Has the "Big Crunch" already started?

Question

I rephrased my question in the space category, and now I'm trying Physics. I received a lot of good answers, but I don't think anyone addressed my core thoughts. If the most recent info about our history is from the closest galaxies (because their light would reach us earlier than the distant ones), and the closest galaxies are not moving away from us (I'm not positive this is true), doesn't that mean that the "Big Crunch" may have started, or at least the expansion is slowing down? Why would the "Red Shift" from distant galaxies be a more reliable indicator of increasing expansion?

Answer 1

I tried answering the other question, but will try again.



Imagine a huge sheet of rubber with ants crawling of it. Now imagine that the sheet is being stretched and that the ants are crawling fairly slowly. On average, two ants will be moving away from each other due to the stretching of the sheet and those ants that are farther away from each other will be moving away from each other faster. However, if you have two ants that are fairly close, they can be moving closer to each other because of the way they crawl., even though the sheet is being stretched.



This is what happens with galaxies in the universe. Space itself is like the rubber sheet. The overall expansion of the universe is like the stretching of that sheet. However, each galaxy is also moving in space (like the ants crawl). The result is that galaxies that are far away from each other are moving away from each other faster on average. But those that are really close to each other can be moving togethe rbecause of their peculiar motion (the crawling) even though the space itself is stretching.



Now, if you want to get an accurate picture of the expansion, it is best to look at galaxies that are far apart since the crawling will be overwhelmed by the stretching. In reality, some close galaxies are moving closer to us and others are moving away, but this is mostly because of the crawl part of the motion.

Answer 2

The Universe would not just suddenly reverse direction. You would see it slowing down to a standstill over a period of millions or billions of years. As someone already pointed out, our current observations show the expansion of the universe accelerating, not slowing. The cause of this is not known, though a new hypothesis has "dark energy" (some kind of anti-gravitational fundamental force) as the culprit. This is supported by the mysterious acceleration of the Voyager craft as they get farther away from the solar system.



So, while it's not impossible that there will be a Big Crunch at some point in the distant future, it's pretty unlikely (as in virtually impossible) that it has already started without us noticing it.



I also recall reading some theoretic physics hypothesis (probably in A Brief History of Time) that states, unless I misinterpreted it (very possible!), time itself would go in reverse during the big crunch because entropy would decrease. So you might know the Big Crunch has started if reality starts to re-wind :D

Answer 3

I think that if the Big Crunch had started the math would show it. Thing is that by the numbers the light or history as you called it travels at a constant speed. It can not fluctuate. So that being said it simply means that if they can measure the speed of the light they can calculate its distance from us. If each time the number is larger then that would mean that it still is expanding. It it were get get smaller then that would mean it is contracting.



As for the red shift I am not very familiar with it. I am going to have to do some studying on this.

Answer 4

It depends on if there is an open or closed universe. If Einstein was right then it is an open universe and will continue to expand and there will be no crunch.

The main thing is: the human race has not existed long enough for pratical observation. It is all pure theory.

Answer 5

No, in fact the universe is expanding faster than ever and may never even have a big crunch. Scientists are still not sure why the faster exapnsion.

Answer 6

The negative merit of Big Crunch is that, something, if not 'we', can start all over again.

But the evidence of that the Big Crunch has already started is none,( or are few.)

One would not see the "Blue Shift" in ones life time.(or never.)

Answer 7

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Answer 8

2012 man -- 2012

Answer 9

no dear