Undergrad Do Black Holes Exist? | Physics & Stephen Hawking

[LightningInAJar]

TL;DR

Do blackholes exist?

Do black holes exist? I have largely only heard that mathematically physics rules break down inside of a black hole by its current definition and that nothing can escape it beyond a point. And Hawking radiation has already shown to escape it beyond an event horizon. And Stephen Hawking in 2014 had supposedly said there is no reason for black holes to exist. Maybe just super dense stars that most light gets absorbed into, but isn't in fact infinite in its density? Nothing truly absolute?

 

[berkeman]

Summary:: Do black holes exist?

Do black holes exist? I have largely only heard that mathematically physics rules break down inside of a black hole by its current definition and that nothing can escape it beyond a point. And Hawking radiation has already shown to escape it beyond an event horizon. And Stephen Hawking in 2014 had supposedly said there is no reason for black holes to exist. Maybe just super dense stars that most light gets absorbed into, but isn't in fact infinite in its density? Nothing truly absolute?

Please post links to where you have "heard" this, and please read through this introductory article and tell us which parts you don't understand. Thank you.

https://en.wikipedia.org/wiki/Black_hole

 

[Ibix]

Do black holes exist?

We've taken a photo of one and detected gravitational waves from the collisions of several more, so yes. Whether we have a completely accurate theoretical model of one is doubtful, but current evidence is consistent with our models.

And Hawking radiation has already shown to escape it beyond an event horizon.

No - Hawking radiation comes from above the horizon.

And Stephen Hawking in 2014 had supposedly said there is no reason for black holes to exist.

Reference, please. If he said anything of the sort I suspect it's a bit more nuanced than that.

Maybe just super dense stars that most light gets absorbed into, but isn't in fact infinite in its density?

Density isn't really something you can define for black holes, since the interior volume isn't well defined. And, despite a lot of popsci nonsense, the singularity isn't a "point of infinite density" - it's more like a moment in time, although that doesn't really do it justice either.

The problem with "super dense stars" is that there is no force known that is capable of stopping gravitational collapse if an object's gravity becomes strong enough to overcome neutron degeneracy pressure. And there are certainly stars massive enough that their gravity will be strong enough once they run out of fusion fuel. A quantum theory of gravity might change our opinion, but we don't have such a theory yet.

 

[phinds]

Summary:: Do black holes exist?

Do black holes exist? I have largely only heard that mathematically physics rules break down inside of a black hole by its current definition and that nothing can escape it beyond a point. And Hawking radiation has already shown to escape it beyond an event horizon. And Stephen Hawking in 2014 had supposedly said there is no reason for black holes to exist. Maybe just super dense stars that most light gets absorbed into, but isn't in fact infinite in its density? Nothing truly absolute?

Clearly you've been reading pop-sci articles and not actual physics. Keep in mind that such articles are entertainment, not science lessons.

 

[Ibix]

Do black holes exist?

I'm going to modify my answer a bit: it depends what you mean by "black hole".

As I said, we've got evidence of the existence of extremely massive and compact non-radiating objects. To our best precision, they match the properties general relativity ascribes to black holes. However, the predictions that general relativity makes for the interiors of black holes aren't entirely plausible. We hope a quantum gravity theory will make more plausible predictions.

So, do black holes exactly as predicted by general relativity exist? Probably not. But any successor theory to GR must allow for extremely massive and compact non-radiating objects (because if it doesn't it can't describe things we can actually see) that we might as well call black holes. Maybe technically "quantum gravity black holes" to distinguish from the more primitive GR model.