What is happening in distant galaxies like Andromeda at present?

[asimations]

the light of stars we c comes to us with delay. Depending upon the distance we observe the past of this universe. My question is what is happening in the distant stars like andromeda at present? Can we know it? Secondly a big event in our universe like big crunch might have already set in but it will come to us very suddenly as we are blindfolded in the past

 

[Vanadium 50]

We won't know what is happening today in the Andromeda galaxy for almost two million years.

There is nothing new about this - you can't find out about an event a mile away until 5 nanosecond later. It's just a matter of degree, because stars are really, really far away.

 

[russ_watters]

Secondly a big event in our universe like big crunch might have already set in but it will come to us very suddenly as we are blindfolded in the past

Unlikely - we know if a big crunch happens, it won't happen for a long time.

 

[asimations]

doesnt that mean that our knowledge is very old

 

[asimations]

why the crunch will not take very long will those events be faster than light?

 

[Drakkith]

Current evidence supports that the universe is no where close to a big crunch. Even taking into account the delay in seeing things.

 

[Drakkith]

doesnt that mean that our knowledge is very old

Yep. Which is why astronomers say that looking at galaxies billions of light years away is looking into the past.

 

[asimations]

i would like to know the evidence that suggests a big crunch not happening soon can you elaborate that further

 

[russ_watters]

i would like to know the evidence that suggests a big crunch not happening soon can you elaborate that further

The rate of observed expansion is too fast.

 

[asimations]

one more thing that confuse me is that big bng happened 13.7 billion yrs ago and the farthest star is 46 billion light yrs from us it means that it traveled faster than light initially ? Can anyone explain

 

[Kracatoan]

one more thing that confuse me is that big bng happened 13.7 billion yrs ago and the farthest star is 46 billion light yrs from us it means that it traveled faster than light initially ? Can anyone explain

Yes, whoever said that it was 46 billion light years away is wrong.

 

[asimations]

then what is the true distance

 

[Kracatoan]

Well the true distance is just however old we think the universe is, in light years. And because we think the Universe is ~13.7 billion years old, we can only see stars up to 13.7 billion light years away. You can't have anythink further away than that, otherwise the light from that star would have had to have been traveling faster THAN the speed of light, which is obviously not true.

Yes, I know stars were formed a little after the Universe appeared, but that would have been an unnecessary irritant.

 

[russ_watters]

Perhaps they were extrapolating how far it has moved in the past 13.1 billion years - expansion of the universe can happen faster than light. In any case:

Astronomers have spotted the most distant object yet confirmed in the universe – a self-destructing star that exploded 13.1 billion light years from Earth. It detonated just 630 million years after the big bang, around the end of the cosmic "dark ages", when the first stars and galaxies were lighting up space.

http://www.newscientist.com/article/dn17035-most-distant-object-in-the-universe-spotted.html

 

[asimations]

well thanks for correcting me a good news in this article

 

[Drakkith]

When we see something that is 13 billion light years away, the light from that object has traveled 13 billion light years. However, since the universe is expanding, the object has since moved away from us. I'm guessing that they extrapolated the 46 billion light years by calculating the rate of expansion from the past until now.

 

[Chronos]

It is an extrapolation as mentioned. 46 bly is the estimated distance now of the surface of last scattering. It is strictly theoretical and depends on a number of assumptions.

 

[asimations]

as all the matter came into existence at once is it possible that the farthest stars have evolved into solar systems like ours

 

[Radrook]

the light of stars we c comes to us with delay. Depending upon the distance we observe the past of this universe. My question is what is happening in the distant stars like andromeda at present? Can we know it? Secondly a big event in our universe like big crunch might have already set in but it will come to us very suddenly as we are blindfolded in the past

We see the sun as it was approx 8 minutes ago. So if the sun were to blink out we would continue to be unaware of it for the ensuing eight minutes. If the star Proxima or Alpha centauri were to blink out, we would see it approx four years later. If a star at approx galactic center were to blink out now, we would see it approx 36,000 years later since that's our distance in light-years from the galactic hub. Depending on the light year distance we see events as seemingly occurring now.

As for a big Crunch, cosmologists have detected an accelerating universe and not one which is decelerating under its own gravity. That makes a Big Crunch very unlikely. In fact, it forebodes a time during which the light from the distant galactic clusters and super clusters will no longer reach us since beyond the the detectable universal edge expansion will have exceeded the speed of light making detection an impossibility because the light will never be able to traverse the distance between us and that source.


However if a Big Crunch were in progress right now then then we would detect its commencement billions of years later. As the crunch would get closer the detection time would shrink correspondingly in accordance with the time the light is taking in reaching us. Remember, the light would always get to us before the crunch does unless the crunch is due to the collapse of space itself.

In that case the crunch could very well accelerate and exceed the speed of light and we'd get hit before detection. But since the crunch is thought to be gravitationally induced that isn't the case unless gravity can induce supraluminal acceleration of matter and such acceleration of matter itself is not possible in our universe according to the Einstein equation.

 

[Drakkith]

Radrook, if the big crunch were taking place, or about to take place, we would know as we would be part of it and not observing something from billions of lightyears away. As we have only observed an expanding universe, we can say that we are not about to have a big crunch take place.

 

[Radrook]

Radrook, if the big crunch were taking place, or about to take place, we would know as we would be part of it and not observing something from billions of lightyears away. As we have only observed an expanding universe, we can say that we are not about to have a big crunch take place.

If we depended on observing our local situation within our galactic local cluster or super-cluster to determine universal expansion or crunch, then the overall impression would be that we aren't part of any universal expansion because within such clusters gravity predominates.

It's only when we observe the overall universal relation among super-clusters that we can begin to apreciate that the universe as a whole is expanding. So for that purpose local observation is useless. Just as universal expansion doesn't overpower local gravitational predominance within galaxies and galactic clusters so too a universal crunch at the outset will not overwhelm local gravitational predominance.

Therefore if indeed it has commenced right "now" as opposed to the relative "now" dictated by light-speed limit, we could be totally unaware of it because the red shifting light leaving those far flung areas is still reaching us before the blue-shifting light coming in after it from those far flung superclusters.

Remember, the local super-cluster and its cluster members are bound gravitationally. So everything within such a cluster will continue to appear normal until the light from the super-cluster surrounding it blue shifts indicating a universal crunch process.

 

[Drakkith]

If we depended on observing our local situation within our galactic local cluster or super-cluster to determine universal expansion or crunch, then the overall impression would be that we aren't part of any universal expansion because within such clusters gravity predominates.

It's only when we observe the overall universal relation among super-clusters that we can begin to apreciate that the universe as a whole is expanding. So for that purpose local observation is useless. Just as universal expansion doesn't overpower local gravitational predominance within galaxies and galactic clusters so too a universal crunch at the outset will not overwhelm local gravitational predominance.

Therefore if indeed it has commenced right "now" as opposed to the relative "now" dictated by light-speed limit, we could be totally unaware of it because the red shifting light leaving those far flung areas is still reaching us before the blue-shifting light coming in after it from those far flung superclusters.

Remember, the local super-cluster and its cluster members are bound gravitationally. So everything within such a cluster will continue to appear normal until the light from the super-cluster surrounding it blue shifts indicating a universal crunch process.

Then the closer galaxies would be less red shifted than they are now. Unless you are talking about a sudden stop to the expansion and a reversal on the scale of a few million years. We currently have no reason to believe that is the case as everything we observe is that the expansion is accelerating.

 

[Chronos]

The current observed mass density of the universe is indistinguishably close to zero. This density is called Omega. If Omega is less than one, the universe does not have enough mass density to recollapse. This is called an open universe. If Omega is greater than one, the universe will eventually succumb to gravity and recollapse. This is called a closed universe. If Omega is exactly one, it will neither expand or collapse. This is called a flat universe. The current observed value of Omega slightly favors the closed model, but, is too close to call with any certainty.

 

[Radrook]

Then the closer galaxies would be less red shifted than they are now. Unless you are talking about a sudden stop to the expansion and a reversal on the scale of a few million years. We currently have no reason to believe that is the case as everything we observe is that the expansion is accelerating.

I didn't say that we currently have reason to believe that a reversal has taken place. In fact, I clearly pointed out that all things indicate an accelleration of the expansion caused by the mysterious dark energy wjich is currently believed to compose most matter in the universe. Neither did I postulate a sudden stop since such a sudden stop goes completely contrary to all known laws of nature. As it stands the universe falls short of the critical mass necessary to stop the expansion and reverse it by two-thirds of the required matter even if we include dark matter in the equation. I merely pointed out that whatever data we are able to analyze is data that informs us of the past which is perceived as the subjective present and not of the nonobservable objective/present which is independent of the perceiver.

 

[asimations]

when we talk of big bang we say expansion faster than speed of light why can't the crunch be faster the same way and arent the black holes a pre_crunch event

 

[russ_watters]

Well it could, but why would we assume something for which we have no evidence and which is contrary to a theory that the evidence we have supports? What you're saying is like suggesting the sun could fail to rise tomorrow. Yeah, we don't know for sure it will until it happens, but there is no reason to believe it won't.

 

[Radrook]

when we talk of big bang we say expansion faster than speed of light why can't the crunch be faster the same way and arent the black holes a pre_crunch event

So what you are saying is that a superluminal crunch could hit us before detection by commencing and accelerating far beyond the speed of its own light in the undetected and undetectable part of the universe--correct?

 

[asimations]

well i think so but by undetectable i mean what we see today as the farthest universe

 

[Radrook]

well i think so but by undetectable i mean what we see today as the farthest universe

If we see it then we detect it and its not undetectable. Undetectable would be beyond what we can detect and that region can be to the detectable what our detectable universe is to an atom especially with the discovery of the dark energy which could have vastly increased the initial Big Bang expansion and drastically reduced the time needed for the universe to reach it's "present" expansion stage.

So based our conclusions about the undetectable on what's going in this minute detectable part might very well turn out to be hasty conclusion based on unrepresentative or scanty evidence relatively speaking. That's why it's best to refrain from being too sure of what's happening beyond that detectable point. Sure, we can say "Well, if what we detect can be extrapolated to what we don't detect then such and such is the case." But that is still an educated guess and nothing more. Agreed?

 

[asimations]

Sorry due to language barrier may be I couldn't express what I meant. Question is unrelated to detectable or undetectable. You are absolutely correct in this regard.I wanted to say that the farthest edge what we see and think 13.7 byrs away ofcousre detetcable, but only its past, its present not detectable. This might have started to come back initiating the crunch. The rate of expansion may be fast which negates the possibility of crunch. But isn't that a finding of the past? And the nearest galaxies may even be expanding before a crunch comes back and hit them.