to worry about that medium causing some distortion of your beam. In which case, you probably want to decrease all the laser photon count rates by an order of magnitude or so, probably more. But those calculations won't fit on the back of any envelopes I have handy, so this is what you get.

drorzel Thu, 07/03/2014 - 03:13

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Typo: two million photons per millisecond -> second?

I don't think the signal has to compare with the star flux to be detected, only the noise. Between that and a very narrow spectral slit, signal detection would be quite a few orders of magnitude easier. The remaining problem, however, is what bitrate you'd be able to detect.

I second Lurker #753's comment: a zero-th magnitude star like Vega will send roughly one million photons per second through an area of one square cm through the common astronomical V-band filter.

I do this sort of calculation for a living, so feel free to ask additional questions.

I had typed both of the stellar fluxes as "per second" then noticed that one was supposed to be "per millisecond." And, of course, when I went back to fix it, I corrected the wrong one, making both figures wrong.

Fixed now.

One thing you didn't mention - that the lunar laser rangers also take advantage of - is that you can concentrate your photons in a narrow pulse. The laser ranging folks use 100 picosecond pulses. Compared to a continuous laser this gives you a 10^10 increase in the rate of photons (during the pulse) that makes it much more easily detectable over continuous sources like stars.

I'm wondering how the figures change if you use microwave or radio frequencies instead. I played around with the equations in yesterday's post -- one immediate conclusion is that the minimum size of the spot, and the size of the transmitter required, both monotonically increase as wavelength increases. But it may be practical to equip the probe with a much larger transmitter than it would for visible frequencies, and it may also be easier to detect a beam aimed directly at the receiving star and allowed to spread to, say, the diameter of Jupiter's orbit, against the background of the sending star. I can't find good figures for radio-frequency emissions for main sequence G/K/M dwarfs.

If one does stick to visible light, another thing that might help is picking a laser frequency corresponding to one of the strong absorption lines in the star's emission profile. Background there wouldn't be zero, but it would be a lot lower than elsewhere.

You could improve detectability by temporally modulating the beam at high frequency relative to the signal modulations imposed on that carrier. Then you've got a narrow band in temporal frequency as well as photon energy.
And you don't have to lock onto the signal in real time like it was a phone call or something. You can record the signal from your detector during the prearranged communication window and then analyze it offline, take a good long time figuring out the synchronization of the whole transmission before trying to extract the actual symbols.

The problem wieth concentrating the beam too much is that you can only detect it whe you're right there. That's not much use if you' ve got a 160 km radius spot, but are orbiting the star at a useful distance. You'd have to know exactly where the probe was in it's orbit - 10 years in advance (not as easy as simply predicting where the star system will be in 10 years).

So better stick with a more spread out beam I think.

SETI researchers have in fact done searches looking for alien optical/infrared laser signals. A few recent examples include
http://adsabs.harvard.edu/abs/2004ApJ...613.1270H
http://adsabs.harvard.edu/abs/2007AcAau..61...78H
and arXiv:0904.2230.

Sorry, it looks like the blogging software has garbled those ADS URLs. I'll try again, this time with explicit html formatting: The references are:

Howard et al, Astrophysical Journal 613, 1270

Howard et al, Acta Astronautica 61, 78

Laser guy here. Why stop at one watt? I work on industrial green pulsed lasers that will put out 350W of average power in 20ns pulses at 10khz. That's a pretty prominent signal.

No reason to stop at one watt. It's just a nice round number for back-of-the-envelope calculations. You can certainly scale up the laser power by whatever factor you like, and the photon counts will go up by a corresponding amount.

Using pulsed lasers for communicating might raise some interesting issues. Most of the low-intensity pulsed communication experiments I know of rely on regular timing to boost their efficiency-- that is, since they know the repetition rate of the laser, they know exactly when to look, and aren't integrating background counts during times when the pulse isn't on.

If you're talking about something like an interstellar space probe, though, you might need to start worrying about relativistic effects on the timing of the pulse train. It's not going to be a huge effect-- you need to be at about 0.14c before you slow time by 1% (homework question)-- but might add up over the long time such a mission would involve.

One way of mitigating this problem would be to have a second transmitter some distance away from the actual star to rebroadcast.

On this end it wouldn't be too hard (for a civilization capable of sending out probes) to stick a few transmitters orbiting the sun a light-year or so away. (You need a few because otherwise there is a reasonably likelihood the transmitter will be in line with the sun when you actually want a transmission.)

On the other end, let's suppose you had a second probe which takes a signal (probably radio, since otherwise you just have the same glare problem for the second probe to see the first) from the first probe and rebroadcasts the message in laser. Is there any distance between the probes for which this would actually be something helpful to do? Or is it the case that the second probe would have to be so far away from the first probe in order to mitigate the glare that the first probe would not be able to communicate to the second?

To my layperson's mind this seems to support the conclusions that:

a) Laser communication is viable for interstellar purposes, from robotic probe missions to inhabited planets in an interstellar civilization.

b) A wide beam at the destination (e.g. Jupiter orbit size) is preferable for ease of aiming, and the reception issues can be overcome within presently-known & existing technologies.

c) It is not likely that our solar system would coincidentally happen to lie within the beam paths of another civilization's communications network. But even so, it is worthwhile to support SETI efforts at detecting any such beam, due to the importance of the potential discovery.

Yes? No? and/or what have I missed?

Back a few days to Fermi Fallacies (see also my comment at #14 and correction at #15 there):

I'm inclined to think that the belief that we are alone & unique, has historically been associated with certain kinds of theology, and has become associated with our collective sense of self-worth or importance.

Conversely it is possible that, not only are we not-alone and not-unique, but "they" won't consider us important enough to be worth communicating with, until we achieve some threshold of development such as interstellar (or even interplanetary) civilization. "You're barely an embryo; call us after you hatch" is not exactly ego-gratifying, but as long as we're speculating about the Fermi paradox, it's not unreasonable either.

Howsabout building some sort of giant lens in space, and focusing the sun's light into a beam?

Fermi Fallacies

drorzel — Tue, 01 Jul 2014 08:53:56 +0000

Fermi Fallacies

I've seen a bunch of people linking approvingly to this piece about the "Fermi paradox," (the question of why we haven't seen any evidence of other advanced civilizations) and I can't quite understand why. The author expends a good deal of snark taking astronomers and physicists to task for constructing elaborate solutions to Fermi paradox on the basis of shoddy and unjustified assumptions. And then proceeds to offer a different solution for the Fermi paradox based on shoddy and unjustified assumptions. Whee!

I mean, there is an element of this that's useful, namely the reminder that "We haven't seen aliens because there are no aliens to be seen" is a perfectly valid solution and at least as likely as anything else anyone has come up with. But really, the entire business is so data-poor and bullshit-rich that I have a hard time taking it seriously.

The paradox comes down to a question of time scales, as the galaxy has existed for (in round numbers) ten billion years, while life on Earth took only four billion years to get from nothing to us. Surely, given the vast number of stars in our galaxy, some other species must've done the same before us, probably long enough before us to reach greater heights of technology, including interstellar travel. And as many people with half-assed network models will happily tell you via preprints on any number of web sites, if you can travel at 0.1c, you can colonize the entire galaxy in just a few tens of millions of years. So, there ought to be alien colonies all over the place.

But there's all sorts of weird stuff behind those estimates, even leaving aside the "physicists don't understand biology"/"biologists don't understand math" sniping that goes on. The biggest neglected issues for me are the "why" questions. If you look at those estimates of time to cover the galaxy, a lot of them are talking about self-replicating robot probes. And while I'll admit that it's a lot more plausible to send a small robot off to another star at relativistic speed, I've never really understood what it is that the launching species is supposed to get out of that gigantic investment of energy resources. Some sort of abstract intellectual satisfaction, I guess. Even a single non-replicating probe to a neighboring system would be a huge undertaking, and require an astonishingly patient community of alien scientists willing to wait a few hundred years for pictures of the neighbors.

And even if robot probes were buzzing into the solar system, self-replicating, and leaving again, I'm not sure why anyone thinks that would be obvious. Space is vastly, mind-bogglingly huge, and that goes for space within the solar system. I mean, if some alien equivalent of Voyager or Cassini zipped past us snapping pictures, I'm not convinced we'd even notice. The only real hope is that whatever they use for a drive system is big and noisy and makes a lot of extra light at a time when we happen to be facing in the right direction.

Even the self-replicating part doesn't need to leave obvious traces. There's no reason at all why the self-replicating part of things would need to happen here, with our relatively dense atmosphere and strong gravity. There are huge numbers of floating space rocks and balls of ice out there in the Kuiper belt and Oort cloud that alien robots could mine to their heart's content, and we'd never even notice.

And the problems are equally puzzling for anybody who could get here in person. Even at a peak speed of 0.1c, you're talking decades to centuries to get from star to star. But if you have the resources and technology to maintain a livable environment in interstellar space over that span of time, I'm not sure why you'd need to visit Earth in the first place. Nostalgia? Some sort of alien-hipster retro affectation for the lifestyle of a dozen generations back? Again, you could park dozens of space arks in the asteroid belt and happily live there basically indefinitely without humans being any the wiser. If you need raw materials, it's still easier to snag the occasional comet than to get on and off a rock ball like Earth.

The use case for alien visitation of Earth is ridiculously narrow-- it's basically limited to civilizations with some sort of hibernation technology that can preserve live specimens for decades or centuries, but only in some sort of suspended state that requires thawing out on a planet at the other end of the trip. And also some means of re-creating enough of their biosphere and technological base to make a viable colony there, but not enough of that technology to make habitats in space, or on asteroids or moons. So, assuming the aliens fall into that really narrow range of parameters, yeah, I guess we should've seen them by now.

Which comes around to the problem of communications, namely that we haven't detected any signs of alien communications. But the electromagnetic spectrum is so huge, and our effort to find them has been so short and half-assed that it's ludicrous to think we've actually ruled anything out.

So, I do agree with the Praxtime post in one very limited sense, namely that it's ridiculously arrogant to think that the kind of calculation Enrico Fermi could dash off on a napkin says anything about the likelihood of alien civilizations. But at the same time, it's equally ridiculous to think that the make claims in the opposite direction, based on the after-dinner napkins of biologists. We know so little about any of the parameters that go into any of this that it's impossible to have a meaningful discussion about the idea.

drorzel Tue, 07/01/2014 - 04:53

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Dark Energy, Faster-Than-Light Travel, and Fine Structure Bombs

drorzel — Tue, 06 May 2014 07:15:10 +0000

Dark Energy, Faster-Than-Light Travel, and Fine Structure Bombs

Last week's talks were using sci-fi space travel as a hook to talk about relativity, and my original idea for the talk was to explain how faster-than-light travel ultimately ends up violating causality. Some observers will see effects happening before the events that cause them, and that's just weird. In How to Teach Relativity to Your Dog, the illustration I use is a stationary dog watching a cat moving by at half the speed of light and a space alien zipping past at four times the speed of light. In that scenario, the dog can hand a water balloon to the passing alien to soak the cat, and everything makes sense, but from the cat's point of view (shown by the slanted grid of lines in the "featured image" above), the alien passes at the cat first, and the dog later, and thus the origin of the water balloon is kind of mysterious.

I didn't end up using this, because I thought it was probably too subtle for the target audience, but I did spend some time thinking about it, and about faster-than-light (FTL) travel in a sci-fi context, and whether there is really any plausible way to make it work. And the causality thing is a big roadblock-- even the ability to send messages faster than light allows you to create paradoxes, and that's not a good thing. If you want FTL to work, you need some way to avoid that problem, which has mostly been ignored by SF writers (though Charlie Stross in Singularity Sky and Iron Sunrise at least acknowledges it, in that the godlike transcendant AI of those stories explicitly enforces a rule against doing anything that would create paradoxes).

I did hit on a goofy idea for a causality-preserving FTL scheme, though, inspired in part by a bit from Alastair Reynolds's House of Suns. The source of the paradoxes, after all, is having parties on both ends of the trip interact in some way, mixing faster-than-light and slower-than-light frames of reference. You might arguably be able to avoid this problem by blocking that sort of contact-- Reynolds does this via magical and unexplained means, but modern cosmology offers a quasi-real method.

That is, thanks to inflation right after the Big Bang, and the dark-energy-driven accelerating expansion of the universe, there are vast regions of space that will never be causally connected to Earth-- galaxies so far away that their light can't have reached us yet, and that are being pushed away from us so fast that their light will never reach us. There's no way to make a paradox from those places.

So, the goofy idea is this: FTL travel that's only good over really huge distances. Like, the radius of the observable universe. You can instantaneously jump from some points in the Milky Way to points in galaxies beyond the visible horizon, with causality being preserved by the accelerating expansion of the universe keeping those points from contact with each other. But each of those transfer points goes to a completely different galaxy, out of causal contact with any of the other points you can reach from points within reach of the first one.

(You might reasonably complain that if these are points that will never be connected at slower-than-light speeds, there shouldn't be any way to connect them to enable the FTL travel in the first place. But you traditionally get one free bit of utter hand-wavey magic per SF story, so I'll cash that in there.)

I have no idea how you'd build a plot around that, which is why I'm throwing it out in a blog post rather than trying to put it in a story to sell to somebody. But you could probably twist that in some fun ways-- if the ultra-long-range FTL is relatively easy, it's a novel explanation of the Fermi paradox, for example: we don't see interstellar empires in the Milky Way, because those empires exist, but consist of one solar system per Hubble volume; if you can hop to a distant galaxy easily, it's not worth the hassle to go to the next star over. Or if you want to do the "deep time" thing, you could play with the fact that over billions of years, as dark energy speeds up the expansion, you'll be able to reach galaxies that are closer to your starting point. I'm sure somebody with some plotting skills could have fun with this; if you do, name something after me.

Another oddball idea that came to mind as I was thinking about this (there were a bunch of annoying delays on my flights down to Houston and back) was to throw in the changing fine structure constant business. The fine structure constant, as you may or may not know, is a dimensionless constant consisting of a ratio involving Planck's constant, the speed of light, and the fundamental charge. This tells you something about the strength of electromagnetic forces in quantum mechanics, and gets its name because it turns up in calculations of the "fine structure" of atomic energy levels.

There are exotic theories in which the fine structure constant changes over time, and some observations that I don't entirely believe that claim to see it changing at different rates in different parts of the sky. Which means that if you were to put the ultra-long-range FTL scheme into a story, you might include trips to places where the constant has a different value.

But then, you have to ask, what would the effect of that be? That is, if you moved something via magic FTL means from one place to another, what would happen to it when it arrived in a place with a different value of the fine-structure constant?

This is the kind of thing that lends itself to back-of-the-envelope Fermi problem stuff, so we can try to estimate the effect. Basically, a change in the fine-structure constant would lead to a shift in the energy levels of all the atoms and molecules making up an object moving from one place to another. the details of this would be kind of complicated, but you might reasonably guess that after a fairly short time, any excess energy produced would go into heat. Because thermodynamics.

So, how much heat are we talking? Well, the general energy scale for atomic energy levels is around an electron volt, or about 10^-19 joules. The fine structure constant is a bit less than 0.01 (very close to 1/137, a fact that drove some famous physicists a little crazy), so we could maybe say that 1% of that energy is associated with the fine structure, or about 10^-21 joules per atom. But if you change the fine structure constant by too much, you would rule out the formation of stars as we known them-- this is one of the things that always comes up in Anthropic Principle arguments-- so any change would need to be much less than that. Let's call it 1% again, so you could get maybe 10^-23 joules/atom out of moving stuff from one galaxy to another.

So, how much total energy is that? Well, if you're talking something like a person, you've got maybe 100 kg of mass, and the average mass of an atom making up a person is probably around 10 atomic mass units, so that's 10²⁸ atoms/person, or a total energy of around 10⁵ joules. The canonical scale for sudden release of thermal energy is the TNT equivalent, with 1 ton of TNT giving up an energy of 4x10⁹ joules, so this would be about one ten-thousandth of a ton of TNT, or tens of grams. Somewhere short of a stick of dynamite, I guess. Which would probably be kind of unpleasant for the person arriving at the end of their trip, but maybe not fatally so.

Of course, I pulled all those numbers out of thin air, other than the unit conversions, so if you wanted to play with this, you'd have wiggle room. Having people and objects making an FTL transition arrive either badly chilled or sweating could be a reasonable detail. Or if you want a weapon, you could imagine connecting to something with a much greater difference, and making a bomb out of it (though anywhere with a fine-structure constant different by enough to make a big boom probably won't contain stars and planets that we would find useful).

Anyway, that's the kind of idle noodling around you get from somebody with a little knowledge of physics and astronomy who's stuck in an airplane thinking about sci-fi space travel. Which ought to be enough to prove a point of some sort.

drorzel Tue, 05/06/2014 - 03:15

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I'm not sure the super-long-range jump on its own really eliminates paradoxes, if it's two-way, because the FTL jump is itself another kind of causal connection. You have to have some reason why you can't jump way outside your light cone, then jump back into the past of your original light cone.

You could make all the superluminal jumping happen along a preferred foliation into spacelike surfaces, for instance: it would violate relativity, but maybe in a gentle enough way to not break existing physics too badly. A lot of SF treatments are sort of implicitly doing this whether or not the author realizes it.

But if you do that, I think you don't even need to specify that you can only jump to causally disconnected regions.

I apparently wasn't clear enough about this, because I got the same basic question on G+, too. I was thinking something location-specific for this-- that is, you could go back and forth between two specific points at a very wide separation, but not from a point in our solar system to a point in a distant galaxy and then back to a point near Alpha Centauri, for example. That would allow FTL in a local area, and open up paradoxes, I agree. But if you had a 1:1 mapping between points, or something like that, then you would need to travel multiple light-years at STL speeds to make a trip to a nearby star, and causality would be safe. Or safer, anyway.

If you wanted to drag classic SF elements in, say that it works via wormholes that are only stable when connecting points separated by Hubble-volume quantities of space.

Doesn't the fine structure constant affect radioactive decay rates and neutron capture cross sections? Maybe somebody could make a ball of plutonium that is subcritical in our galaxy but explodes when it's mailed through your portal.

FTL commuting to causally disconnected regions has boojums. Nothing dictates one shape of space during all creations. Local vacuum temperature of 1000 C or a universe filled with dilute neutral hydrogen (early after a Big Bang) would be inconvenient immediately after arrival.

Open a wormhole to obtain an unlimited energy source or sink. The trick, as with piercing an aperture into a tightly inflated balloon, is not to shatter the membrane during or after.

The jumping between regions with physical constants reminds me of Asimov's novel "The Gods Themselves," in which a limited exchange between universes with different physical constants gets exploited as an energy source, but eventually turns out to pose a danger to the universe as the different physics "leaks through".

"I was thinking something location-specific for this– that is, you could go back and forth between two specific points at a very wide separation, but not from a point in our solar system to a point in a distant galaxy and then back to a point near Alpha Centauri, for example."

OK, so it's really a more limited version of the "special foliation" case. You've got two timelike worldlines (for the two different "places") that are mapped onto each other, with the events on one mapped to the events on the other with a consistent temporal order.

I was more thinking it was similar the old cliche of "dream worlds". In that the vehicle of FTL (dreaming), allowed the user to travel (or rather teleport as I tend to view travel as continuous) to a "far off world" that is completely separated from the origin. Though once he arrives back (back to the original or "back" to the dream world), his place and time would still fall in line with what if he were a non-FTL user.

With your comments on the fine structure constant you are approaching Eddingtons fundamental theory, which is a throughly confusing work, He is one of the folks you are referring to about the value of 1/137. He had a nice theory when it looked like the fine structure constant was 1/136 but then experiments destroyed that beautiful theory. So he just said we will add one because it seems a nice thing to do. making it 1/137.

I am not too clued in around the physics of causality, but to me it seems that the extent of the problems that come with broken causality would be dependant on how the universe would deal with paradox's and then you would have to wonder if there could be such a thing as a paradox as for all we would know is that once a person has done a thing during time travel, that thing will always happen and said travellers were always there and are incapable of changing any order of events up to when they originally left. Such a temporal loop was made substantially , for me anyway, in the Warhammer 40k novel Desert Raiders which, despite the phenomena being used as book ends to the story, displays a temporal loop well and how said causality disreprancies would not change the timeline.

Even if it's possible to construct examples where FTL travel seems to subjectively violate causality, does that make it impossible? If I'm hit by an artillery round fired from beyond visual range at supersonic speed, I die before I've been subjectively able to register the boom, but that doesn't mean that overall causality has been violated. Unless FTL travel actually reverses the arrow of time, and I can arrive at my point of origin before I started, I might end up highly confused but not in true violation of causality.

@Mu: I think the prohibition is not against FTL travel per se, but rather crossing the speed of light barrier. If you cross that barrier, then you are not in an inertial frame, and somebody who is (and is therefore privileged over your non-inertial frame) will see your arrow of time reverse. That means you could return to the same point in space time, violating causality. A tachyon does not necessarily violate causality as long as it does not interact with anything in the subluminal universe.

10^5 joules would heat 10^5 grams 1 deg C, so if that's all, arrival would be like a bad fever (or hypothermia on the return).

@Sili, #12: you are off by a factor of 4.16 or so.
Heating would be less than by a quarter of K.
So no bad fever only some sudden feeling of internal heat :)

Five Billion Years of Solitude by Lee Billings

drorzel — Mon, 03 Feb 2014 07:36:50 +0000

Five Billion Years of Solitude by Lee Billings

It's taken me a disgracefully long time to finish the review copy of Lee Billings's Five Billion Years of Solitude I was sent back in the fall, mostly because I didn't read anything not immediately related to the book-in-progress for most of November and all of December. Which is to say, the long delay is not in any way a reflection of the quality of this book, which is excellent.

The title comes from the observation that the span from when life arose on Earth to the distant future when the expanding Sun will swallow the planet entirely is around five billion years. The span when the planet is actually hospitable to life may be much shorter than that, though, which may play into the fact that we have yet to unambiguously detect any signs of life anywhere but here on Earth (claims by the colorful characters on Ancient Aliens notwithstanding). The book is a look at the science of all this: the interaction of planetary science and biology, the various attempts to detect extraterrestrial life, and so on. It mixes detailed profiles of some individual scientists with clear summaries of the science involved in detecting planets, determining whether they'd be habitable, and trying to sort out the signatures of life.

This could be an incredibly depressing story, and in some ways it is-- there's a lot of stuff that demonstrates both our piddling insignificance in the grand scheme of things and the essential fragility of life as we know it. And the sections about our bumbling public policy regarding the funding of basic science research will make you want to slap a legislator if you don't already. Despite that, though, Billings keeps it from being a hard slog to read, which is a great testament to the clarity of his writing and storytelling. Even when he's describing public policy debacles that you know can't end well, the story is told compellingly enough to keep you reading rather than, you know, tossing the book aside in favor of something with featuring characters with more potential to be redeemed, like a George R. R. Martin novel.

The science is a little outside my field of expertise, so I can't completely vouch for its accuracy. It fits well with what I know, though, and more importantly, avoids the trap of sensationalism in either direction. Given the subject matter, that's a pretty significant achievement-- navigating between the ecstasy of "There are planets everywhere!" and the despair of "We're all gonna die!" is no small feat. Billings provides all the necessary caveats, though, without letting them bog the story down.

If you're interested in a concise, compelling overview of the current state of our understanding of the limits of life in the universe, this is a terrific read. I'm taking my copy to the office to push on my colleagues who teach an elective course on Astrobiology, and really, if I like it enough to be the kind of jerk who throws copies at people who know more about the subject matter than I do, well, that's saying something.

(Full disclosure: In addition to getting this for free, I know Lee a tiny bit via social media, and his time at Seed, back when they ran ScienceBlogs.)

drorzel Mon, 02/03/2014 - 02:36

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I thought the span would be around 9 or 10 billion years. Won't the Sun turn into a red giant in another 4 or 5 billion years?

The claim is that life took a while to evolve, and that the gradual brightening of the Sun will make the Earth uninhabitable well before the Sun burns itself out. So the Sun's life is ten billion years, but you chop a billion or so off the start, and several billion off the end, and end up with five.

Gravity's Engines by Caleb Scharf

drorzel — Wed, 03 Apr 2013 13:40:43 +0000

Gravity's Engines by Caleb Scharf

The last week or so of silence on the blog has been due to my trip to Ohio (which was very enjoyable), and a lack of child care for the early part of this week. A day and a half home with both kids was just exhausting, but the trip was useful in that it provided me time to read Gravity's Engines by Caleb Scharf, on the plane to and from Columbus (I got the paper edition at Science Online, and figured as long as I had a printed book I wanted to read, I might as well dodge the stupid argument about whether my Nook is likely to interfere with the plane's navigation systems).

This book comes with the lengthy subtitle: "How Bubble-Blowing Black Holes Rule Galaxies, Stars, and Life in the Cosmos," which pretty well serves as a summary of the whole thing. You might be thinking "Why do we need yet another books about black holes?" but this is actually taking a different angle on the subject than most other treatments I've seen. Most popular books writing about black holes focus on the exceedingly weird effects of general relativity-- the event horizon, the warping of spacetime, things like Hawking radiation and the information paradox. While those topics get mentioned here, the primary focus of the book is on the outside of the black hole, particularly the supermassive black holes at the centers of galaxies, and the titanic amount of energy released as matter falls into them.

This is a good topic for a book, because there's really a mind-blowing amount of stuff being slung around. These black holes power quasars that outshine entire galaxies (in a fairly narrow beam, anyway) making them detectable across the entire visible universe. They also, counterintuitively, propel vast quantities of matter outward, producing gigantic "jets" extending outward from galaxy cores, and changing the flow of matter in galaxies and clusters of galaxies on a scale that boggles the imagination.

As we're a Department of Physics and Astronomy, and three of my colleagues work on either galaxies or black holes, I've heard a lot about these subjects over the last dozen or so years, but never all laid out like this. Scharf brings together a wide range of material relating to galaxy evolution, star formation, and interactions between galaxies, and ties it all together in a compelling way. Having heard bits and pieces of research that ties into this story in a decade of colloquium talks makes it particularly nice to see everything brought together in one place. I wouldn't say that this prior sorta-kinda-knowledge is in any way required to make this make sense, though-- on the contrary, the basic ideas are explained clearly and comprehensively enough for a wide range of readers.

If I have any quibble about this book, it's that it's highly speculative, and thus incomplete. Scharf is making an argument for a very particular view of the role black holes play in the universe as a whole, but it's not clear that this is in any way settled scientifically. A lot of the evidence he presents is more suggestive than conclusive, and there are a number of points where he basically punts on the details of some mechanism for how this stuff all comes together. Which is fine, as far as it goes-- there's no need to wait to talk about science until everything is nailed down and becomes boring-- but it does leave the faint possibility that ten or fifteen years from now, new research will make the whole thing seem quaint and naive.

But then, whatever we may learn in the next ten or fifteen years of research isn't going to help me pass the time on a couple of boring flights last week, which this book did. And it did an excellent job of that, so if you're looking for something to read about truly cosmic events, I recommend picking this up.

Also, because I can, here's a wholly gratuitous music video:

drorzel Wed, 04/03/2013 - 09:40

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Exploring Space: Don't Sell Robots Short

drorzel — Wed, 09 May 2012 09:02:55 +0000

Exploring Space: Don't Sell Robots Short

One final thought on the Big Science/ Space Chronicles stuff from last week. One of the things I found really frustrating about the book, and the whole argument that we ought to be sinking lots of money into manned space missions is that the terms of the argument are so nebulous. This is most obvious when Tyson or other space advocates talk about the need for "inspiring" people, but it shows up even in what ought to be relatively concrete discussions of actual science.

Take, for example, the argument over humans vs. robots. Given the success of the robotic missions to Mars and other bodies, many people ask why we should bother to send people to any of those places. Tyson himself estimates the cost of sending a human to be around fifty times the cost of sending a robot, and says that "if my only goal in space is to do science, and I'm thinking strictly in terms of the scientific return on my dollr, I can think of no justification for sending a person into space." But then, he turns around and tries to justify it on fairly standard grounds: that humans are more flexible, while a robot can only "look for what it has already been programmed to find." Having humans on the scene would enable faster and more "revolutionary" discoveries.

This is an argument that sounds fairly convincing on a surface level, but on closer inspection it breaks down in two ways: it's too generous to humans, and too hard on the robots.

One line of argument in favor of sending humans is that, being autonomous multi-function life forms, humans can notice things that robots wouldn't, and adjust accordingly-- Tyson cites the example of Apollo 17 astronaut Harrison Schmitt, a geologist by training, noticing some oddly colored soil that turned out to be interesting after he sampled it. The claim being that a robot, following a strict program, would not be able to adjust on the fly and sample that soil rather than some other soil.

Which would be true, if we were dealing with Apollo-era robot technology. But we're not. In fact, the actual existing robot rovers on Mars have the capability to do exactly what he wants: they send back pictures of the surface of Mars to Earth, where human geologists study them. Based on the pictures, they select what targets to investigate on more or less the same criteria Schmitt used: that rock is an interesting-looking shape, or this spot is a different color than that other spot. That's been the beauty of the robot rover program from the beginning.

And, in fact, if you go down the list of discoveries made by the Mars rovers, a large number of them have been serendipitous in exactly the manner that you're supposed to be able to get from a human. The hematite "blueberries," for example: scientists on Earth looking at the pictures sent back by Opportunity saw some odd little spherules on the ground, and directed the robot to investigate.

This also oversells human ability a bit-- by definition, serendipitous discoveries have an element of chance. There's no guarantee that even a human geologist would happen to notice everything interesting. In fact, tons of psychology research has shown that humans are just as susceptible to not noticing things as robots are supposed to be-- people miss gorillas right in front of them, after all. A human geologist on Mars with limited time to work might well miss some things that would turn out to be interesting.

Another branch of the flexibility argument holds that humans could move more quickly past problems-- Tyson cites the 12 hours that it took to navigate Spirit past the airbag from its lander, and says that a human could've cleared it in seconds-- and make on-the fly repairs-- "Give a person a wrench, a hammer, and some duct tape, and you'd be surprised what can get fixed," he says. This again, is true to a point, but also elides a lot. For one thing, a mission including humans would be vastly more complicated than a robot mission, and a more complicated mission has many more possible failure points. So, yes, a human is less likely to be thwarted by an airbag on a ramp, but then a robot doesn't have to worry about maintaining a pressurized breathable atmosphere, or securing supplies of food and water, or a comfortable temperature, or adequate radiation shielding, or waste disposal, or any of a host of other problems that preserving human scientists on Mars and returning them to Earth would entail. There are lots of possible failures that are just as stupid as an airbag on a ramp that could easily trap a human inside for as long as Spirit was stuck.

The repair argument also has its flaws, the most obvious being that any repairs would be limited by the available materials. Glib comments about duct tape are great if the only failures you worry about are gross mechanical ones, but nobody's going to make a new Mössbauer spectrometer out of duct tape. Any Mars mission worth doing will include a lot of highly specialized components, and you can't send spares of everything.

It also slights the ingenuity of the humans controlling the robots. Spirit famously had one of its wheels lock up in 2006, but the scientists "driving" it not only worked out a way to get around the stuck wheel (by driving the rover "backwards," basically), but it turned out to be the vehicle for another of those serendipitous discoveries: the dragging wheel scraped away dust, revealing a silica layer underneath.

So, again, a lot of what appear to be more concrete arguments in favor of human space missions don't seem to hold up very well, and end up turning on things that are as vague and unquantifiable as "inspiration." There's no question that certain things would go faster for humans than they do for robots, but then, they would need to go faster, because there's no way we'd be able to leave a human on Mars for the nearly 3000 "sols" that the current robot rovers have been operating there. And it's not at all clear that the small advantage in flexibility from having a human there rather than at the other end of a radio link would make a positive difference.

The one unquestionable advantage would be that a mission putting humans on Mars would eventually return to Earth, and could bring samples back that could then be subjected to a vast range of tests that can't be done by a robot rover with a limited instrument set. Which is true, but then, you could get the same thing from a robotic sample return mission, at one-fiftieth the price.

So, while the pro-human arguments based on science sound convincing at first, they're ultimately not that great, and fall back on the same sort of vague and airy platitudes as the general "inspiration" argument. And given the gigantic cost multiplier involved in sending humans rather than robots (or in addition to robots), I'd really like to see more than that.

drorzel Wed, 05/09/2012 - 05:02

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I still wonder, thirty-five years after the event, what a manned mission would've made of the Viking Life Sciences anomalous results... that's the best argument I can think of for manned planetary missions. (And that's far from a knock-out blow in its favour, I'll admit.)

-- Steve

Even if you believe that human missions to Mars and beyond are so glorious that they're ultimately the sole purpose of having a space program, you should STILL favor robotic missions today.

First reason, you have to send numerous robots to survey and understand your target before planning the scientific goals, tackling the picky engineering details, and risking the lives and resources of a manned mission.

Our civilization currently excels impressively at robotic missions, but has very poor capability for deep manned missions. The 50:1 cost ratio shows that. Even if the technology and expense issues somehow start improving at an astounding pace thus enabling fantastic manned missions unexpectedly soon, we'd find that...OOPS!!!...we're gonna be badly delayed in actually USING our imagined wonderful new manned technology because now we're stuck waiting for years catching up on all those necessary robotic missions that we could have done so well so much earlier.

Second, if manned missions to Mars and beyond ever become practical, that will likely require new and different approaches to propulsion and other technologies. It's a lot easier, quicker, cheaper, and safer to try out bold new approaches on robots. So, curiously, focusing on robots instead of humans now is probably a far faster route to manned-flight technology breakthroughs.

Summary - Favoring manned missions over robots now and in the near future results only in rather dull manned missions, and ironically it badly delays exactly those man-on-Mars-and-beyond fantasies that are motivating the manned-mission cheerleaders to demand lots of funding now.

You're correct in your assessment of humans vs. robots, and you're too charitable with respect to Tyson.

I think the 50:1 is also baloney. The ISS bill to date is (according to Google) pushing 150 billion. The Spirit/Opportunity Mars Exploration Rover Mission ran (according to Wikipedia) 1 billion. I'm no expert, but I think the scientifically, Spirit and Opportunity were much more productive than the ISS. Actually, I can't think of a single significant scientific discovery that came from the ISS.

These days, any decision to send humans into space has nothing to do with science and everything to do with spectacle. Maybe spectacle is OK. The Romans had the Colosseum, we have the NFL and manned space flight. Why not? But let's stop pretending we send humans to space for science, and just admit we do it for amusement.

I am a funding proponent but I would love to see advancement in both areas. There is a symbiotic relationship between manned and unmanned exploration. Robotic exploration is obvious cheaper and safer for the human explorers who get to sit behind a console and sleep in their own beds at night. Our space program is in dire shape and needs some small wins so that we can stop talking about renting space station trips from the Russians. Unmanned projects fit the bill now but they need to be geared toward manned projects in the future. The psychological issue of 'doing it ourselves' will always need to be fulfilled.

Not to mention, the "inspirational" part of humans being in space comes with the downside of putting humans in the path of so many extreme harms it's hard to count them all... and every time something goes wrong, the whole program gets shut down for a few years.

Actually, come to think of it, you can make almost exactly the same arguments for robotic space craft vs manned missions, as you can for unmanned vehicles of any stripe (military UAVs, Google robotic cars, etc) vs human-piloted ones-- at some point, the human becomes a cost bottleneck.

It might be reaction time, it might be training time, it might be reduced vehicle performance to keep the squishy humans alive, it might be life support/safety equipment, etc, but that point does come. When it does, you need to look at those variables rationally, not, uh, inspirationally.

If you sent a human to mars the human would be in a can and would not directly interact with the environment. So the human would see things, but it turns out cameras can see more and better with a larger range of wavelengths. So its not clear what the 50 to 1 cost ratio buys you.

The voyager, hubble, and mars rovers have provided a wealth of inspirational images and have fired the imagination of millions. I would love to see robotic missions to Titan and Europa. Those are both doable for a fraction of the cost of a manned mars mission

Robots are poised to eliminate most USAF fighter and bomber pilots. Commercial diving at depths beyond 300' is declining due to advances in remotely-operated vehicles. The trend is clear. Dangerous, dull, or dirty-time for robots. I for one welcome etc.-you've heard it before.

Shall we all look forward to the day when Humans are simply lumps of unthinking protoplasm tended by a vast network of robots who have surpassed us in every field?

I have several counter-points so this comment is long...

I have not read the Tyson book, but I have strong opinions on manned vs robotic space flight. And I think we should clearly be pursuing both solely robotic missions and manned missions augmented with robotic.

Why am I qualified to have an opinion on the topic? I worked as an Aerospace engineer for 11 years until 2009 (when I'd seen one layoff too many). I have worked on the F-22, the Apache (very briefly), Shuttle payloads, Astronaut training, military satellites (Systems/Controls - pointing lasers at a very small spot a very long way), and Guidance, Navigation and Control on the ISS. And I spent the entirety of my time in engineering school (BSME and MSEE with an emphasis in Controls) working towards the ultimate goal of putting robots into space (hopefully with AI).

I really, really, really like robots - especially in space.

That said, I think it is a terrible idea to remove people from space. Manned space flight is worth pursuing despite the costs.

First, in my opinion, the science derived from the ISS is minimal because of budget issues not for lack of good science opportunities. In the beginning the ISS was designed for science but first we had to get an infrastructure to support people in orbit. Then when the infrastructure was done and the time came to fund the science modules (admittedly after many budget adjustments) the US and our allies weren't as willing to spend any more money. So not all of the science modules that were planned are in orbit.

Also, for most of the ISS's life there have been only 3 people on-board. So long as there were only 3 people on-board they had their hands tied up doing maintenance and operations activities. Now we've learned a lot about operations and the hardware is broken in so there are fewer operations related duties (at least that was true when I left in 2005). But the science modules got cut and NASA handed the politicians the ax to do it.

Most politicians and NASA people seem to focus on the biology of what happens to people in space due to radiation and long term exposure to zero Gs (which is really micro-gravity at the ISS not truly zero G). This gave the politicians (and NASA) a way to say we're accomplishing ISS's mission of science in orbit - by studying the people up there. That's great but I think the biology can, at this stage of our infantile knowledge of biology in micro-gravity, be studied with a host of sensors on-board and upon the astronauts' return - without interfering while we do other science. My main interest/hope for the ISS (that will never be realized) was Materials. There are alloys you could make in micro-gravity you could never make at 1 G because the 2+ constituent materials will separate before they cool. Also, metals inherently have a crystalline structure. A piece of metal typically exists as a series of crystals bound together. The bonds between crystals are much weaker than the bonds between atoms and thus the failure mechanisms of metal usually revolve around the crystal size and crystal boundaries (where one crystal meets another). For the F-22 APU (auxiliary power unit - small turbine engine) that I worked on the turbine blades were made of a single crystal because that allowed for much better stress and heat characteristics. However, again gravity is one of the limiting factors in our ability to grow a larger single crystal and so the maximum turbine blade size is limited so long as the blade is made on Earth.

Remember what materials have done for our standard of living and our economy over the past 30 years - graphite, titanium alloys, carbon fibers, and ceramics? Everything has gotten lighter and stronger. I see a whole new wave of materials impossible to manufacture on Earth that brings with it decades of new military, entertainment, and sports equipment all revolving around items much stronger and lighter than ever before. I think it would make us look like we live in the Middle Ages today.

Second, I have heard since I was high school that we (in the US) are not graduating enough scientists & engineers. China and India produce plenty and we have been importing them as fast as we can for decades. China and India both have manned missions to the Moon in development and have had for years. Obviously, they won't be the first people to the Moon. So why are spending billions on an exploration mission to a body we've already "explored"? Because they recognize, as we once did, that the US mission to the Moon inspired 10s of thousands to pursue careers in science and engineering. And the US gained military superiority and TRILLIONS in economic benefits for the following 4-5 decades as a result.

The Moon missions made a lot of kids pursue science & engineering in college and once there they didn't all stay focused on space, NASA, or the Moon but many did stay in science & engineering. Thus we get all the inventions for Space plus a flood of engineers into the rest of the economy fueling our technology based economic growth and productivity gains for the past roughly half century.

While robotics leads to a number of inventions it doesn't inspire nearly as many people as manned missions do. The level of passion and dedication (by the engineers) to ISS and Shuttle missions despite constantly getting kicked around for budget was unmatched by anywhere else I worked after leaving college. You had 60 year old engineers with the passion and dedication of a college kid working on manned space programs. I worked (as a contractor or direct) at Allied Signal, Boeing, Lockheed Martin, and a smaller aerospace company name Ball. Nowhere were the engineers more fired up than on the manned space flight missions. Not by a long shot.

That energy and dedication led to innovation (mostly small things, but some were big) on a nearly weekly basis in the GNC ISS group I worked in. Manned space flight, in my experience, is how you fuel a half century of technological innovation. Innovation not driven by profit motive (which always inspires short term thinking) but tackling the next big obstacle to the men and women whose lives depend on your ingenuity. Huge profits come later and the economy as a whole benefits tremendously. How's that for payback on your manned space flight dollar? I suggest that any manned space flight mission is a much better way to stimulate the economy than an equivalent amount in tax breaks. You just have be willing to wait approx 10 years to see the benefit. But once you flood engineering schools with students you will see benefits for decades to come. (Manned space isn't the only thing that inspires; the oceans, climate change, or nanotech might be the next big inspiration I don't know but it's the inspiration that's crucial to these downstream economic benefits.)

Third, while nothing would make me happier than working on robotic space missions for the rest of my life, robots are limited by the imaginations of those who designed them and those who operate them (for now at least). Every mission is limited by the designers' imagination but a person on-site brings a level of adaptability that robots commanded by people with 10s of seconds of delay time (travel time of light from Mars to Earth and back) just can't. The people driving the rovers make much less progress each day than they would if they were on-site due to the delay. They also have to be very conservative with how they operate the rovers because they are limited to essentially just one sense - sight - and that from a camera with a limited field of view providing you data in a non-intuitive way. Would you feel comfortable driving your car through only a camera even if the images were enhanced using false colors and infrared? I wouldn't - not without a lot of practice in a safe environment. So while the rovers (and their drivers) generate tremendous amounts of science, I believe they would have generated that same science in a much shorter time frame with someone driving the rover nearby rather than 10s of seconds of delay time away. And with proper mission design, it should not add any cost to the rover to make it command-able from Mars as well as Earth since the signals (if memory serves) all pass through a satellite orbiting Mars. (It would however add some cost, mostly in additional software and testing, to the manned portion of the mission.)

Fourth, I believe we've lost our sense of wonder and tolerance for risk in this country. We didn't expand the US westward without losing a lot of people to Native Americans, disease, starvation, and weather. Those people took that risk because they wanted a better life than they had in the more settled Eastern portion of the country. Today we have astronauts who fully understand the risks of riding a controlled explosion into an entirely hostile environment. So why exactly are we shutting everything down and doing a bunch of soul searching when something goes catastrophically wrong? Did we miss the memo on this being a risky endevour? Were we so arrogant as to assume nothing would ever fail? Or too stupid to realize that when certain somethings go wrong astronauts were going to die? The astronauts realize this why don't the rest of us? The only real valid questions for me after Columbia were: how best to honor the fallen, and how best to improve the design of future spacecraft to be more robust - fewer ways for a single failure causing a catastrophic failure of the vehicle.

Our handling of risk in manned space flight is all wrong (and I think indicative of a societal misunderstanding of risk how ot manage it but that's a much bigger topic than this). We fixate on eliminating the risk of the failure we just witnessed which is utterly idiotic even though it seems entirely rational. It leads to design band-aids that always mean safety design trade-offs because of weight or budget. We eliminate the one failure mode we've just seen (even though it wasn't a failure mode the last 100 launches) while making several other failure modes more likely or more likely to be catastrophic instead of recoverable because of what we did to band-aid the design for the failure we just saw. Assessing the risk and doing nothing is never an option even if the astronauts would be safer for it.

Finally, as Steven Hawking has suggested we are exactly 1 catastrophe (asteroid, plague, etc) from extinction or near extinction. Sending robots to space is a great idea for a memorial but not a good survival technique.

Space Chronicles by Neil deGrasse Tyson

drorzel — Thu, 03 May 2012 08:35:48 +0000

Space Chronicles by Neil deGrasse Tyson

I was tremendously disappointed and frustrated by this book.

This is largely my own fault, because I went into it expecting it to be something it's not. Had I read the description more carefully, I might not have had such a strong negative reaction (which was exacerbated by some outside stress when I first started reading it, so I put it aside for a few weeks, until I was less mad in general, and more likely to give it a fair reading). I'm actually somewhat hesitant to write this up at all, for a number of reasons, but after thinking it over a bit, I think I have sensible reasons for being disappointed in the book, and it's probably worth airing them.

As mentioned in yesterday's post about "Big Science", this is a book whose central message is that we ought to be spending more money than we are on space exploration in order to boost science as a whole. And when I saw Tyson promoting this on either the Daily Show or the Colbert Report, I was excited by the idea. As anybody who's been reading the blog for any length of time knows, I'm all in favor of bringing science to a broader audience (which is why I write books where I discuss physics with my dog). While I'm skeptical the space is the most effective tool for getting the job done, I'm prepared to hear a good argument for that, and Tyson seemed like just the guy to do that: to provide a clear and coherent vision of what space exploration ought to be in order to serve as a driver of science in general.

But this is not that book. Instead, it's a collection of... stuff. Some essays, some speeches, some interview transcripts, a whole bunch of Twitter posts. Collectively, they're all about space exploration as a general matter, and many of the individual pieces are as good as you would expect. But it's not a sustained and coherent argument. And that's a missed opportunity.

This is frustrating for a couple of reasons. First, a lot of it just feels kind of lazy. I read it as an ebook, and on the iPad at least its 360 "pages"; Amazon lists the hardcover as 384 pages. And really, whichever number you pick, there's a really good 200-page book waiting to be made of this stuff. But a huge amount of what's here probably shouldn't be, at least not in this form.

There are verbatim interview transcripts. There's a verbatim transcript of a Colbert Report segment. There are numerous speeches, many of them including the introductory "warm up the crowd" sort of material. The longer things are broken up with the inclusion of vaguely relevant tweets, done up like Twitter screen captures, and there's one whole segment that's nothing but a bunch of collected tweets about Space Shuttle missions.

All of this stuff works very well in its proper context, but it doesn't work nearly as well on the printed page. I saw the Colbert Report segment that's included here, and it was great tv, but the only reason it works at all is because I know what it should look and sound like. The same with the speeches, particularly the opening jokes-- I can see how it would be great live, but in print...

This also makes for a very disjointed and repetitive read, even if you skip the bits that are total filler. Because each of the individual pieces was intended to stand alone, it has to be self-contained. But there are only so many relevant anecdotes and examples to go around, and as a result, they get repeated over and over, needlessly. By the third or fourth mention of how the flawed Hubble optics led to better cancer screening, I was gritting my teeth and muttering "Skip to the end" like Prince Humperdinck to the Impressive Clergyman.

There's also a problem caused by the fact that these were all for different outlets, in different contexts. So, there are pieces that are somewhat critical of NASA, written for one set of outlets, but then there are speeches delivered at NASA events, which are much more flattering to the agency. There are pieces taking the view that robots are the best way to explore the solar system, and others going on about how robots are no substitute for a human presence. It's a little hard to get a coherent picture of what he really thinks.

And this is a big problem, because Tyson is an extremely gifted communicator. So, when he's pro-robot, I find myself nodding along, saying "yes, yes, of course." And when he's anti-robot, he sounds equally convincing that humans have to be part of space exploration. When you try to put the pieces together, though, they don't always fit.

That's what makes the book frustrating and disappointing. I would love to see what could've been made out of this, had he chosen to put his prodigious communication skills behind a single, sustained argument for some clear vision of space exploration. Even better, had he backed up the repeated discussions of the value of space exploration with something more than plural anecdotes. As it is, the well-argued parts don't really make a coherent whole, and they're surrounded by an awful lot of filler-- very good filler, to be sure, but still.

As I said, I'm a little hesitant to write this, in part because I fear it will come off as sour grapes-- I haven't gotten on the Colbert Report, after all. And my feelings about it are undoubtedly colored by the fact that I've been working on something that would re-use ideas from the blog, but spending hours re-working those posts so that they fit together into a coherent whole, rather than just sticking together a bunch of independent pieces (both because I'm not famous enough to sell that and because it just seems like bad craftsmanship to do that for a book that purports to make a single argument).

But even taking that into consideration, and doing my best to be objective about the whole thing, I was sorely disappointed. It's a perfectly fine book for what it is, but what it could've been with a bit more effort and editing would have been far, far better. And that's a shame.

drorzel Thu, 05/03/2012 - 04:35

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Came across this unexpectedly, and agree, but also do disagree. I'll agree the book was definitely disjointed, and yes repetitive. I did get tired of reading the same thing over and over. I do disagree with the pro-robot, anti-robot discussion. I obviously didn't come to the same conclusion as this blog, because I came away reading that dr. Tyson was advocating for both. He mentioned that both have their own merits, and need to be explored. It's not necessarily a one or the other. I don't see how he was pro then anti-robot.

Chad,

I understand your frustration. You're speaking to the perceived lack of a coherent thread that ties many successful books' arguments together while simultaneously informing the reader, and carrying him/her along for the ride - effortlessly. While I can not say I have read all of Doctor Tyson's published works (I am slowly making my way however...), I do believe he had certain intent on publishing this book, and on who his target audience would be: the electorate.

In my humble opinion, it was his goal to often repeat, using slightly differing linguistic vehicles (those sections you saw as being redundant) the "enriched guts" of his argument, so that even someone with the attention span of a flea, would get his main points, understand them, and remember them. If you are familiar with his premise at all, then you know that *he knows* that the only way NASA's budget is going to be increased, is through public pressure on their elected officials. So, getting his core message across to them is a primary goal in his mind. Also, as an educator, I am certain he wants to point people to information that's easy to digest and take in, especially in this sound-bite culture we're all used to living and breathing each day.

Having said all that, do I think the book could have been better constructed? It was what I expected, because much of what I see of Doctor Tyson's work is on YouTube and on the daily news. The book, as you stated, reflects that format, while retaining the richness of his very accurate examinations of our attitudes as a culture toward space exploration. Also, try to remember, this is a man who has often said he was, "called by the Universe." The only other place I've heard that phrase used is in religion, as in, one who was called to serve a God. Someone who believes they were carved to serve a higher purpose, knows exactly what their goals are, and where they need to go to accomplish them.

This book, while it may not be classically formatted, fits his current mission regarding NASA, to a tee!

Trickle Down Science

drorzel — Wed, 02 May 2012 12:53:18 +0000

Trickle Down Science

A week or so ago, lots of people were linking to this New York Review of Books article by Steven Weinberg on "The Crisis of Big Science," looking back over the last few decades of, well, big science. It's somewhat dejected survey of whopping huge experiments, and the increasing difficulty of getting them funded, including a good deal of bitterness over the cancellation of the Superconducting Supercollider almost twenty years ago. This isn't particularly new for Weinberg-- back at the APS's Centennial Meeting in Atlanta in 1999, he gave a big lecture where he spent a bunch of time fulminating about what idiots politicians were for cancelling the project. If anything, the last decade and a bit has mellowed him somewhat.

Sort of in parallel with this, I've also been reading Neil deGrasse Tyson's latest book, Space Chronicles (I say "sort of" because I actually stopped reading it for a couple of weeks, because I found it maddening for reasons that I may go into in another post). This is a collection of things from other sources that collectively sort of advances the argument that we need to spend flipping great wodges of cash on space exploration, for the good of science and society as a whole.

While these aren't directly related to each other-- and, indeed, are somewhat in conflict, as Weinberg has no use for manned space flight-- they're both making a similar argument: that we should be spending money on Big Science projects, because they're important for science as a whole. Which is fine, to a point-- I'm all in favor of increasing the amount of money we spend on scientific research-- but I can't help thinking that it's awfully easy to make this argument when the Big Science projects just happen to fall very close to your area of interest.

Weinberg's piece is more of a historical survey, so most of the advocacy is implicit. Tyson is more direct, and includes this jaw-dropping statement at the end of one of the pieces collected in his book, after talking about how image-processing techniques used to correct the flawed Hubble optics were adapted to medical imaging:

So why not ask investigators to take direct aim at the challenge of detecting breast cancer? Why should innovations in medicine have to wait for a Hubble-sized blunder in space? My answer may not be politically correct, but it's the truth: when you organize extraordinary missions, you attract people of extraordinary talent who might not have been inspired by or attracted to the goal of saving the world from cancer or hunger or pestilence.

I'm a physicist by training, and thus know a thing or two about arrogance, but this is just breathtaking. And I suppose serves as another demonstration of a law of discourse as inescapable as the laws of physics: that any reference to "politically correct" ideas will soon be followed by something asinine.

There's a somewhat more reasonable version of the same basic argument a little later on:

Let's say you're a thermodynamicist, the world's expert on heat, and I ask you to build me a better oven. You might invent a convection oven, or an oven that's more insulated or that permits easier access to its contents. But no matter how much money I give you, you will not invent a microwave oven. Because that came from another place. It came from investments in communications, in radar. The microwave oven is traceable to the war effort, not to a thermodynamicist.

That's the kind of cross-pollination that goes on all the time.

Again, this is a nice argument for funding science in general. But really, it's an argument for funding a wide range of different areas of research, not an argument for funding space travel per se, or any other kind of Big Science project. I suppose you could use this to argue that the space program is particularly useful in that it brings people from multiple different fields together to work on a single larger project, but by that logic, the best thing for scientific progress would be to start a war with Germany and Japan-- the payoff from wartime operations like the Manhattan Project and research into radar, and aircraft design, and all the rest is vastly greater than anything that can be traced to the space program. For that matter, it probably ought to include all the advances claimed for the space program, given that the space program got its start with wartime research.

To make the argument specific to Big Science requires some bafflegab about how "inspiring" big projects are-- in Tyson's case, he writes glowingly about the uplifting effect of the Apollo program; in the high-energy case, Weinberg and others speak grandly about the pursuit of the most fundamental laws of nature. These lofty goals are supposed to inspire huge numbers of young people to want to be part of those pursuits. That way, our best and brightest will be motivated by the grand challenges, and flock to careers in math and science, to the benefit of us all.

Which is great when you're in one of the fields that's meant to serve as the grand and inspirational challenge. For the rest of us, though, this is trickle-down science: the best and the brightest get fired up to be rocket scientists, or high-energy particle physicists, and those who aren't quite the best or the brightest, well... they can study condensed matter physics, or something less inspirational. They'll still be an upgrade over the riff-raff who are presumably populating those fields now. You know, the ones motivated by wanting to save the world from cancer, or hunger, or pestilence.

Not only is this kind of insulting to those of us who have chosen to make careers in fields that aren't driven by Big Science, it's not remotely sustainable. If getting people to go into science and engineering is dependent on something as ephemeral as "inspiration," we're forever going to be careening from boom to bust. Once we land humans on Mars, how do we inspire the next generation? Once we merge the Standard Model with general relativity, do the last string theorists leaving the party just turn out the lights and declare physics closed?

A sustainable solution to the supply of scientists and engineers can't be built around lightning-in-a-bottle scenarios like the Apollo era space race, where an exceptional combination of military goals and national pride happened to align with science for a time, spurring great progress. It's great if it happens, but as David Kaiser documents in How the Hippies Saved Physics, it had a cost for the generation of physicists who were coming along just as the national security establishment started to lose interest. It looks a little like the same sort of thing might be happening in the life sciences, where a huge influx of cash into the NIH drove unsustainable growth for a while, and the flattening out of those budgets is creating a big problem for young researchers.

Those kind of events are great when they happen, but they can't be relied upon for a steady supply of, well, anything. Grand challenges are inspirational for a while, but when you solve the target problem, or even hit a particularly rough patch that delays progress for a while, well, they stop being quite so inspiring. We don't stop needing scientists and engineers just because high-energy physics is having trouble locating physics beyond the Standard Model.

If we want security for science, not just a sequence of spikes and crashes, we need to build a broad base. We need to teach people that there are interesting things in science beyond astrophysics and particle physics. We need a generation of science students who go into condensed matter physics because it's genuinely interesting in its own right, and not because they were inspired by particle physics but couldn't hack the math.

Because while throwing $20 billion to make a Gigantic Hadron Collider, or a Sagan Space Telescope might get you a few spin-off benefits that make life better for people, if you want bang for your buck, you'd be better off giving $20 million to a thousand different research groups in a wide range of relevant subjects. If you want to encourage cross-pollination, throw a few bucks into open access publishing and interdisciplinary conferences to get people talking. There are real payoffs to NASA's research efforts, but the payoffs from research funded by the National Science Foundation are at least as big, for far less money invested.

Which is not to say that I'm opposed to the idea of Big Science projects-- I think we should do both. Contrary to the absurd claims of our more reactionary political elements, we have ample resources as a society to do grand and ambitious projects, and we ought to be funding those along with a broad range of smaller projects in less abstract fields. What I object to is the idea that Big Science projects are the be-all and end-all of science, and that we ought to structure our whole science policy around them, and wait for the benefits to trickle down to the smaller sciences.

While the inspiration of the space program or the heyday of experimental high-energy physics certainly produced some high points, the current slump is just as much a product of the inspiration-based model as any of the great achievements. Trying to extend this for another generation with some grand new project in the same mold is going to end up in exactly the same place thirty years down the road.

drorzel Wed, 05/02/2012 - 08:53

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