What are black holes and did Stephen Hawking say they don't exist?

03/03/14 Seán Kinane
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Tags: astronomy, space, black holes, National Geographic, Stephen Hawking, time travel, science, physics


Computer simulated image of a black hole of ten solar masses as seen from a distance of 600km with the Milky Way in the background (horizontal camera opening angle: 90°). http://www.spacetimetravel.org/galerie/galerie.html

photo by Ute Kraus (background Milky Way panorama: Axel Mellingerexterna) July 14, 2005. Creative Commons.

In January, renowned physicist Stephen Hawking ignited a minor controversy when he wrote “there are no black holes

The statement was latched onto by some in the media, but it likely was taken out of context.

WMNF spoke about black holes with Michael Finkel, a writer for National Geographic magazine.

His cover article about black holes in the March issue called Star Eater.

In the second half of the interview Finkel talks about how black holes are related to time travel and whether we’re in danger of a black hole swallowing the Earth.

"Black holes are real. Black holes are dead stars. All stars will eventually run out of fuel and die. Our sun will run out of fuel in about 5 billion years but it will not become a black hole when it dies, it's not big enough. You need a star about 20 times the size of the sun. When it runs out of fuel the core of the star collapses and gravity takes over. It crushes the core of the star smaller and smaller, denser and denser until shockingly, but true, it basically disappears from the universe. The velocity needed to escape a black hole, greater than the speed of light. Nothing moves faster than the speed of light therefore nothing escapes a black hole."

So now that you've told us what black holes are, there's something called an event horizon and a singularity, explain those things.

"Right, so black holes are real. They exist at the center of every galaxy including our own, Milky Way galaxy. The black hole in the center of the Milky Way has the fancy name; Sagittarius A . It's about 4 million times more massive than our sun, huge black hole. Now, the dividing line between the inside and the outside of a black hole is called the event horizon. Once you cross this event horizon you are lost to the universe essentially forever. You cannot escape. You have to move faster than the speed of light to get out. That's what the event horizon is. You asked what a singularity is. A great question, one that I wanted to know immediately is 'what's inside a black hole?' The short answer is 'we don't know'. It's a one way doorway, if you went in there to find out you can never come back out to tell us so it's a very difficult thing to know. It is believed by theoretical physicists to be extraordinarily dense and extraordinarily tiny. I mentioned Sagittarius A, our black hole at the center of the Milky Way? It's about 4 million times more massive than the sun and yet it is compressed. All that weight is compressed into something trillions of times smaller than the tip of a pin and they call that point, that very dense, very small thing, a singularity, which is a physicist's fancy speak for a question mark. We're not sure, but they call it a singularity."

So far during the interview you've used the phrase, 'black holes are real' twice. I have a feeling that that goes to something that came out in January when some media reported that renowned physicist Stephen Hawking wrote, 'there are no black holes', but what did he mean by that?

"Dr. Hawking is one of the great thinkers in black hole physics. If you've noticed I've said 'essentially lost forever, millions...' One of Dr. Hawkings great discoveries is that black holes also have a finite life span, they also die. They leak a little bit. It's called Hawking radiation and that given enough time, and I'm not talking millions of years or even billions of years, I'm talking trillions of years. But given enough time a black hole will eventually evaporate and disappear. So when I say you're lost forever, you're not really lost forever you're lost for a really, really, long time. Nothing is forever. That's one of basically...that's a very simplified version but a true version of Dr. Hawking's theories is that it eventually will evaporate and die so everything I'm saying about black holes is true but when I say forever I mean a really, really, really long time. But essentially, like everything else in the universe, they'll die also."

You've also mentioned that at the center of our galaxy is this black hole called Sagittarius A and scientists are going to be looking at Sagittarius A over the next year or so to help us understand black holes for what reason? What will they gain?

"Black holes have been proven to exist but this proof is primarily mathematical and if you're like me, I'm a journalist, I like to see things with my own eyes. For the first time in human history within the next year it's hoped to have an image of a black hole in action. I mentioned Sagittarius A*, our enormous black hole at the center of the Milky Way, right now it is drawing a large gas cloud towards it and it's about to swallow part of the gas cloud and at that point many of the radio telescopes on Earth, which are telescopes that use radio waves rather than light waves so you can cut through the interstellar dust and see this area of the Milky Way. We're going to take an image of a black hole in action. We won't be able to see the black hole itself, it's purely black. But I don't know if you've ever seen a picture of say, a total eclipse of the sun? When the moon's in front of the sun it looks like there's a black hole in front of the sun and a sort of corona of material around the outside, a ring of material, that's what it's going to be like. It's going to be the action of a black hole and that should dispel any doubts or most any doubts that black holes exist."

How are black holes like time machines?

"Okay, this is one of my favorite mind-bending topics. Time and black holes. It takes about a minute and a half to explain this and I need you to come with me on this. I will use no math, here. Black holes and time; you've probably heard the phrase 'time is relative' that's one of Einstein's great discoveries. What does time is relative mean? It means that time does not tick at the same rate for everyone. This is an example I use in my magazine article and I like it. If you put a very accurate clock in every floor of a skyscraper they will all tick at slightly different rates. Why? The ones on the bottom floor, closer to the center of the earth where gravity is stronger will tick a little bit slower than the ones on the top floor. This is true and has been measured. We don't notice it because I'm talking billionths of a second, not applicable on human terms. However, GPS satellites they work on different clocks than those on the surface of the earth. If they didn't, GPS wouldn't be accurate. That's just little old earth where gravity is easy to defeat. If you raise your hand in the air you've already defeated earth's gravity. Now let's move over to Sagittarius A where gravity is enormous, as I've said before, the pull of gravity is so great that not even light can escape. You keep a wristwatch on your wrist, here on Earth. I'm going to get in my spaceship, I'm going to cruise over to Sagittarius A . I'm going to get extremely close to the event horizon but I'm not going to cross over. You cross over the event horizon, you're lost almost forever. I'm going to stay on my side of the event horizon. My watch on my wrist is ticking along at normal. Yours here on Earth is ticking along at normal. However, for every minute that I spend at that spot, right at the event horizon, a thousand years can pass on Earth. Now this does not seem believable but I promise you it is one hundred percent true and has been proven time and time again that time is very flexible and gravity defeats time. My heart is not beating any more times than your heart but I'm back to Earth and it's year 3,000. It doesn't seem possible, it's hard for humans to get their minds around it but that's the way the universe works."

Another thing that might be hard to get your mind around is whether we live in a universe or what some physicists call a multiverse and what does that have to do with black holes?

"Wow, we're really going into the wormhole now, which I.. this is stuff I love. Yes, in recent years, this is relatively new, the last ten, twenty years physicists have theorized, now this is less the realm of fact. This time dilation that I talked about, this is fact and it's been proven. I'm now going to enter the realm of hypothesis so I just wanted to let you know. It has been thought that the universe is not all there is. That really our universe, almost 14 billion years old, is just a bubble in the grand Swiss cheese of reality, that there's multiverse, they call it; many universes. I won't get into the mathematical basis of why this has been thought to be true but a lot of the equations rely on a multiverse or they don't work. Now, how do you get from one universe to another? Again, same warning, I'm in the realm of deep theory here, not fact. It has been thought that a black hole might be the one way doorway of how we travel to another universe. In other words, if I fell into the black hole at the center of our galaxy, Sagittarius A* , I might end up in another universe. Now, I wouldn't because I'd get shredded by the gravity but the particles of me that did actually make it through the black hole would end up in another universe. Again, a lot of the reasoning for believing this, these aren't just shots in the dark, these are great physicists from the major universities around the world. Theoretical physicists. The math sort of supports this contention."

We're running out of time so I want to ask one final question. The laboratory in Europe called CERN, did experiments there result in a black hole?

"Basically we've made an atom smasher. What CERN has done, and we used to have a nice atom smasher in the United States; you take particles and you speed them up to very close to the speed of light, you smash them into each other and you break them into little pieces to see what else is in there. We want to find out, what's the smallest particle? What's the basic building block of the universe and we're trying to figure that out. So your question is, can a black hole be created there? Well I guess the short answer is perhaps, yes. But the better answer, the more relieving answer is it's no big deal, it's not going to effect us. If a black hole happens to be created it will last a nanosecond and not cause any damage so there is a one hundred percent chance that we are perfectly safe from this so of all the things that we have to worry about on planet Earth, and there are plenty of them, that is not one of them."

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