Space question

For the discussion of the sciences. Physics problems, chemistry equations, biology weirdness, it all goes here.

Moderators: gmalivuk, Moderators General, Prelates

Bright Shadows
Posts: 645
Joined: Mon Dec 15, 2008 2:56 pm UTC

Space question

Postby Bright Shadows » Mon Dec 15, 2008 3:07 pm UTC

Is it possible to reverse the expanding space thing and create pockets, so to speak? I think I finally get expanding space, and am now trying to apply it, so forgive me if this is downright silly. It would be kinda convenient, though, if it weren't totally impractical.
Image

User avatar
Woofsie
Posts: 705
Joined: Fri Jun 20, 2008 1:11 pm UTC
Location: Ireland
Contact:

Re: Space question

Postby Woofsie » Mon Dec 15, 2008 3:57 pm UTC

I've been wondering this lately as well. I can see it being important for a civilization far in the future to try and prevent the heat death of the universe.

User avatar
Xanthir
My HERO!!!
Posts: 5410
Joined: Tue Feb 20, 2007 12:49 am UTC
Location: The Googleplex
Contact:

Re: Space question

Postby Xanthir » Mon Dec 15, 2008 4:42 pm UTC

You can safely file this into the "Nobody has a fucking clue, and likely won't for some time" drawer.
(defun fibs (n &optional (a 1) (b 1)) (take n (unfold '+ a b)))

User avatar
doogly
Dr. The Juggernaut of Touching Himself
Posts: 5531
Joined: Mon Oct 23, 2006 2:31 am UTC
Location: Lexington, MA
Contact:

Re: Space question

Postby doogly » Mon Dec 15, 2008 4:43 pm UTC

You can have zones which do not expand, like galaxies. If the dark energy source is a cosmological constant (most likely, not conclusive yet) then gravitationally bound systems like galaxies will not expand. But, they will still lose their heat to the outside of the system, so heat death is unavoidable. Even if you got the entire universe to stop expanding, you'd still have a heat death in your future, since we can't fight thermodynamics forever.
LE4dGOLEM: What's a Doug?
Noc: A larval Doogly. They grow the tail and stinger upon reaching adulthood.

Keep waggling your butt brows Brothers.
Or; Is that your eye butthairs?

User avatar
frezik
Posts: 1336
Joined: Wed Jan 10, 2007 7:52 pm UTC
Location: Schrödinger's Box

Re: Space question

Postby frezik » Mon Dec 15, 2008 5:24 pm UTC

Isn't the working theory that time is linked to the exapansion of the universe? Therefore, if you stopped the expansion, time would stop moving forward. If the universe shrank ("Big Crunch") time would go backwards (along with entropy). This would seem to apply to a localized pocket just as well as the universe as a whole.
I do not agree with the beer you drink, but will defend to the death your right to drink it

User avatar
danpilon54
Posts: 322
Joined: Fri Jul 20, 2007 12:10 am UTC

Re: Space question

Postby danpilon54 » Mon Dec 15, 2008 6:03 pm UTC

frezik wrote:Isn't the working theory that time is linked to the exapansion of the universe? Therefore, if you stopped the expansion, time would stop moving forward. If the universe shrank ("Big Crunch") time would go backwards (along with entropy). This would seem to apply to a localized pocket just as well as the universe as a whole.


I don't believe there is a causal relationship there, just a correlation. Stephen Hawking, however, would have you believe differently.
Mighty Jalapeno wrote:Well, I killed a homeless man. We can't all be good people.

User avatar
doogly
Dr. The Juggernaut of Touching Himself
Posts: 5531
Joined: Mon Oct 23, 2006 2:31 am UTC
Location: Lexington, MA
Contact:

Re: Space question

Postby doogly » Mon Dec 15, 2008 8:35 pm UTC

frezik wrote:Isn't the working theory that time is linked to the exapansion of the universe? Therefore, if you stopped the expansion, time would stop moving forward. If the universe shrank ("Big Crunch") time would go backwards (along with entropy). This would seem to apply to a localized pocket just as well as the universe as a whole.


No, there is no way to even formulate this sensibly. There's no reason to suspect that the laws of thermodynamics would realize the universe reached some critical density and decide to swap signs to match the swap in sign of the scale factor.
LE4dGOLEM: What's a Doug?
Noc: A larval Doogly. They grow the tail and stinger upon reaching adulthood.

Keep waggling your butt brows Brothers.
Or; Is that your eye butthairs?

User avatar
Dezign
Posts: 88
Joined: Sun Oct 12, 2008 3:03 am UTC
Location: North of the Land o' Fruits 'n' Nuts

Re: Space question

Postby Dezign » Mon Dec 15, 2008 10:45 pm UTC

Someone should come up with a good reason to bump a Time thread other than the time travel one...

The search function is my friend.
Last edited by Dezign on Wed Dec 17, 2008 10:28 am UTC, edited 2 times in total.

Bright Shadows
Posts: 645
Joined: Mon Dec 15, 2008 2:56 pm UTC

Re: Space question

Postby Bright Shadows » Tue Dec 16, 2008 12:53 am UTC

So I was thinking more along the lines of small scale, for storage.
But it appears to be a rather mysterious topic, so I'm going to let it lay for a while...
Image

User avatar
doogly
Dr. The Juggernaut of Touching Himself
Posts: 5531
Joined: Mon Oct 23, 2006 2:31 am UTC
Location: Lexington, MA
Contact:

Re: Space question

Postby doogly » Tue Dec 16, 2008 2:45 am UTC

Bright Shadows wrote:So I was thinking more along the lines of small scale, for storage.
But it appears to be a rather mysterious topic, so I'm going to let it lay for a while...


No, it's fine. The expansion of the universe doesn't rip apart gravitationally bound systems, unless it is driven by some more mysterious force than seems likely. You don't need to make a special pocket to avoid this.
LE4dGOLEM: What's a Doug?
Noc: A larval Doogly. They grow the tail and stinger upon reaching adulthood.

Keep waggling your butt brows Brothers.
Or; Is that your eye butthairs?

Bright Shadows
Posts: 645
Joined: Mon Dec 15, 2008 2:56 pm UTC

Re: Space question

Postby Bright Shadows » Tue Dec 16, 2008 8:12 pm UTC

No no no no no, not what I meant. Again. I was asking whether it was feasable to, on a small scale, reverse universal expansion to create a pocket of space containing more space than was apparant. Storing material in an area cut off from our space by a fold.

However, I realized that this would only work on a universal edge, so even if it were possible / practical, we can't exactly go about doing it.
Image

User avatar
doogly
Dr. The Juggernaut of Touching Himself
Posts: 5531
Joined: Mon Oct 23, 2006 2:31 am UTC
Location: Lexington, MA
Contact:

Re: Space question

Postby doogly » Wed Dec 17, 2008 5:33 am UTC

Bright Shadows wrote:No no no no no, not what I meant. Again. I was asking whether it was feasable to, on a small scale, reverse universal expansion to create a pocket of space containing more space than was apparant. Storing material in an area cut off from our space by a fold.

However, I realized that this would only work on a universal edge, so even if it were possible / practical, we can't exactly go about doing it.


Oh, yeah I don't think there's any way for this to happen. And while you can write down spacetimes that aren't continuous, it seems pretty reasonable that our universe will not have anything like an edge.
LE4dGOLEM: What's a Doug?
Noc: A larval Doogly. They grow the tail and stinger upon reaching adulthood.

Keep waggling your butt brows Brothers.
Or; Is that your eye butthairs?

User avatar
thoughtfully
Posts: 2253
Joined: Thu Nov 01, 2007 12:25 am UTC
Location: Minneapolis, MN
Contact:

Re: Space question

Postby thoughtfully » Wed Dec 17, 2008 6:42 am UTC

doogly wrote:Oh, yeah I don't think there's any way for this to happen. And while you can write down spacetimes that aren't continuous, it seems pretty reasonable that our universe will not have anything like an edge.

Pinching off a bubble wouldn't require having an edge; cell membranes don't have edges, but produce vacuoles all the time. There's some neat stuff in The Elegant Universe concerning the tearing and resealing of spacetime. Whether or not there's a conceivable way to do this in a physically sane way is another question.
Image
Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away.
-- Antoine de Saint-Exupery

User avatar
doogly
Dr. The Juggernaut of Touching Himself
Posts: 5531
Joined: Mon Oct 23, 2006 2:31 am UTC
Location: Lexington, MA
Contact:

Re: Space question

Postby doogly » Wed Dec 17, 2008 7:25 am UTC

I can't really think of a meaningful way in which the universe might be like a cell membrane.

So, there are two ways I can think of you can get these pockets. One is to glue them on to an edge, which you can do formally but is not constructable physically. It's conceivable that some discontinuities could exist somewhere, but I wouldn't bet on it. You can also get these things with fields in different phases. The theory of inflation says there is a field in some vacuum which pervades space, it seems like a pretty good theory so far, but if you could excite it into an even lower vacuum then you wouldn't have something that reversed expansion, it would expand even faster than the rest of space.
LE4dGOLEM: What's a Doug?
Noc: A larval Doogly. They grow the tail and stinger upon reaching adulthood.

Keep waggling your butt brows Brothers.
Or; Is that your eye butthairs?

davetp425
Posts: 70
Joined: Thu Jul 24, 2008 7:20 am UTC

Re: Space question

Postby davetp425 » Sat Dec 20, 2008 9:58 pm UTC

Are you trying to build Dyno-Capsules? :D


Return to “Science”

Who is online

Users browsing this forum: Thesh and 11 guests