Reverse Time Could Explain Dark Matter

idot writes "According to Lawrence Schulman of Clarkson University, who will get his work published in the Physical Review Letters, the universe could contain reverse-time regions. The article from New Scientist says that this phenomenon could explain the yet mysterious dark matter. " The reverse time regions can help explain the "dark matter" problem because, as potential relics from the future, stars could have re-ignited under The Big Crunch and while we wouldn't see them, we would feel their gravity. Needless to say, more details will be needed then this small article.

Comments

New Scientist Link

[headshrinker]

Seeing as there wasn't a link - for more info, look at http://www.newscientist.com /ns/19991127/newsstory3.html

mean this does what?

[pen]

I have often thought about time travel, but I have come to the conclusion that even if it were possible, it wouldn't lead anywhere. Here's an example:

1. I know how to travel through time.
2. My friend gets hit by a car.
3. I travel back in time and save him.
4. My friend doesn't get hit by a car.
5. I don't travel back and save him.
6. My friend gets hit by a car.

Pointer to Phys Rev article

[StupendousMan]

You can find a postscript version of the article on the astro-ph preprint server:

http://xxx.lanl.gov/abs/cond-mat/9911101

I don't understand the physics ... but I find the idea that local dark matter (yes, within our own galaxy) may be remnants of stars from a far-future universe very unlikely.

gniht hcus oN

[PhilHibbs]

.emit esrever ni eveileb t'nod I !hsibbur fo daol a tahW

But will there be a big crunch ??

[Manifest]

As said in the article(New Scientist),the reverse time region needs an opposite of the Big Bang called the Big Crunch. But will a Big Crunch occur ?? Out of the 3 models by of non-static Universe, Big Crunch is the end-effect of just one of the models, the other being Ever Expanding and just exanding enough to avoid a Big Crunch.

So questions arises, will there be a Big Crunch ??

Manifest

Re:But will there be a big crunch ??

[Robert Link]

A "Big Crunch" seems unlikely given our current knowledge of astrophysics. There are several factors that would seem to argue against an eventual recollapse of the universe. The first is that if we total up all of the matter that we "see", including dark matter detected only through its gravitational effect, we only find about 20% of the critical mass density needed to close the universe. It would be a bit surprising to find that there was another 80% of critical density lurking, undetected even through its gravitational effects.

Another factor that argues against a recollapse is that the time scale test heavily favors open (i.e. expanding forever) models. Basically, for a fixed Hubble constant, closed models are younger than open models. Since the age of the universe derived from the expansion is just barely consistent with globular cluster ages for open models, closed models are real losers unless there is some serious revision in the ages of globular clusters.

Finally, recent measurements suggest that there is a nonzero "cosmological constant", an extra term in the General Relativity field equations that acts as a repulsive counter to gravity. What's more, the measurements seem to indicate that the cosmological constant is not only nonzero, but in fact dominant at the current epoch. If true, and if the cosmological "constant" really is constant (it is typically assumed to be constant with time, but that is not a theoretical necessity) then this would preclude a recollapse, irrespective of the mass density in the universe. (Recollapsing models with positive cosmological constant are possible, but only if the big crunch occurs before the cosmological constant term becomes dominant.)

Re:Let me see...

[jd]

Let's see if I can explain the basis behind Occam's Theory.

Ok, try this. Say you notice that apples fall off trees. Now, let's say there are three theories as to why this happens. Let's call these the "Murple" theory, the "Fzoom" theory and the "Quirp" theory.

Now, according to the "Murple" theory, Apples are influenced by the mass of spaghetti in nearby houses, the phase of the moon, and the sunlight, moonlight and starlight pushing down on it.

The "Fzoom" theory, on the other hand, speculates on the existance of a force that pulls the Apple down off the tree, emanating from the planet as a whole.

Finally, the "Quirp" theory predicts that Apples are affected by the same force as predicted by the "Fzoom" theory, but also adds in the effect of Maple Syrup and roast marshmallows.

Let's start with the first two theories. Occam's Razor predicts that the simpler theory that explains the phenonima is the most likely to be correct.

Yes, it's possible to do experiments to filter out the various sources of light, but let's say that we can't do that, for some reason. (Not all theories can be tested that way, such as the reverse time one.) Where does that get us?

Well, according to Occam's Razor, the second theory adequately explains the phenomina, in a simpler form, and so is the more likely to be true. Note that it does NOT say "it IS true". It is an expression of liklihood, not certainty.

Now, let's take the second and third cases. This reflects the case of multiplying entities. Here, the mysterious force accounts for all the behaviour of the apple. The effects of the Maple Syrup and roast marshmallows are, therefore, zero and can be omitted.

This is how additional entities can often be detected. The more you observe them, the smaller they get, until they vanish entirely. In the meantime, they've obscured important relationships and hidden details. That's why they should never be added, until you're certain there's something that simply CAN'T be accounted for with the existing model.

(A case in point is the theory of gravity, where the fact that the strength of a gravitational field at a distance N from a mass is proportional to the area of a sphere of radius N is not shown in the classic equations. Constants have been randomly folded into each other, in a hodge-podge that would win an award for obscure logic today.)