Ok , first of all let me state that I am by no means knowledgeable about physics but a couple of comments on other threads got me thinking of a Horizon ( a very well respected science program on BBC )episode which was aired last year .
In this program they looked at the finding of supernovae hunters who have seemed to show that the universe isn’t in a *Big Bang / Big Crunch * situation of a * expand slower and slower one either * . They are saying that the universe is accelerating away still .
Is this theory still the case or has it been dismissed since this program was aired .
I’m not sure this will answer your question. There are three possible fates of the Universe (note-- critical density proportional to the square of the Hubble Constant):
Big Crunch (critical density higher than Hubble Constant)
Expand Forver (critical density lower than Hubble Constant)
Expand Forever (critical density equals the Hubble Constant)
The way scientists figure which will happen is to try and determine the geometry of the Universe (4-D geometry). If there’s to be a Big Crunch the Universe is positively curved like a sphere.
If it’s the Expand Forever the Universe is negativley curved and shaped like a horse saddle.
If it’s going to be the second Expand Forever (listed above) then the Universe is flat like a pancake.
It seems that very recently scientists measuring the Cosmic Microwave Background have come to the conclusion that the Universe is flat ( http://abcnews.go.com/sections/science/DailyNews/universe000426.html ) hence the Universe will expand forever (no Big Crunch in our future…just a very lonely Universe).
As to accelerating I don’t think so. Either everything is maintaining its speed or perhaps slowing down (negative acceleration?).
I should mention that I used to think that if the Universe was flat and the critical density was equal to the Hubble Constant that the Universe would reach equilibrium (neither expanding or contracting). Since it’s hard to believe such a delicate balancing act could be maintained I suppose it has to be Big Crunch or Expand Forever. The article I linked in my post above says expand forever so I’ll go with that. That said it’s a much slower expansion than you would see in the negatively curved Universe so it’ll be awhile before everything gets so far away (as if it isn’t far now) that the Universe will be a truely lonely place.
I wonder what a Universe expanding forever will really be like? I suppose there’d be sometime in the extremely distant future where there won’t be a star shining anywhere (sooner or later all the fuel will get used up). Somehow a Big Crunch seems preferable. At least one can speculate that a new Universe would be born following the Crunch starting the whole cycle over again. Expand forever just seems like an infinite fade away to nothingness.
You haven’t heard the latest thing. Some scientists trying to figure out the fate of the universe used distant supernovae somehow to tell them. What they measured indicates that the universe is still accelerating apart, and they believe it will forever (although the acceleration should slow down as things get farther apart).
The popular explanation has to do with some kind of “pressure” due to the creation and annihilation of virtual particles in empty space.
It’s still considered a good possibility that the expansion of the universe is accelerating. But it is still a preliminary conclusion based on some recent evidence. More research is being conducted.
But it’s a much stronger theory that the universe will continue to expand forever (no Big Crunch).
Umm , maybe I’m missing something but did you guys click the link . It’s linked to the word program in the OP .
It seems to me that these guys found something very interesting . A friend of mine ,who is almost definitely lurking and reading this post ( Hi Mick ), while having a drunken conversation said it could be something to do with anti-gravity .
If there was enough gravity (i.e., mass) in the universe, then the expansion would be slowing down. So this acceleration may appear to be a type of “anti-gravity”. But I think a different mechanism is at work. Perhaps a faint pressure associated with the energy of spacetime itself?
I’ve heard the same story, but can’t recall the details presently. I’m thinking it was some kind of red shift analysis of the Hubble Deep Field Survey.
I’m sure Feynman or Chronos will be along to enlighten us shortly.
Very interesting stuff. In the interest of re-clouding Yojimbo’s brain:
What happens if I make a vaccuum chamber here on earth (or in space if that makes a difference)? Does the chamber get bigger to contain the extra space (therefore we are all getting bigger)? Will the chamber shatter, unable to contain the new space? Does the new space seep out of the chamber?
If things are going faster and faster doesn’t that mean that time is slowing down for us? I realize we can never notice the difference our selves just wondering if that’s the case.
How fast can this all accelerate to? Near light speed? Are we accelerating at an accelerating rate?
And finally…
The faster you go the greater your mass so, if the Universe is expanding and accelerating, does that mean I can blame my few extra pounds on this phenomenon instead of too much beer?
No Things are just moving apart. Space does not exert pressure.
No. Time dialation is only relative to a “stationary” observer. You cannot notice time slowing down.
There is no upper limit on the speed of expansion. Far enough away things are receeding at faster than 186,000 miles/sec. This is no a problem because they are not going faster than light locally.
Jeff42 - The expansion of the universe is only significant on cosmological scales (like, over lightyears or millions of lightyears), not on the scale of a vacuum chamber or even a solar system. Also, there can be local regions where there is no expansion (e.g., a cluster of galaxies may have enough gravity to stop the expansion of space in that region). The expansion of the universe is measured as the Hubble constant which, I think, is in units of kps per megaparsec.
