Comments of the Week #167: From failed stars succeeding to migrating the Earth

“Sometimes the silences, the gaps, tell us more than anything else.” -Peter Ackroyd

Did you know that there's even more going on than before here at Starts With A Bang!? Yes, we have our articles at Forbes; yes, we have our Podcasts on Soundcloud; yes, we have our first book out and our second available for preorder. But we also have had a recent appearance on Portland's NBC affiliate to talk about the eclipse, I've also been doing podcasts to promote Treknology and will be recording another interview this afternoon, and I've been researching and speaking with scientists and engineers constructing the E-ELT, which will become the largest optical telescope in history with a 39-meter primary! (Look for a feature later this month.)

So with all that in the background, let's take a look back at our new articles from this week:

• Can the Universe ever expand faster than the speed of light? (for Ask Ethan),
• Three spectacular nebulae caught together, revealing stunning details about star birth (for Mostly Mute Monday),
• From wartime devastation to academic discrimination, Cecile DeWitt-Morette overcame it all (a retrospective by Paul Halpern),
• Goodbye, Planet Nine! New and better data disfavors a giant world beyond Neptune,
• LIGO’s successor approved; will discover incredible new sources of gravitational waves, and
• Are mass exinctions periodic, and are we due for one?

Before we jump in, I'd like to invite everyone to the Oregon Historical Society in Portland, next Sunday (the 9th) at 2 PM, where I'll be talking about the last Great American Eclipse, and sharing some important information about the upcoming one. Now, let's jump in to what you've had to say, and what else we can learn from it. Come join us for this edition of 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, such as miniature black holes. Image credit: Wikimedia Commons user Pcharito.

From Elle H.C. on a theory for how repeated collisions might destroy the fabric of space: "But as with the breaking of a glass they can record one *tick* on the glass to record its tone and than play it ‘artificially’ on repeat so the glass start to wobble excessively until bindings are cut off and the glass bursts, and the tension of the excitement is released."

I don't expect you to know this, but the only way the LHC can produce miniature black holes -- which is how you conceive of creating this additive phenomenon -- is if the Universe contains extra dimensions beyond our three known spatial ones. This would be due to gravity "spreading out" into the other dimension(s), opening up the possibility of miniature black holes having different properties than those you can calculate from standard physics.

The thing is, even if you change the number of dimensions, and even if you build up many or larger black holes, you do nothing to destabilize space itself. Your imaginings are yours to imagine, of course, but the fear that the fabric of space can get worn out runs contrary to both classical general relativity and the extensions to physics that would enable the existence of miniature black holes at LHC energies, which also (as we now know) don't exist, experimentally. So we can be confident that we are safe.

Image credit: Universe Review.

From Pentcho Valev, misunderstanding length contraction: "Length contraction is irrelevant here – it can only be defined and calculated for objects moving at a speed smaller than c, and the pulses are not such objects."

Length contraction is not calculated for the light itself; the light is neither an emitter nor an observer. What length contraction depends on is the relative speed of the emitter and the observer, so that means the source emitting the light and the observer observing the light. That is exactly where length contraction is relevant, and the signals passed between those two objects -- the light itself -- is how you see it.

As Sinisa notes, you have been dishonest with yourself for decades about relativity, what we know, and how you argue against it. There's always an opportunity to get it right, though! As Carl Sagan said, "When you make the finding yourself - even if you're the last person on Earth to see the light - you'll never forget it." If you choose to learn relativity for real this time, then even after all this time, you might finally get it. The rewards will be your own intellectual satisfaction.

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.

From Denier on whether unequal outcomes indicate unequal opportunity: "In reading through your linked piece from Souter I didn’t find anything on the issue of opportunity versus outcome.
[...]
Souter’s speech seemed more about judicial activism versus constructionalism and his personal justifications for violating the separation of powers by legislating from the bench. Funny enough I thought he shot a hole in his own justification with the Plessy and Brown juxtaposition. Activist Judges in the Plessy case took the temperature of the nation which influenced the outcome. Activist Judges in the Brown case took the temperature of the nation which influenced the outcome, but because the mood of the nation changed the earlier Activist Judges were wrong."

Did we not read the same piece? (You can go back and check.) Perhaps we just add different parts to ourselves of to the reading when we do. When Souter talks about the 1896 Plessy case and refers to separate but equal, he talks about what judges back them asked themselves. Were the facilities physically equal? Did they all satisfy the same equal requirements? Were those allowed to use one set of facilities governed by the same rules as those governing the other? According to the objective criteria they chose, they were satisfied.

But choosing the criteria they chose to evaluate is a human process, not an objective one. What they didn't ask (except for the dissenter in the case) was what impact this would have on those given the separate-but-equal treatment. Segregating by race held with it an assumption of inherent inferiority, and the systemic power structures in our society bore that out as segregation inherently leading to unequal outcomes. When Vanessa Williams won Miss America (switching gears a little), she talked about how a black woman giving 110% was only considered as good as a white woman giving 90%. Some people were flabbergasted, but when you look at the results, it's very hard to argue that the tables weren't tilted in favor of a certain race. That's inherently an unequal system, and it's unequal results that strongly suggest the presence of unequal opportunity. You may (and clearly do) disagree, but -- at least for now in America -- that's both of our rights.

From Naked Bunny With A Whip on ringing glasses: "...if protons are like ringing glasses, and CERN risks the destruction of the world, then ringing glasses also risks the destruction of the world."

The important thing you must realize about a ringing glass is that the amount of energy you put into it is greater than the energy required to break the bonds between the glass molecules. That is why you can destroy a glass with the right sounds/sonic energy; it doesn't take a lot of energy to destroy a glass structure. In the case of a micro-black-hole, or a large series of micro-black-holes, you are aware of the tiny, tiny amount of energy that actually produces them (it's not the same as the energy of proton-proton collisions), and how quickly and successfully the fabric of space and the matter absorbing the energy dissipates it, right? Because the energy you need to risk destruction of the world in any fashion is calculable, and you are off by perhaps 20 orders of magnitude, even if you include a "cumulative" effects. (Not a knock at you; I know what this was in reference to.)

The dark nebula Barnard 68, now known to be a molecular cloud called a Bok globule. Image credit: ESO, via http://www.eso.org/public/images/eso0102a/.

From Tom P. on how brown dwarfs can form a star: "Just as a extra possibility, what would happen if a brown dwarf happened across a really big gas cloud?"

This is a hard one. You see, brown dwarfs need to reach a critical mass threshold, and very, very few of them are just a tiny, little bit (1% or so) away from the fusion threshold. That's all you're likely to see gained if a brown dwarf travels through a gas cloud. Gravity, in order to work well, needs time and a sustained force in order to transfer large amounts of mass. If a brown dwarf is just "passing through" a gas cloud, due to their orbits around the galaxy, accretion of a large amount of mass is unlikely. That's why binary systems or collisions are more likely to work. What you ask about will, no doubt, happen, but its frequency is low enough that it can in almost all cases be safely neglected.

For the first time in almost 40 years, the path of the moon's shadow passes through the continental United States. This visualization shows the Earth, moon, and sun at 17:05:40 UTC during the eclipse. Image credit: NASA's Scientific Visualization Studio.

From Sinisa Lazarek on the next great European eclipse: "This article made me wanna check when the next total eclipse will be in Europe. Saw the one in 1999. Next one to pass me will be in far away 2081, which I most likely won’t live to see."

Total solar eclipses are rare enough, with only about one happening every year or two on average. The Moon's shadow is very small compared to Earth, and Europe itself is very small, taking up only about 2% of Earth's surface. But eclipses tend to happen in clusters in various locations, rather than evenly spaced out. If you miss the 2017 eclipse in the USA, there will be another in 2024. And parts of Europe (like Greece) will see one in 2088, just seven years after 2081. Unbelievably, the antikythera mechanism would have been able to predict that!

Also, too bad you don't count Spain as being in part of Europe; one of the most spectacular total eclipses of all -- the 2027 one lasting over six minutes -- will occur there!

Typically, temperatures drop during a total solar eclipse by approximately 10 degrees Fahrenheit, although drops as large as 28 degrees have been recorded. Image credit: Luc Jamet.

From PJ on a little-talked about phenomenon associated with total eclipses: "As the time approached, nature displayed itself in the form of birds settling down for the ‘night’, ants scurrying back to their homes; then silence filled the air. You could almost feel the onset of darkness sweeping over you as the event began.
Managed to get some shots off (35mm film in those days) in between clouds, but missed the totality. Natures preparations are still a highlight of the experience. After the apparition of darkness passed, life returned to normal; birds waking again, the rest of life getting about its business as if a new day had dawned."

This is a really incredible part of the eclipse story. Animals are "programmed" a lot like we are: with a variety of sensory organs and "detectors" which enable us to sense the world around us. During a total eclipse, the light and heat from the Sun decreases tremendously, with the heat more noticeable than the light. The light in the sky definitely feels changed, although as totality approaches, you'll likely have a hard time putting your finger on how. I'm not entirely sure what it is that the animals are perceiving, or what the plants perceive, but it's an experience that I absolutely encourage everyone who possibly can make it to go. Those last few tens or hundreds of miles (or kilometers) to get to totality is completely worth it!

The gravitational wave signal from the first pair of detected, merging black holes from the LIGO collaboration. Although a large amount of information can be extracted, no images or the presence/absence of an event horizon can be gleaned. Image credit: B. P. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration).

From Michael Hutson on LIGO's signals: "What’s needed is a vastly higher, cleaner, more obvious signal to noise ratio. If it takes sophisticated statistical analysis just to tell if you’re looking at something real or random fog, your detector technology just isn’t good enough."

Well that is entirely not fair. First off, looking at the first LIGO detection, you can seriously see the signal with your naked eye. It's unambiguously real! The top panel in the above images shows this; you don't need a template to see there's something far beyond the noise. But is this a >5-sigma detection? That's where you need the templates.

If what you're saying is, "well, the signal is this size, but I'm uncomfortable with the size of my noise," then you have to go to space. You are limited by the noise that the Earth itself produces, due to the fact that we're on a planet with layers, plate tectonics, tides, volcanism, etc. Everyone knows there are ways LIGO can be improved.

What's incredibly annoying is that many of these improvements and upgrades -- not going to space, obviously -- that would pretty much halve the noise that LIGO currently is experiencing, were planned to take place over the next few years. But with a catastrophic cut to the NSF's budget of over $800 million, around 15% of the total budget, LIGO will not have the funds they were counting on to make those upgrades. And that's something worth being upset about.

Even with the analysis of the team from Denmark, a strong gravitational wave signal emerges from both LIGO detectors. But so does a large amount of correlated noise, which may mean a bit of signal-and-noise are being mixed up. Image credit: Comments on our paper, 'On the time lags of the LIGO signals', J. Creswell et al.

From John on the robustness of the LIGO signal: "The last paragraph of the Forbes page says it all, and the science is better for it."

Just so everyone sees it, here's what the last paragraph said:

What you're witnessing is one small aspect of how the scientific process plays out in real-time. It's a new development (and one that makes many uncomfortable) to see it partially playing out on the internet and on blogs, rather than in scientific journals exclusively, but this is not necessarily a bad thing. If not for the original piece that drew significant attention to the Danish team's work, it is possible that this potential flaw might have continued to be ignored or overlooked; instead, it's an opportunity for everyone to make sure the science is as robust as possible. And that's exactly what's happening. The Danish team may still be making an error somewhere, meaning this whole exercise will be a waste of time, but it's also possible that the analysis techniques will be improved as a result. Until this finishes playing out, we won't know, but this is what scientific progress unfolding looks like!

There are still gravitational waves out there, and LIGO is still detecting them. The concern is that there is signal in the noise, and that is a valid concern. But it doesn't invalidate the conclusion, it just means that there may be a sub-optimal analysis method used.

The relationship between luminosity and rotational velocity for spiral galaxies, for both stars (left) and total normal matter (right). Simulation curves by the team are shown in solid lines, with data for individual galaxies indicated as points. This agreement is unprecedented. Image credit: A. Cattaneo et al., arXiv:1706.07106, submitted to MNRAS.

From Louis Wilbur on modified gravity vs. dark matter: "Thank you for the fabulous article Ethan. I have a message for the modified gravity people: give up, you are fighting a battle that you cannot possibly win."

I actually don't mind that they keep fighting the battle to seek a modified theory of gravity that explains all the observations. The only thing I do mind is when they misrepresent the successes and failures of modified gravity models and dark matter models. MOND is very good at explaining some dynamics for small-scale structure, but at its heart it's just an empirical correlation. 'Empirical correlation' means that when we observe one thing, we can know another thing, but only because we have seen "this is how these things appear to be related," not because we understand the underlying physics behind it.

The Tully-Fisher relation has been one such correlation for about 40 years. With this new study, it may now move from empirical to theoretically understood/derivable. That would be incredible. But we are not yet there with MOND.

A great variety of galaxies in color, morphology, age and inherent stellar populations can be seen in this deep-field Hubble image. James Webb will go even farther. Image credit: NASA, ESA, R. Windhorst, S. Cohen, M. Mechtley, and M. Rutkowski (Arizona State University, Tempe), R. O'Connell (University of Virginia), P. McCarthy (Carnegie Observatories), N. Hathi (University of California, Riverside), R. Ryan (University of California, Davis), H. Yan (Ohio State University), and A. Koekemoer (Space Telescope Science Institute).

From Omega Centauri on what contributes to galaxy dynamics: "So to what extent do the interplay of star formation, supernovas, and black holes create difficulties in understanding/simulating galactic evolution? I’m under the impression, these are able to heat and expel gas, and thereby stop or at least modulate star formation. I would think the luminosity to mass ratio would be sensitive to such details."

A lot, but not exclusively. Which is to say, there are a lot of factors other than the ones you've listed that are required to understand/simulate galactic evolution. There is considerable scatter in the mass-to-light ratios of galaxies, there's a lot of variation in the time since the majority of star formation occurred in similar/comparable galaxies, there is feedback from galactic interactions, there is an entire history to worry about when it comes to the baryon fraction in a galaxy. Luminosity-to-mass ratios are sensitive to the details you mention, but also many others. When we paint with broad strokes, we have a hard time capturing accurate predictions for any one particular galaxy we choose.

The CMB is a consequence of the Universe redshifting and cooling, due to the expansion, after the Big Bang. Dark energy is an extra ingredient that has nothing to do with the CMB's existence, and only very slightly affects even its temperature. Image credit: Whittle Rodman, University of Virginia.

From Pentcho Valev on what seems reasonable to him: "It is unreasonable to claim that “empty space has more energy than everything in the Universe” (Ethan Siegel, 2012) and at the same time to believe that the noise now known as CMB is not a product of this energy but just traverses it, unchanged."

So you, yourself, cannot personally see reason in both accepting dark energy (what I wrote about empty space) and accepting that the leftover glow from the Big Bang -- the CMB -- isn't related to dark energy. (Hint: it's not.) Well, luckily for you I wrote a book that explains in gory detail where both of these things come from, how we know they're real, and what they are related to and how it isn't each other. Chapters 6 and 10 in particular. If you choose to learn science instead of going with what you define (incorrectly, BTW) as "unreasonable," you will likely find it very intellectually rewarding.

Image credit: Moonrunner Design, via http://news.nationalgeographic.com/news/2014/03/140318-multiverse-infla….

And finally, from Adam on whether there's an edge to our pocket of non-inflating space: "if the universe is finite, is there an edge between the space we’re use to, with space that’s still inflating beyond?"

So here's the thing: inflation happens everywhere in space, but it should preferentially end in some regions before it ends in others. So if it ended in ours, but not in an adjacent region, what does that boundary look like? That's the crux of what Adam wants to know.

Image credit: me, of how space expands (blue) during inflation, and where Big Bangs occur (red X's).

It's very difficult to say, because we have no way of knowing the geometry of the region, whether there's a "hard boundary" or not, and how far into the non-inflating Universe one would need to be to be "safe." (After all, it's centimeters-to-meters we're talking about that define the entire observable Universe at the end of inflation!)

But the simplest answer is that there would  be what looked like a discontinuous "wall of nothing" stretching across the sky. Stars, galaxies, gas, dust, and radiation would all just appear to end. There would be an empty hole in the CMB as though a flat slice cut through the observable Universe, with no signature of a Big Bang in that particular direction. It would look like those overpriced sliced sphere light fixtures. Yes, this is model dependent, but that's the most naive, straightforward, zeroth-order prediction for what you'd expect.

Thanks for a great week, everyone, and let's work hard to make the next one even greater!