“They always say time changes things, but you actually have to change them yourself.” -Andy Warhol
Any week that passes by that leaves you knowing more than when you started is a good one here at Starts With A Bang! I hope this past week didn’t disappoint, as many of you became acquainted not only with our latest podcast on parallel Universes, but with some amazing new articles on science and the Universe. Even as the year winds down, there’s plenty more to explore! Here’s what the past week held:
- How do gravitational waves escape from a black hole? (for Ask Ethan),
- An X-ray surprise! When black holes stop eating, galaxies fade away (for Mostly Mute Monday),
- Has LIGO already discovered evidence for quantum gravity?,
- Mystery of ultra-fast solar flares solved by plasma physics,
- Top 10 gifts for lovers of outer space, and
- How the Universe changed in 2016.
As always, articles go up on a one-week delay over on Medium ad-free, thanks to our Patreon supporters. And I’m almost done with a draft of my next book; so excited for October of next year when it debuts! With all that said, let’s dive right into our comments of the week!
From Craig Thomas on what you can find in the sky: “I saw a great satellite on Friday night – it was two satellites following in exactly the same track (on what looked like a polar orbit), and they were as close together as one side of the square bit in the middle of Orion.”
You might be surprised to learn that co-orbiting satellites, where two satellites share the same mean orbit and almost the exact same path, are not only common for artificial satellites, but for natural ones as well! Saturn has two moons, Janus and Epimetheus, that not only share the same orbit, but swap positions every so often, with one overtaking the other and then the reverse happening.
Thankfully, Earth-orbiting satellites are so low in mass that their mutual gravitational influence is negligible, and so what you’re seeing is merely a trick of perspective. Also, most satellites are orbiting incredibly quickly: at a mean speed of a little over 7 km/s. So even two satellites that look close together are going to be separated by large distances… if it takes just 3 seconds for one satellite to reach the point where the one it was chasing previously was, they’re separated by approximately 21 km (13 miles). And if their orbital periods differ by just 1%, that means after 24 hours, they’ll be separated by more like 6000 km (4000 miles). In other words, what you saw was most likely a very temporary configuration, but pretty to look at nonetheless!
From Denier on right and wrong: “Right and wrong are often subjective and are absolutely up for debate. For the same reason you want to tell people their opinions don’t matter, it is not fair to expect the public to know exactly where politics stop and where science starts.”
Do you really want to argue against what I said in context? Just as a reminder, that was:
It is everyone’s job — scientists, the press, and ordinary citizens (and non-citizens) — to make the truth matter. Right and wrong shouldn’t always be up for debate. We don’t vote on the sky color, and voting on it doesn’t change it. Perhaps we have a right to be free from misinformation masquerading as truths, too.
Yes, you can find instances where right and wrong are subjective and are ethical, moral, or other unprovable issues. But there are demonstrable facts out there where you can either be honest and truthful about what reality says — something that’s right — or you can distort it and lie and mislead and dissemble about it. When you say,
As an expert if you want the truth to ‘win’, publish science in peer reviewed journals and do more science and publish that too.
I retort that, quite clearly, that is not enough. That has been done. That has been tried. That does not seem to play a very large role in whether the truth wins. More must be done, and it should be done and advocated for by all of us. Scientific truths may not necessarily have a one-to-one correspondence with policy, but we should at least all be able to agree on what they are. Until we get there, until we can agree on basic facts, we’re going to have a very hard time moving forward together in this world.
From Omega Centauri on what else is visible from black hole mergers: “I have a question about other merger observables. If we were so lucky as to be able to observe a merger from close by (say a lightyear), with large telescopes, could we see anything other than gravitational waves? I’m assuming neither has an accretion disk, although that case might be interesting as well.”
You may remember a scandal earlier this year where NASA’s Fermi team claimed a detection of electromagnetic signals from the LIGO merging black holes, where they knew how to do the analysis correctly and chose not to. But there ought to be an electromagnetic signal of some type depending on how much matter is around the black hole(s) and how they’re configured. The question is, what would we see?
That’s something we’re only beginning to get an understanding of. Remember, until LIGO detected its first merging pair, we didn’t even know that black holes of these masses existed for certain. So electromagnetic properties of mergers are going to be the data that guides the theory/models, not the other way around!
From PJ on black hole eating: “Is the BH eating, or being spoon fed?”
There is definitely no spoon. (Oh, Matrix reference!) No, what I mean by that is when you say “spoon-fed”, you think about a small amount of matter neatly being pulled into a black hole, entering the event horizon and disappearing. “Blip.” That’s it.
But the overwhelming majority of the matter “eaten” by the black hole doesn’t go towards its growth, but rather gets accelerated and expelled, and that’s why the activity looks the way it does. But it’s kind of surprising that the turn-off and the dimming can be so fast. It doesn’t extend over the whole galaxy that fast, of course, but the overall flux can drop so quickly and that’s a new discovery. Not spoon fed; more like dumping a gallon into a shot glass.
From t marvell: “Why isn’t our universe a black hole? Certainly at the time of the big-bang there was plenty of mass, in a small enough space, to create a black hole.”
If the fabric of space weren’t expanding, it would have done so immediately. In fact, if the fabric of space were initially expanding by one part in 10^25 less than it did at the Big Bang, the Universe would have recollapsed into a black hole already. You have to look at the Universe as a race — between the expansion of space and the gravitational pull of all the mass inside — and the Big Bang is the starting gun. The expansion is winning, but just barely.
From Denier on superseding Einstein: “If the echo signal were to be proved, would that mean Einstein’s Field Equation is wrong?”
Although there were some good nuanced comments on wrong in science by both ketchup and Anonymous Coward, there are some additional points that need highlighting. Yes, we know that Einstein’s general relativity is incomplete. For example, imagine the double slit experiment. An electron passes through the double slit, and you don’t make a measurement, so it acts like a wave. You can calculate its wavefunction, its probability distribution and observe where it lands on the screen behind the slit.
But what happened to the electron’s gravitational field as it passed through that double slit? Einstein’s general relativity doesn’t tell you — can’t tell you — because general relativity is a “classical,” non-quantum theory. The closest we can get to quantum anything in gravity is to do the semiclassical approach, where we use the background GR spacetime as the curved “classical” space to do our quantum calculations for the other three forces.
But this modification is different. This is a particular approach that doesn’t just venture where GR doesn’t; it’s an approach that says quantum gravitational effects get large around a black hole’s event horizon, not just at the central singularity. It’s a non-standard approach, with incredible consequences. If this particular approach to quantum gravity is borne out by further black hole merger data, it means that not only is Einstein wrong, but he was more wrong than the minimum “wrongness” level we expected. And that’s incredibly interesting, if true!
From PJ on Celestron Firstscope pricing: “Careful on the telescope pricing […] New (3) from $99.00 + $14.99 shipping”
That is a shame that Amazon jacked up the price so fast. It should never be more than $50 (USD), because that’s what it sells for on the Celestron website. In fact, according to Camelcamelcamel, the price just shot up… like, right after I posted it.
Don’t go to Amazon if that’s what you’re going to get. The beauty of the firstscope is its ease-of-use and setup for young kids, not for its utility or quality for the discerning adult. I enjoy astronomy binoculars tremendously, and Wow gave some excellent advice on that front; if you’re an adult amateur skywatcher with no equipment, start out there instead!
And finally, from Omega Centauri on nearby supernovae, “So if a SN did go off in our galaxy, even if behind thick dust, could we miss it? Clearly we wouldn’t see it in visible light, but IR, radio, X-ray, and even neutrinos might be capable of announcing its occurrence. So is there much of a chance we could still miss it?”
I am getting a theme from you, Omega. Something about nearby catastrophes and your fascination with them… hopefully nothing too bad is going on over by you. But that aside, the answer is, “optically, yes; neutrino-wise, no way.”
The last supernova that went off nearby us — SN 1987a — occurred 168,000 light years away, in a satellite galaxy of the Milky Way. And we detected on the order of about a dozen neutrinos from it. Our galaxy is about 75,000 light years away from us at its farthest point, so less than half of that distance, and our detectors currently online are now about a thousand times more sensitive than they were 30 years ago. In fact, last year, IceCube detected neutrinos from outside our own galaxy for the first time!
The galactic gas and dust could render a distant supernova so faint that we wouldn’t see it right away in all wavelengths, but the neutrino signal wouldn’t like. We’d see thousands coming from a single source at once, and then optical follow-ups would ensue immediately. The next supernova will either be detected by the naked eye or by neutrinos first. Regardless, it won’t go unseen for long!
Thanks for a great week, everyone, and see you back here tomorrow for more fantastic stories of the Universe here on Starts With A Bang!