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Rik8367 t1_j4dil9r wrote

Reply to comment by mfb- in What is the smallest possible black hole? by Durable_me

If making black holes is a really a potential outcome of the LHC I'm mildly shocked we just let the LHC run without some appropriate protections (if that's even possible)

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RobotFolkSinger3 t1_j4do002 wrote

This was a concern that was discussed quite a bit in pop-science, tabloid, and conspiracy circles back when the LHC was first starting up. In short, these black holes would not destroy the Earth. Due to their small size they grow much slower than they would decay due to Hawking radiation. Even if Hawking radiation works differently than we think at those scales and they don't decay, they grow so slowly it would take eons for them to eat the Earth.

Cosmic rays with way more energy than the LHC bombard the Earth all the time. So the fact that the Earth still exists would tell us that these micro black holes, if they form, won't destroy a planet in less than billions of years.

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IllstudyYOU t1_j4em61v wrote

What if thats not the case, and every galaxy with a black hole in its center was a civilization with their own LHC and accidently made a black hole.

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theonebigrigg t1_j4fj04r wrote

What? That's just not how black holes work. As someone in another comment said "Black Holes are not vacuum cleaners".

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Shoelebubba t1_j4exk6e wrote

Because it won’t matter if they do.

Black Holes aren’t special, they still obey the laws of physics outside their Event Horizon. That means Mass is still King.

If the LHC only fires electrons and protons and smashes them together…all they can get is Black Holes made from that mass at best.

Black Holes are not vacuum cleaners. They don’t suck in anything other than what their gravity allows them to. A 50 Solar Mass Black Hole can’t attract anything a 50 Solar Mass Star can’t. A Black Hole the mass of a few electrons or protons would only have that much gravity which ain’t much. It’d have to get lucky to collide with anything in order to “feed”.

Speaking of, the smaller the black hole the less time it has to live before it evaporates away; they’re not eternal. One the size of a few electrons/protons won’t last long and couple that with the sheer amount of luck needed for it to slam into something else in order to feed…well.

Long story short it’s kinda like worrying about someone making a nuke out of a single Uranium 235 or Plutonium atom. Sounds scary but honestly not really a concern.

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Rik8367 t1_j4ft785 wrote

Great thanks for the extensive reply! Always love learning about black holes :)

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Mt_Koltz t1_j4h2f9n wrote

>Speaking of, the smaller the black hole the less time it has to live before it evaporates away; they’re not eternal

Can you explain how black holes evaporate away? I can't see how any mass would escape the schwarzchild radius.

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Shoelebubba t1_j4h4xuq wrote

Hawking Radiation. There’s better explanations but the tldr of it is: particles pop in and out of existence all the time by “borrowing” power to pop in and giving it back when it pops out.
Every now and then, a pair of these pop in near a Black Hole. One of them falls into the Black Hole while the other shoots out taking a little bit of the Black Hole’s rotational energy and mass. And I mean minuscule.

Ordinarily this isn’t enough for a Black Hole to evaporate since it’ll consume WAY more matter than it evaporates. But as it stops consuming content, it’ll start -slowly- loss mass from Hawking Radiation.

This process is thought to happen faster as a Black Hole becomes smaller. It’s why massive Black Holes have an absurd theoretical lifespan like 10^100 years and small micro black holes live maybe like an octillionth of a nanosecond.

Btw I also neglected to mention the LHC likely would never be able to make black holes even if everything went perfect. Smallest theoretical Black Hole is a Planck Length wide (smallest unit) and the LHC slamming what they can into each other would make Black Holes about 10-15 orders of magnitude smaller than that…which isn’t possible.

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CircularRobert t1_j4h1ln7 wrote

I always thought of it as a kind of binary problem. Either we make one, and it becomes a problem, then it's our problem, or it's not an issue, then it's fine, or we don't make one, and then that's also fine. So either we have a problem, or we don't. And then either everything ends, or it doesn't.

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