Primordial Groove

<a href="http://www.msnbc.com/news/837200.asp" target="_blank"> Fascinating </a>

fando

Wow! The pace of astronomical discoveries is astounding. It's getting so very hard to keep up.

crocodile deathroll

I wonder what phyical shape they will take just as they merge.
I assume all black holes are spherical, but as they collide then that I sure would change.
Could it be like a great black donut like a black hole crater in the fabric of space-time?
The event horizon istead of being neatly warped around a sphere would instead be warped around in the shape of a donut.
The gravitational lensing effects it would have on stars galaxies behind would be interesting.

fando

croc, check this link out:

<a href="http://archive.ncsa.uiuc.edu/Cyberia/NumRel/BlackHoleEvolution.html" target="_blank">http://archive.ncsa.uiuc.edu/Cyberia/NumRel/BlackHoleEvolution.html</a>

There's a link to movies that show how merging black holes would distort spacetime, among other nifty cases.

Edit -- The movies are here:

<a href="http://archive.ncsa.uiuc.edu/Cyberia/NumRel/MoviesEdge.html" target="_blank">http://archive.ncsa.uiuc.edu/Cyberia/NumRel/MoviesEdge.html</a>

[ November 19, 2002: Message edited by: fando ]</p>

crocodile deathroll

Those videos were a lot of fun!. It goes to demonstrate the dark empty space is not as straight forward as I thought when gravity from colliding black holes a factered in.

Gauge Boson

You can find tons of astrophysics papers at the <a href="http://www.arxiv.org/" target="_blank">arXiv</a> e-print archive. More than you would expect are understandable by interested ameteurs. Some of them are written specifically for non-professionals and only on the archive. Others are available the month before they appear in journals. Hot topics right now are cosmological acceleration, quantum cosmology (almost all of this stuff is technical), neutrino physics, and variable 'constants'. They also have e-prints on a whole range of physics topics, with varying degrees of difficulty.

Shadowy Man

croc:

No. Spinning black holes would not be spherical.

crocodile deathroll

No, I was quoted out of context. I at one time did assume all black holes were shperical, but spinning and colliding black holes may of changed all that. Some spinning ones may even be donut shaped.

[ November 20, 2002: Message edited by: crocodile deathroll ]</p>

Shake

Yes, I read about this story in my local newspaper with great interest, because black holes have become sort of a hobby of mine. Among other good books is Black Holes and Time Warps by Kip Thorne!
OK, now this would be a bit of a technicality, but aren't black holes often referred to as "point singularities?" So reference to being spherical or flattened in the case of spinning ones is actually a reference to the space-time immediately surrounding the hole. This would be the area near and around the event horizon. My point is that a true singularity would, by definition occupy no real space, in the way a point on a line has no dimension, just location. The reason we notice spherical (or toroidal) form of a black hole is not really the object as it exists now, but the remnants of the collapsed star.

Shadowy Man

Shake:

No, this is not true. In the Kerr Metric, a rotating black hole will have a disc singularity. Additionally, it will have two infinite redshift surfaces, as well as two event horizons. It will not be spherical.