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Help an idiot understand

  1. May 23, 2003 #1
    alright, im only in middle school and not that smart so dont laugh at my question.

    [?] I read some other response to a post about a worm hole saying that if you reach the speed of light time will stop. But wouldnt that mean that only time for you would stop. Saying that everything around you would be going normal speed because the universe doesnt revolve around how fast YOUR going. anyway saying that you could get close to the speed of light where time would be going slower than the surroundings and there was some way to just stop. wouldnt that mean that when you did stop you would end up way ahead in time from when you started because all of the surrounding would be going way faster than you? im confused! someone help me understand what would happen! [?]
  2. jcsd
  3. May 23, 2003 #2
    I'm in middle school too!

    For a you, yes. So a photon from the big bang is still the same 'age' as it was then now.

    Um, can you say that again? I don't understand what you're trying to ask.
  4. May 23, 2003 #3
    sorry 4 the confusion

    what i was asking is...

    if you could go almost the speed of light and time would go slower for then STOP wouldnt you be farther into time (the future) because while your were going slow the rest of the universe was still going its normal speed
  5. May 23, 2003 #4
    The rest of the universe has speeds that are all relative. The expanding of the universe on the other hand is apparently c (c is a constant that specifies the speed of light, which is ~186,000mi/sec).

    Well, if you're traveling at the speed of light, time does not flow, on account of the fact that you are using all your energy to travel in 3D space, and not the usual 4D space. So, if you stop, you would have not aged or anything, so you'd be in the future.
    Personally, I don't believe saying you've arrived in the future is right; you didn't skip your whole life and arrived in the future. You just traveled so fast that time didn't flow for you.

    I should also like to point out that light is not relative, and is the same for all observers.

    see, it isn't that complicated!
  6. May 23, 2003 #5
    Yes, that's pretty close. Say you were to leave earth in a spaceship and travel to alpha cenaturi, 4 light years away, and travel at 90% the speed of light.
    v = .90 x 3x108 meters/second = 2.7x108 m/s.
    γ for this velocity is:
    γ = 1/(1-(v/c)2)1/2 = 2.2942
    the time on the earth while crew to go to apha centauri is v=d/t => to=d/v = (4light years * 9.461x1015m/ly)/(2.7E8m/s) = 1.4016x108seconds or 4.44 years.
    t = to/γ = 1.94 years.
    so after travelling for 1.94 years the travellers will be in a universe where the earth is 4.44 years older. If they were to make a round trip of it, they would age about 4 years while the earth they returned to would be 8.8 years older.
    Last edited by a moderator: May 23, 2003
  7. May 24, 2003 #6


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    Right, so if ure, hypothetically, traveling at c, and you travel a round trip of 10 light years, the people on earth will have aged 10 years and their life will have changed by 10 years, but to you it would be as if nothing had happened, and you are still the same age as when u left.
  8. May 24, 2003 #7
    I'll answer this in a bit less technical terms than others, since you're in middle school.

    1. If you and your twin, who were born at the same time, stand next to eachother on your lawn, and then you fly off into space at, let's say half the speed of light, and you take a tour around some planets, and come back, your twin will be ALOT older than you. So yes, if you go "fast" (speed of light speeds) and then stop, the things you once knew will be alot older.

    2. If you travel at the speed of light exactly, time does stop. Let me give you an awesome explanation from the book THE ELEGANT UNIVERSE....

    There are 4 dimensions. An object, a mass, has a given amount of motion it can exhibit within these 4 dimensions combined. It can use them in any of the dimensions it chooses, but it only has a certain amount to use. Let's say you have 100 units of motion you can use.

    If you're sitting still, in a chair, you're not using any motion in the 3 spacial dimensions. Thus all 100 units are in the time dimensions, and so you are moving through time at the maximum motion.

    But, let's say you travel half the speed of light, flying around the solar system. Then you are using 50 units in the spacial dimension (because the 100 units equal the "motion" of light or speed of light), so you are now only using 50 units in the time dimension. Thus you are moving through time at half the motion, or speed. And thus you will "age" half as fast.

    So in conclusion if you used all 100 units in the spacial dimension, meaning you are traveling exactly at the speed of light, none of your units are in the time dimensions, and so you are not aging at all whatsoever.

    This is why the light that first exited the big bang, is still the same age it is now. It's always gone at 100 units, and thus has never aged at all!

    Let me know if that helps!

    Great that you're thinking about these things at such a young age!
  9. May 24, 2003 #8
    thanks everyone!!!!!!!! i understand now!!!!!!
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