How do black holes “consume” light?
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Like vacuums consume dust, except they use gravity instead of suction, and it needs to be extremely strong because light moves so fast.
The thing is that black holes don’t “suck” things. Things fall to them the same way they would fall into any planet. Black holes have so much mass that even photons can’t escape their gravitational pull. The holes are black because that’s the radius around it where light can’t go up anymore
One aspect of black holes needs to be specified:
The event horizon, the “black ball” of a black hole, is not a thing, an object like a star. It’s a place, a point of no return. Below that point, to escape it’s gravity, an object needs to travel faster than light to avoid falling further in. Light, or anything else, does not travel faster than light. That’s why it’s black.
There’s another bizarre aspect of a black hole. Space and time flip places. The centre of the black hole is no longer a point in space. It’s an inevitable future. All roads lead to ~~Rome~~ the singularity. Any attempt to try to accelerate away just makes you reach it faster.
Light has no mass but still subject to gravity?
Imagine you are driving down a highway. It’s out in the middle of the desert, and the road just stretches on and on, in a straight line, seemingly forever. You drive and drive, and you don’t turn. You’re going in a straight line, right?
Wrong. You are traveling in a curve. The Earth itself is curved. If you were to look at the road from an angle, from outer space, you could see that it was curved. But on the road you don’t notice that it’s curved.
The gravity around a black hole is so strong that *space itself* is curved. It’s curved all the way in a circle. Not a real circle, but like a freaky circle. You can go forever in a straight line and wind up back in the same place. Even light can’t get away, because it is traveling in a *straight line* through *curved space*. A freaky infinite circle.
What’s it like inside? Nobody knows.
They don’t. Light travels through spacetime in a straight line. Gravity distorts spacetime.
Put a train on a track, it can only go straight on that track. Bend the track and the train will curve, even though the train has not started moving in any other direction but straight.
So light always follows a straight line through space. Black holes however bend space to such a degree that “straight” means towards the black hole.
If it helps you can visualize space as a grid, and a black hole being a spot where the lines all curve into a single point. Light just “follows the lines” as it were, and end up inside the black hole.
This is also why things can’t get out of a black hole once they pass a certain threshold(called the event horizon), the space past that point is so twisted and curved in on itself that every direction you go brings you closer to the center.
So as to where the light goes once it passes the event horizon, it basically just spirals around the mass at the center until it eventually hits it. If you were to pass through the event horizon of a black hole, you’d probably get incinerated by the intense light that’s going around in circles slowly spiraling into the center.
We think of gravity as a force that pulls things together. This is accurate for all our calculations, and it’s easy to conceptualize. However, it’s not how it actually works. If it was, there would be a way to “block” gravity by putting something in between you and the source of gravity. There is no way to “block” gravity.
A better way to think of it is think of spacetime as the largest superfreeway conjunction in the world. Everything is moving all the time. Nothing is every stationary because every is moving relative to something else. The paths themselves are changed by gravity. A seemingly straight line curves. We see the distance between two points as straight because light is coming to us and telling us it is straight, but light is going very, very, very fast. If you go slower, you take a different path that veers towards the center of the greater mass you are closest to. This is easy to prove. Throw a ball at an object that is a mile away. Why didn’t you hit the object? Well because the ball took a curved path and crashed into the ground. That’s the difference spacetime exerts on a path relative to the speed of the object relative to the center of mass.
If you launched a projectile fast enough, it would find a path to escape earth, but every slower path would simply crash on earth. This speed is known as “escape velocity”. Essentially, you have to be going a minimum speed to find a path that will eventually lead away from the center of mass.
Now, as the mass increases and the diameter of the mass decreases, the escape velocity from the surface keeps increasing until… you guessed it, it reaches the speed of light. At this speed, there is no speed below the speed of light where you will be able to leave the center of mass. When the escape velocity exceeds the speed of light, light can’t escape. Hence, it’s a “black” hole.
Imagine a trampoline thats completely flat. If you put something really heavy in the middle, like a basketball then draw a straight line from the edge of the trampoline to another edge (imagine any line other than the diameter just to make this explanation make sense) notice how the line bends slightly towards the heavy thing in the middle. This is called gravitational lensing.
Now- in the case of a black hole, instead of a basketball, its now a bowling ball. Its so heavy that any “straight line” you draw from edge to edge just ends up leading to the bowling ball in the middle, this is how black holes or anything with gravity “sucks up” anything. As you probably noticed, the black hole doesnt suck anything, everything just goes forward and all the black hole does is change WHERE this forward is. Using the same example, light doesn’t need to interact with anything, the literal curvature of space is bent in a way that makes its forward direction, towards the black hole. Its not attracted to the black hole in any way, in the same way that straight line you drew on the trampoline is in no way attracted to the bowling ball.
another way of looking at it, is escape velocity. you know how to escape earth’s gravity rockets have to push astronauts to a certain velocity. the greater the mass of the planet, the faster the rockets have to accelerate. If you keep increasing mass, the escape velocity eventually reaches the speed of light. then at that point nothing can escape, not even light.
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