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Spaceman Spiff
2010-Apr-28, 07:16 PM
so argues Sean Carroll at Cosmic Variance (http://blogs.discovermagazine.com/cosmicvariance/2010/04/28/the-universe-is-not-a-black-hole/) -- sounds reasonable to me.

Swift
2010-Apr-28, 07:24 PM
Since this seems to be a report on astrophysics, and not a question, I've moved it to Astronomy. If someone thinks Q&A or somewhere else is a better location, please Report this post (black triangle, lower left corner).

Spaceman Spiff
2010-Apr-29, 05:13 PM
Since this seems to be a report on astrophysics, and not a question, I've moved it to Astronomy. If someone thinks Q&A or somewhere else is a better location, please Report this post (black triangle, lower left corner).

Oops! Yes, you're correct.

Cougar
2010-Apr-30, 02:17 AM
The Universe is Not a Black Hole
so argues Sean Carroll at Cosmic Variance (http://blogs.discovermagazine.com/cosmicvariance/2010/04/28/the-universe-is-not-a-black-hole/) -- sounds reasonable to me.

Although the approximate mass and radius of the visible universe might fit pretty well into the formula for the Schwarzschild radius (http://en.wikipedia.org/wiki/Schwarzschild_radius#Formula_for_the_Schwarzschild _radius), as Carroll writes....




You may have noticed that the universe is actually expanding, rather than contracting as you might expect the interior of a black hole to be.

Tough to argue against that one, all right. He notes our universe is more like the opposite of a black hole, i.e., a white hole. I always kind of thought (to myself) that the idea of a white hole was pretty ridiculous... I didn't realize I could be living in one.

Spaceman Spiff
2010-Apr-30, 12:58 PM
I liked these:


Thatís because, if anything, our universe bears a passing resemblance to a white hole (http://en.wikipedia.org/wiki/White_hole). Our universe (according to conventional general relativity) has a singularity in the past, out of which everything emerged, not a singularity in the future into which everything is crashing. We call that singularity the Big Bang, but itís very similar to what we would expect from a white hole, which is just a time-reversed version of a black hole......Our universe is not going to collapse to a future singularity, even though the mass is enough to allow that to happen, simply because itís expanding; the singularity youíre anticipating already happened.

Once inside a black hole, time and space reverse roles: inside the event horizon we can (in principle) dither about in time, but we have no choice in our direction in space -- the singularity. That isn't our universe.

01101001
2010-Apr-30, 01:36 PM
The Universe is Not a Black Hole

I bet you were just trying to help the oft-questioning tommac, maybe others who think they are in Singularity City, notice the news. I'll pitch in and try to remember a link to this the next time(s) we get the question.

Maybe under similar circumstances, try the Canadian finesse: The Universe is Not a Black Hole, Eh?

noncryptic
2010-May-06, 10:24 PM
I liked these:
Once inside a black hole, time and space reverse roles: inside the event horizon we can (in principle) dither about in time, but we have no choice in our direction in space -- the singularity. That isn't our universe.

Right. But for there to be a black hole there need not be a singularity.
The radius of the object causing the black hole only needs to be smaller than its Schwarzschild radius.

Afaik for all intents and purposes, event horizon = black hole.
The specialty of a singularity is that it has an event horizon pretty much regardless of how much or how little mass it contains.

tommac
2010-May-10, 05:47 PM
I dont get the white hole comment. From what I understand a white hole is just the time reversal of a black hole. Thus a white hole would be equally gravitational as a BH and the universal expansion would be slowing down. Wouldnt it?


I liked these:



Once inside a black hole, time and space reverse roles: inside the event horizon we can (in principle) dither about in time, but we have no choice in our direction in space -- the singularity. That isn't our universe.

astromark
2010-May-10, 07:54 PM
Being the new boy on the block ( In regards to the English Language.) What is... Afaik ? thanks.

The idea of a white hole is way off in ATM thinking, as no science supports it. We can not call the universe a Black Hole. As it does not exhibit ANY of the clues of such does it ? ie; its expanding ever quicker... ( looks to bread maker on bench ) Yes its a white thing without the time reversal component... Lets define it by calling it a 'Universe.' and dare I add 'The.' ?

slang
2010-May-10, 08:39 PM
As Far As I Know. Google has a nice trick: search (http://www.google.nl/search?q=define%3AAFAIK) for "define:AFAIK"

noncryptic
2010-May-13, 04:04 PM
The idea of a white hole is way off in ATM thinking, as no science supports it.

S. W. Hawking
Black holes and thermodynamics
Received 30 June 1975; published in the issue dated 15 January 1976
http://prd.aps.org/abstract/PRD/v13/i2/p191_1
...
"Black holes behave in a completely random and time-symmetric way and are indistinguishable, for an external observer, from white holes."


http://en.wikipedia.org/wiki/White_hole
"A white hole in general relativity, is a region of spacetime which cannot be entered from the outside, but from which matter and light may escape."