Re: Time Travel Is Impossible and heres Why!
<div class='quotetop'>QUOTE(\"lucidus\")</div>
This may be off-topic, but this got me to thinking. As the universe expands at an accerlerating pace, our observable universe should get smaller and smaller as other objects move away from us at greater than the speed of light and we can no longer observe them. Eventually, if there is nothing to stop this expansion,the observable universe will shrink to the point that each subatomic particle is unable to \"observe\" or interact with another. In a way, each subatomic particle would exist in its own tiny universe. Weird. But if the expansion continues then eventually even the smallest particles will not fit in the universe.
I am probably wrong about this, but I thought it was interesting anyway.[/b]
I want to use this reply to address something I've noticed on this board.
It seems that many of you think that the expansion of the universe entails all the mass in the universe flying away from some central point. Nothing could be further from the truth.
All the massive things in the universe (galaxies, stars, planets, etc.) are moving according to the forces (mostly gravity) being applied to them. They are not flying away from us through space into some empty space beyond. It may be hard to visualize but space itself is what's expanding here. I'm sure many of you know this already, those that don't can find the "dots on a balloon" example by googling the expansion of the universe. There is no center of the universe. The entire universe occupies the same space (albeit much larger) that the original "cosmic egg" singularity occupied prior to the big bang.
This applies to your statement above, Lucidus. While it is true that constant acceleration will eventually result in (apparent) lightspeed, please remember that the masses themselves are not actually travelling at these speeds in the universe's reference frame. It is the reference frame itself that is changing. Nor is it necessary for the expansion velocity to reach the speed of light before other galaxies begin to disappear. It is the nature of the expansion (see dots on a balloon) that the further from the observer an object is, the faster it's apparent speed. This is the definition of the "observable universe", since there are trillions (probably) of galaxies that are distant enough to be travelling at apparent lightspeed and thus invisible to us.
As an aside, I should say that were we on a planet in one of those distant galaxies, we would notice no high speed, we would observe that on the average, every other galaxy was retreating from us, that the more distant galaxies were retreating faster and that the galaxy known as the milky way is invisible to us because it's moving away at the speed of light.
As for your idea about subatomic particles, sorry man but local effects rule. Although the universe is expanding, we (our bodies) are not (at least not due to the universe's expansion!) Local forces like the electromagnetism holding molecules together overcome the force of expansion. Were it not for the expansion, we would be a tiny fraction smaller because the EM forces would settle at a different equilibrium point. Local gravity is similar. Were it not for the expansion, we might orbit an inch or so closer to the sun.
However if the expansion continues, even at a constant rate (not accelerating), eventually most of the observable universe would be unobservable.
Don't forget that most of the stars you see in the sky with the naked eye belong to our galaxy though, and that the milky way is part of a galactic cluster known as the local group. Members of the local group are orbiting each other and will not be separated by the universe's expansion.
Harte
