On March 14th, 2018, theoretical physicist Stephen Hawking was in the news again, this time sadly with the announcement regarding the premise and timing of his passing away. However, we look forward to the future of science thankful for Hawking’s tremendous contributions. For physicists and space fans alike, he was somebody who showed us there are no limits to achieving our dreams, owing credit to his unrelenting passion for exploring the cosmos.
Today, SkyFeed has two of his biggest contributions, including his final paper that was published only two weeks ago.
What happens to the stuff that gets swallowed up by a black hole has always been a pressing question for theoretical scientists. One accomplishment Hawking made was finding the solution.
It will probably be a while before we know exactly what it is, so let's start with the basics; black holes form when a star collapses, creating an area of space with such a strong gravitational pull that once you cross a certain point, known as the event horizon, nothing can escape. It’s the point of no return. Whatever gets past that event horizon is not coming back out. But there's a problem, and it has to do with something that Hawking himself proposed back in the 1970s.
Black holes actually emit radiation, which is weird, right? An object with gravity so strong even light can't escape it, yet it releases radiation. This energy today has become known as Hawking radiation.
But black holes don't just keep spewing it out forever. They release it until there's nothing left, and then the black hole dies. And according to Hawking's calculation, the radiation’s properties, like its energy and intensity, don't depend on anything that entered the black hole. You could study the radiation from a black hole all you wanted, and you'd never be able to tell what it had originally swallowed. All the original properties of that matter and energy that entered the black hole are permanently erased, but this disturbs physicists, because that violates one of the fundamental laws of quantum mechanics. Energy must always be conserved throughout the Universe - it can't be created or destroyed. Thus, the Black Hole Information Paradox was born.
Physicists describe it as being like an instance where you’ve burnt a piece of wood. That wood turned to ash. No, you cannot just grab all the ash and turn it into wood again, but you could at least take a look at its chemical components under a microscope, and be able to tell that it was indeed wood at one point.
But when we take our instruments to analyze black hole radiation, we can’t make any sense of it. Physicists including Hawking have been trying to solve this paradox for a long time, and it wasn’t until two years ago at a conference that Hawking provided a solution.
He suggested that as information passes the event horizon, it leaves a sort of imprint, and all those imprints are able to affect the way the black hole emits radiation. Furthermore, the information isn't lost after all, but as of today, that is still all we know.
It was prior to this discovery, though, that Hawking already had his name associated with black holes. In 2014, he was headlining every news outlet and Twitter feed with the claim that he didn’t believe black holes even existed.
Hawking himself proclaimed “there are no black holes.” That's right. Actually, it's not at all right. But naturally, the whole of the internet took the TL;DR route and didn't bother reading what he actually meant.
Before Hawking introduced the concept of Hawking radiation, he revisited the idea of the event horizon and published a paper he called Information Preservation and Weather Forecasting for Black Holes.
Hawking suggested that maybe black holes don't have event horizons, but instead have something like what he calls apparent horizons - boundaries that are essentially as temporary as the black holes themselves.
So, when the black hole evaporates, the apparent horizon goes with it, and theoretically, at least all that precious information that was stuffed into the black hole gets released back out in the Universe somewhere, sometime. Essentially: event horizons may not exist, however apparent horizons may persist for a period of time. It’s a concept we continue to consider during black hole studies today.
But black holes weren’t the only scientific studies Hawking made his mark upon. We are part of a great big universe, and for a long time, one of the greatest challenges in all of science has been figuring out how we even got here.
Most scientists think it has a lot to do with the Big Bang, when basically, everything started out compressed, and very, very hot.
Then at some point, around a hundred decillionths of a second after the Big Bang, something triggered cosmic inflation, when the Universe suddenly expanded. Then, it quickly started cooling down, eventually developing into the Universe we know today, full of things like mass, and energy, and light.
Working out the details of just that whole process was hard enough. But the fact is that we are still totally clueless about what happened before the Universe started to expand. This initial fraction of a fraction of a fraction of a fraction of a second is the one period in the history of the Universe that physics, as we know it, cannot explain.
It’s known as the Planck Epoch, stretching from the literal beginning of time to ten million trillion trillion trillionths of a second later (that’s 42 zeroes).
It’s named after Max Planck, the physicist who proposed that energy was organized into tiny packets called quanta. He basically kickstarted the study of quantum mechanics - the science of the very small.
But figuring out exactly what happened during the Planck epoch is a little bit tricky, because we simply don’t know enough about how physics worked during that very brief time. All we really know is that, according to the more widely accepted models, right after the Big Bang, the Universe was so hot and dense that all of the forces in the universe were bundled together at the same time.
That means that what we understand today as the four fundamental forces of physics - electromagnetism, weak and strong subatomic forces, and gravity - were all the same thing. Then, as the universe started to cool, they began to separate into distinct forces that had their own individual effects.
But that’s basically all we know. Because we don’t have a way to describe all four fundamental forces at once, using the same set of equations.
Getting these competing sets of rules to match up is kind of the Holy Grail of physics. That’s what Stephen Hawking and countless other physicists have been questing after for decades: a theory that explains all of the forces in the same equation.
A Theory of Everything.
For now, no such theory exists. But for the vast majority of cosmic history, science has a pretty good handle on how the Universe got here, and the phenomena it holds such as black holes, even if we’re still working out some of the details.
But those first few moments are still a mystery - one whose solution will completely change how we study the Universe. Until then, we lend our thanks to brilliant and beautiful minds, such as Stephen Hawking’s.
See you in the next one.
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Citation: Rovira, Lia N. "Stephen Hawking's Contributions That Revolutionized Space Exploration." SkyFeed. 21 March, 2018. Web article.