"Wayne Throop" wrote in message
...
| :: I fail to see what it is about the possibility that the universe
| :: might end in a singularity some billions of years hence that makes
| :: you compare it to egglaying emerald elevating elephants.
|
| : Erik Max Francis
| : The Universe potentially ending in a singularity doesn't make it a
| : black hole in any meaningful sense, unless you decide to play
semantic
| : games with what "black hole" means. A closed FRW universe and a
| : Schwarzschild geometry really have nothing useful in common except a
| : bad day at the end of the journey.
|
| Ah. OK, but even so, the structure of such speculation seems
| widly divergent from that related to oviparous primary-colored
pachyderms.
|
|
| Wayne Throop http://sheol.org/throopw

Very widly.
Androcles

: "Androcles" Androcles@ MyPlace.org
: Got a question for ya

Do you indeed. How droll.

: Einstein can prove nothing can go faster than a turtle?

Nope.

: Oops!... Did I say 'a turtle'? Sorry...'light'.

Not light either. Nor could Newton "prove" that gravity is inverse
square, nor that F=ma (or dp/dt), nor could Aristotle "prove" that
objects will run out of impetus as they move.

Einstein could, and did, derive a consistent physical model under the
assumption that lightspeed is isotropic in all reference frames.
It's consistent. It matches the various facts of the various matters.

Of course, "proof" is beside the point. The point is, is it sensible
to speculate that the universe is closed (or more restricted, has a
Schwarzschild geometry). Apparently, you have no actual reason it is not.


Wayne Throop http://sheol.org/throopw

"Wayne Throop" wrote in message
...
|: "Androcles" Androcles@ MyPlace.org
| : Got a question for ya
|
| Do you indeed. How droll.
|
| : Einstein can prove nothing can go faster than a turtle?
|
| Nope.
|
| : Oops!... Did I say 'a turtle'? Sorry...'light'.
|
| Not light either. Nor could Newton "prove" that gravity is inverse
| square, nor that F=ma (or dp/dt), nor could Aristotle "prove" that
| objects will run out of impetus as they move.
|
| Einstein could, and did, derive a consistent physical model under the
| assumption that lightspeed is isotropic in all reference frames.
| It's consistent.

A consistent physical model that's consistent...
As consistent as your assertions, perhaps? How droll.

It matches the various facts of the various matters.

Facts of matters... matches... hmm..

| Of course, "proof" is beside the point.

Of course. A definition is never a proof.
I notice you were careful to snip that.


| The point is, is it sensible
| to speculate that the universe is closed (or more restricted, has a
| Schwarzschild geometry). Apparently, you have no actual reason it is
not.

Ah, the famous 'logic' of the deranged. You have no reason not to
believe bright green flying elephants lay eggs in black holes, nobody
can prove they don't, so it must make sense that they do, right,
phuckwit?
Then we call that "science", Throopy baby.
What was your point again?
Androcles.

In article ,
Erik Max Francis wrote:

AA Institute wrote:

Suppose a black hole enters a binary system or a triple star system or
even a small, tightly-packed open cluster. Once it's finished
swallowing the first star, can it go onto swallowing a second star, and
then a third star, and so on... as it continues along its destructive
path? What is the *limit* (if any) as to how much theoretical mass that
can go into a black hole, before it's 'filled to capacity' as it were?

There is no theoretical limit.

Just to be pedantic, you should probably say that there is no
theoretical limit in asymptotically flat space.

Aaron

There is no theoretical limit.

That's of course just a theoretical assumption. I wonder what the
equations are that leads one to that conclusion? Isn't it a wonderful
puzzle when we speculate that limitless amounts of mass can disappear
through these things, without knowing where it all goes to...

If memory serves me right, I seem to recall from one of the 'Space'
series (with Sam Neill), a while back, that a black hole gets bigger
and more powerful as more material gets sucked into it. So,
theoretically speaking, given an unlimited length of time and an
endless supply of matter, wouldn't a supermassive black hole like the
one thought to reside at the core of our galaxy, just grow big, big and
bigger... until there's only a dark cinder of the Milky Way left as
every last one of its stars has winked out by spiralling in?

Another interesting scenario comes to mind, where two black holes
swallow one another... something really bizzarre must happen there,
with space-time continuums and the like? Has anyone read any fictional
accounts of what *could* happen when two black holes merge together in
space. That must surely be the realm of Stephen Hawking science


AA
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"AA Institute" wrote in message
ups.com...
If memory serves me right, I seem to recall from one of the 'Space'
series (with Sam Neill), a while back, that a black hole gets bigger
and more powerful as more material gets sucked into it.


I remember from an Asimov book I've got somewhere that black holes can
"leak", and so if they don't suck stuff in faster than it leaks, they
eventually disappear (perhaps in some kind of shower of radiation). I think
this was part of the evidence supporting the big bang theory - that mini
black holes would have been created during the explosion, and they'd be
disappearing Real Soon Now, so the scientists looked for the radiation - and
found it.

Paul

Paul Harman wrote:

I remember from an Asimov book I've got somewhere that black holes can
"leak", and so if they don't suck stuff in faster than it leaks, they
eventually disappear (perhaps in some kind of shower of radiation). I think
this was part of the evidence supporting the big bang theory - that mini
black holes would have been created during the explosion, and they'd be
disappearing Real Soon Now, so the scientists looked for the radiation - and
found it.

Black holes lose mass over time due to Hawking radiation for quantum
mechanical reasons. The loss rate is exceptionally low for anything
other than minute black holes -- literally smaller than atoms. A black
hole about the mass of an asteroid at the Big Bang would be just
evaporating now; anything less than that would have already evaporated,
and anything more than that would have gained in mass in the interim
rather than shrunk.

This isn't evidence supported by the Big Bang; it's deduction ancillary
to it. And Hawking radiation has not been specifically detected; the
x-ray and gamma ray background is merely consistent with some fairly
significant density of primordial black holes, which doesn't prove
anything either way.

All that being said, that's not particularly relevant to the question of
maximum black hole size (since Hawking radiation limits the minimum
mass, not the maximum mass), and, as Aaron was kind enough to remind us,
maximum black hole mass could only come into play only in particularly
queer universes, of which ours does not to seem to be one.

--
Erik Max Francis && && http://www.alcyone.com/max/
San Jose, CA, USA && 37 20 N 121 53 W && AIM erikmaxfrancis
I don't like principles. I prefer prejudices.
-- Oscar Wilde

"Erik Max Francis" wrote in message
...

| Erik Max Francis && && http://www.alcyone.com/max/
| San Jose, CA, USA && 37 20 N 121 53 W && AIM erikmaxfrancis
| I don't like principles. I prefer prejudices.
| -- Oscar Wilde
"Common sense is the collection of prejudices acquired by age eighteen."
- Albert Einstein
"Experience is the name everyone gives to their mistakes."--Oscar Wilde
Einstein was very "experienced", I'll keep my prejudices -- Androcles.

:: There is no theoretical limit.

: "AA Institute"
: I wonder what the equations are that leads one to that conclusion?

You seem to be thinking of it as a fixed-sized door, through which
objects pass. That turns out not to be the case.

: Isn't it a wonderful puzzle when we speculate that limitless amounts
: of mass can disappear through these things, without knowing where it
: all goes to...

The mass doesn't "go anywhere". It's still right there.
The notion of a black hole as a portal to another universe,
or to another part of this universe, is the notion of "wormholes",
which aren't quite the same thing as a black hole.

: If memory serves me right, I seem to recall from one of the 'Space'
: series (with Sam Neill), a while back, that a black hole gets bigger
: and more powerful as more material gets sucked into it.

In the same way that a planet's gravity gets stronger the more
material has fallen upon it. This is hardly a mysterious and
strange thing. The "equations that lead one to that conclusion"
are basically those that show that the more mass an object has,
the "more gravity" it has.

One way of thinking about black holes is to look at them as drops of
fluid, enclosed in a "membrane" which is the event horizon. The more mass
inside, the bigger the membrane. This can be misleading in detail, since
after what's inside isn't realy a "fluid", but as a simple mental model
describing how they interact with other objects, I've seen it recommended
in various popularizations... I think in a Scientific American article
of a few years ago.


Wayne Throop http://sheol.org/throopw

AA Institute wrote:
Okay, this is a light hearted question... but serious answers are
equally invited!

Suppose a black hole enters a binary system or a triple star system or
even a small, tightly-packed open cluster. Once it's finished
swallowing the first star, can it go onto swallowing a second star, and
then a third star, and so on... as it continues along its destructive
path? What is the *limit* (if any) as to how much theoretical mass that
can go into a black hole, before it's 'filled to capacity' as it were?

There is no mass limit to a black hole. Well, let me put it this way:
there appears to be no limit to the mass of a black hole according to
Einsteins theory of gravity. However in the future when we finally
arrive at an acceptable theory combining quantum mechanics and gravity
(string theory is a candidate) there may in fact be a limit.

The black holes that exist at the centers of galaxies are suspected of
having masses up to billions of Sun's.

The universe cannot be a black hole because it is expanding, and the
expansion rate appears to be accelerating!

A black hole need not have a "destructive path". A black hole could fall
in orbit around another star and be quite well behaved (as long as
nothing enters its event horizon :-)) with other planets orbiting the
star as well.


It's one of those questions that's been bugging me for a while, and I'm
not certain what the latest theoretical assumptions are about black
holes.


AA
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