After decades of effort, scientists are finally seeing black holes:
While working on his doctorate in theoretical physics in the early 1970s, Saul Teukolsky solved a problem that seemed purely hypothetical. Imagine a black hole, the ghostly knot of gravity that forms when, say, a massive star burns out and collapses to an infinitesimal point. Suppose you perturb it, as you might strike a bell. How does the black hole respond?
Teukolsky, then a graduate student at the California Institute of Technology (Caltech), attacked the problem with pencil, paper, and Albert Einstein's theory of gravity, general relativity. Like a bell, the black hole would oscillate at one main frequency and multiple overtones, he found. The oscillations would quickly fade as the black hole radiated gravitational waves—ripples in the fabric of space itself. It was a sweet problem, says Teukolsky, now at Cornell University. And it was completely abstract—until 5 years ago.
In February 2016, experimenters with the Laser Interferometer Gravitational-Wave Observatory (LIGO), a pair of huge instruments in Louisiana and Washington, reported the first observation of fleeting gravitational ripples, which had emanated from two black holes, each about 30 times as massive as the Sun, spiraling into each other 1.3 billion light-years away. LIGO even sensed the "ring down": the shudder of the bigger black hole produced by the merger. Teukolsky's old thesis was suddenly cutting-edge physics.
"The thought that anything I did would ever have implications for anything measurable in my lifetime was so far-fetched that the last 5 years have seemed like living in a dream world," Teukolsky says. "I have to pinch myself, it doesn't feel real."
[...] But no one could be sure those black holes actually are what theorists had pictured, notes Feryal Özel, an astrophysicist at the University of Arizona (UA). For example, "Very little that we have done so far establishes the presence of an event horizon," she says. "That is an open question."
Now, with multiple ways to peer at black holes, scientists can start to test their understanding and look for surprises that could revolutionize physics. "Even though it's very unlikely, it would be so amazingly important if we found that there was any deviation" from the predictions of general relativity, Carroll says. "It's a very high-risk, high-reward question."
[...] In September 2019, Teukolsky and colleagues teased out the main vibration and a single overtone from a particularly loud merger. If experimenters can improve the sensitivity of their detectors, Ohme says, they might be able to spot two or three overtones—enough to start to test the no-hair theorem.
[...] In the meantime, the sudden observability of black holes has changed the lives of gravitational physicists. Once the domain of thought experiments and elegant but abstract calculations like Teukolsky's, general relativity and black holes are suddenly the hottest things in fundamental physics, with experts in general relativity feeding vital input to billion-dollar experiments. "I felt this transition very literally myself," Ohme says. "It was really a small niche community, and with the detection of gravitational waves that all changed."
[The story provides a well-written and eminently readable history of research into black holes. Best treatment on the subject I've ever seen. --martyb]
(Score: 0) by Anonymous Coward on Friday January 08 2021, @05:38PM (4 children)
"The thought that anything I did would ever have implications for anything measurable in my lifetime was so far-fetched...."
This sounds like everyone in my department. The ideal is to be so removed from doing any practical work so you exist as a pure thought-form only - while being on a nice tenure track surrounded by starry eyed students.
(Score: 2) by istartedi on Friday January 08 2021, @07:12PM (3 children)
Fond memories of the "ideal" meme from E-school: The ideal gas, the ideal op-amp, etc.
At some point, I believe the question "What do you consider to be your ideal position?" was asked. I was sorely tempted to hit back the interviewer with "Obviously, the one where I do nothing and receive the entire global GDP". Of course I didn't do that, but seriously, if you're interviewing engineers it ought to be the only valid answer.
Appended to the end of comments you post. Max: 120 chars.
(Score: 2) by PiMuNu on Friday January 08 2021, @07:40PM (1 child)
> do nothing and receive the entire global GDP
What would you do with the entire global GDP? Wouldn't you get bored?
(Score: 2) by VLM on Friday January 08 2021, @11:05PM
I could be picky and point out there's no time bound so the GDP for the previous nanosecond likely isn't quite as much as the GDP for the previous year.
(Score: 0) by Anonymous Coward on Friday January 08 2021, @08:48PM
Meanwhile, Elon Musk was only able to expand his fortune by $400M/day over the past year.
(Score: 2) by stormwyrm on Friday January 08 2021, @07:30PM (1 child)
Numquam ponenda est pluralitas sine necessitate.
(Score: 2) by sjames on Friday January 08 2021, @10:06PM
There have been a lot of changes in computing since the early '70s. Many of them greatly expanded the availability of computers. While postgrads in the early '70s could get their hands on computer time if they needed it, it was expensive enough that if you COULD do it with pencil and paper, you would. At least the preliminary work.
It's easy to forget that now that toddlers have more powerful computers they can use to play shape matching games and watch silly videos on.
(Score: 2) by ElizabethGreene on Friday January 08 2021, @07:53PM (5 children)
Noob question: Would it be possible to optically image the black hole that LIGO-Virgo heard eat its binary companion in 2019?
(Score: 2) by VLM on Friday January 08 2021, @11:35PM (4 children)
Sounds too small too far away to even get close to this list.
https://en.wikipedia.org/wiki/List_of_stars_with_resolved_images [wikipedia.org]
https://www.ligo.org/detections.php [ligo.org]
Going thru the journalist filter for LIGO its not that it happened 1.3B years ago its that it happened 1.3B lightyears away
The black holes were 30 or so solar masses
https://www.omnicalculator.com/physics/schwarzschild-radius [omnicalculator.com]
Implies both black holes were about 110 miles in diameter
Betelgeuse disk can be imaged on the earth and I believe is about 0.66 billion miles across and 548 light years away, friggin huge and practically next door but quite a technical challenge.
So optically imaging the black holes from the LIGO event would be 6 million times smaller and 2.3 million times further away so its very handwavy gonna need optics 120 trillion times better than what it takes to image the betelgeuse disk.
So pretty much a bucket of nope.
One problem; there were two datapoints fractions of a light second apart that detected the event, and AFAIK they're not sure exactly where to point the telescope with any accuracy. Just kinda vaguely handwave to the south AFAIK at this time. Its possible they massaged the data to coordinates since the event to something more accurate than "vaguely point at Australia" Still its pretty small indeed.
I remember hearing a buddy who got his degree in astronomy and ended up working at a bookstore that he was at a site with a 4 meter scope that took a CCD image of betelgeuse that was clearly several pixels wide vs the other stars being point-ish sources. Or I mean it was spread a couple pixels wider than the more distant stars if that makes sense. Or maybe rephrased it took a 4 meter scope which is big but not record breaking. There's a couple in Hawaii.
Palomar's 200 inch was the biggest for a long time but there's an absolute shitload of bigger scopes came on line since 1990 or so, like 20 or 30 scopes bigger than that.
(Score: 0) by Anonymous Coward on Saturday January 09 2021, @12:16AM (1 child)
"The speed of gravitational waves in the general theory of relativity is equal to the speed of light in a vacuum,"
-According to this citation: Hartle, J.B. (2003). Gravity: An introduction to Einstein's General Relativity. Addison-Wesley.
You said:
"Going thru the journalist filter for LIGO its not that it happened 1.3B years ago its that it happened 1.3B lightyears away
I must be missing something, cause would not the waves have to travel 1.3B years to be detected if they are 1.3B light years away?
(Score: 0) by Anonymous Coward on Saturday January 09 2021, @02:45AM
Short answer. Yes, every time you look out into space you are looking back in time. Just take a look at the Moon and you are looking back 1.3 seconds.
He is just emphasizing the distance is too great to see it optically, rather than the fact that it was so long ago.
(Score: 0) by Anonymous Coward on Saturday January 09 2021, @12:45PM
Distances on the intergalactic scale tend to be screwy thanks to the fact that the universe is itself expanding:
https://en.wikipedia.org/wiki/Distance_measures_(cosmology) [wikipedia.org]
You can't just multiply the speed of light by a cosmological time interval to get a distance, or divide a cosmological distance by the speed of light to determine when something "actually happened". That only sorta works at relatively short distances where spacetime is closely approximated by flat Minkowski space. When you start getting to around a billion light years or so the curvature of the universe that results in the expansion of space needs to be taken into account.
(Score: 2) by ElizabethGreene on Saturday January 09 2021, @06:24PM
Thank you for filtering through that. That size and distance is infeasible for any planetary based telescope.