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Ok so these days, everything I read about the nature of the universe says that it's expansion is accelerating. Because of this, it is said that the universe may end with everything just ripping apart.
My question is: Why do physicists or whoever think that the universe won't slow down again?
Ok, now, I would like to make sure my understanding of the big bang is correct. Obviously this is a very simple understanding of it and I may be totally wrong here but I guess that's why I am asking.
Is it correct for me to interpret the big bang as something like an infinitely small spinning point, that suddenly explodes in mass, spinning out matter/energy in all directions outward from it's center point?
I ask because if that is how the universe has been formed, then wouldn't it only be natural that some matter would be shot out farther and at a much higher rate than other matter?
Like, if the milky way was somewhat near the center, it would have shot out slowly and "quickly" began deceleration. Whereas a galaxy much farther away from us could be likely to still be accelerating, but eventually slowing down, no? Just like if you put some paint in the middle of a paper plate and spun it at an extremely high rate. What is flung out closest to the center decelerates the fastest, and what is flung out the farthest continues to accelerate longer.
Is my understanding of this incorrect anywhere?
 
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lol shit how do i edit the title
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Korea (South)17174 Posts
what tare you talking tabout
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cant
only mods are able to
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Uhhh if the 'explosion' or big bang is the only thing propelling the galaxies outwards, then there is no force causing any of the galaxies to continue accelerating away from the center. Like, whatever force causes the Milky Way to decelerate should cause further galaxies to also decelerate, even if the effect is smaller. I think this is the surprising part of the expansion, not the fact that some things are further/started out faster.
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Korea (South)17174 Posts
maybe the big bang is still banging and making shit go faster yo
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On April 07 2009 04:48 Rekrul wrote:
maybe the big bang is still banging and making shit go faster yo
That would be my guess. They're just anticipating on the trend continuing.
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I think the theory of expanding-contracting is more popular than expanding-ripping apart? that the galaxy is expanding and at some point will reach some critical limit and then contract again, like with a rubber band; if you stretch it far enough at some point it's going to snap back to its original position (or just rip I guess)....
so I suppose:
expanding universe -> decelerating rate -> eventual contraction
expanding universe -> accelerating rate -> ripping apart
don't know which is correct (if any of them are) O_O!
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On April 07 2009 04:47 bludragen88 wrote:
Uhhh if the 'explosion' or big bang is the only thing propelling the galaxies outwards, then there is no force causing any of the galaxies to continue accelerating away from the center. Like, whatever force causes the Milky Way to decelerate should cause further galaxies to also decelerate, even if the effect is smaller. I think this is the surprising part of the expansion, not the fact that some things are further/started out faster.
Yes and what I am saying is that it will cause them to decelerate, it just hasn't begun to yet.
Basically I don't understand why it's such a big deal to astronomers that expansion is still accelerating.
Unless my understanding is wrong and everything is accelerating, not just the points further from the "center"
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Korea (South)17174 Posts
whats gunna rip anyways? and who cares
we'll b dead
wtf u gunna do about it when ur dead? fancy that astronomers
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Sanya12364 Posts
There is no way to know where the center is, but astronomers seem to think that galaxies are in general spreading out faster.
Currently that means that the matter -> energy conversion is causing matter to move apart faster. The amount of energy being produced is stronger than gravity. I'm not sure what the long term trends are.
Acceleration could be decreasing. In which case there may be an eventual slow down of expansion or even a contraction. Acceleration could be increasing in which case, matter will fly apart faster than ever.
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On April 07 2009 04:52 travis wrote:Show nested quote +On April 07 2009 04:47 bludragen88 wrote:
Uhhh if the 'explosion' or big bang is the only thing propelling the galaxies outwards, then there is no force causing any of the galaxies to continue accelerating away from the center. Like, whatever force causes the Milky Way to decelerate should cause further galaxies to also decelerate, even if the effect is smaller. I think this is the surprising part of the expansion, not the fact that some things are further/started out faster. Yes and what I am saying is that it will cause them to decelerate, it just hasn't begun to yet. Basically I don't understand why it's such a big deal to astronomers that expansion is still accelerating. Unless my understanding is wrong and everything is accelerating, not just the points further from the "center"
I think the main problem here is that... things that are a big deal to astronomers are a big deal because they don't have a lot to be excited about, not necessarily because they're a big deal. They must do the most interpretation of the least data out of any field of science... or anything at all.
I still think the fact that the expansion is still accelerating is surprising and a big deal, because something must be propelling these fringes away from the center in order for the acceleration to increase. Even if something will cause them to decelerate, the fact that they haven't yet, and are still accelerating, is odd, even if that trend reverses itself at some point. This would also imply the whole ripping apart consequence if it continues, which would also be interesting because that implies a non-cyclic fate of our universe (no return to a single point followed by future big bang).
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I'm not really pro at this subject but like moving objects in space never stop accelerating right?
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it was recently discovered that different galaxies expand at different speed = small spinning point that exploded was not ideally round? 
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My question is: Why do physicists or whoever think that the universe won't slow down again?
If there is enough matter in the universe then all that matter has enough mass, causing enough gravity, to make it contract again.
Currently the universe is expanding at increasing velocity and it doesn't look like it has anywhere close to enough to start to contract.
Is it correct for me to interpret the big bang as something like an infinitely small spinning point, that suddenly explodes in mass, spinning out matter/energy in all directions outward from it's center point?
No. The universe is expanding and if you calculate back everything it came from one single point. It's not a singularity that exploded or spewed out matter. The universe isn't expanding right now because the outer shell of stars is being thrown away from the center. No, the space between the stars is increasing. Ignore the matter in the universe itself. The universe itself inflated from a single point into what it is now. During all that time a lot happened to the matter inside the universe. But that's a different issue.
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On April 07 2009 04:49 Xeris wrote:
I think the theory of expanding-contracting is more popular than expanding-ripping apart? that the galaxy is expanding and at some point will reach some critical limit and then contract again, like with a rubber band; if you stretch it far enough at some point it's going to snap back to its original position (or just rip I guess)....
so I suppose:
expanding universe -> decelerating rate -> eventual contraction
expanding universe -> accelerating rate -> ripping apart
don't know which is correct (if any of them are) O_O!
contraction is not part of an expanding universe you mean total loss of entropy or freeze over which is the consensus of how the universe will end.
Really both gives the same result total loss of entropy leads to even the 4 main powers in the universe loosing their ability to hold anything together.
speeding up leads to a state at which the 4 powers are overpowered and all matter is torn into nothingness
Really they are the same results.
Only reason why there is a theory of speed up is that dark energy is currently release its energy causing an acceleration of the expansion, it has been known for quite some time that with the creation of the universe that there is dark energy to a fineamount that will always be around it's just not until recently that it's realse of energy has been noticed.
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United States581 Posts
You know what escape velocity is, right? It's the velocity an object must be travelling in order to ecape the pull of the gravity of any given mass.
We can measure the rate of expansion of the universe (if you want more details, ask), so the theory is, if the universe is expanding faster than its own escape velocity, then it will never compress back down to the original size from just before the big bang. Seems like a straightforward problem, right?
Well, that's where the whole thing with "dark matter" comes in. "Dark matter," put simply, is matter that we cannot detect by typical means. Obviously, this puts a significant hurdle in the problem of figuring out whether or not the universe will expand forever or not, because it means we cannot accurately estimate the total mass of the universe.
On April 07 2009 04:49 Xeris wrote:
I think the theory of expanding-contracting is more popular than expanding-ripping apart? that the galaxy is expanding and at some point will reach some critical limit and then contract again, like with a rubber band; if you stretch it far enough at some point it's going to snap back to its original position (or just rip I guess)....
so I suppose:
expanding universe -> decelerating rate -> eventual contraction
expanding universe -> accelerating rate -> ripping apart
don't know which is correct (if any of them are) O_O!
As I understand it (and I am by no means an expert on this subject), the bolded is correct. The reason for that is the gravity of the universe is constantly pulling inwards on itself, causing the expansion to occur at a decelerating rate. I could be wrong though.
However, whether or not the universe will contract is dependant on more than just the decelerating rate. It's also dependant on how fast the universe is expanding currently, as I mentioned above.
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On April 07 2009 05:13 Zoler wrote:
I'm not really pro at this subject but like moving objects in space never stop accelerating right?
they should, because of gravity
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ok this is starting to get a little more complicated hehe
will read up when im done doin my yoga !
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EPT
