The mind-blowing science of black holes | Michio Kaku, Bill Nye, Michelle Thaller & more | Big Think

The mind-blowing science of black holes
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When it comes to black holes, science simultaneously knows so much and so little, which is why they are so fascinating. Focusing on what we do know, this group of astronomers, educators, and physicists share some of the most incredible facts about the powerful and mysterious objects.

A black hole is so massive that light (and anything else it swallows) can't escape, says Bill Nye. You can't see a black hole, theoretical physicists Michio Kaku and Christophe Galfard explain, because it is too dark. What you can see, however, is the distortion of light around it caused by its extreme gravity.

Explaining one unsettling concept from astrophysics called spaghettification, astronomer Michelle Thaller says that "If you got close to a black hole there would be tides over your body that small that would rip you apart into basically a strand of spaghetti that would fall down the black hole."
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TRANSCRIPT:

MICHIO KAKU: First we think that out of the Big Bang came dark matter, invisible matter. If I held dark matter in my hand it would literally ooze its way right though my fingers, go right to the center of the Earth, go to China and then go back and forth between China and my hand. That's dark matter. We think that dark matter began to clump first because of gravity. Then matter was attracted to the clumpiness creating the super massive black hole and then later the galaxy itself began to form. We have computer simulations about this, but still the relationship is not yet clear. Now remember, stars. We know almost everything about stellar evolution. That's because the pentagon has given us physicists billions of dollars to model hydrogen bombs, and a star is nothing but a hydrogen bomb. However, a galaxy consists of over a hundred billion stars so it's much more difficult to tell which came first, the black hole or the galaxy itself.

BILL NYE: The way I like to describe a black hole. It's a star. A black hole is a star. Now when you and I think of stars we think about the sun which is giving off all this light. But the other thing about the sun to keep in mind is it has a lot of gravity because it's huge. One of Einstein's discoveries, Albert Einstein's discoveries was that gravity changes the path of light. It can bend light. It's just not in our everyday experience. To measure it we usually find objects way out in space and we have known brightness and we see where we think they're going to be and then where they really appear to be and then we infer or figure out that they're not where we thought they were going to be because gravity bent the beam of light. It's amazing. Anyway, so a black hole is a star so massive that not even light can escape from it.

MICHELLE THALLER: What you're looking at is something called the shadow of a black hole. Now, black holes tend to have material orbiting around them. Black holes have a lot of gravity and gas begins to fall in towards the black hole and it begins to spin up into a disk around the black hole. And as that gas gets closer and closer to the black hole its accelerated faster and faster. And so in this disc of gas some of it is traveling very close to the speed of light. You have a lot of friction. You have lots of things rubbing up against each other at very high speeds and incredible amounts of heat and light are generated in this disk. So black holes usually are surrounded by disks of very, very bright, very hot material and that's how we find them. Black holes themselves give off no radiation at all. Any light gets absorbed into the black hole and when I say light I mean every possible form of light from gamma rays, x-rays, infrared light that we think of as heat, radio waves. Nothing comes out of a black hole at all. So what you're looking at in this image is the black hole is sort of framed by this bright ring. And that bright ring is this hot material that's orbiting around the black hole.

One of the first things you'd say well okay, it's really kind of a wonderful stroke of luck that the particular black hole we're looking at the ring was right face onto us. You see this bright ring exactly around the black hole. And, in fact, that's probably not the case. The disc of material could be at many different orientations around the black hole. Light itself has no mass. Light should not be attracted by gravity, right. I mean gravity is the force between two things that have mass. Light has no mass. It just flies straight through space...

Read the full transcript at https://bigthink.com/videos/black-hole-science-facts