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Thread: Universal Inevitability

  1. #1 Universal Inevitability 
    Bud
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    Since the beginning of time, all matter has raced to join with other bodies of matter, by way of gravitational forces. We can speculate, that galaxies range in all sizes, and even collide with other galaxies by way of gravity. Now think about it, those are the facts. There is unlimited space out there, but everything is bound by gravity. No galaxy in this universe is unaffected by another. Galaxies will only get bigger, and bigger, and bigger. This is inevitable, this is not refutable, I'm sorry.


    Taking those facts into consideration, I would speculate that in the end, gravity will create two super giant eliptical galaxies,, also bound by gravity to eachotherbut in harmony, this being the 2nd stage of the universe, the real multi-verse, the entire universe devided into 2 bodies. These two bodies, after billions and billions of years of new stars being formed, intertwining the 2 bodies, enough so that in the end, gravity will bring everything together, to start over the big bang, again.


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    Moderator Moderator Janus's Avatar
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    Quote Originally Posted by Bud View Post
    Since the beginning of time, all matter has raced to join with other bodies of matter, by way of gravitational forces. We can speculate, that galaxies range in all sizes, and even collide with other galaxies by way of gravity. Now think about it, those are the facts. There is unlimited space out there, but everything is bound by gravity. No galaxy in this universe is unaffected by another. Galaxies will only get bigger, and bigger, and bigger. This is inevitable, this is not refutable, I'm sorry.

    Yes this is refutable. For one, all our measurements show that except in a few cases, the galaxies are flying apart from each other. Not only that, but this expansion is actually [i]accelerating with time.

    But even if we neglect the acceleration, It still is not inevitable that the universe will collapse in on itself due to gravity. This depends on the mass of the universe and the energy of the initial rate of expansion. If the initial rate was high enough, the expansion would continue forever, even while slowing over time.

    This is related to the concept of escape velocity. For example, if I throw a rock up into the air, it will usually fall back the ground. The harder I throw it, the higher the rock will travel before it starts to fall back. If however, I were able to throw the ball at a speed of ~11.2 km/sec or faster something different happens. At this speed, the rock climbs so fast that the fact that gravity falls off with distance becomes an important factor. After 10 sec, the rock will have only slowed by ~ 98 m/s (0.09%) and is now ~110 km above the Earth. At this distance, the Earth's gravity will have decreased by 3%.

    The end effect is that the force of gravity slowing the rock down decreases at a greater rate than the rock's speed does, and no matter how long the rock climbs away from the Earth, gravity can never bring it to a complete stop, so that it can pull it back to the Earth.

    The same holds true for the universe. If its expansion rate starts out fast enough, gravity can never pull it back together again. If it was lower than that, it would eventually collapse back in on itself. How fast was fast enough depended on the mass of the universe.

    Now to the acceleration.

    Up until the 1990's this how things stood, we knew that the universe was expanding, but not whether or not the expansion would continue. Then Saul Perlmutter, Brian P. Schmidt, and Adam G. Riess, produced the results of a study they had done. In essence, what they did was compare the distance of galaxies over a large range of distances and compared this to their red-shift, which was a measure of how fast it was receding.

    Since light travels at a fixed finite speed, when they did this, they were also looking back in time. If they were looking at a galaxy 1 billion ly away, they were seeing it as it was 1 billion years ago, and if they were are looking at one 2 billion years ago, they were seeing it as it was 2 billion years ago. By studying a large number of galaxies at differing distances, they could get a plot that would tell them how fast the universe was expanding at different times.

    To be clear here, they were expecting to find that the expansion had decelerated over time. What they were looking for was whether or not this deceleration was enough to ever lead to a re-collapse of the Universe. What they found surprised everyone. It turned out that the universe's expansion hadn't slowed down at all over time, but had actually sped up. Something was pushing the Universe apart. For lack of a better name, they labeled this something "Dark Energy".

    And this is where things are now. We have no idea as to what Dark Energy really is, only the effect it causes.


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    Bud
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    Would it not be correct to assume that every body of mass within space, is currently bound by gravity to something else. A planet to a star, a star to a large group of stars, a large group of stars to another large group of stars, galaxies to other galaxies. Everything should currently be bound by gravity to something else, so if we were all able to continue rocketing into empty space, with no other forces for a single galaxy to be bound to by gravity, then would it not rocket at infinite speeds out to the infinite? I don't think that will happen to any galaxy, or any single star for that matter, and I hope it doesnt, because that would rule out a perpetualy living and dying universe.
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    A planet to a star, a star to a large group of stars, a large group of stars to another large group of stars, galaxies to other galaxies
    Up to the size of the super local group, i.e. 200 million lys. On a scale larger than that, Universal expansion overwhelms gravity, so it's safe to say that while gravitational fields never reach zero, at greater than 200 million lys, there is no longer gravitational binding.
    Its the way nature is!
    If you dont like it, go somewhere else....
    To another universe, where the rules are simpler
    Philosophically more pleasing, more psychologically easy
    Prof Richard Feynman (1979) .....

    Das ist nicht nur nicht richtig, es ist nicht einmal falsch!"
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