Date: 02-22-91 13:02
From: Arnold G. Gill
To: All
Subj: New Black Hole stuff
Hi Y'All!
Since so many people here are interested in black holes, I will present
below the results from a set of talks that I attended the last couple of
days. The title of the talks were "Going through a Black Hole" given by Eric
Poisson (a good name for a physicist!). As we found out later, there is
supposed to be a question mark at the end of the title. Oh well! This is
part of his PhD thesis, working with Werner Israel at the University of
Alberta.
Many of you have probably read stuff from Hawkings and others that
suggest that it might be possible to navigate through a rotating black hole
and emerge somewhere else in our universe or, actually, in another universe.
Well, this talk killed that idea completely, possibly for good. I'm going to
try to draw a Penrose diagram of a charged, rotating black hole below --
please bear with the bad graphics.
| \ \ BH |
| \ \ <---|---- r=r- inner event (Cauchy) horizon
| \ \ |
| \ \ | <-- r=0 singularity
| \ \ |
| \ \ |
| \ BH \| In this picture, time increases upwards,
| \ X radius to the right.
| \ / \
| \ / \
| \ / <---\---- r=r+ outer event horizon
| \ / \
| BH \ / \ <--|
| \ / \ |
| X U \ |
| / \ / |-- outside universe
| / \ / |
| / \ / <--|
| / \ /
| / U \ /
| / \ /
| / \/
In the above picture, U areas are the universe outside the black hole's
event horizon, BH areas are not viewable from the outside universe, being
within the black hole.
In the old picture, one could navigate through the black hole as long
one avoided the vertical r=0 singularity by moving at angles less than 45
degrees from the vertical on the diagramme. (Greater than 45 degrees would
be equivalent to travelling faster than the speed of light.) However, there
is another singularity, namely the r=r- inner event horizon which is at
exactly 45 degrees. What happens is that *any* incoming radiation, including
reflections of the outgoing gravitational radiation due to the collapse of
the star into the black hole, will in exponentially blue-shifted at the inner
horizon -- producing what Poisson calls Mass Inflation, namely infinite mass
(i.e. a singularity) along the r- event horizon for the observer moving
*inside* the black hole. Note that nothing changes for the observer far away
from the black hole -- mass is still measured normally.
The net result is that no matter what one does, any travel within a
black hole will result in the ship smashing into a infinitely hot, infinitely
massive singularity in some short finite time. Time travel or wormhole-type
`warp' travel is *not* possible!
Oh well, another great idea shot down by facts. Now I'm going to have
to change my view of the universe all over again. Hot damn!
Arnold Gill --- astrophysician in training
---
|
|
Disclaimer: The file contained in the
box above or displayed in a separate window from a link in the
box above is NOT owned nor implied to
be owned by BeYoND THe iLLuSioN. Most files at BeYoND THe
iLLuSioN are originally from public Bulletin Board Systems
(BBS) which were popular in the days before the Internet or
from gopher, web, and FTP sites from the early days of the
Internet which no longer exist today. Essentially, all files
were acquired from the public domain in one for or another.
However, there have been occasions when copyright protected
material has appeared on BeYoND THe iLLuSIoN without permission
of the copyright holder. In these instances, we have and will
continue to remove the copyright protected file as soon as it
is brought to our attention. This can now be done using our Report Copyright Material form. Fill
out the form, and the webmaster will be notified of the
situation.
There are also times when files found on BeYoND THe iLLuSioN
have a real home somewhere else on the Internet. In these
instances, we will gladly replace the file with a link to its
true home whenever it is brought to our attention. If you know
of the true home of any of these files, you can use our Report Original URL form to bring it yo our
attention.
|
