Cosmology Questions

[Giacomo525]

A couple of questions to lively up this board.

 

Is there any evidence for wormholes? and What's the latest news on if there is enough dark matter to cause the Big Crunch, or will we end up in the Big Chill?

[aguy2]

if there is enough dark matter to cause the Big Crunch, or will we end up in the Big Chill?

 

You might want to check out http://physics.about.com/b/a/034824.htm

 

aguy2

[Giacomo525]

I don't think that adequately answers the questions...

 

Does no one know the answers to these things?

[aguy2]

I don't think that adequately answers the questions...

 

Does no one know the answers to these things?

 

How about the question, "Why wasn't the post inflationary expansion more uniform?"; this was a question that wasn't directly addressed by the model of the model.

 

aguy2

[timo]

I don't think that adequately answers the questions...

Does no one know the answers to these things?

I don´t really know the answers for sure' date=' but I can give it a try:

Is there any evidence for wormholes?

None that I knew of.

 

What's the latest news on if there is enough dark matter to cause the Big Crunch, or will we end up in the Big Chill?

The relevant quantity for the fate of the universe is not Dark Matter but Dark Energy (those are two different things which easily leads to confsion). I don´t really know a definite answer, but I found a quote from a book (which is a pretty easy read in case you´re interested in the subject):

Fate

In the currently-favoured cosmological models, the Universe survuves forever rather than recollapsing, and indeed the inferred cosmological constant [=Dark Energy] is leading to an accelerated expansion at present. Nevertheless it´s dangerous to try and second-guess what physics might take over in future; the cosmological constant might be a transient phenomenon, as was the similar quantity believed to have driven inflation in the early Universe, and so the acceleration may one day decease. If a small negative value of the cosmological constant were ever to appear, it could proomote recollapse in the future.

[Giacomo525]

Thank you Atheist for that quote. The matter is of grave importance to me, though to explain why is not appropriate here.

 

As for wormholes, if there is no evidence for them, why were they posited in the first place? Is there mathematical logic behind it? Did it factor into equations? I remember reading an article almost a decade ago about certain scientists working on wormholes. It was a popular article, so it didn't go into any detail, but perhaps someone here might remember it. It was about proving Einstein wrong, about how wormholes would be "faster than light" (though still Einstein would be right, but you know how sensationalist articles can get).

 

And where can I get some information on the differences between dark energy and dark matter? Are they equivalent to normal energy and matter, i.e. can dark matter turn into dark energy and vice versa?

 

Many thanks.

 

How about the question, "Why wasn't the post inflationary expansion more uniform?"; this was a question that wasn't directly addressed by the model of the model.

I have wondered this also, if I understand the question. Why the background radiation is uneven, right?

[aguy2]

I have wondered this also' date=' if I understand the question. Why the background radiation is uneven, right?[/quote']

 

You might want to check out bascule's thread 'The Axis of Evil?' in this forum.

I think this evidence could indicate a non-isometric expansion in the form of a jet or pulse.

 

aguy2

[Giacomo525]

Do you think you could fix the link? Try using BB tags.

[timo]

As for wormholes, if there is no evidence for them, why were they posited in the first place? Is there mathematical logic behind it?

It´s mostly playing with the math of the spacetime of a Black Hole:

You allow the coordiante r (which initially was supposed to be a radius and therefore >=0) to become negative. This effectively leads to a "parallel universe". The only path reaching this "parallel universe" is through r=0 which is the singularity. This is supposed not to be possible. There are, however, attempts to slightly modify the spacetime geometry close to the singularity to make a small region passable. If I recall this correctly, energy needed for this would need exotic properties (properties which no known matter has; can´t remember the details).

Now you could also claim that this "parallel universe" you get by extending your coordiante range is simply the old one and that you´d simply come out at a different position. If the position is sufficiently far away, you might have found a shortcut through spacetime, which is the basic idea of Wormholes.

It´s well possible that there are other ideas about Wormholes, but above is the one I know of.

 

I didn´t read through it but from the pictures it seems like promising read: http://io.uwinnipeg.ca/~vincent/4500.6-001/Cosmology/Black_Holes.htm

 

It was about proving Einstein wrong, about how wormholes would be "faster than light" (though still Einstein would be right, but you know how sensationalist articles can get).

They wouldn´t prove Einstein wrong (unless he said "there are no Wormholes", which I doubt). Being faster than light is not that much of a deal when the path you take is shorter. Think about shooting a ray of light to a mirror on Jupiter and reflecting it back to your kitchen. I think you´ve got a good chance being there faster.

 

And where can I get some information on the differences between dark energy and dark matter? Are they equivalent to normal energy and matter, i.e. can dark matter turn into dark energy and vice versa?

Dark Matter: Matter with normal properties, we simply don´t know what it is (but there are some guesses). Needed to explain some astronomical observations (e.g. the observed rotational movement of spiral galaxies).

 

Dark Energy = Something with (at least for matter) "exotic" properties; instead of working gravitational attractive, it works repulsive. There´s no explanation of what it is that relates it to anything known to standard physics (none I knew of, that is). Dark Energy is also called "Cosmological Constant". I use these terms as interchangable. If that´s not correct, I´d really like to hear an explanation on what the difference is.

 

I think for such a general question, Wikipedia is also a good source and the people there are certainly better in explaining things than I am: http://en.wikipedia.org/wiki/Dark_matter

 

^^ An interesting note on above link: In the heading it sais that Dark Matter doesn´t emit enough EM-radiation to be detected. A few month ago, I attended a talk by an experimentalist who claimed to have found Dark Matter radiation in the WMAP (=a satelite experiment) data. Never heard of this again afterwards, but the talk was quite convincing (except that he didn´t show the raw data, of course).

[aguy2]

 

^^ An interesting note on above link: In the heading it sais that Dark Matter doesn´t emit enough EM-radiation to be detected. A few month ago' date=' I attended a talk by an experimentalist who claimed to have found Dark Matter radiation in the WMAP (=a satelite experiment) data. Never heard of this again afterwards, but the talk was quite convincing (except that he didn´t show the raw data, of course).[/quote']

 

Do you think a case can be made that a lot the 'dark matter' is interstellar 'comets' acting as near 'black bodies' that only 'vent' when their internal temp reachs a certain point?

 

aguy2