Science a GoGo's Home Page Forums General Discussion Physics Forum Nothing or nearly nothing?

According to current evidence, it appears that the universe won't be terminated in a 'Big Crunch'. Thinking about that scenario, however, I find that I'm not clear about what it actually means. I know the idea is that 'everything' collapses into a singularity. What's unclear is, which of the following is true:

(1) space itself would contract, with the result that the universe becomes a dimensionless singularity.
(2) all matter would be drawn together 'through space' by gravity, leaving the singularity within a space-time continuum still inhabited by virtual particles.

If (1), then space-time would come to an end.
If (2), then space-time would not come to an end.

I suspect that it must be (1), but does anyone know for sure what the theory predicts.

2 not 1. Though that idea is no longer considered credible.

Neither theory is currently extant.

Our best guess is that expansion will continue to accelerate and we know not where that might lead.

Nobody can answer with any certainty the future of the Universe.
Theories abound. Out of fashion these days is "The Steady State Theory" when it was found that the Universe was expanding.

It might well be, when we look outward in distance.

Then again the giant rotating Galaxy Andromeda, is rushing towards us and will eventually join to us physically.
That means our area of space will become denser.

Yet is the reason our Milky Way Galaxy is expanding, due to a Universe of lesser density surrounding us?

Or is our Milky Way expanding due to the 'popping in and out' of particles that make our density a little greater than elsewhere?

Since I have no reason to believe that these virtual particles
are special to our part of the universe.
One must assume that they are virtual particles generating everywhere within the total Universe.

This would not alter the dense or less dense spaces that are proposed to exist, in any way at all. Everything being equal.

Therefore given after eons of time has passed the universe's density should have averaged out to a common density (between
any communicating Galaxies, that is)

Then theoreticaly, expansion to a lesser density should stop, leaving no way to go except regression. Prehaps the virtual particles would change to particles of negative matter.
Either way onec expansion has stopped, Gravity would come into play, slowly at first, but than ever faster.

Look at it this way suppose there were just two particles of matter floating at opposite ends of 'their' Universe (and we just dont know how big 'their' Universe would actually be)
The miniscule Gravity attraction between them would ultimately bring them together.

Note: I believe that the universe has been in existence forever, and will forever do so. For you cannot destroy matter/energy, it will exist in a changed form, prehaps for eons, even destroying previous galaxies, even life. But matter in the form of dense black holes, that spew out ever more material, will redress the status quo, continually remaking Universe's similar to the one we now exist in.

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"You will never find a real Human being - even in a mirror."

.....Mike Kremer.
.

What I found interesting about our galaxy and others as well is that they don?t spin right. The inner parts should be moving faster than the outer sections but actually they all move together meaning that the outer portion is moving faster than the inner part. There is not enough visible mass for it to do this.

DA
Yes, I know the theory is dead (for now - "...in the future this mechanism leads to a decelerated cosmic expansion described by the well-known Einstein-de Sitter cosmological model." - see link below), but I realised that I hadn't given a thought to the physics. I assumed that it would be a reversal of the expansion of space but, taking what you say as correct, it would not be. It would just be a gravitational collapse within space. Finally, there would be a black hole, which would evaporate by Hawking radiation, right?

Even so, what would be the effect on the curvature of space? Is it possible that space would 'contract' owing to the increasing density of matter?
_______

Mike

"Nobody can answer with any certainty the future of the Universe."

- That's for sure, but the physics of the hypothetical alternatives is very interesting.

"Yet is the reason our Milky Way Galaxy is expanding, due to a Universe of lesser density surrounding us?"

- Is the Milky Way expanding, Mike? I understood that the expansion of space is apparent only on the intergalactic scale, where the effects of gravity are too weak to overcome it. Intragalactic gravity prevents galaxies from expanding. Groups of galaxies are also held together by gravity. The Great Attractor is a good example of gravity overcoming the expansion of space over hundreds of millions of light years.

"Then theoreticaly, expansion to a lesser density should stop"

- I think there's something conceptually amiss there, Mike. What's your basis for the idea that overall decrease in density decreases the expansion of space?
_______

scpg02
Yes, it's very interesting - and topical:

Source: Observatory of Paris
Date: April 7, 2007
Toward A Unified Description Of Dark Energy And Dark Matter
http://www.sciencedaily.com/releases/2007/04/070407175959.htm

"Science Daily ? From various independent observations, cosmologists have established that ordinary matter, made of protons and neutrons, accounts for only 4% of the total energy content of the Universe. The remaining 96% is made of puzzling ingredients Dark Matter and Dark Energy. Researchers at the Laboratory Universe and Theories from the Observatory of Paris and the Belgian Fonds de la Recherche Scientifique have recently suggested the Abnormally Weighting Energy (AWE) Hypothesis to describe the dark side of the Universe as a revolutionary aspect of gravitational physics...Jean-Michel Alimi and Andr? F?zfa, have proposed the AWE Hypothesis (? Abnormally Weighting Energy ?) in which the dark sector of cosmic matter violates the equivalence principle on cosmological scales."

Hi redewenur,
I'm afraid this is an item where I buck the trend of conventional thinking

Namely 'The Great Attractor' which in my view cannot possibly be attracting our Galaxy, the Milky Way, plus Andromeda, and others, towards itself, by Gravity, over those thousands of light years. Were that true we would see many closer pairs of Galaxies approaching each other. In fact we do not see that, rather most galaxies are all moving away from each other.

Similar to spots painted on the surface of a balloon which is being blown up.

Where I am at odds with conventional thinking is that objects are moving towards the Great Attractor because it is a v large region of particular low density, with a large number of very big Spiral and other Galaxys that make up the Great Attractor.

At first sight, this might seem to be counter intuitive.
Until you realise that all the gases and material in the Attractors area have long ago been condensed down by gravity into the mass of Galaxies that now make up the Great Attractor....leaving a vast region of low density.

Hot may flow to cold, but not in the vacuum of space.

However high density can flow to low density, and operate across the Universe, even better in the vacuum of space.

Globular clusters (probably the oldest collection of stars in the Universe) present some difficulty in accounting for their shape, and formation.

My similar answer to this is - that I personally think Globular clusters will be found to be sitting in an area of low density.

All the original high density gas being 'gravidensed' into what it represents now.

All pictures of gas clouds that Hubble has taken are obviously local regions of a very high density.

You might also note that there are no clouds of matter around any Globular clusters

http://antwrp.gsfc.nasa.gov/apod/ap070218.html
and
http://antwrp.gsfc.nasa.gov/apod/ap061126.html
and
http://antwrp.gsfc.nasa.gov/apod/ap060312.html

I dont like to dismiss the existance of invisible matter, but until someone proves that it actually exists, I personally would rather forget about it, and look for other mechanisms to account for the so called gravity of the Great Attractor.

--------------------
"You will never find a real Human being - even in a mirror."

.....Mike Kremer.
.

Well, Mike, that's original. I totally disagree, because I can see too much evidence against it . All evidence suggests to me that, the effect of expanding space notwithstanding, gravity rules - unless new evidence shows otherwise.

Mike: "Were that true we would see many closer pairs of Galaxies approaching each other. In fact we do not see that, rather most galaxies are all moving away from each other."

- Galaxies do tend to approach each other except when a great enough distance of expanding space between them counters this tendency.

Mike: "Where I am at odds with conventional thinking is that objects are moving towards the Great Attractor because it is a v large region of particular low density"

- It's not an area of "particularly low density". see:
http://www.solstation.com/x-objects/greatatt.htm

"The overdensity of galaxies in the region of the Norma Supercluster was first detected in the 1980s. Although astronomers have since observed a large excess of galaxies with optical and infrared telescopes in this region, no dominant cluster or central peak has been identified. This strongly suggests that a significant fraction of the Great Attractor's overdensity could still be obscured by the Milky Way, possibly in another rich cluster of galaxies around the strong radio-source PKS1343-601"

Ask yourself this: In your theory, why would millions of galaxies stream toward The Great Attractor when other nearby regions are much less dense?

Furthermore, how would your theory account for the string-like, or web-like, large scale structure of the universe? How would those strings of superclusters have formed?

Mike: "You might also note that there are no clouds of matter around any Globular clusters"

- I wouldn't expect to see them. I would expect matter to coalesce into the cluster. As I said there's no evidence to support the theory that matter defies gravity, except where the expansion of space is the dominant factor. That is, unless you have the evidence.

By the way, re: the links - great pictures. I've added them to my collection. Thanks

Hello again Redewenur,

Interesting URL about the Great Attractor you posted. Tnx.

I wonder what you might think, if you were living on a planet within the Attractor? .......Think about this.
.....That the Universe was contracting?

I have no problems were there small pockets of a lower density
residing within the low density areas of the Attractor.
Why? Because-
The Great Attractor area is so huge that any small pockets of a lower density would be evened out fairly quickly.

The drawing in the URL you supplied seemed to give me the impression that the G Attractor makes up approx a 1/6th of the known universe?
Its unbelievably huge.
No wonder millions of Galaxies are moving in, trying to average out the low density pockets left by the loss of the hot gasses from which they were born from.

Every Planet, Sun, or Galaxy, was once a huge mass of hot gas floating in a vacuum. Once gravity gets to work and the gasses coalese into matter and suns, there exists areas of a lower density (where there is no gas) than there was before.

That certainly dos'nt mean to say that the Suns and planets
can't gravitate into small, and then larger galaxies. Contracting and therefore spinning faster as they do so.

Nor did I say or imply that matter defies gravity. I even went as far to show how two particles, each, on the other side of the Universe from each other....sitting in a perfectly even density of vacuum, would eventually coalesce,and bind together using their miniscule gravity alone.

Matter does not defy Gravity. But two galaxies at great distances from each other are far more liable to be attracted to areas of low density, than by gravity. Gravity is a small force that operates over small distances.
Gravity operating upon you from two opposite directions, will cancel out. And show no effect at all.
The Lagrange points between Earth and Moon are two points in question. A tiny puff of air, or a suction tube would move you about with ease, while you were within that area. Thats a practical explanation of high and low density in space.

Another proof that Gravity however strong can cancel out is:-

If you were placed within a 6ft void in the exact center of the earth, you could not detect the force of gravity, although it was very strong, all around you.
You would just float about, and so would anything you threw or dropped. Gravity for you, would not exist.

I repeat that the known Universe is expanding into an area of low density, where the unknown, or no, Universe resides
helped upon its way, by the action of these virtual particles
that pop in and out of every part of the Universe everywhere.

But I am sure we can agree to disagree. And its certainly very interesting to read your comments in this and other parts of the Forum.
Glad you liked the pics.

--------------------
"You will never find a real Human being - even in a mirror."

.....Mike Kremer.
.

Mike: "I wonder what you might think, if you were living on a planet within the Attractor? .......Think about this.
.....That the Universe was contracting?"

- If the research resources on that planet were the same as ours, they should be capabable of reaching the same (correct) conclusions.

Mike: "The drawing in the URL you supplied seemed to give me the impression that the G Attractor makes up approx a 1/6th of the known universe?"

- Not 1/6 (17%), only about 1/370 (0.27%). The Great Attractor is 400m lt yrs across. The estimated size of the universe is more than 150 billion lt. yrs. In terms of volume (in Euclidian geometry!), that's < 1/50,000,000 (0.000002%).

see:
http://www.space.com/scienceastronomy/mystery_monday_040524.html

Mike: "...two galaxies at great distances from each other are far more liable to be attracted to areas of low density, than by gravity."

- I disagree.

Mike: "Gravity is a small force..."

- I agree, it's a weak force - but there's a lot of it

Mike: "...that operates over small distances."

- I disagree, it also operates over cosmic distances (as you know).

Mike: "the known Universe is expanding into an area of low density"

- disagree. It's not expanding "into" anything. There's no "area" beyond it.

Interesting arguments, Mike. Keep it coming. While I disagree with you, I think some of the greatest advances in modern science have there origins in minds that are able to intuit the counter-intuitive!

In science we tend to say things like, "It's this, not that". It's often reasonable to say that as though it were a matter of fact - especially if we happen to experts in the field. Sometimes, what we mean is, "It seems to me most likely that it's this, not that" - especially if we don't happen to be experts in the field. Such is science, right?

Hello again scpg02,

Well you are both right and wrong. The inner core is moving faster than the outer parts, or arms, in all cases.
Its because the arms are gradually spiralling out and wrapping around the central core that we can tell whether a Galaxies motion is clockwise, or anti
This can be verified by checking the small difference in redshift between opposit arms.

It so happens that there are a few, very few Galaxies where you are right. These are rotating with their arms leading into the rotatation.
But its proposed that they been subject to some kind of stressful struggle, with another Galaxy, and like humans, have come out twisted. Hi.

Normal Rotations
http://antwrp.gsfc.nasa.gov/apod/ap040410.html

http://antwrp.gsfc.nasa.gov/apod/ap991206.html

http://antwrp.gsfc.nasa.gov/apod/ap070314.html

Problem rotations
http://www.newscientist.com/article.ns?id=dn1902

http://antwrp.gsfc.nasa.gov/apod/ap020125.html

--------------------
"You will never find a real Human being - even in a mirror." .....Mike Kremer.
.

Mike, I think scpg02 was referring to the fact that the rate of rotation of the outer regions of spiral galaxies in not consistent with the gravitational effects of the amount of visible matter in those galaxies. The dark matter theory accounts for that unexpected rotation rate.

(correct me if I'm wrong, scpg02)

http://www.crystalinks.com/darkmatter.html
Scroll down to 'Galactic rotation'
"...Galactic rotation curves, which illustrate the velocity of rotation versus the distance from the galactic center, cannot be explained by only the visible matter. Assuming that the visible material makes up only a small part of the cluster is the most straightforward way of accounting for this. Galaxies show signs of being composed largely of a roughly spherical halo of dark matter with the visible matter concentrated in a disc at the center..."

Those 'Problem rotations' are interesting!

Redewenur ... scpg02 is correct as is, I believe, your understanding of the issue.

Without dark matter galaxies don't work, in theory, as they obviously work in reality.

My guess ... axions. But we will just have to wait a bit longer for CERN.

Now I'm going to have to read about axions

Incidentally, from what I've read about the 'velocity curves' of spiral galaxies, they are almost flat. That means that, from the core outward, the observed velocity of rotation is about the same. The spiral arms are the result of the orbit sizes, but not of velocity differential.

Try these:
http://web.mit.edu/~redingtn/www/netadv/specr/345/node3.html
http://web.mit.edu/~redingtn/www/netadv/specr/012/012.html
http://www.astro.princeton.edu/~dns/MAP/Bahcall/node16.html
http://www.osti.gov/bridge/servlets/purl/572563-WFWpIu/webviewable/572563.pdf

Greetings!

Dark matter has been proved to exist in recent observations of the bullet cluster:

http://chandra.harvard.edu/press/06_releases/press_082106.html

The galactic rotation curves are a problem and can be solved by two popular ideas:

1) Dark matter component - more popular
2) MOND - Modified Newtonian Dynamics - less popular, but it doesn't require dark matter.

No one really argues about the existence of dark matter anymore, everyone just argues about what it is. The most likely candidate for dark matter is probably supersymmetric particles (neutralinos in particular). The 511keV emission line from the galactic centre region would be hard to explain without dark matter, but it also hints at what the dark matter might be. It has been suggested that the population of positrons at the galactic centre could be the result of neutralino decay.

LHC will be a great advance in looking for dark matter candidates, but we'll have to wait a little longer for it: http://www.timesonline.co.uk/tol/news/uk/article1626728.ece

I won't explain the link since the page does it well, but this is very nice and relevant to this discussion. - http://www.mpa-garching.mpg.de/galform/millennium/

Thanks,
Durante.

Anyone seriously interested in the subject might want to check this out:

http://www.ftpi.umn.edu/dsu07/

Durante, thanks for the info and the link for those amazing videos.