Listen: Why are we all so excited about the black hole image?
"There was so much excitement. This week around seeing the first picture of a black hole. Why was it deserving of so much excitement? Ferriol? I think part of it is that it's a new frontier, it's something we haven't seen before it's something that we didn't even think we could see and it's been so long in the making both the technological developments and the theoretical understanding to interpret the data. So I'm I'm really happy that everybody's excited to see the image. Shep you said in the press conference and even here on on our program that black holes are essentially unseasonable. So how do you explain what we're seeing that? We are seeing one now. Yeah. See there naked. If there's nothing around them, but black holes attract just everything around them because they're intense gravity, and they're trying to get into a small volume that it's like when you rub your hands together. They get hot all the fiction heats that guest hundreds of billions of degrees. So black holes are surrounded by these three D flashlights of this hot luminous plasma. And then there. Gravity warps the light from that plasma into these distinct shapes. You're really seeing Einstein's geometrical gravity laid bare. You're seeing just how light moves along space time yet, Einstein even though he came up with the theory about warping space that he not well, he wasn't really convinced that black holes might exist. Yeah. Got. He did struggle with that far awhile the theory. I mean, practically breaks down at the center of a black hole, it predicts a singularity an infinite space time curvature and energy density. So he was very unhappy with that. And he thought maybe there there's a reason why nature would not form. These objects talk a little bit Ferriol about the image itself. So we can explain to folks because it's it it's not quite wooded appears to be a lot more stuff going on there. And let's get right into the reddish ring of light. We're is that coming from? That is coming from right from the inner part of the accretion flow and the base of the jets so uh ship was saying as this plasma. That's the black hole gets from the stars around it swirls around and makes its way down to the black hole. It heats up and the emission that. We are seeing at this particular wavelength of light is coming from right outside of the point of no return. So there's the event or orison outside of that is the photon ring and outside of that is the the part that that truncates the disk and where where we think jets form. So the source of the light is right in the vicinity of that point of no return, and it is being lens than to the circular shape. Well, that's the that's the question I'll continue with that. Because if if it's a three dimensional image shouldn't that shouldn't it be surrounded by that glowing red, so we should? Not be seeing into it as we look straight. That's a very good question. And it's something that I with worked out twenty years ago. So part of the reason we are seeing it is because it's Taurus shaped, so it's not really completely spiritual. But even if it were we have to pick a wavelength of light that satisfies two things. One is we wanted it to be emitted right near the horizon. So it lights it up. We didn't want something that comes from farther away. But it's a double edged sword as you're saying if there's too much of that light too much of that guess then it will interfere with our ability to see down to the horizon by picking the one point three millimeter wavelength of flight. We're we have walking that tightrope. There is light that is lighting up the black hole. But it is not so much that it is actually obscuring our view to the black hole and ship. Actually, is it not true that that light that is heading toward. Toward the black hole will be bent around the back of it and come forward towards us. So it's still say's still face black that way. Yeah. It's a it's a good idea to try to hide behind the black hole because the light from me will always be bent around when in one thousand nine hundred when they looked at it affliction of light during a solar eclipse of stars to verify Einstein at first the deflation was one two thousand of a degree. And now we're looking at light that does loop two loops. So it's a completely different ballgame from that perspective. And and your Senate very, well, you have this flashlight this this light that's close to the event horizon. But not in the event, of course, and with that means that the latest Lynn's around this last photon orbit all the light grazes this last photon orbit. If it goes a little bit inside there is lost forever in the event horizon. And with that means is that we see a ring, which is a projection on this three dimensional flashlight. But then for example, if there were another civilization fail screwing the Milky Way. They would also see a ring or in eighty seven. They would see that ring to. So everybody gets to see a ring because of the Lenzing Einstein's gravity. Why? Then is some of the ring whitish seems brighter than red. Oh, it's a phenomenon that it goes from what very was saying the gas is moving around so quickly. It's a near light speeds. So when it defends all the way into this gravitational, well, it's really moving quickly. And when material moves that fast when it emits light the light is boosted energy in the direction, it's moving. So you're seeing some of the gas coming towards us from underneath the black hole. It seems like it orbits clockwise around. What you see that? And so it's bright on one side and on the other. So is it like a candle? It's hotter. As on that side to a glows brighter. Brighter. It's not so much hotter. Right. So so the color map that we've chosen is a good representation of how bright it is. So the the parts that you're seeing in a lighter color are actually the brighter parts, and that is the reason is the swirling plasma. So the half of it roughly the half that's approaching us is the sprite or emission. And the part receding from us is slightly damore. Chef you talked about that. There is still light inside the black hole. What happens to that light in their la-? Well, there's no light coming to us from the within the event horizon. But as very sad, you have gas always falling into the black hole at all levels. And it emits you really not seeing anything too much interior to the last orbit which that ring that UC everything that is in there tends to go through the event horizon. We don't see it anymore. It just disappears from our causal existence. But where does it go? Well, that's that's the interesting you Larry. Right. If anyone tells you they know don't believe them. This Stephen hawking spent his life trying to figure that out. Didn't he? Well, I. Yeah. I wanna see I think for many people in in our collaboration. It was. It was bittersweet. We lost even hawking just a little while before we made this discovery we had a chance to describe it to him a little bit which was great and wish he'd been alive to see it. Our number eight four four seven two four eight two five five we have so many phone calls. I'm going to get to them after I ask a couple more questions at a lot of people been asking of can you explain the difference between the event horizon, and you you touched on a bit the event horizon the black hole and black holes shadow. Sure, I can do that. So Geno, relatively not only predicts this point of nor return, which we call the event horizon. But it also predicts the existence of a few other special distances from a black hole. The first one is when matter starts plunging in we call it the innermost stable circular orbits. I know it's a mouthful, but it's basically the last points that matter can be in actual orbits around the black hole. If it's interior to that is just gonna start plunging in next up closer to the black hole is the photon ring the point where the lights does the Luke two loops and makes a really bright image that we are able to see as a as a circle in the sky and interior to that is is the event or Isan. And that's where basically the everything is moving toward the singularity. There. The space time have switched. Signs, and that's where all hell breaks loose. So if we were falling into the black hole, we would know that we're going through these places, maybe we would put ten -cially notice the innermost stable circular orbit. But after that, we're just falling in, and we wouldn't necessarily know that we've crossed the horizon it's for a distant observer like us that's these things become"