Ask Ethan: Why Is The Black Hole Information Loss Paradox A Problem?
“Why do physicists all seem to agree that the information loss paradox is a real problem? It seems to depend on determinism, which seems incompatible with QM.”
There are a few puzzles in the Universe that we don’t yet know the answer to, and they almost certainly are the harbingers of the next great advances. Solving the mysteries of why there’s more matter than antimatter, what dark matter and dark energy are, or why the fundamental particles have the masses they do will surely bring physics to the next level when we figure them out. One much less obvious puzzle, though, is the black hole information loss paradox. It’s true that we don’t yet have a theory of quantum gravity, but we don’t need one to see why this is a problem. When matter falls into a black hole, something ought to happen to keep it from simply losing its information; entropy must not go down. Similarly, when black holes evaporate, a la Hawking radiation, that information can’t just disappear, either.
So where does it go? Are we poised to violate the second law of thermodynamics? Come find out what the black hole information paradox is all about, and why it compels us to find a solution!
What Was It Like When The First Stars Died?
“It’s theorized that this is the origin of the seeds of the supermassive black holes that occupy the centers of galaxies today: the deaths of the most massive stars, which create black holes hundreds or thousands of times the mass of the Sun. Over time, mergers and gravitational growth will lead to the most massive black holes known in the Universe, black holes that are millions or even billions of times the mass of the Sun by today.
It took perhaps 100 million years to form the very first stars in the Universe, but just another million or two after that for the most massive among them to die, creating black holes and spreading heavy, processed elements into the interstellar medium. As time goes on, the Universe, at long last, will begin to resemble what we actually see today.”
Our Universe, shortly after the Big Bang, proceeded in a number of momentous steps. The first atomic nuclei formed just minutes after the Big Bang, while neutral atoms took hundreds of thousands of years. It took another 50 to 100 million years for the very first star to be created, but only, perhaps, a million or two years for the most massive among the first stars to die. They may have been short-lived, but the first stars were truly spectacular, and their deaths set up the first steps in a changing Universe that would take us from a pristine set of materials to, eventually, the Universe as we know it today.
Take a major step in the cosmic journey of how we got to today by looking at what it was like when the first stars died!
Ask Ethan: Could The Energy Loss From Radiating Stars Explain Dark Energy?
“What happens to the gravity produced by the mass that is lost, when it’s converted by nuclear reactions in stars and goes out as light and neutrinos, or when mass accretes into a black hole, or when it’s converted into gravitational waves? […] In other words, are the gravitational waves and EM waves and neutrinos now a source of gravitation that exactly matches the prior mass that was converted, or not?”
For the first time in the history of Ask Ethan, I have a question from a Nobel Prize-winning scientist! John Mather, whose work on the Cosmic Microwave Background co-won him a Nobel Prize with George Smoot, sent me a theory claiming that when matter gets converted into radiation, it can generate an anti-gravitational force that might be responsible for what we presently call dark energy. It’s an interesting idea, but there are some compelling reasons why this shouldn’t work. We know how matter and radiation and dark energy all behave in the Universe, and converting one into another should have very straightforward consequences. When we take a close look at what they did, we can even figure out how the theory’s proponents fooled themselves.
Radiating stars and merging black holes do change how the Universe evolves, but not in a way that can mimic dark energy! Come find out how on this week’s Ask Ethan.
6 Facts You Never Imagined About The Nearest Stars To Earth
“4.) There are no neutron stars or black holes within 10 parsecs. And, to be honest, you have to go out way further than 10 parsecs to find either of these! In 2007, scientists discovered the X-ray object 1RXS J141256.0+792204, nicknamed “Calvera,” and identified it as a neutron star. This object is a magnificent 617 light years away, making it the closest neutron star known. To arrive at the closest known black hole, you have to go all the way out to V616 Monocerotis, which is over 3,000 light years away. Of all the 316 star systems identified within 10 parsecs, we can definitively state that there are none of them with black hole or neutron star companions. At least where we are in the galaxy, these objects are rare.”
In the mid-1990s, astronomy was a very different place. We had not yet discovered brown dwarfs; exoplanet science was in its infancy; and we had discovered 191 star systems within 10 parsecs (32.6 light years) of Earth. Of course, low-mass stars have been discovered in great abundance now, exoplanet science has thousands of identified planets, and owing to projects like the RECONS collaboration, we’ve now discovered a total of 316 star systems within 10 parsecs of Earth. This has huge implications for what the Universe is actually made of, which we can learn just by looking in our own backyard. From how common faint stars are to planets, lifetimes, multi-star systems and more, there’s a huge amount of information to be gained, and the RECONS collaboration just put out their latest, most comprehensive results ever.
We’ve now confidently identified over 90% of the stars that are closest to us, and here’s what we’ve learned so far. Come get some incredible facts today!
Ask Ethan: Could The Universe’s Missing Antimatter Be Found Inside Black Holes?
“It is a mystery why we see matter without corresponding antimatter. Some remote and old super massive black holes evolved much faster than current theory is able to predict. Could the missing antimatter be hiding inside those primordial black holes? Does the total mass of super massive black holes come even close to the amount of missing anti matter?”
When we look out at the Universe today, we see that everything is made of matter and not antimatter. This is a puzzle, because the laws of physics appear to be symmetric between matter and antimatter: you can’t create or destroy either one without creating or destroying an equal amount of the other. Is it possible that we actually created equal amounts of both, and that the antimatter collapsed into black holes, which might be responsible for either supermassive black holes or primordial black holes as dark matter? While, on the other hand, the normal matter didn’t collapse, and became the stars, gas, galaxies, and more that we observe today?
It’s a fascinating alternative to the standard picture that our Universe is fundamentally asymmetric, but does it hold up? Find out on this week’s Ask Ethan!
The Milky Way Is Hiding Tens Of Thousands Of Black Holes
“This study is of tremendous importance, since it provides us with the first real evidence of what LISA will be looking for, further motivating us to look for these events that, as we now know, must exist. Unlike LIGO’s black holes, these inspiraling events will give us weeks, months, or even years of lead-up time, allowing us to pinpoint exactly where and when we’ll need to look to see these mergers coming. This is the first confirmation of the theory that tens of thousands of black holes ought to exist around supermassive ones at the centers of galaxies, and allows us to better predict how many gravitational wave events we’re likely to see coming from them.“
At the center of our Milky Way, our galaxy houses a supermassive black hole: Sagittarius A*. At four million solar masses, it’s the most massive object in our entire galaxy, while orbiting around it are stars, gas, dust, and many other astrophysical objects. This is a region where new star formation is rampant, and so, in theory, there ought to be many thousands of black holes within just a few light years of Sagittarius A*, some of which ought to be detectable through their emission of X-rays from binary companions. For nearly 20 years, such a detection was elusive, since the flares that occur when black holes absorb large amounts of matter are too rare. But now, using the full suite of archival data from the Chandra X-ray observatory, scientists have found the steady, low-level X-ray emission these systems give off, revealing a population of approximately 10,000 black holes within 3 light years of Sagittarius A*.
The Milky Way is hiding tens of thousands of black holes near the galactic center, and for the first time, we’ve just revealed the surefire signs that they exist.
The Black Hole Information Paradox, Stephen Hawking’s Greatest Puzzle, Is Still Unsolved
“Despite our best efforts, we still don’t understand whether information leaks out of a black hole when it radiates energy (and mass) away. If it does leak information away, it’s unclear how that information is leaked out, and when or where Hawking’s original calculations break down. Hawking himself, despite conceding the argument more than a decade ago, continued to actively publish on the topic, often declaring that he had finally solved the paradox. But the paradox remains unresolved, without a clear solution. Perhaps that’s the greatest legacy one can hope to achieve in science: to uncover a new problem so complex that it will take multiple generations to arrive at the solution. In this particular case, most everyone agrees on what the solution ought to look like, but nobody knows how to get there. Until we do, it will remain just another part of Hawking’s incomparable, enigmatic gifts that he shared with the world.”
When anything falls into a black hole, it adds to the black hole’s mass, electric charge, and angular momentum, which is what General Relativity predicts. But there’s also quantum information encoded in what falls in, and that information can’t be destroyed. There’s a neat solution for that: information can be encoded on the event horizon of a black hole, getting “smeared out” from the perspective of an outside observer. But then, what happens to this information when the black hole evaporates via Hawking radiation? Hawking himself predicted that information was lost, which is now thought to be wrong. But the question of exactly how that information gets encoded onto the outgoing radiation is still a matter of massive uncertainty. Despite declarations by many (including Hawking) that the paradox has been resolved, the fact is that the black hole information paradox is still an open area of study.
Come find out what the greatest problem in black hole physics, the one that plagued Hawking all his life (and continues to plague him even posthumously) is all about!
How Stephen Hawking’s Greatest Discovery Revolutionized Black Holes
“Increasing entropy, over time, should be okay, but decreasing it should be forbidden. The only way to ensure that would be by forcing an increase in the black hole’s mass to cause entropy to go up by at least the largest amount you can imagine.
The way that people working on that problem – including Hawking – assigned an answer was to make entropy proportional to the surface area of a black hole. The more quantum bits of information you can fit on a black hole, the greater its entropy was. But that brought up a new problem: if you have entropy, then that means you have a temperature. And if you have a temperature, you have to radiate energy away. Originally called “black” because nothing, not even light, can escape, now it became clear it had to emit something after all. All of a sudden, a black hole isn’t a static system anymore; it’s one that changes over time.”
Stephen Hawking may be most famous, today, for his popular accounts of astrophysics and cosmology, for his inspirational personal story, and for his overcoming of adversity and disability to achieve all that he has. But he was truly a tremendous physicist, and his contributions to our understand of black holes was truly transformative. His greatest discovery was that they weren’t merely static objects in space, but that they were active and evolving. They didn’t just absorb mass, but had an entropy, a temperature, and radiated energy away. How this occurred was far from intuitive, and it took a decade of research for Hawking to arrive at his incredible 1974 result, where he derived the existence of Hawking radiation. All of a sudden, black holes had a finite lifetime, and would eventually evaporate away entirely.
Here’s the story of Stephen Hawking’s greatest scientific find, and his greatest contribution to the canon of scientific knowledge. If you want to understand what he did and why it’s so important, you won’t want to miss this.
The 4 Scientific Lessons Stephen Hawking Never Learned
“His work, his life, and his scientific contributions made him an inspiration to millions across the world, including to me. But the combination of his achievements and his affliction with ALS — combined with his meteoric fame — often made him immune to justified criticism. As a result, he spent decades making false, outdated, or misleading claims to the general population that permanently harmed the public understanding of science. He claimed to have solutions to problems that fell apart on a cursory glance; he proclaimed doomsday for humanity repeatedly with no evidence to back such claims up; he ignored the good work done by others in his own field. Despite his incredible successes in a number of arenas, there are some major scientific lessons he never learned. Here’s your chance to learn them now.”
Hawking’s contribution to physics, from the existence and meaning of singularities to properties of a black hole’s event horizon, entropy, temperature, and the radiation they generate were remarkable in the 1960s and 1970s. His popularizations of science were groundbreaking, too, exposing a general audience to a wide variety of wild and speculative ideas, igniting an interest in theoretical astrophysics in the minds of millions around the world. But as brilliant as Hawking was, there were a number of lessons about science and humanity that he never learned for himself, from the Big Bang and black holes to lessons about communicating speculative or unproven information as though they were facts. We have a tendency, when we turn people into heroes, to lionize their achievements and ignore their failings, but to do so cheats humanity out of recognizing all the facets of a complicated character.
Come learn, for yourself, the 4 scientific ideas that Stephen Hawking never managed to learn and incorporate while he was still alive.
Stephen Hawking: modern cosmology’s brightest star dies aged 76:
“One, remember to look up at the stars and not down at your feet.
never give up work. Work gives you meaning and purpose, and life is
empty without it.
Three, if you are lucky enough to find love, remember
it is there and don’t throw it away.” – SH
RIP Stephen Hawking. We will miss you for ever.