Thursday Throughput: AAS Bumper Crop Edition
Hold on to your hats, folks. It’s gonna be a long one this week. Right now, in Hawaii, the 235th meeting of the American Astronomical Society is going on. That means lots of press releases about really cool results. By the time this posts, I expect another five or six cool results to be announced. So let’s tuck in.
[ThTh1] This week’s “Ask an Astronomer” comes from long-time Twitter follower Rob Prather, who asks, “Is there a simple way to explain how a planet orbits two stars? I get the intuition on just one.” As it happens, we just had a discovery of a planet orbiting around two stars.
As for how it works. When you have two bodies in orbit around each other, the physics is pretty straight forward. They orbit with the same period around a common center of mass — a point where the weighted mass distribution balances out. That point is closer to the heavier object. So if you consider just the Earth and the Sun, they both orbit around each other. But the Sun is much more massive than the Earth, that point of balance is inside the Sun itself. The Earth orbits around the Sun and the Sun “wobbles” slightly in response to the Earth. Many planets have been detected this way: by the wobble of their host star.
When you have multiple bodies, however, the math gets really complicated. But, most of the time, we don’t worry too much about that. The gravitational forces in our Solar System, for example, are dominated by the Sun, which contains a thousand times as much mass as the planets combined. Other planets, like Jupiter, can have an effect on us, but it’s fairly minor.
But what if you have two stars? Then it gets complicated. The three-body interaction would make planetary orbits unstable and even eject some planets from such systems. But there are two areas where planets could exist in a stable orbit. If a planet were very close to one of the two stars, the nearby star would dominate and the effect of the more distant star would be fairly minor. In the case of TOI 1338, you have the other solution: if a planet is far enough away from its parent stars, their gravity would be effectively that of a single star. Using Kepler’s law, I estimate that the planet is about three times as far away from the two stars as they are from each other. That’s enough that its orbit changes a bit but it will still hang around for an indefinite time.
[ThTh2] This has to be seen to be believed. Pulsars are the shriveled husks of stars that went supernova. A typical pulsar would be the size of a small city, weigh 1.4-2.2 times as much as the Sun and spin about once a second. It would have a magnetic field so intense that if you tried to use a compass, the atoms in it would come apart. We’ve now gotten our first detailed look at the surface of a pulsar. And it’s incredibly messy and complex, with a tangled magnetic field that looks only vaguely like what you’d see in a textbook. Astonishing work here. Click through for the animation.
[ThTh3] Massive black holes are usually found at the center of their parent galaxies. But not always.
[ThTh4] Fast Radio Bursts — short intense radio signals from the cosmos — have long been a mystery. But we’re slowly learning more about them. And now we’ve found where one of them is coming from. I’m not saying that it’s aliens but…it’s probably not aliens.
[ThTh5] So will eating Impossible Whoppers give men breasts? In a word: no. Soy contains hormones that are similar to estrogen. It is theoretically possible that if a man consumed a lot of faux burgers, it would cause hormonal problems. But he’d have to consume A LOT of soy. As in a gallon of soy milk a day or 5-10 soy burgers a day. And if you’re eating 5-10 Whoppers a day, you’ve got bigger problems.
[ThTh6] The better out telescopes get, the more amazing our Galaxy gets:
A cluster of newborn stars was found on the outskirts of the Milky Way by @FlatironCCA's Adrian Price-Whelan (@adrianprw) & colleagues. Presented today at #AAS235. The gif shows position of the stars relative to our galaxy & the Magellanic Clouds. For more https://t.co/ABDRxZqH3W pic.twitter.com/KUd9jETJ66
— Flatiron Institute (@FlatironInst) January 7, 2020
[ThTh7] Yep. That’s how science works.
I produced a tribute to my wrongness. pic.twitter.com/1aJRAUJlIm
— That’s Dr. Monkiewicz to you (@jmonkiew) January 6, 2020
[ThTh8] Is streaming TV shows destroying the planet? Probably not. I clicked through to the original publication which is less of a scientific research paper than a screed. It’s true that the energy needs of data centers is a growing concern. But … at most, we’re looking at about 4% of energy use for all technology, including manufacture. Data centers are 20% of that, so less than 1% of global energy use. That will increase over the next few decades but will still be small. So their calls for “digital sobriety” seems badly misplaced. The real challenge here is to decarbonize the electrical grid. Do that and you can binge-watch all you want. In fact, you can do it now; the energy will be dwarfed by what you’re using just to keep your house running.
I’ve talked about this before, but I’ve grown a bit tired of these occasional bulls from the Church of Climate Shaming. I don’t think it motivates anyone. It’s simple puritanism; deciding that if people enjoy something it must be bad and must be sacrificed on the altar on environmentalism. But I don’t find that it motivates people. It either makes them ignore the problem or give up hope (so much so that some activists think that’s the point).
As I mentioned in my post on straws, we need to focus on big picture things, not tiny details that only matter on the fringes. Those problems are hard enough to solve without making anyone feel guilty because they watched His Dark Materials.
[ThTh9] And speaking of global warming, Germany has phased out their nuclear plants. The result? Much burning of coal with billions in social costs, hundreds of death from pollution and a warming planet. The deaths alone will be anywhere from 10-100 times what Fukushima cost us…every year.
Nuclear is part of the solution. We need to keep pretending it isn’t because radiation scares us.
[ThTh10] Astonishing:
Absolutely beautiful video created using still images taken by the Cassini spacecraft during its flyby of Jupiter and while at Saturn. Shown is Io and Europa over Jupiter's Great Red Spot and then Titan as it passes over Saturn and it's edge-on rings. Credit NASA/JPL/Kevin M.Gill pic.twitter.com/CrIPHxtsld
— Domenico Calia (@CaliaDomenico) January 1, 2020
[ThTh11] A wonderful visualization:
To count an animal population if you can't catch them all: capture some, mark them, release, and capture again. The ratio of new vs already seen tells you something about the total number. Shown here is iterated mark-and-recapture with a Bayesian updates to belief about pop size pic.twitter.com/jZF7HXddiq
— Andrew M. Webb (@AndrewM_Webb) January 2, 2020
[ThTh12] And another:
Over the last five years I've collected eclipses with this single composition in mind. I call it "Cyclipse". It's made of a total solar eclipse, partial solar eclipse, total lunar eclipse, and waxing crescent Moon. It feels so good to see it come together over the years. #eclipse pic.twitter.com/FkQkzQShzp
— Marc Leatham (@quarkmarc) December 28, 2019
[ThTh13] You know I love me some optical illusions:
For the hungover…Hypnotic. Each ball is moving in its own straight line pic.twitter.com/n1hUj5oufH
— Bernie'sTweets (@berniespofforth) December 26, 2019
[ThTh14] And I’ll close this one out with yet another discovery from the world of exoplanets: an Earth-sized planet in the habitable zone.
A gallon is not that much. I easily consume a gallon of fluids a day. If I replace all of that with soy milk, I’d be drinking a lot of soymilk. But I don’t like soymilk (even though I like tofu, especially the firm kind). And while 5-10 soy burgers is a lot, that is because the actual soy content in these burgers is less than in firm tofu. to get some statistics, in a soy burger, there are 19g of protein. Let’s suppose all of this is soy protein. a 1/4 block of extra firm tofu contains 26g of soy protein. In order to get 95-190g of soy protein, I have to eat 1-2 blocks of extra firm tofu. Over two meals a day, I could easily see myself eating 1 block of extra firm tofu. Tofu shrinks when its fried so its not that filling. Just google tahu goreng. 1 tahu goreng is a block of deep fried tofu covered in peanut sauce. It is a meal (and sometimes only part of a meal). If I didn’t have peanut allergies, could I have tahu goreng (or gado gado or any other dish made from a block of firm tofu) for lunch and dinner? It’s not unimaginable. Some combination of the two can easily set you over the safe limit.Report
[ThTh13] I love this.
I just wanted to say…
I love this.Report
If soy products could cause feminization, trust me, a certain segment of the population would be able to demonstrate it empirically.
It doesn’t.Report
[ThTh8] – I don’t think the conclusions in the article add up, and I think it comes down to using old data for the energy efficiency of modern networks.
The only figure with an effective denominator I found in there was 1.6 kg CO2 / 0.5 hrs of video. Assuming 1 GB / hr of video, that’s 3.2 kg CO2 / GB. The Shift Project document they link to estimates 0.519 kg CO2 / kWh, so a bit over 6 kWh / GB of data transferred.
So, where does that power / GB estimate come from?
Googling around, I found a few papers from about 2010 – 2012 that had estimates in that range. (Possibly relevant – 2011 is when Netflix started their transition to streaming-only, splitting off the DVDs-by-mail business)
I also found this from 2017
Moore’s Law. It’s a hell of a thing. But what’s a couple orders of magnitude among friends?
It takes the equivalent drive from the 3.9 miles in [ThTh8] (“you probably didn’t have to drive that far for your VHS fix”) to driving 70 yards (if you lived 2/3 of a block from the video store you probably walked).Report
ThTh8 and 9 go together well and I just wanna make a point of agreeing entirely with both points.
I swear to God(ess?) that some of the loonier cohorts of the eco-left make me seriously wonder if there’s something to the socialcon shibboleth that if you get rid of organized religion then people will just organize new religions or religious-ize existing social structures.Report
[ThTh1] I’d think the Sun-Earth-Moon system is also a three-body problem, since the Sun attracts the Moon twice as powerfully as the Earth does.Report
Yep. However, the distance to the sun makes planet-moon systems generally tractable.Report
Didn’t some one just get an AI, or a neural network, to solve a three body problem?Report
As with most things AI or neural net, sort of. Given a sufficient library of previously solved problems for training, the AI takes a new problem and builds a prediction of the trajectories. With lots of weaknesses: fundamentally, underneath, it’s a statistical thing; no one knows exactly what parameters the statistics are based on, or how; it is, apparently, an iterative process and there are no established convergence criteria.
That said, I have started a real-time control project that has an image recognition component, and will no doubt be training some sort of AI/NN for that. Or using someone’s already trained open-source one. At least initially, the software just has to answer the (relatively common) question, “Is that a feral cat inside the target zone?”Report
I’m pretty sure it is formally unsolvable, at least in terms of analytic functions, although I should probably check that. I recall that Poincare argued that it was unsolvable, mostly based on topological considerations of phase space —
Which leads to a really cool bit of math trivia. A lot of Poincare’s motivations to explore topology was in service to understanding the geometrical aspects of differential equations. Think of it this way, any system of N second-order ODEs can be transformed into a system of 2N first-order ODEs. (This is what happens when you move from classical Lagrangian dynamics to Hamiltonian dynamics.) So, if you think of those 2N variables as dimensions in a 2N dimensional space, and then if you think of all the dx/dt’s and dy/dt’s as describing a vector field in that space, then you can think of the various solutions to your equation as flows in that space. Families of solutions form hypersurfaces. Those hypersurfaces often have an interesting topology.
(I assume you’ve at least seen “phase space” described during your engineering training.)
See also the Liouville’s Theorem: https://en.wikipedia.org/wiki/Liouville%27s_theorem_(Hamiltonian)
(You’ll get to use your knowledge of fluid dynamics to think about ODEs. Ain’t math grand!)
Anyway, this was the kind of thinking that led to the conclusion that there was no analytic solutions. (Formally: “analytic” more or less means something can be solved as a power series.)
I just checked. This according to the wiki page:
That’s kind of cool. It’s not analytic, but it is a series.
In any case, we can readily solve three body problems using numerical methods. In fact, because we can represent spheres as point-masses, and because we can usually represent oblate planets as point-masses plus a quadrapole moment, we can actually get pretty freaking accurate for a lot of problems. In the Hamiltonian form, the numerical methods can exploit the “symplectic geometry” of the problem to get wicked accuracy. Google “geometric integration” for more.
(I like math because I get to use words like “symplectic” non-ironically.)Report