Black Holes - DenHolm GAZZETTE

What exactly are black holes? And should we be afraid of them?

words-Dharma Stuart

I asked astro physicist Anna Smith-Railey & James Bell of the New York Institute of Space Studies. Here is their eight minute and thirty second answer:

Me: Hello to you both. Go easy on me today- I barely finished high-school. So, most of us know what a Black hole is – but, what is a Black hole?
0:03

ASR: Ok , so simply put black holes are the largest collections of pure
violent energy in the universe.
0:06
JB: If you come too close, they’ll devour you and add your energy to their collection.
0:11
Me: Ok good start. Petrified.
0:14
ASR: And it would seem that this energy is lost to us forever? But is it? It turns out there’s a universe cheat code.
0:18
ASR: A way of powering civilizations until the very death of everything, or of constructing the largest bomb in the universe.
0:26
Me: I’m both terrified and excited to ask- HOW?
0:27
JB: Well we know that all energy is trapped forever in black holes.

0:32
Me: Even light, right?
0:32
JB: This is true.
0:33
JB: Everything you think you know about the weirdest thing in the
universe is about to get weirder, for one simple reason:
0:40
Black holes are spinning.
Me: (very fake suprise gasp)
0:57
JB: When really really massive stars die, their cores collapse under their own gravity into black holes.
1:03
This means something very big becomes very, very tiny. Like the tiniest
anything can be in this universe.
1:11
But stars are rotating and a fundamental property of our universe is that things that are spinning don’t want to stop spinning.
1:18
We call this: angular momentum.
1:21
And this angular momentum can’t go away. A big thing that spins and becomes smaller, spins faster.
1:29
So, as the core of a star collapses, its momentum makes it spin faster and faster and faster, until it collapses into a black hole .
1:38
And the black hole keeps on spinning, inconceivably fast.
1:42
JB: Some of them spin millions of times a second.
1:50
Just like non spinning black holes,

1:52
…spinning black holes have an event horizon and a singularity at their core, where all of their mass is concentrated.
1:59
The singularity is usually described as a single infinitely small point with no surface area.
2:05
ASR: But points can’t rotate, so a rotating singularity can’t be a point.
2:11
Instead, it’s a RINGularity. (both giggle sheepishly)
2:13
Me: (fake laughing- pretending I know why)
2:15
JB: Yes, a ringularity is a ring with a thickness of zero and no surface, spinning extremely fast, containing all the mass of the black hole.
2:22
The black hole is spinning so fast, that it morphs space and time itself.
2:27
It literally drags space with it, such is its power.
2:31
This creates a new and super weird region of space-time: the Ergosphere, which envelops the black hole.
2:39
If space and time are completely broken inside the event horizon, then they’re only half broken inside the ergosphere.
2:47
ASR: Inside the ergosphere, nothing makes sense.
2:50
Me: Much like this conversation now to me.. so just answer me this- should we be afraid of them?
2:56
ASR: Well, it’s possible to enter it and then leave it again, but it’s probably not a great experience.
You can imagine it like this: Falling into a static black hole is like sliding down a hole
Me: That sounds fun!
3:02
JB: Perhaps not fun exactly. Being inside the ergosphere of a spinning black hole is like spiraling down a deadly drain.
3:08
The black hole transfers its own kinetic energy in the form of rotation, to everything that enters the ergosphere.
3:15
The ringularity makes you dance whether you want to or not.
3:19
You need to move faster than the speed of light just to stand still here, which is impossible.
3:25
ASR: But listen-listen, here’s our cheat code: We can steal this energy, and there’s a lot of energy to steal!
3:36
Take the supermassive black hole at the center of the Milky Way.
3:40

We could steal as much energy from it as every single star in the Milky Way emits in a billion years combined.
3:47
The easiest way to steal this energy is, oddly enough, to drop something into the black hole.
3:53
We’ve seen that the ringularity forces energy on us when we enter the
ergosphere,
3:58
JB: ..which is a lot like being in a whirlpool, with space-time rushing around and around.
4:02
If you’re clever you can use the water to your advantage, and swim faster than
before.
4:09
ASR: In practice, this means sending a rocket into the ergosphere, and making a trade with the black hole:
4:15
We give it some mass-energy, and it gives us some of its rotational energy.
4:20
JB: Yeah but it’s not a fair trade, we get the better deal. (laugh/snorts loudly)
4:24
Me: Guys as much as I can see your mouths moving and hear what
appears to be words coming out I genuinely don’t have a fucking clue, respectfully, what you are on about.
4:27
ASR: ok ok listen, normally, if you fire a rocket, you exchange chemical energy for kinetic energy.
4:30
This is like pushing yourself forward in a swimming pool.
4:34
But if you fire a rocket inside the ergosphere, it’s like pushing yourself
forward in a wave pool.
4:40
Me: I like wave pools.
4:42
ASR: (Ignoring me) The rotational energy of the waves gives you a much stronger boost than you could get just by pushing yourself.
4:47
The boost from the rotation of the back hole is so big, that you leave the
ergosphere with much more energy than you entered it.
4:54
The black hole gives a tiny amount of its rotational energy to you, and slows down a little.
5:00
JB: Obviously, this requires a lot of food.
5:03
ASR: Fortunately, black holes aren’t picky eaters. (both snort/laugh- I
remain utterly mystified as to why).
5:06
JB: An advanced future civilization would probably harvest asteroids to drop them into the black hole when they needed an energy boost.
5:13
ASR: But there’s an even better way to get energy from a black hole, and
oddly enough, it builds the biggest bomb any living thing could ever hope to build:
5:26
Me: ok that word, (the first in many) bomb, I understand – so they are deadly and we are petrified, right?
5:30
JB: Yes bomb, we only need two things to build a black hole bomb: a fast-spinning black hole, and a big mirror.
5:32
The mirror has to completely envelop the black hole,
5:35
…which is similar to a Dyson Sphere, a mega structure that harvests the
energy of an entire star.
5:41
ASR: Although, our mirror would be easier to build.
5:43
JB: Mirrors are simpler, and black holes are much, much more compact than stars.
5:50
If we made the mirror 10 centimeters thick, the metal of a big asteroid would probably be enough material for a black hole with the mass of our Sun.
5:58
Once our mirror is in place, we only need to open a window, and shoot
electromagnetic waves at the black hole.
6:05
You can imagine what happens next, by imagining tossing a ball at a wall, and it coming back faster than a bullet.
6:12
The waves hit the black hole at light speed.
6:15
A small proportion of the waves falls past the event horizon to disappear
forever.
6:19
But a much larger amount sloshes through the ergosphere,
6:23
…where the black hole forces some of its rotational energy on them, and
amplifies them.
6:29
They now begin superradiant scattering, which are fancy science words
meaning:
6:34
“Bouncing around between mirror and black hole and getting stronger.”
6:38
Every time they go around, they are getting exponentially stronger.
6:42
By opening some windows in the mirror, we can extract the energy from the waves as fast as they grow.
6:48
ASR: Which we could use, in theory, to create what would be for all
practical purposes, an endless source of energy for trillions of years.
6:56
JB: Or, we could blow it up.
6:59
ASR: Yes! If the waves are not released, they will continue to get stronger and stronger,
7:03

…and take more and more energy from the black hole, until the mirror
shatters.
7:08
A supermassive black hole would release as much energy as a supernova,
7:12
…making the bomb the largest explosion any living being could ever create.
7:18
Me: Fucking awesome.
7:21
ASR: The beauty of the black hole bomb, the Penrose process, and the
super radiant scattering, is that they are not science-fiction.
7:28
JB: Yes, in the far far future, this might be the only way to survive in our
dying universe.
7:34
After all the red dwarfs have cooled down, and all the white dwarfs
transformed into black dwarfs, the universe will turn dark forever.
7:43
Rotating black holes might be the only sources of energy in the entire universe that life could harvest.
7:49
If so, the last living being in existence might one day end its life around a black hole. It turns out that even without any light, there are places we can go.
7:57
Me: Ok I am equally scared shitless and uplifted. So, Black holes may well be our friend? the heros of our civilisation?
8:01
……hero friends. I like that. What about Spaghettification if we get sucked in? wouldn’t that hurt?
8:04
JB: Ah ok, Spaghettification.. would it hurt? Actually, no.
8:07
Me: Wait what? explain that. Really simply please. Really! It sounds painful, very. So it would not hurt? Why?
8:11
JB: It is because electricity isn’t faster than light. Light particles
travel through empty space at 186,000 miles per second but black holes still grab ‘em.
The electricity which flows through the nerves in your body to communicate with the brain then back to design a feeling called pain travels much slower: only about 1/100th the speed of light.
8:12
ASR: Yeah, the black hole will pull you so fast that electrons transmitting the pain signals will not be fast or strong enough to escape the gravitational pull in
order to make it to the brain.
8:14
Me: Fuck me. Wow. So you’ll die a good death. Just a fucking frightening one.
8:17
JB: Ha yes! Black holes are as interesting as they are mysterious, but not really that scary, not to us anyway. Because the nearest black hole known to
mankind is V616 Monocerotis which is 3,000 light years away from us.
….It would take 3000 years for you to reach the nearest one if you travel at speed of light, neither of which is not possible.
8:22
Me: Ok so a big relief on all counts! Wow, there’s actually a surprising amount we do know about them isn’t there? I mean considering we can’t even really see them.
Or do you guys just make all this shit up because you know no one is smart enough to challenge you?
8:25
ASR: No no haha, using math we can calculate things and come up with
theories.
8:29
Me: Like about how we die if we fall into them?
8:32
JB: Well yeah, if you’re the sort of person who gets excited about that? I
prefer the maths and get excited about calculating these things for people like you to enjoy.
8:37
Me: People like me? You mean the ones that barely finished high-school, let alone a harry potter book.. brilliant, cheers James and Anna. Let’s leave it there then.