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Space

The Disappearing Universe 358

Posted by Soulskill
from the and-for-my-next-trick dept.
StartsWithABang writes: "If everything began with the Big Bang — from a hot, dense, expanding state — and things have been cooling, spreading out, but slowing down ever since, you might think that means that given enough time (and a powerful enough space ship), we'll eventually be able to reach any other galaxy. But thanks to dark energy, not only is that not the case at all, but most of the galaxies in our Universe are already completely unreachable by us, with more leaving our potential reach all the time. Fascinating, terrifying stuff."
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The Disappearing Universe

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  • by X10 (186866) on Wednesday June 04, 2014 @07:37AM (#47163417) Homepage

    How can that be? I thought nothing could go faster than the speed of light.
    Or does the universe not have to obey it's own rule?

    We're talking about expansion of space itself, not about a body traveling in that space.

  • by Anonymous Coward on Wednesday June 04, 2014 @08:25AM (#47163667)

    For Andromeda, just wait (very long term stasis recommended) it's comming at us, not sure it's a good thing.

  • by bhagwad (1426855) on Wednesday June 04, 2014 @08:48AM (#47163829) Homepage

    The speed of light in a vacuum is always c. It doesn't matter if you're moving at 0.9c. If you shine a torch of light ahead of you, it will still move at speed "c".

    What is meant here however is that there is no limit to how fast space itself can expand. So say we have two ends of a ruler 1 meter apart. After a while, space itself would expand meaning that the ruler will now be longer than what it was. There is no theoretical limit to how fast this can happen. It can be greater than c.

    After a while, the space between the nucleus and electrons or within the nucleus itself will become too large, ultimately ripping apart for the fabric of reality itself.

  • by luis_a_espinal (1810296) on Wednesday June 04, 2014 @10:13AM (#47164443) Homepage

    That's not right; only from the light's perspective maybe.. it's still "only" traveling at 186kmph a second, it's not truly instantaneous. And I've never heard of the theory that suggests that if a person leaves earth and travels near light speed he'll be younger when he returns. He might not have aged, but not younger... unless he actually exceeds light speed.

    Probably it was some type of a typo where he meant the returning brother is way younger than the brother that stayed (as opposed to just being "way younger" as stated in the OP's poorly worded response.)

    Also, and playing Devil's Advocate a bit more, when the OP wrote this:

    The time for light to travel from Earth to Andromeda is, essentially, zero (0) seconds

    I'm reading it as the time that light (or anything travel AT the speed of light) "experiences" traveling from Andromeda to the Earth (or pretty much from any point A to any point B) is zero because of time dilation. True, it will take 2.5 million years (when measured from the POV of an observer not traveling at relativistic speeds), and travel is not instantaneous, but the traveler itself will experience time at a complete stoppage when travelling at the speed of light (or falling down a singularity) regardless of having traveled one inch or the entire width of the observable universe.

  • by PvtVoid (1252388) on Wednesday June 04, 2014 @10:30AM (#47164641)

    No. That would be assuming you can go faster than the speed of light, without limits, which isn't the case.

    Even if you were a massless particle, you would reach the speed of light in less than 1 year of accelerating at 1G, and then, you wouldn't be able to go faster.

    Nope. GP was correct: note he said 30 years ship time You can accelerate at 1G indefinitely and you won't exceed the speed of light. You will asymptotically approach the speed of light, and time dilation will make the trip seem very short to the crew on board the ship.

    Now calculate the reaction mass required.

  • Re:terrifying? (Score:4, Informative)

    by Jeremy Erwin (2054) on Wednesday June 04, 2014 @11:19AM (#47165057) Journal

    pardon me. I get my science from xkcd [xkcd.com], which recently stated:

    Suppose there are 40 billion habitable planets in our galaxy, and every one of them hosts an Earth-sized population of 7 billion Ted Olsons.

    There's your quadrillion. Are you a fan of hive minds?

  • by Rufty (37223) on Wednesday June 04, 2014 @11:42AM (#47165263) Homepage
    There was a young lady named Bright,
    Who could travel, faster than light.
    She went out one day,
    In a relative way,
    And returned the previous night.

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