Starts With A Bang

Double Comments of the Week #170: From terraforming Mars to what is and isn’t expanding

Our most powerful telescopes can peer back into the ultra-distant Universe, but can only see the pristine clouds of gas if there's a very, very distant light source beyond to illuminate them. Image credit: NASA.

“Someone once told me that time was a predator that stalked us all our lives. But I rather believe that time is a companion who goes with us on the journey and reminds us to cherish every moment because they’ll never come again. What we leave behind is not as important as how we’ve lived.” -Brannon Braga, Ronald D. Moore, and Rick Berman

After being away for last weekend, it’s time to take a look back at the past two weeks on Starts With A Bang! There’s been no shortage of stories, of news, or of scientific matters of interest, so let’s see what we’ve got:

Next week, I’ll be at two days of the official Star Trek convention in Las Vegas, on August 3rd and 4th, and the full schedule is now online! While the Perseids are coming up, followed by the total solar eclipse, there’s still a whole lot to do before then. You’ve had a lot to think about and a lot to say, so let’s get right into our comments of the week!

The particle tracks emanating from a high energy collision at the LHC in 2014. Although these collisions are plentiful and incredibly energetic, they have not yet yielded any compelling evidence of physics beyond the Standard Model. Image credit: Wikimedia Commons user Pcharito.

From Elle H.C. on a (non-)problem with the LHC: “…while the LHC is all about creating as much noise possible (luminosity)…”

Hang on. Are you contending that you can’t know what goes on in a proton-proton collision, because there are bunched of protons being fired at each other, multiple collisions happening, and therefore we can’t pull the signal out of the noise? Because although that certainly makes things more difficult, it’s not at all a cause for concern in these experiments. Colliding composite particles means we need to be able to tell the difference between a collision of interest and a glancing collision, noise, or other particles that find their way (or their daughter particles find a way) into the detectors.

But we know how to do that: we trigger on large transverse-momentum events. For those events, we record the entirety of the data, and can determine which particle tracks originated from which collision. If you’re not concerned with disrupting spacetime or creating a catastrophe at the LHC, then perhaps I’ve misunderstood what you’ve been contending for a long time.

Photo by Paul Ehrenfest, in December of 1925.

From Pentcho Valev on walking the walk: “No need to ban me – I’m leaving your blog.”

I’ll believe it when I see it. Your “leaving my blog” lasted for an even shorter duration than a Jay-Z retirement.

Once you cross the threshold to form a black hole, everything inside the event horizon crunches down to a singularity that is, at most, one-dimensional. No 3D structures can survive intact. Image credit: Ask The Van / UIUC Physics Department.

From Adam on falling into a black hole with a tether: “I’m not getting the Option C listed here. If a particle emits a force mediating particle, and the force mediating particle crosses or goes deeper into an event horizon, even if it hits some other particle in some random location, how’s the original particle going to know?
Am I missing something obvious? Is a return force mediating particle not required?”

Imagine you’re falling into a black hole. You know that once you cross the event horizon, nothing can get out. You also know that, with enough power, something that’s outside the event horizon, if you do it just right, can escape. There are also tidal forces at play, working to stretch (in the “towards-the-singularity” direction) and compress (in the “perpendicular-to-that-previous-direction” direction) that you just can’t avoid.

So what could possibly happen to you as you fall in? Or, if you prefer, as you, in your ship outside, try and deal with a tether that extends to an object that’s just fallen inside the event horizon?

The outside part can try and escape! If you try too hard, you’ll snap the tether. If you don’t try hard enough, you’ll be pulled in. And if you try just right — which means just hard enough that if you tried any harder, the tether will snap — then what? Well, the answer is that you’ll fall in as slowly as possible. In particular, the particles outside will continue to communicate (i.e., exchange forces) with the particles outside; the particles inside will communicate with the particles inside; and the particles just inside the event horizon will exchange forces with the particles that were outside the event horizon when those virtual particles were emitted, but by time those signals are received, those particles now must be inside the event horizon. Which means you really do only have two options: either you’ll be pulled in or the tether will snap. But you can continue to not have the tether snap if you fall in at the minimum possible rate, which is governed not by the material strength of the tether, but rather by the laws of relativity and causality. (And FYI, no, a “round-trip” force exchange isn’t necessary. One way exerts forces on both particles. That’s physics!)

A visualization of a black hole exhibiting quantum effects, which we’d need a quantum theory of gravity to understand what was happening near the singularity at the center. Image credit: University of Nottingham, via

From Denier on quantum gravity: “

Ethan: you are of the mindset that spacetime fabric is a thing, rather than nothingness itself. We can create visualizations of it; we can write down the laws that govern it; we can quantify the interrelationships of its various components. But it’s not a physical thing that you can poke holes in or tear apart

Denier: That sounds an awful lot like you’re declaring LQG to be fiction.”

Hold on! Saying “spacetime is a fabric” is true in General Relativity, which is our theory of gravity today. Space and/or time may be quantized or discrete at a fundamental level, but those scales at which we’d observe such effects are Planck-scale effects, something we don’t have any way of accessing with current or even envisioned future technology. LQG, or any discrete quantum theory of spacetime, could still be true, but it would have to reproduce classical GR in the low-energy limit.

I thought I said something to that effect when I first brought that up? Oh wait, I did! Here’s the rest of that quote:

But it’s not a physical thing that you can poke holes in or tear apart; it’s a mathematical structure that’s well-defined, and the conditions where that structure breaks down — Planck scales — are also well-defined. The LHC doesn’t reach those scales, so we’re positive that we’re fine. Your analogy isn’t applicable here.

QED, I think.

This movie shows the star VB 10 moving across the sky over a period of nine years. The blue ellipse shows the (magnified) orbit of the unconfirmed planet VB 10 b (red dot) and its movement relative to the star. Image credit: NASA / JPL-Caltech / Palomar.

From Michael Mooney on the (perceived?) invalidity of Special Relativity: “I’m still waiting for Ethan to disambiguate the difference between apparent length contraction (re: differences in what observers see) and actual physical shrinkage of physical objects as promoted by SR.”

You wrote three things that you addressed here as a “response to my challenge.” Only one was physics:

Regarding length contraction, It would take a clear disambiguation of the difference between *apparent* contraction (as seen/measured by various observers) and *actual physical shrinkage* as claimed in the pole- in- a- barn and the train- in- a- tunnel SR thought experiments… also applied to flattened planets (as seen by…) and contracted distances between stars, as per fast travelers with slow clocks.

If we had a way to travel close to the speed of light and take 3D measurements, we would be able to do exactly that. We’d be able to combine the effects of length contraction along with frame-of-reference motions of light-emitting objects (i.e., arrival times) to measure if length contraction is real. We can do this for individual particles (or bunches of particles) and confirm that special relativity’s predictions are right. We’ve done it for fields (they exhibit length contraction at high speeds, like the electric field of an electron). But we haven’t been able to do this for large, composite, macroscopic objects because of practical constraints. But there’s no reason to believe that the physics is any different.

Your other two things that you wrote, however, complained about ontology. As a physicist, I’m not really interested in your (or my, or anyone’s) inability to wrap your head around a physical interpretation/visualization/ontology of what these well-defined entities actually are. You are of the mindset that such a definition is nonsense and incomplete and insufficient. You are entitled to your own opinion, but, like I said, I don’t find it interesting enough to even have a conversation about; it’s not physics, nor is it physically interesting. You are going to disagree and ask me to respond, and I will tell you that I won’t. Why not? Because I don’t waste my time explaining myself to someone who’s committed to misunderstanding me. And in this, you are.

The flow of a dried-up riverbed is an unmistakable signature of a water-rich past on Mars. With the right terraforming work, perhaps it could be habitable once again! Image credit: ESA/DLR/FU Berlin (G. Neukum).

From Frank on terraforming Mars: “Only possibility I see is if we can modify orbits of large asteroids and comets someday to collide with Mars to add both mass and water, and also make its orbit come closer to Sun.”

Wait, and you thought bringing material to Mars the old-fashioned way was difficult? How much mass do you plan on adding? Because the entire asteroid belt is 0.5% the mass of Mars. You want to bring Mars closer to the Sun? How are you going to dissipate all that orbital energy? I think the bigger lesson is that if you add just atmosphere and then water, you get a world that works, as is, for hundreds of millions of years. That’s pretty good!

Mars, the red planet, has no magnetic field to protect it from the solar wind, meaning that it loses its atmosphere in a way that Earth doesn’t. But the timescale over which Mars will lose an Earth-like atmosphere needs to be calculated. Image credit: NASA / GSFC.

From Steve Blackband on the same topic: “So a magnetic field not needed to maintain the atmosphere. Cool.
However there is still the issue of radiation exposure without one, unless you live underground or under a dome.”

Radiation exposure is an interesting question. While I may do lousy on Mars, someone who grew up in a radiation-rich environment would likely be fine. Somehow, if you grow up in a radiation-rich natural environment, you don’t suffer the same ill-effects that someone who grew up in a more typical Earth environment would when exposed to such radiation.

The most radioactive inhabited location on Earth is the city of Ramsar in Iran, and here’s the deal (from Wikipedia) on that:

Ramsar’s Talesh Mahalleh district is the most radioactive inhabited area known on Earth, due to nearby hot springs and building materials originating from them.[8] A combined population of 2,000 residents from this district and other high radiation neighbourhoods receive an average radiation dose of 10 mGy per year, ten times more than the ICRP recommended limit for exposure to the public from artificial sources.[9] Record levels were found in a house where the effective radiation dose due to external radiation was 131 mSv/a, and the committed dose from radon was 72 mSv/a.[10] This unique case is over 80 times higher than the world average background radiation.

People don’t die or get cancer as expected. You might have “zero-generation” problems with radioactivity on Mars, but I have a feeling that the surviving colonists are going to wind up just fine.

32 images of the 2016 eclipse were combined in order to produce this composite, showcasing not only the corona and the plasma loops above the photosphere with stars in the background, but also with the Moon’s surface illuminated by Earthshine. Image credit: Don Sabers, Ron Royer, Miloslav Druckmuller.

From Ragtag Media on a great list of eclipse apps: “It’s all about the apps:

This is beautiful, and worth sharing. Also, if you haven’t caught it, did you know I just did a new podcast on the upcoming eclipse?

Have a listen; it’s worth it!

If these three different regions of space never had time to thermalize, share information or transmit signals to one another, then why are they all the same temperature? Image credit: E. Siegel / Beyond The Galaxy.

From eric on the horizon problem: “Can’t the horizon problem be solved by the notion of these causally separated locations obeying the same laws of physics?”

As Michael Kelsey said, the problem isn’t that the laws of physics are the same; the problem is that different regions of the Universe are the exact same temperature despite being millions of light years apart! But if that’s too hard, think about it in this other fashion: the Big Bang must have occurred at the exact same moment with the exact same initial conditions everywhere. How exact is exact? For the temperature fluctuations we see, the “bang” must have occurred in all locations with the same energy separated by timescales of no less than about 10^-33 seconds.

Over millions of light years, how can you make anything line up to that incredible degree of precision? I don’t think you can, not without invoking some “the initial conditions were just finely-tuned like that.” And maybe they were… but that’s the essence of the horizon problem.

Binary stars with planets around them are common, but if the world containing Westeros orbited a binary planet, particularly if those planets were much more massive than it itself, physics can give us the orbits we need. Image credit: Stuart Littlefair / University of Sheffield.

From Sinisa Lazarek on the science of the Game of Thrones homeworld: “Would there be dragons?”

Physics will only get you so far, Sinisa. I can get you a world with chaotic rotations and seasons… but as far as exobiology, I don’t think our science is there yet. Someday, perhaps.

Also, I noticed the arrival of jimbob on this post. This is a science blog, not a bible study group. He is now banned.

The Voyager 2 spacecraft took this color photo of Neptune’s moon Triton on Aug. 24 1989, at a range of 330,000 miles. The image was made from pictures taken through the green, violet and ultraviolet filters. Image credit: NASA / JPL.

From Pawel on the possibility of life on Triton: “I cannot find any information on “black smokers” volcanoes on Triton. Sure, there is volcanic activity there, but what makes them similar to black smokers?”

Well, if you google “black smokers triton” you’ll find that there’s the Triton grill which can be used for smoking food, and that won’t help you much. But Voyager 2 was remarkable in the science it collected. Yes, it found a mostly nitrogen atmosphere with some methane, where the methane was indirect evidence of volcanic activity. It has evidence of resurfacing, so that’s more evidence of geological activity. And the presence of methane is different in different parts of the world, indicating a seasonal component — seasonal heating from the Sun — as well.

But we are absolutely certain that Triton is volcanically active. Along with Earth, Io, and Venus, only Triton also exhibits surefire volcanic activity. (This is likely due to tidal forces from Neptune.) But there’s also this:

Image credit: Voyager 2.

Those dark spots and streaks? Volcanic activity. As the New York Times reported back in 1989:

One of the pictures showed a five-mile-high, geyser-like plume of dark material erupting from the icy surface of Triton, the blue and pink moon that all but stole the show from its planet when the Voyager spacecraft had its rendezvous with Neptune last August.

The discovery, scientists said, confirmed the hypothesis advanced immediately after the Voyager encounter that explosive volcanoes probably fueled by liquid nitrogen accounted for much of the rugged terrain on Triton. This meant that Triton is only the third object in the solar system, after Earth and Jupiter’s moon Io, known to have active volcanoes.

You can find more about it in the 1999 book, Satellites of the Outer Planets, by David A. Rothery.

The fabric of the Universe, spacetime, is a tricky concept to understand. But, thanks to Einstein’s general relativity, we’re up to the challenge. Image credit: Pixabay user JohnsonMartin.

From CFT on mathematical constructs: “Nothing actually moves in a mathematical construct like space time, It can’t even accommodate an impulse to motion, so the entire idea of it somehow affecting physical reality is quite pointless Platonistic hand waving.”

You know that there are many mathematical spacetime constructs; Einstein’s General Relativity was hardly the only one. The reason Einstein’s formalism is remarkable, though, is because it accurately describes our observed, physical reality. That’s all you need for physics. Mathematics is like taking the square root of 4. You get multiple answers: it could be +2 or it could be -2. Mathematics gives you all the possibilities a setup can admit. Physics? It has one answer, and that answer gives us our physical reality. If you can’t wrap your head around it, you can either listen to the (dissatisfactory) analogies that people who are educated in it make, or you can go and become educated about it yourself. Enjoy the Christoffel symbols!

Look, it’s everyone’s favorite lunar Rover! The angles of the shadows on the Moon and the illuminated portion of the Earth in the sky clearly don’t line up. Also, the dog is photoshopped. Image credit: NASA / manipulator unknown.

From Steve on fake astro pictures: “Its such a sad sad sad reflection of the ignorance in this nation regarding science and education that you felt it necessary to tell the audience that the dog digging on the moon (without a dogsuit) is photoshopped in.
And that I felt it necessary to add ‘without a dogsuit’…”

You are aware that there are many people who don’t even believe humans landed on the Moon. They also think it was a hoax perpetrated by the American government, and that there was some sort of secret “staged area” where the Moon landings took place. So when you show them a picture like this, it jibes with their worldview. It confirms their belief, and so they’re likely to dig in deeper. This may happen frequently in your own life, depending on who you encounter and what issues you speak about.

For me, I prefer to just watch the Rammstein video that gave the best “how to fake a Moon-like video” I think I’ve ever seen.

From dean on the climate science issue: “All true, but as denialists know, all they have to do is repeat their lies and let them sit. It’s quick and doesn’t require any science but they do seem like common sense statements to most people.. They know refuting them takes time and longer explanations that will lose the attention of people. Not promising.”

You know, I am not a climate scientist. And I’m not really qualified to do climate science research. Which is why I ran my article past three separate Ph.D. climate scientists (technically, two climate scientists and one climatologist), all of whom vetted it and approved of all of my points.

But they made a separate point, one that I thought was quite important: their goal is to mislead. Their goal is to manufacture debate and uncertainty. Their goal is not to get the science right, nor to consider the full suite of evidence. Their goal is to keep the status quo in place. And perhaps if I keep taking the, “we have to all agree on the facts before we can discuss policy,” then all they have to do is keep muddying the facts and they win. So maybe I need to take a different line of argument if I want to make a difference.

I’m thinking on this.

The size, wavelength and temperature/energy scales that correspond to various parts of the electromagnetic spectrum. Image credit: NASA and Wikimedia Commons user Inductiveload.

From Pentcho Valev on Einstein: “Spacetime is a consequence of Einstein’s constant-speed-of-light postulate, and this postulate is OBVIOUSLY false.”

I’ll tell you what: show me one measurement from any reference frame that indicates that the speed of light in a vacuum is not exactly 299,792,458 meters per second (I even gave you the value!), and we can talk about your ideas. Also, you’re going to love yesterday’s Ask Ethan when you get to it… but you have to read it. Writing your own “wall of text” (as other commenters have rightly called it) is equivalent to promoting your own pet theories and nonsense here. If that’s all you have to write about, get your own blog, because if you don’t knock it off, you won’t be welcome here any longer.

Last chance to behave!

While most of the sky will darken in a total eclipse, there are portions during a total eclipse that will remain bright, as the Moon’s shadow is smaller than your view of the entire 360-degree horizon. Image credit: Luc Janet.

And finally, to end this on a high note, here’s Alan G. on… I don’t really know, but it doesn’t really matter: “Can’t wait to pop the corn and pop the top for reading these Sunday night. This is gonna be epic, and the start is not disappointing…”

There’s always a lot to say, think, and reason out, and if you’re curious about the Universe, I hope this blog (and even the forum) gives you something interesting to ponder. There’s some amazing stuff going on in the Universe all the time, and I hope to see you continue on this journey with me. Have a great rest-of-your-weekend, everyone!