# The event horizion of a white hole

Yes, I know white holes violate the 2nd law of thermodynamics, etc, etc.
But imagine if you that you had a whitehole, Am I correct in my assumption that it’s event horizion would mark the line that no matter coming from outside of it could go past?

Bump! Someone should know this, but to help I’ll explain my reasoning: A white hole is the time symetric version of a black hole and is predicted by the thoery of general relativity (which is time symetric), so if you were to take a video camera and film a black hole, then run that film in reverse you would be looking at a white hole.

I think you’d be correct, but I think it would be more right to say that after that point, any matter being spewed from the hole couldn’t go back, if that makes sense.

It does but maybe better stated as the point where it can start heading back.

Well, if you’re going to speculate about the properties of an object that, by your own admission, can’t exist, you can make up any rules you feel like, frankly.

No, it isn’t specifically forbidden from existing (infact their existance is implicity implied by general relativity) as the 2nd law of thermodynamics is only a function of probability and may only hold true for our locality or time frame within the universe. the reason why I asked the question orginally is that I saw a creationist theory that described the whole universe as a white hole and I am checking my debunking as white holes are something that I am unsure of.

Anyway you should know tht they exist, one of the episodes of Red Dwarf was called ‘White Hole’!!

Oh, okay. If it was in a Red Dwarf episode, I guess we’ll have to accept its existence and seriously discuss its properties.

Well, maybe later. Voyager is on and I hear this episode will offer a serious analysis of time travel!
[sub](somewhere in the multiverse is a dimension where sarcasm doesn’t exist, so I try to pick up the slack)[/sub]

Ok, white holes are one of those things like tachyons that have been co-opted by sci-fi, but they are described in GR, though I seriously doubt that they exist.

The Red Dwarf thing was a reference to smegheads name!

I’m pretty sure you’re right about the event horizon of a white hole. A more interesting question, in my opinion, is whether “Hawking Radiation” would cause a white hole to gradually gain mass in the same manner that it causes a black hole to lose mass. I think so, but it’s hard to visualize.

No matter actually falls into a black hole, hence energy gathers around a white hole’s event horizon to form matter, which is jetted away from the white hole…

Matter does fall into black holes, it may not appear to as the light reflecting off it becomes very slow, but it does fall in.

I see what your saying now, because of the time warp, I did do all the equations to model an astronaut falling into a hole and I think from an outside perspective (i.e. not the astronauts) you maybe right, but I’d have to check again.

For an observer outside the black hole the astronaut (or whatever) never seems to enter the event horizon. To the outside observer the astronaut would seem to stop at the event horizon and would then fade from view (they would get redshifted out of vision).

From the perspective of the astronaut he/she would most certainly pass the event horizon (in the case of a sufficiently large black hole the astronaut might not even notice anything…for a smallish black hole the astronaut would be stretched into spaghetti before entering the horizon [assuming they were going in feet/head first]).

Yes, I do remember now (I should do as I did a reasonable amount of research on blackholes at uni), the path that the light is travelling from the astronaut to the observer represents a severely warped region of space time, though you could argue that it is just the light from the astronaut that you are seeing and the astronaut himself has fallen in the whole, it is dependant on the relativistic perspective that you take.

There are two major theoretical problems with white holes. First, they’re non-determinate. Anything that can go into a black hole, can come out of a white hole… But anything can go into a black hole, so anything can come out of a white hole, and we have no reason to expect anything in particular.

The other problem is that creating one would violate the Third Law of Thermodynamics. You can have a universe with a white hole in it, but it has to be born with the universe. You can’t take a universe without a white hole and put one into it.

The Second Law is also an issue, of course, but as long as you’ve got something other than your white hole in the universe, you can just increase its entropy to compensate.