Starts With A Bang

Comments of the Week #166: from expanding faster than light to periodic mass extinctions

The Hercules galaxy cluster showcases a great concentration of galaxies many hundreds of millions of light years away. The farther away we look, the less reliable the assumption that we can treat an observed object as being in the same location in space and time that we are. Image credit: ESO/INAF-VST/OmegaCAM. Acknowledgement: OmegaCen/Astro-WISE/Kapteyn Institute.

“Already in my original paper I stressed the circumstance that I was unable to give a logical reason for the exclusion principle or to deduce it from more general assumptions. I had always the feeling, and I still have it today, that this is a deficiency.” -Wolfgang Pauli

There’s never a shortage of scientific topics to explore and take interest in here at Starts With A Bang! While we have our usual slew of articles, controversies, opinions and more this week, I’m also so pleased to share a new podcast with you! This month, thanks to our Patreon supporters, we took on a very bold topic, the one of our very existence. Believe it or not, there’s one quantum rule that makes it all possible, and that’s the Pauli exclusion principle!

So have a listen to 20 minutes of incredible science goodness, and then take a look back at everything we’ve covered this past week, including:

With everything we’ve covered, you’ve had plenty to say, and I want to address as much of it as possible! Come join us for this edition of our comments of the week!

Although we’ve seen black holes directly merging three separate times in the Universe, we know many more exist. Here’s where they must be. Image credit: LIGO/Caltech/MIT/Sonoma State (Aurore Simonnet).

From Paul Dekous on criticism of LIGO: “To my knowledge it is the first ‘official’ criticism so it’s not like they have to use their time to fight of any other criticism, at least they could have said; “sure, now is a bad time, but you’ll get a response in a month or two”.”

There are a lot of reasons to be skeptical of what someone is doing, but it’s vital to not be overly skeptical. This is not the same situation as faster-than-light neutrinos, as the BICEP2 results, or even as WMAP claiming insanely early reionization. If the Danish group is right, it means that the LIGO detections are still there, and still robust, but at a lower significance. It also means that there is a component to the LIGO noise that they haven’t correctly accounted for, and that might be problematic.

That’s best-case-scenario for the Danish group. The other major (and favored) scenario is that it is the Danes that are wrong. This has courted enough controversy that this time I will likely write a piece myself this week on LIGO, its criticism, and what it all means.

A Higgs boson event as seen in the Compact Muon Solenoid detector at the Large Hadron Collider. This one high-energy collision illustrates the power of energy conversion, which always exists in the form of particles. Image credit: CERN / CMS Collaboration.

From Elle H.C. on a strange phenomenon from CERN: “Well I was always curious if collisions at the LHC could cause tiny vibrations in SpaceTime and shake up surrounding matter with the risk of disrupting protons, like how you can shake and break a glass from a distance, with a speaker with a strong enough amplitude.”

I have never heard of this theory. How would it work within the Standard Model and/or General Relativity? I, myself, am not aware of any physically consistent scenario that has this sort of consequence arising from the LHC. I brought up Hitchens’ razor this week — what can be asserted without evidence can be dismissed without evidence — and I am curious whether that applies here?

A single dish that’s currently part of the MeerKAT array will be incorporated into the Square Kilometer Array, along with around 4,000 other equivalent dishes. Image credit: SKA Africa Technical Newsletter, 1 (2016).

From Frank on how telescopes create images: “I never understood how radio telescopes create images.”

How is a radio telescope different from any other telescope? When a signal arrives, you only need to deduce just a few pieces of information about that signal:

That’s it. The first one can tell you the “apparent brightness,” the second tells you a combination of the rest-frame frequency and the cosmic redshift, and the third one tells you angular position. So point your telescopes, they reflect and focus the waves to a point, and we assign a color/magnitude to that particular position dependent on how we choose to visualize/represent the radio signals.

It’s really no different than how we “color the Universe” in any other light. I strongly recommend, in that vein, if you want to learn more in general, that you read the book Coloring The Universe by Arcand, Watzke and Rector, which I reviewed in a bit of depth around a year ago here.

The theoretical ‘island of stability’ (circled) in nuclear physics.

From eric on the nuclear physics phenomenon of the island of stability: “A word of caution for the layfolk: “stability” is a relative term. It’s entirely possible that the nuclear shell effects Ethan talks about increases the stability of the isotopes in the ‘island of stability’ by a factor of 1,000 or even 1,000,000. But that may mean increasing their expected half-lives from nanoseconds to milliseconds. AFAIK nobody int the business expects these elements to be truly stable or even stable enough to allow us to build up macroscopic supplies of them as we do the actinides. But hey, we won’t know for sure unless/until we produce them.”

This is a really good point. When we talk about nuclear physics, we’re dealing with tremendously complicated systems where the strong nuclear force and electromagnetic force — and even the weak force — are all at play in extremely large composite systems. A single proton has three valence quarks; these nuclei in question have over 250 nucleons each, with around 800 valence quarks alone, all in a single quantum system. We can predict that these various isotopes of particular nuclei will be more stable than the ones surrounding them on the periodic table, but exactly how much needs to be determined experimentally.

And that is still, apparently, quite a ways away.

The farther a galaxy is, the faster it expands away from us, and the more its light gets redshifted, necessitating that we look at longer and longer wavelengths. Beyond a certain distance, galaxies become unreachable by anything we emit today, even at the speed of light. Image credit: Larry McNish, RASC Calgary.

From Frank Bennett on whether the Universe can expand faster than light: “I think you need to show, as you have in other articles, that the effect is a purely geometric consequence of the expansion.”

It’s quite difficult to show that for a single object. When you measure the light from, say, a distant galaxy, you can measure the same things I talked about when the other Frank asked about how radio telescopes create images, including the wavelength and distribution of light from that object. Some of that redshift will be due to the stretching of spacetime; some of that redshift will be due to “peculiar velocity,” or the motion of the object itself relative to its local frame-of-reference.

The only way to know how much is one type versus the other is to measure a large variety of objects at a variety of distances; you’ll wind up with a picture of the overall expansion of the Universe and another picture, superimposed atop it, of the local effects of gravity pushing and pushing individual galaxies at speeds of tens, hundreds or even thousands of km/s relative to the overall Hubble flow. But on large scales, that geometric effect is easily seen, and extraordinarily prominent.

In this illustration, one photon (purple) carries a million times the energy of another (yellow). Fermi data on two photons from a gamma-ray burst fail to show any travel delay, showing the speed of light’s constancy across energy. Image credit: NASA/Sonoma State University/Aurore Simonnet.

From Pentacho Valev on what the constancy of the speed of light means: “Any correct interpretation of the Doppler effect implies that the speed of light varies with the speed of the observer.”

Not quite, and I have read many of your comments to attempt to see where I think you’re making a mistake. You’re saying, basically, that:

And therefore, you conclude, that the speed at which the pulses move must be different for different observers, and hence the speed of light is constant. That’s what I think your reasoning is.

But what Einstein’s theory says is that the speed at which the pulses move is always the speed of light in a vacuum for any type of light or any observer. So what’s changing, for different observers, is twofold: the distance between the pulses, which you have right, by the fact of length contraction, but also the way that each observer measures time, due to the effect of time dilation, which is not encoded anywhere in your plain-English descriptions but which matters nonetheless. That is how the speed of light remains constant for all observers.

Read this a few times and think about it for a while, and see if you don’t rethink how you’ve conceived of this problem.

Cecile DeWitt-Morette at her desk in her office in R.L. Moore Hall. Image credit: University of Texas at Austin, News and Information Service / L. Murphy.

A classic Ethan vs. Denier moment as related by Denier this past week on the topic of Cecile DeWitt-Morette: “Ethan: When you have rules that treat men and women equally in theory, but the practical application of the rules leads to unequal results, that’s a classic example of a rule that doesn’t work.
Denier: No Ethan. Bad!
When the practical application of rules leads to unequal opportunity, that’s a classic example of a rule that doesn’t work. The insistence of equality of outcome is a nightmarishly illiberal idea.”

So there’s a lot more to Denier’s comment(s) that you’re welcome to read, but the crux of this is very difficult, because I don’t inherently disagree with the premise here. Unequal opportunity is bad; if everyone has equal opportunity and we see unequal results, that’s not inherently bad. In fact, that would be, ideally, what a true meritocracy would look like.

The problem arises when we get into the practical applications. How do you measure whether the opportunity is equal or unequal? Is that something that’s even possible? The original rules of UNC appeared to be equal, right? That if one spouse was faculty, then anti-nepotism rules just prohibited the other one from becoming faculty. But practically, most qualified male/female couples had the male member be older and more career-advanced when hired, which effectively barred the female member from access to a full professorship. You will notice that UNC’s rules and goals are very, very different now.

The best argument I ever read about this issue was written by David Souter, when he spoke at Harvard in 2010 on the topic of Plessy vs. Ferguson. It’s incredibly nuanced, talking about the different questions one was asking about the topics of what equal/unequal opportunity means: does it mean equal facilities, equal access, equal results, etc.? And while the answer to the question of race and segregation and barring access is a no-brainer today, he does a good job of getting into the heads of judges circa the late 19th century. So you can argue about opportunity vs. results, but when you see unequal results, boy, does it strongly suggest the presence of unequal opportunity.

Cécile DeWitt-Morette (on ladder) and colleagues, circa 1973, give a temporary observatory that will be used in Mauritania a dry run in a UT campus parking lot. Image credit: University of Texas at Austin.

From Elle H.C. on what Cecile DeWitt-Morette actually faced: “Some comments here are distasteful, and all this because she dared to speak up about some inequality along the way.
What do you want, that she just had kept it quiet and only talked about how good life has been to her?”

You can read an entire history of the event in an interview that the American Institute of Physics did with Bryce and Cecile when both were still alive. You are, of course, free to think whatever you like about it, but this is what they have to say in their own words. Here are some relevant parts:

Bryce: “But in the meantime, the people at Chapel Hill has persuaded me to consider putting this thing in Chapel Hill. And I was assured by the department there that it would be bona fide and it wouldn’t be run by Bahnson. Chapel Hill is a beautiful place, and I was wanting to get out of Livermore for an academic position, so we went there, both of us, as visiting research professors. After a few years I was given a regular professorship and Cecile was demoted to a lecturer.”

Cecile: “Without being told it was a demotion. “Oh, it will be so much better for you.” And that’s the part I didn’t like, the hypocrisy of letting me believe that it was better. And in the French context, it could have been better, so I took it for granted.”

Cecile was, no doubt, an opportunist, like a great many other people. And she demanded good things for herself, like many others. Should she just have settled for whatever was offered to her? I would again point to the changes in how spousal hiring is done at UNC and across academia as evidence that her decisions helped affect some tremendous positive change.

In theory, Planet Nine would likely be similar to the exoplanet 55 Cancri e, which is approximately twice the Earth’s radius, but eight times the Earth’s mass. This new study, however, disfavors the existence of such a world in our outer Solar System entirely. Image credit: NASA/JPL-Caltech/R. Hurt (SSC).

From John on the demise of the evidence for Planet Nine: “The falsifiability of the Planet Nine theory made it Science. The observations made it unlikely. Sic transit gloria mundi novem.”

I liked Planet Nine as an idea, even though I was skeptical. There are other, indirect pieces of evidence that have come out against Planet Nine, largely based on the observations of TNOs in the outer solar system, but I thought it was most important to highlight the fact that Batygin and Brown’s original dataset that motivated it in the first place is now looking… shall we say, woefully insufficient.

Also, I can never see “sic transit gloria” without thinking about Max Fischer anymore.

An artist’s impression of the three LISA spacecraft shows that the ripples in space generated by longer-period gravitational wave sources should provide an interesting new window on the Universe. Image credit: EADS Astrium.

From Steve Blackband on LIGO, LISA and noise: “How is this affected, if at all, by your recent post that casts doubts on the LIGO observations and suggests that all they saw was noise?”

First off, no one (serious) is suggesting that “all LIGO saw was noise” at all. People are suggesting that LIGO is seeing correlations in noise that shouldn’t be there, and that may pose an issue for the robustness and reliability of the signals, which still show up even with that correlated noise.

But what’s awesome about LISA is that the overwhelming majority of sources-of-noise that LIGO must contend with disappear for LISA. LISA will have the vacuum of space to contend with, rather than the best vacuum we can make inside a long chamber here on Earth. LISA will be in orbit around Earth, and will lose all the sources of noise from the Earth’s ground. Thermal noise will be at a minimum due to active and/or passive cooling on the spacecraft. (I’m not sure that’s been finalized.)

One of the best parts of LISA, that I tried hard to emphasize, is how non-noisy it will be compared to LIGO. And if there is this mysterious noise correlation, that will be incredibly interesting, and perhaps will lead to — if not new physics — at least new advances in understanding the sources of a new type of interferometer noise.

Special relativity (dotted) and general relativity (solid) predictions for distances in the expanding Universe. Definitively, only GR’s predictions match what we observe. Image credit: Wikimedia Commons user Redshiftimprove.

From Sinisa Lazarek on dealing with relativity/Einstein deniers: “And then at the end of the day, when scientists call you cranks, you feel in your arrogance/ignorance that there is some conspiracy that no one is allowed to question GR/SR, when it’s not the case. There are hundreds of valid scientific papers out there with valid arguments on how to build/change something beyond GR. Questioning GR doesn’t make you cranks… HOW YOU question GR makes you cranks.”

What do you do when you’re presented with something that doesn’t make sense to you? You think about it, you listen to it, and yet it just defies common sense. You know, in your gut, that it can’t be right. What do you do?

We all get that knee-jerk reaction, the one that says, “that’s gotta be wrong!” I had it yesterday; a friend of mine was telling me about kissing bugs, and that they bite your lips and put something into your blood that just lays there, dormant, for a decade or more, and then you develop symptoms and die. And I had that reaction, and said that it sounded like those made-up animals that Australians tell tourists about to trick them, like ‘drop bears’ and ‘circle snakes.’ (And yes, I know ‘rock melons’ are real; thanks Australia.) But what did I do? Did I just talk about how that can’t be right, and tell what I knew to argue the point? Or did I look it up, and learn that kissing bugs are a common name for the insect that transmits the protist that causes Chagas’ Disease?

My point is that it’s easy to rely on common-sense and decry something that runs counter to that as an obvious falsehood. But life isn’t obvious, and in particular, science isn’t obvious. In fact, the fact that science isn’t obvious is why it’s so hard, why it takes so much training, and why the knowledge it takes to engage in it is so specialized. If it were obvious, we wouldn’t need to be scientists to make the advances we’ve made. Think about this the next time someone advocates “common sense” solutions to our problems. Do you want common sense? Or do you want hard work, science, and evidence? Think about it, because if you’re willing to put in the hard work, you can learn it all for yourself.

A large, rapidly moving mass that strikes the Earth would be certainly capable of causing a mass extinction event. However, such a theory would require strong evidence of periodic impacts, which Earth doesn’t seem to have. Image credit: Don Davis / NASA.

From Denier on my opinion about our ability to introspect: “Were the last few words just a throw-away bit with truthiness feel used only to provide punctuation to the end of your piece? Or is there an epistemological school you are drawing from for that statement? Do you think that as a species we don’t do collective introspection well?”

What I said, in particular that led to this question was: For the foreseeable future, the Earth isn’t at increased risk of a natural disaster coming from the Universe. Instead, it looks like our greatest danger is posed by the one place we all dread to look: at ourselves.

It isn’t about introspection that I was getting at, but rather the well-documented fact that humans are quite bad at evaluating risks. In particular, we’re very bad at evaluating low-probability high-consequence risks, and almost always overstate those in our minds, compared to higher-probability risks. The idea of a catastrophic impact — the focus of my entire piece — is one such example of a low-probability high-consequence event, and it’s one that humanity really frets about. The idea that the LHC would create a black hole and then that the black hole would destroy the Earth was another. And yet, actual problems like the deadliness of mosquito-borne diseases or simply the flu are just brushed off.

It is our ability to fret about phantom problems and exceedingly unlikely scenarios while failing to mitigate actual, ongoing, tangible dilemmas that frustrate me.

These are the two brown dwarfs that make up Luhman 16, and they may eventually merge together to create a star. Image credit: NASA/JPL/Gemini Observatory/AURA/NSF.

And finally, from Jose Pacheco on brown dwarfs: “One thing’s for sure, Brown Dwarf. You’ll never be bright enough to make Dad Star proud.”

But this isn’t because of a failing on either the brown dwarf’s part or of another star that ever existed in the Universe; it’s because all the other stars — parent stars, sibling stars, etc. — likely will no longer exist by time the brown dwarf merges with another to become a true star. The rate of decay is slow; gravitational radiation carries away mere Watts of energy for this brown dwarf system. But give it enough time, like all the time the Universe has left, and eventually this orbital decay will make a star. No matter how long-gone your progenitors are, you still shine bright, all the same.