Astrum Space - The Disturbing Conclusion Black Holes Imply About Your Reality | Black Holes Part 3

Episode Date: January 8, 2024

Join with me today as we explore the strange relationship between mass and space curvature, and how when it comes to black holes, something very strange is going on with reality.

When you're walking on a beach and you make a footprint in the sand, there is no question in your mind that it is your foot that caused the footprint. The order of causality is quite clear here, so much so that it seems laughable to even need to assert it. You made the footprint, the footprint didn't make you. But what if it did? What if I told you that on the cosmological scale, the fundamental relationship between foot and footprint might be a little more blurred, than you would intuitively think. And shockingly, due to the nature of black holes and hawking radiation, there is some evidence that this might just be the case.

I'm Alex McColgan and you're listening to the Astrum podcast. Join with me as we explore the strange relationship between mass and space curvature, and how when it comes to black holes, something very strange is going on with reality. But to begin with, we're going to need to look at a principle called relativity. But no, not that relativity. Galilean relativity. First described by Galileo Galilei in 1632, the idea of this form of relativity is that there is no difference between being completely still and moving at continuous speed.

Imagine there are two rooms, one on a ship and another on land. Both are soundproof and have no windows. Imagine the sea is calm so there's no rocking at all. The only difference between the two rooms is that one is moving and the other is not. Can you tell the difference between the two from the inside? You might think that you'd be able to sense movement, but this is not the case. For instance, right now, you are careening through space at 110,000 kilometers per hour due to the Earth's movement around the sun, and if you are sitting down at home while watching

it, it's likely you would have said you weren't moving at all. In fact, Galileo realized that there was no test that could be done to tell the difference between the two scenarios. He even found that if you dropped a ball in the ship, from your perspective, it would look like it fell straight down, even if, from the perspective of a person on land, it would look like it was falling diagonally. Galileo realized that if you remove all frames of reference, say, by being in space, there is no way of telling if a planet is moving towards you or you are moving.

towards a planet. According to relativity, both are equally valid interpretations. You might have noticed this yourself if you ever looked out of the window on a train, just as another train suddenly passed by, quickly overtaking you. Although both trains are going forwards, the other train is going faster than yours, and because you no longer have a frame of reference to compare your motion to, it might look as if you are suddenly going backwards. Einstein took this idea further with his equivalence principle. Here he took the idea of two rooms again, but this time he was making an observation about gravity.

If you were inside a windowless room floating in the vacuum of space and someone started accelerating your room in the up direction, say by strapping a rocket to the bottom of it, if the rocket accelerated at just the right speed, then it would feel identical to if you were standing in a room on the surface of Earth. In other words, there is no way to tell the difference between the exception. acceleration caused by gravity, and the acceleration caused by a rocket, assuming you couldn't stop the rocket shaking you with all its rumbling, of course. Both these principles rely on the idea of inertia, that objects do not like to move if simply

left on their own, and do not like to stop moving once they have started. Any time you want a mass to do something different to what it is doing, a new force must be applied, otherwise it will remain inert. Why would it feel to the man in the room with the rocket as if he were under the effects of gravity? Or perhaps a better question, why would it feel to us on Earth as if we were being accelerated upwards by the effects of a rocket? The Earth is not expanding in all directions at once, pushing us with it, surely. While this is true, Einstein realized that the two felt similar because they both were the same

thing, a form of acceleration. However, there is another form of acceleration that better explains how gravity works than simply applying a force to an object to push it like a rocket does. Consider this spinning fairground ride. If you have ever been on such a ride, you will know the power of changing direction as a form of acceleration. When you stand against the wall of the ride, once it gets up to speed, you feel a constant force pressing you against the wall, even when the ride spins at a constant speed.

This is because your mass is trying to move in a straight line at each point in the ride, but the curvature of the ride is forcing you to alter your direction. The battle between your inertia trying not to change what you're doing and the wall trying to alter your direction of travel manifest as the force you feel. And as far as acceleration is concerned, there's not much difference between the earth beneath you accelerating you up and you trying to accelerate down. Einstein realized that this form of accelerating, accelerating, accelerating. inspiration caused by a curving path was the best explanation for gravity.

He came up with a theory that matter and energy cause a warping in the space around it, kind of like how a ball might bend the surface of a taut rubber sheet it was placed on. The larger the mass, the greater the curvature. And once space was curved, any object trying to travel through it would be deflected by that curve. In the words of physicist John Wheeler, space tells matter how to move. move. Matter tells space how to curve. For small masses, this curve in space would be very slight, but in dense masses, this curvature could get so great that it would be impossible

for an object that got too close to it to escape it. These other conditions we find near a black hole with its event horizon. So going back to our very first analogy of the footprint and the foot, If a black hole is the foot, the curvature of space around it is the footprint. It's interesting to see all of this in action and to understand how Einstein came to conclusions, which would have been almost universally validated by scientists even 100 years on. But there's nothing particularly weird about any of this so far. Understanding the exact mechanisms behind it doesn't make it any stranger. The black hole tells space how to curve, and once curved, any object moving near it

is told how to move. Nothing here is outside our expectations based on day-to-day observations, but when we start to look at Hawking radiation, something very strange happens. For those unfamiliar, Hawking radiation is currently undetectable radiation that physicists Stephen Hawking theorize is emitted by black holes due to principles in quantum uncertainty. This radiation is thermal and is almost always extremely long wavelengths. But the most important thing to bear in mind about it for the purposes of our current video is that it is non-local. This means that it does not appear from the black hole itself, but appears from the area of space

around it. To be clear, I do not mean beyond the singularity of the black hole but still within the black sphere. That's hard to define anyway, spaces we know it doesn't exist there. Remember, the black ball you see here is simply the demarcation point, because of the black The barcation point between inescapable curvature and escapable curvature, the event horizon. I do not even mean right up against the event horizon, although that is sometimes how this theory is portrayed.

People sometimes speak of two particles popping into existence right up against the event horizon, with the antimatter particle just inside it so it falls in, while the normal particle is just outside and so escapes. This is not what is happening. Instead, the region of space this radiation can pop into existence is several times the size of the event horizon, a distance up to billions of kilometers away. And when the largest black holes we have can comfortably fit multiple solar systems side by side inside of their event horizon, the idea that a photon of radiation can pop into existence

this distance again outside the event horizon is crazy. It happens even in a place where there is literally not. nothing there. So in short, it is not so much that Hawking radiation is coming from the black hole directly. Instead, it is coming into existence from the curvature of space that the black hole is creating, and can happen quite far away from the black hole itself. But if that is true, then things work completely opposite to what we might expect, as you will see in a moment. Consider what happens in this order. As energy leaves the curvature of space, The curvature lessens because of something known as the conservation of energy.

And as this reduction of curvature happens, the black hole then shrinks. This is crazy. This is like the footprint getting smaller, and so the foot shrinks accordingly. It feels very wrong. Things can't possibly work that way. And yet Einstein hinted that such a thing might indeed be possible. In one of his equations, he stated that the curvature of space-time was proportioned. proportional to the mass energy of an object.

But proportional is not causational. There's no presupposition that one causes the other in this relationship. We are comfortable with the idea of changing mass and so changing curvature, but it works just as well if you go the other way and change the curvature to change the mass. If this is true, then it hints at a universe where mass is simply a projection caused by space curvature. you shine a light at an object, say your hand, and it makes a shadow on the wall. The shadow is a projection caused by the existence of your hand interacting with the light.

Normally in this analogy, you might be forgiven for believing that we are the hand. It is our mass that creates the curvature of space around us. And yet, do we really know that it doesn't work the other way round? Are we simply projections? Shadows on the wall of the universe being brought into life by something more fundamental going on in the curvature of space-time. And yet, we're going around thinking that we're the thing that's real. We don't really know.

Given that all you know is the reality you experience, it would be difficult for you to be able to tell the difference between the two scenarios. But if relativity has taught us anything, it's that if there's no way of telling the difference between the two situations, then we can't completely dismiss that we're in one and not the other. Either that or the two might be more linked than we thought. Of course, obviously, this is all just a theory. There is no hard proof that Hawking radiation is even a real thing, although there have been

some experiments that hint that it might be. But this is just something interesting to think about. And even if it does prove to be the case that reality is a projection, it's not going to affect your day very much. You will still think and feel, and that's more than enough reason for you to go about, doing what you're currently doing. But it is an example of how when we start to examine the very fundamental building blocks of reality, by exploring the weird warping effects of black holes, it can cause us to challenge assumptions about our very nature. After all, when you're asking the question, am I real? And the answer is, it's not certain, that's more than a little concerning. Well, that's all we have time for today. I hope you've enjoyed listening to this

podcast on Black Holes. If you like what you've heard, please feel free to follow us for more podcasts on other fascinating space topics. But for now, I'm Alex McCulligan, and this has been Astrom. All the best, and see you next time.