universe is 1 trillion years old

[gib65]

In the late 90's some astrophysicists (Reiss' date=' anotherbignamei'veforgottenbutwilllookuplater, et al) did some work to determine how fast the universe was expanding. They were using supernovae to do distance/redshift measurements, and hoped to measure how much the expansion of the universe was decelerating. The first big paper was actually included the word "deceleration" in its title. For the past 60-70 years a deceleration was assumed because there was no known force to cause an accerleration, and there was a known force to cause a deceleration - gravity.

 

There was a problem with their paper though. If you read to the very end, they come up with a negative value for this deceleration. Over the course of the next couple of papers they published it became clear that the universe is accelerating its expansion. Many groups have repeated this study. There is little or no argument that it is valid.

 

Since there is an acceleration, there must be a force. This is typically called the "cosmological constant," thanks to our most famed and overrated scientist, Einstein. You may also see it called "quintessence." That this force exists there is little doubt. Of its exact value and whether this value is constant over time and space, there is much more doubt.

 

The fact that there is this potential energy threw a huge monkey wrench in quite a few theories, especially string theory*, but actually did a great deal to validate the inflationary big bang theory.

 

 

*I remember reading a paper at the time saying something like "you can get anything you want out of string theory except a small, positive cosmological constant"... but of course, that was five years ago, so its ancient history. Now people working in string theory will tell you that a small, positive cosmological constant is a natural outcropping from their... well, whatever you want to call what they've got.[/quote']

 

That fascinating!

 

Doesn't this put a different spin on the Big Bang Theory? It seems to suggest that instead of a Big Bang, there was a Slow Emergence.

[Locrian]

Locrian this is a really nice brief account of cosmological constant history. Loved it.

 

I'm glad you liked it. I've done a better job in the past, and if the question comes up in the future I'll do a better job then. And you are right about Permutter. I also see a Schmidt. Here are the papers I have jotted down, though there are several others that are important:

 

Riess et al. “SNAPSHOT DISTANCES TO TYPE Ia SUPERNOVAE: ALL IN “ONE NIGHTS WORK.” Astrophysical Journal, 504 935-944 (1998)

 

Schmidt et al. “THE HIGH-Z SUPERNOVA SEARCH: MEASURING COSMIC DECELERATION AND GLOBAL CURVATURE OF THE UNIVERSE USING TYPE Ia SUPERNOVAE.” Astrophysical Journal, 507 46-63 (1998)

 

Unfortunately though I am embarassed to say you have misjudged me. I am neither quickwitted nor well informed. This leaves me in a tough position to respond to the rest of your post, and the suggestion that my response should be interesting definitely (and maybe thankfully) precludes me from putting my neck on the block.

 

I hope someone else gives it a shot, as you deserve a response.

[Locrian]

One other thing though I would like to add to this discovery of the cosmological constant:

 

Schmidt's first appeared in the astrophysical journal. The second, which blew the lid off the acceleration business, did not. It appeared in a much less well known journal. At a later date, a third appeared again in the astrophysical journal.

 

I've always thought it fun to question why those were published where they were. I could be wrong, but I'd think there is some drama in that story somewhere.

[Martin]

...position to respond to the rest of your post' date=' and the suggestion that my response should be interesting definitely (and maybe thankfully) precludes me from putting my neck on the block.

 

I hope someone else gives it a shot, as you deserve a response.[/quote']

 

in this context it is unlikely anyone will if you decline. it is safe to stick your neck out. I dont feel obliged to chop. this probably is a case that actually CALLS for some risky speculation

 

bounce is just getting into focus. the familiar thermodynamics theory really is IMO inadequate to cover bounce thermodynamics. Penrose is the only one making a big deal of it and it is entirely possible he's wrong. just like any of us.

[GuardianTech]

I have one question. How can you people sit here and talk about the age of the universe, when you don't even know how large it is?

[Dr. Dalek]

I have one question. How can you people sit here and talk about the age of the universe, when you don't even know how large it is?

 

There have been measurements of the size of the Universe.

Check out: http://www.space.com/scienceastronomy/mystery_monday_040524.html

also: http://en.wikipedia.org/wiki/Observable_universe

The wikipedia article suggests that the observable universe is finite, but the spatial universe may be infinite.

[GuardianTech]

That's the known universe. The scientific community has no idea the actual size of the universe. We've only been able to observe a small amount.