Thread: White holes

Reference : New Scientist, 19 July 2014, page 42

We all know about black holes. Those things that have so much gravity that they suck everything in, including light. Nothing escapes, but where does it all go?

Some astronomers think there may be an opposite to black holes, called white holes. Where black holes suck, white holes spew. White holes blaze with light rushing out, and possibly a whole lot of other stuff too. There are suggestions that white holes may be connected to black holes via wormholes, with the possibility that a black hole in one universe may be connected to a white hole in another, meaning that anything sucked into a black hole will travel through a wormhole to a different universe.

There is just one small problem with this idea. No one has ever seen a white hole. However, that may change. New radio telescopes may have the resolution to discover a white hole at great distance. Already we know of galactic nuclei that are much brighter than they should be. Possible white holes? With enough radio telescope resolution we might detect a small bright spot at the centre of these galaxies.

Or is it possible that some gamma ray bursters might be white holes?

If we discover that there are, in fact, white holes and we can learn more about them via those new telescopes, might that prove that there are many universes? What will that mean for our appreciation of reality?

There is just one small problem with this idea. No one has ever seen a white hole.

I would not expect white holes to physically exist. They are a valid solution to the Einstein equations, but you would need a perfectly spherically symmetrical body with zero angular momentum undergoing a perfectly radial collapse to actually form such a construct. No real-world astrophysical body fulfils these conditions; Schwarzschild geometry is a good approximation for many scenarios, but that does not mean that all its aspects are necessarily physically real.

Markus

It is a fair comment for you to say that, in your opinion, they are improbable. But would you agree that they are not impossible? While improbable, there is a reasonable chance they might be real?

Is worse than that though isn't it Markus? - white holes are an analytic continuation of the standard solution and so you not only require very specific initial conditions but some other mechanism to drive you from the one solution to this other branch.

I don't suppose a Pulsar could have any similarity to what a White Hole could be like?

Originally Posted by river_rat

Is worse than that though isn't it Markus? - white holes are an analytic continuation of the standard solution and so you not only require very specific initial conditions but some other mechanism to drive you from the one solution to this other branch.

Yes that's true. The problem with the Schwarzschild chart is that you need two coordinate patches to span the entirety of space-time, and the continuity conditions imply that one is a time-reversed version of the other. The connecting region ( the Einstein-Rosen bridge ) is not traversable, so there is no ( classical ! ) mechanism to get from the black hole to the white hole or vice versa. It will be interesting to see who quantum gravity affects this.
Schwarzschild charts are really not the best way to map the maximally extended geometry here - one is much better off in a coordinate system such as Kruskal-Szekeres, which spans the entire space-time manifold without the need for separate coordinate patches.

The other issue we have here is that the Einstein equations constrain only the local geometry, but not the global topology of space-time - in other words, there is no way for us to tell whether we are dealing with two separate singly connected manifolds, or one multiply connected manifold. Given asymptotical flatness, both of these are valid Schwarzschild space-times.

Originally Posted by Markus Hanke

There is just one small problem with this idea. No one has ever seen a white hole.

I would not expect white holes to physically exist. They are a valid solution to the Einstein equations, but you would need a perfectly spherically symmetrical body with zero angular momentum undergoing a perfectly radial collapse to actually form such a construct. No real-world astrophysical body fulfils these conditions; Schwarzschild geometry is a good approximation for many scenarios, but that does not mean that all its aspects are necessarily physically real.

Or you could take a standard donut hole and sprinkle powdered sugar on top.