“A theory is a supposition which we hope to be true, a hypothesis is a supposition which we expect to be useful; fictions belong to the realm of art; if made to intrude elsewhere, they become either make-believes or mistakes.” -G. Johnstone Stoney
It’s been another exciting week here at Starts With A Bang! This coming Thursday, I’ll be speaking at Jacksonville University in Florida; if you’re around that area come and say hello! Before we get any further, I’m pleased to announce that thanks to two very generous new Patreon donations from Ryan Schultz and Samir Kumar (shout-out!), we’ve now hit the next rewards tier on my Patreon campaign, meaning that we’ll be commissioning the creation of the most scientifically accurate, beautifully illustrated history-of-the-Universe poster of all-time! Come be a part of our Patreon if you’re not already, and get in on the rewards!
We’ve also, as always, had a slew of fantastic articles come out this past week. If you’ve missed anything, check them all out below, including:
- Does dark energy mean we’re losing information about the Universe? (for Ask Ethan),
- The nearest supernova of our lifetimes turns 30, and still shines (for Mostly Mute Monday),
- Recent Claims Invalid: Emergent Gravity Might Deliver A Universe Without Dark Matter (by Sabine Hossenfelder),
- How NASA’s James Webb Space Telescope will answer astronomy’s biggest questions (a live-blog event),
- 7 ways Earth would change if our Moon were destroyed, and
- NASA’s MAVEN discovers how Mars lost its atmosphere.
You’ve had your say in the comments section, and now it’s time for me to call out the ones that I have the most (or most important) things to say about them in this edition of our comments of the week!
From Paul on how much we still don’t know: “It’s humbling to read such articles and realize how little we understand of everything that is around us……”
I think this is one of the most important things to recognize about science. Whenever we seek to answer a question, scientifically, it demands that we gather new data, make new observations or perform new experiments. We need additional degrees of precision and accuracy, and more information to decide on what the correct outcome/answer is. But even when we obtain them, it raises more questions. What’s there at the next significant figure? Where does the current explanation break down? What’s the next fundamental question to answer? And what additional puzzles arose because of the new information we have?
Our total knowledge about everything may be fundamentally limited, but we haven’t hit those limits yet. In fact, we’re not even close.
From Omega Centauri on Ben Franklin: “Franklin’s kite experiment is not something you should try at home. I’ve heard that people have been killed trying it. Franklin was lucky.”
Of course you shouldn’t fly a kite in a lightning storm; Beavis and Butthead once did a whole episode about it. The legend of Ben Franklin — that he flew a kite in a lightning storm grounded by a key and some silk — and the likely actual story, that he tied a kite to a metal cage, are vastly different.
Don’t try and attract lightning to your body, kids.
From Denier on climate science and climate scientists: “I laughed out loud when I read this. Of course climate scientists are real scientists and I’m blatantly trolling when I say otherwise.”
I will always take you at your word, so that makes me a very easy target for trolling. Just FYI. My other option is to selectively ignore what you say, which isn’t really my modus operandi. Recently, Tucker Carlson had Bill Nye on his program and asked him, what percentage of the observed warming comes from human activity. The above figure, although it’s a decade old, gives the approximate answer: around 125%. The light-blocking and light-reflecting properties of other human activities — like pollution, additional cloud cover and jet exhaust — actually help with the warming. It’s observations like this that make geoengineering even possible; there are human activities we can perform that reduce the amount of incident sunlight.
The question is what’s the optimal path forward? And this is something we can only model or simulate. There may be only one answer for orbital mechanics, but try simulating a more complex system — like the large-scale structure of the Universe — and each independent simulation will give you different answers in the details. Because you can’t simulate something that requires more computing power than you have, so you make simplifying (and wrong) assumptions: that dark matter particles have masses of 10^9 suns; that the Universe acts like a mesh far away and individual masses act like particles up close; that the gravitational interaction “turns off” when you’re too close; etc. Simulations are incredibly useful, but they are only good to the limits of the simulations.
And yes, there are bad scientists and unethical actors anywhere you go, and climate science is no different. We’re not going to get anywhere arguing over who is smarter, more gifted, etc. The point is that this is robust, reproducible science, with quantifiable errors and uncertainties that lead to an overwhelming conclusion: humans are the cause of Earth’s warming and that the consequences are increasing for the planet. Undark had an interesting piece on the assumptions that the left and right makes with respect to climate science. I make assumptions #2 and #4 from the left and none of the ones on the right. Which ones are you?
From Naked Bunny with a Whip on what string theory predicts: “I thought the biggest problem with string theory is that you can’t use it to make predictions because there are so many different solutions.”
Let me ask you a question: what’s the energy contained in empty space? This is something we’ve recently measured (or perhaps more accurately, inferred) thanks to the discovery of dark energy. People’s intuitions told them it would be “zero” for a long time; then they tried to calculate it and got a value that was so large it would destroy the Universe in about a Planck time; then they measured it to be ~10^-120 times the size of that second number. That value is known as the vacuum expectation value (or VEV) of the vacuum.
String theory doesn’t have the same unknowns that the Standard Model does: masses, charges, quantum numbers, etc. That’s all calculable. But the VEVs of each of the strings? No predictions. You can put in literally anything; they’re free parameters. That’s where the “so many different solutions” ideas comes in. Because you’ve taken a hard problem and made it even worse. That’s definitely a big problem.
From Paul on doubting the Big Bang: “here’s problem with the “Big Bang idea…..it comes from the observation of dozens of galaxies…..what about the other billion trillion zillion ????????”
So I wrote a pretty well-reviewed book that addresses where the Big Bang idea comes from and how it was verified in chapters 3, 4, 5 and 6. The idea of the expanding Universe initially came from only dozens of galaxies; that number is now in the tens of millions. (Which are the ones we have data for.) The Big Bang idea came as one of many ideas out of that observation coupled with General Relativity, and — as Denier says later — was verified and validated by observations of the cosmic microwave background.
It is on much more solid footing than you give it credit for.
From CFT on dark matter: “Dark matter is a fudge factor used to prop up failing cosmological assumptions and calculations based on those assumptions…”
Dark matter is a “fudge factor” in the sense that anything indirectly observed is a fudge factor. You could have said the same thing of atoms, of electrons, of the quantum wavefunction or of quarks. The fact that it makes predictions that have been borne out by observations is tremendous in the scientific sense. The fact that it hasn’t been detected directly is a constraint on its (unknown, by the way) cross-section with normal matter and itself, not evidence of its absence.
Keep asking questions and learning, though. Eventually, you’ll come to the dark side.
Two supernova questions from PJ: “What would cause the SN to form a disk of material from the center of the star (assumed center) with ejected material symmetrically expanding along the objects axes? Why not explode in the form of a spherical apparition?”
Quite simply to your first question: rotation. Rapid rotation means that the equatorial material is less tightly bound to the star and easier to eject into space. We launch rockets closer to Earth’s equator for that reason, and the effect is pretty small on Earth. Some stars can rotate at thousands of km/s, meaning any outward “push” preferentially pushes material out along the equatorial plane.
The second question is a big misconception that existed among even supernova scientists until the late 1990s/early 2000s when (surprise!) simulations got good enough: supernovae aren’t spherically symmetric! If you start the supernova explosion off-center even by a tiny bit — whether type Ia or core collapse (type II) — you get a very non-spherical explosion.
From Axil on emergent gravity: “The growing acceptance of Erik Verlinde’s work…”
STOP. You do not pass go. You do not collect $200. There is no growing acceptance of Verlinde’s work, period. Verlinde’s work is work in its infancy: it is the beginning of science. In two particular ways, it makes some predictions. One of those predictions was claimed to be falsified; that claim was incorrect. That is what the article states. That is what the article is about. There is no growing acceptance of his work or his ideas. It merely has not been ruled out yet.
From Anonymous Coward on Verlinde’s work and the true challenge: “Welp, seems that there’s still no word on whether it’s actually going to work for the ultimate test of any dark matter alternative: galaxy cluster and cosmological scales.”
This is a big deal. You see, on galactic scales, it’s relatively easy to modify gravity (or modify something) and reproduce the observed behavior. But on larger scales, dark matter is the only thing that works. So what about large-scale clustering? Well, it hasn’t gotten as much attention, but as entropy changes (grows) over time, the emergent gravity phenomenon that acts like dark matter should grow. Meaning that observations of distant galaxies and clusters and filaments should show less evidence for dark matter, with the first galaxies showing practically none at all.
I believe that if this were put to the test, Verlinde’s theory (or at least one of his equations) would be falsified. But no one is taking this approach yet, and I am kind of busy.
From MandoZink on JWST, its launch and what it means: “I have been waiting so eagerly for this launch event, complete with all of the magnificent things it would reveal. I was expecting this would be an unbelievable shift in my view of the universe.
Unfortunately I will not be here. I am laying in my new temporary hospital bed here at home, as cancer eats away at my body, with probably only a week or two to live.
Ethan, your explanations of the workings of the universe have been absolutely delightful. I cannot say how much this website has meant to me. Really!
I also want to thank you for the kind sentiments you expressed to me in the past when I was enduring totally unnecessary legal troubles. It was genuinely an uplift to receive your understanding comments.”
My usual approach here is useless. I am happy I’ve been able to add a little bit of joy and wonder into your life, but sad that your journey is coming to an end. If you’ve got perhaps a few weeks left, feel free to privately (at startswithabang at gmail dot com, the same place Ask Ethan submissions go) send me the address of where you’ll be and I’ll send you a little something. If you want to speculate as to what the next great breakthroughs of James Webb (or WFIRST, in the 2020s) might bring, here was the best I could come up with.
From Nerd on destroying the Moon: “Hmmm…. what could possibly destroy our moon?”
An asteroid made of antimatter. A large enough (e.g., moon-sized) impactor. The death star. Princess Celestia. Or, as Michael Kelsey suggested, Chairface Chippendale.
You never know.
And finally, from Gab on the idea of a cosmic supercluster: “When I think of cluster I think something bunched together, I think some parts might move away, but generally its a clump or cluster. It still exists/ed.”
You know, before dark energy, it made a lot of sense to call these huge collections of galaxies in space “superclusters.” We said that we, ourselves, lived on the outskirts of the Virgo Cluster. Why? Because, in a decelerating Universe with overdensities of the magnitude these objects have, we would someday see ourselves fall into Virgo, and wind up bound together with the rest of the Virgo Cluster galaxies. We’d also see these clusters merge together — often along the dark matter filaments — into a true, bound supercluster.
Dark energy now means that we are not a part of Virgo; we are part of our local group and that will remain forever isolated from not only Virgo, but from all the nearby groups like the Leo group, the M81 group and even the Maffei group. But it also means that of all the “superclusters” we’ve drawn circles around, none of them are real structures. All of them will wind up forever unbound. That’s why there’s no such thing. At least, not according to a reasonable definition of structure.
Thanks for a great past week, and looking forward so very much to the coming one!