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View Full Version : Discussion: Will the Universe Expand Forever?



Fraser
2005-Aug-30, 04:57 PM
SUMMARY: What is the nature of the mysterious dark energy which is accelerating expansion of the Universe? In a recent study published in the Physical Review Letters, physicists are proposing two scenarios: thawing and freezing. In thawing, the expansion of the Universe should eventually come to a stop, and maybe even reverse. In "freezing", the acceleration should continue indefinitely. A new mission: the Joint Dark Energy Mission (JDEM) has been proposed by NASA and the US Department of Energy, and should be able to determine which of these two scenarios is correct.

View full article (http://www.universetoday.com/am/publish/berkeley_scientists_test_dark_energy.html)

What do you think about this story? Post your comments below.

antoniseb
2005-Aug-30, 05:09 PM
I've been looking forward to the SNAP mission for a while. I hope it passes all future budget cuts and produces the kind of data they're hoping it can (thousands of distant SN per year).

Grant
2005-Aug-30, 09:59 PM
If the Universe is expanding why are Galaxies colliding?

Is there some surge effect or is it all down to centrifugal force(S)?

Is antimatter causing differential acceleration / decelleration?

Are there other factors?

Tyrael
2005-Aug-30, 10:07 PM
I think that i some moment Universe will stop and then its going to muster in to one litle atom and then again Big Explosion and so the proces will repeat again

p.s if something is not corretly please forgive me

J. C.
2005-Aug-31, 12:32 AM
To answer a few of your questions . . .

The universe as a whole is expanding, but relatively near galaxies can still interact via their mutual gravitational pull on eachother. For example, the Milky Way will collide with Andromeda billions of years from now because we are close enough to effect each other substantially in this way. So, while nearby galaxies can collide and interact, distant galaxies will always be moving apart because they are too far apart to interact in this way.

Antimatter probably isn't causing acceleration because what is causing the accelaration is difficult to detect and does not interact much with regular matter. We can detect antimatter because it looks the same as regular matter, and the moment it collides with regular matter it annihilates completely. Now that's interaction!

sam_lelime
2005-Aug-31, 02:40 AM
Hmmm, maybe Einstein's cosmological constant falls under a derivative equation with limits i.e a variable constant. which is directly proportional to the level of energy in the universe.. since it is possible to accelerate particles under extreme gravity and pump new energy into the universe in turn matter.. the variable for the cosmological constant could change with that...

that could also explain why it is only 10 billion years old..... and once the constant reach the upper limit, logically it would be a level that interferes directly with gravity on a local level... energy production is lost and the constant will begin to shift towards the lower limits.

before I get hammered by opinions this is just an idea.. I haven't refined it in anyway.

I'll have to check this idea Mathematically... which means more study... and I have two more years before I can do that.. so hopefully by then I can come back to something solid to major in... :)

plakhapate
2005-Aug-31, 06:01 AM
It is necessary to find the properties of DARK ENERGY and record the same.

Over a period of time the variation in properties will tell us whether the universe is Thawing or Freezing or something else is happening.

Only the observations/ measurements will help.

What is to bemeasured has to be decided and to be compared again and again.
Proper KNOWLEDGE MANAGEMENT will help.

With this approach it is possible to find the status of the Univese.

P.J.LAKHAPATE
plakhapate@rediffmail.com

Molecular
2005-Aug-31, 09:00 AM
I just can't help but think that if the universe is expanding, meaning infinately, that it's doing so for good reason. Imagine if, at this very point in time, that everything in the entire universe were still, or just suddenly came to a complete hault. Now, with this in mind, there are quite a number of natural occurances going on in our part of the viewable universe, besides what things we cannot yet see.......stars being born, etc. A lot of khaotic stuff going on out there. It appears to me that in order for such things to occur, such distances between stars, galaxies, and planets are necessary, so that if anything out there (and here) were to survive, it could.

At the point in which a galaxy has drifted off to an area where nothing else exists around it except itself, then maybe this is where another change occurs........possibly, the cycle of a new universe. :huh:

Just my 2 cents. :)

mark mclellan
2005-Aug-31, 12:08 PM
Accepting that the expansion is inevitable, and that every single atom will one day be impossibly far away from the next atom.......we are talking billions of years. Intelligent species will be by then creating thier own stars for power and life itself.........life will stop the universe from completely expanding into nothing....only when life itself is ended does the body it inhabits decay into 'nothing'.........put my name down for this one so that i will be remembered in the future when we reverse the expansion of the universe lol :P :D

Guest_James
2005-Sep-01, 12:05 AM
The expansion of the universe is in clear violation of the law of thermodynamics which states that the total amount of energy in the universe is not changing but remains constant. This is along the same lines as matter can neither be created nor destroyed, but can be converted to energy (in nuclear reactions). Someone needs to go over these assumptions with a fine tooth comb as they are observing the accelerating expansion of the universe. I think dark matter/energy is not a necessary requirement for the expansion of the universe if you could just admit that the exception (universe is observed to be expanding at an increasing rate) proves the theory (matter and energy CAN actually be created and destroyed).

<edited>

Svemir
2005-Sep-01, 06:02 AM
The expansion of the universe is in clear violation of the law of thermodynamics which states that the total amount of energy in the universe is not changing but remains constant.
Not so in Bing Bang Theory.
All energy/matter was created from quantum fluctuations of something
(singularity with infinite density of matter/energy)
As Universe expands forever and on an ever increasing rate, matter/energy density goes to zero (->0, never have to reach zero), total amount of matter/energy remains the same.
It&#39;s the creation of matter/energy (and space) that is in violation with thermodynamics (and other physics laws).
But, it is assumed thet laws of physics, as we know them, break down on such small scales (singularity).

antoniseb
2005-Sep-01, 02:22 PM
Originally posted by Svemir@Sep 1 2005, 06:02 AM
Not so in Bing Bang Theory.
All energy/matter was created from quantum fluctuations of something
Not every model of the expanding universe claims that it started with a quantum fluctuation. Most of us observe that it is expanding, and agree that we don&#39;t know why.

Guest_James
2005-Sep-01, 06:41 PM
Problems I have with the Big Bang Theory:
1) The Laws of Physics prevents the possibility of a singularity of infinite mass and energy from forming, that&#39;s just common sense.
2) If a singularity just popped out of nowhere once, why isn&#39;t it observed to happen in other parts of the universe...even with an extremely small probability of this happening, it should still be observed to happen in other places and times.
3) Why are there no ideas on how to create a singularity of infinite mass and energy in a physics laboritory experimentally, even on a much smaller scale.
4) Let&#39;s focus on the "Big Crunch", the thing supposedly preceding the "Big Bang"
A) It&#39;s impossible for every single star, planet, asteroid, speck of dust, essentially every atom in the universe, to just collide at a point of singularity. (I can&#39;t even hit the bullseye 3 times in a row when playing darts)
B) If this did happen, you would have total annihilation (i.e, all mass converted into light energy), however a Black Hole with an escape velocity infinitely times larger than the speed of light would distort space-time preventing any Bang from ever happening, thereby remaining in a self stabilizing singularity state forever with no external forces being applied to it.

antoniseb
2005-Sep-01, 06:56 PM
Originally posted by Guest_James@Sep 1 2005, 06:41 PM
1) The Laws of Physics prevents the possibility of a singularity of infinite mass and energy from forming, that&#39;s just common sense.
Hi Guest_James, you can believe the universe is expanding without believing that it was once a singularity. Note that I&#39;ve never seen anyone claim it had infinite mass. Also, I&#39;d like to point out that common sense is something that we have based on things we see and experience. The conditions leading to the start of the Universe may have little to do with our common experiences today.

2) If a singularity just popped out of nowhere once, why isn&#39;t it observed to happen in other parts of the universe...even with an extremely small probability of this happening, it should still be observed to happen in other places and times.

Again with this singularity. The universe started and began expanding. We don&#39;t know that there was such a thing as space for it to start in. The conditions in our universe are not guaranteed the same as those it started in.

3) Why are there no ideas on how to create a singularity of infinite mass and energy in a physics laboritory experimentally, even on a much smaller scale.
It&#39;s sounding like you object to the idea of a singularity of infinite mass and energy. I&#39;m saying the expanding universe never had to have that.

4) Let&#39;s focus on the "Big Crunch", the thing supposedly preceding the "Big Bang"
I&#39;m not sure who supposes that. I don&#39;t. I think the Universe started expanding, and will expand forever. No big crunch. Questions related to the Big Crunch don&#39;t matter.

Guest_James
2005-Sep-01, 07:36 PM
I think, in order for the universe to be expanding at an accelerating rate, there must be 1 of two things:
1) Infinite mass and energy would be necessary for the universe to be expanding forever
2) A finite amount of mass and energy would create a universe which expands at an accelerating rate, runs out of energy, and then contracts due to gravitation
3) I believe in intelligent design, and I have my own theories why this is, which, apparently, is illegal for me to discuss here.
Well, it is against the rules, but not illegal. We appreciate that you are extending yourself to discuss your ideas outside of the context of your beliefs. Thank you for the effort.

note, apology to Guest_James, I accidentally removed part of this post. There was nothing wrong with it, I just went into edit instead of quote mode. -A

antoniseb
2005-Sep-01, 08:51 PM
I think, in order for the universe to be expanding at an accelerating rate, there must be 1 of two things:
1) Infinite mass and energy would be necessary for the universe to be expanding forever.
Wouldn&#39;t an infinite amount of mass prohibit any expansion at all? afterall this would mean in infinite amount of force preventing expansion. You keep using this word infinite, and I&#39;m sure you know what it means, but I&#39;m not seeing the path to your conclusions.

2) A finite amount of mass and energy would create a universe which expands at an accelerating rate, runs out of energy, and then contracts due to gravitation
I&#39;m not sure how that follows. Suppose you have a finite amount of mass, such as two billiard balls, and they each were given a finite amount of kinetic energy, enough to be travelling away from each other at 10 meters per second. Do you think they will eventually be drawn back together again? No, they have enough energy to escape from each other&#39;s gravity (and then some).

3) I believe in intelligent design, and I have my own theories why this is, which, apparently, is illegal for me to discuss here.
Well, it is against the rules, but not illegal. We appreciate that you are extending yourself to discuss your ideas outside of the context of your beliefs. Thank you for the effort.

Guest_James
2005-Sep-02, 08:11 AM
My apologies for being against the rules. Just bad ettiquite?

You are totally correct about the billiard balls escaping each other&#39;s gratitational force fields. You made me think about my bad assumptions, thanks.

So the universe has a finite amount of mass, it didn&#39;t start with a singularity, and the universe is expanding at speeds fast enough to escape the net gravitational forces within it.

If the universe has a finite amount of energy, then how come we observe it to be jerking out in all directions? Should I take into consideration electromagnetic and nuclear forces? Should I attribute it to dark matter/energy AKA mass/energy that just exists to make the theoretical match the observed?

I do assume that there are more variables than equations and that makes any future predictions for the universe impossible. Take the idea of three masses colliding into each other at once in a collision...you can predict the resulting tragectories of those masses in terms of probabilities and not absolutes. I assume that predicting the future of the universe is as random as predicting the weather a month or so from now.

antoniseb
2005-Sep-02, 02:08 PM
Originally posted by Guest_James@Sep 2 2005, 08:11 AM
If the universe has a finite amount of energy, then how come we observe it to be jerking out in all directions? Should I take into consideration electromagnetic and nuclear forces? Should I attribute it to dark matter/energy AKA mass/energy that just exists to make the theoretical match the observed?
Does it take infinite energy to cause motion of finite mass?

I do assume that there are more variables than equations and that makes any future predictions for the universe impossible. Take the idea of three masses colliding into each other at once in a collision...you can predict the resulting tragectories of those masses in terms of probabilities and not absolutes. I assume that predicting the future of the universe is as random as predicting the weather a month or so from now.
I&#39;m not sure how the three masses colliding question is part of this. The answer depends on how elastic the collisions are, and the speed at which the collision happens. At the moment though I don&#39;t see how it relates to the Big Bang questions you&#39;ve been asking here.

Guest_James
2005-Sep-02, 03:58 PM
Well, I had this physics professor whom described a collision as being the same thing as the gravitational interaction of two or more masses (ie the earth is constantly colliding with the moon and the sun every second). He also explained how it is possible to find the resulting momentums of two masses colliding elastically (I answered a test question on this so I understand the math), but how finding the resulting momentums of collisions of 3 or more masses leads to infinitely many possibilities (more variables to solve for than equations given). If you put these two ideas together you get chaos in your predictions as far as the future positions of the galaxies goes. I guess this doesn&#39;t preclude from knowing whether the universe will expand out forever as I was originally thinking it would.

Does this make sense or is it bad logic?

antoniseb
2005-Sep-02, 04:14 PM
Originally posted by Guest_James@Sep 2 2005, 03:58 PM
Does this make sense or is it bad logic?
I think it helps explain what you are thinking about.

Stars within galaxies have their trajectories randomized by interactions with other massive bodies within the same galaxy, and that galaxies inside galaxy clusters have their trajectories randomized somewhat by such interactions (though there are some broad statistical tendencies). Galaxy clusters, however, rarely interact very strongly with each other, and will continue to mostly get further and further from all other galaxy clusters as the universe expands.