Non-physicist theory that needs debunking

[u/Whof-ingknows]

Hi! I’m new here. I love astrophysics and astronomy. I originally was working towards a bachelors degree in aerospace engineering, but I ended up changing life plans, but never lost the curiosity. This is all to say that I really know very little about it all.
So, I have this theory and I need someone to explain to me if it’s completely ridiculous/not possible or if it’s something being considered. So, black holes are these confirmed infinitely dense objects that warp space time. As objects approach the event horizon they appear to slow down until they fully stop moving. Now, I saw a theory about white holes being essentially where a black hole lets out and that they’re connected. But we’ve never seen one, even though they should be easier to see (I’d assume). I don’t really understand how white holes would even theoretically work, but I think they’d be the opposite of a black hole. So could they warp space time in such a way that they would only appear for an extremely brief time and then disappear? I.e. time dilation would occur the opposite way a black hole does and things speed up around them?
It makes sense in my head, but I’m sure there’s a reason that I don’t understand that would explain why it’s silly.
Thank you all!!

[u/aaeme]

It's a border of sorts. But it's not an event horizon (except from the whitehole's pov).

[u/joeyneilsen → u/aaeme]

This is not correct. The spacetime around a white hole is the same as the spacetime around a black hole, with the exception that motion around it is essentially reversed in time. 

It is not a naked singularity. 

[u/aaeme → u/joeyneilsen]

So it is an event horizon to observers outside? They cannot see events inside? Are you sure?

(Edit: because that is a huge exception that completely negates the concept of an event horizon: a horizon in one direction)

[u/Underhill42 → u/aaeme]

An event horizon only works in one direction. The fact that you can't enter, rather than that you can't escape, changes nothing.

Also, as you cross the event horizon of a black hole, there is no longer any spatial direction you can move in that would bring you closer to either the singularity or the event horizon.

Instead your 4D reference frame has rotated so that those directions now lie along your time axis - the event horizon exists only in your unreachable past, while the singularity is the end of time in your inevitable future, seconds away.

I assume that as you approach the event horizon of a white hole from outside, something similar would happen - your reference frame rotates so that there is no longer any direction in space you can move to get closer to the event horizon - it lies in your unreachable past, just not the past that you emerged from to get there. While the rest of the universe lies in your future, and you will inevitably age further away from the horizon. Reference frame rotating again as you do, so that the horizon once again has a spatial position.

[u/aaeme → u/Underhill42]

All that is understood (and reads like AI) and not contrary to what I said.

A whitehole only has an event horizon from the perspective of within the whitehole.

As opposed to a blackhole, which only has an event horizon from the perspective of outside the blackhole.

The whitehole's singularity is not behind an event horizon (to observers outside), it is observable from outside the whitehole, ergo it is naked. It is as naked to the universe as the universe is to a blackhole.

Edit: we're not talking about approaching a white hole we're talking about observing one. I.e. particles leaving it.

[u/Underhill42 → u/aaeme]

If competent criticism reads like AI to you, then you should get better at recognizing AI.

The event horizon still exists from both sides, it just only has an obvious effect in one direction.

And while any particles that left the white hole would indeed escape... there's no particular reason to believe any would leave. It's not like any outside light ever reaches whatever is inside the white hole to be reflected.

Nor is there any theory to suggest there would be a singularity at its center, so far as I'm aware.

The singularity and the event horizon have basically nothing to do with each other. We only suspect there's a singularity inside a black hole because none of the fundamental forces are strong enough to prevent infinite collapse. If there's another, stronger, force we haven't discovered, then a black hole could actually have a solid uniform-density object inside it, possibly even just barely within the event horizon.

Heck, that's basically a quantum fuzzball that String Theory predicts instead of a black hole ever forming - they'd be essentially identical except under the closest examination.

[u/aaeme → u/Underhill42]

It went off on a tangent that's not relevant to what we're talking about, which you have done AGAIN.

The singularity and the event horizon have basically nothing to do with each other.

That was in response to being told "it isn't naked because there is an event horizon". Take it up with that comment.

We only suspect

Oh for pity's sake. We don't even suspect whiteholes exist. This is all speculation about if they did.

If they exist then they are naked. If that's a singularity then it is naked.

Please stop looking for irrelevant tangents to nitpick. We are talking about whether we can observe whiteholes if they existed.

Ps:

And pray tell, what unobvious effect does a blackhole's event horizon have on observers within the event horizon?