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Originally posted by auujay If you move the Earth 800 light years and the blackhole 800 light years so the meet in the middle then the total time will be 800 years (obviously moving at the speed of light) to cover the 1600 light years.

Not really. You see, that's the funny side of relativity. Regardless of the reference frame it will always take a minimum of 1600 years for two objects that are 1600 light years apart to reach each other. If we take a spot that's right in between those two objects (the Earth and the hole), they will both seem to move towards that point at the speed of light, but their speed relative to each other will also be equivalent to the speed of light. Sounds impossible, but that's the way it is, because every reference frame is equally valid and in each reference frame no object can go faster than light.

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1+1=10

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Originally posted by occrider OMG who won american idol??? I NEED TO KNOW THIS!!!!

Ummmm.....Carrie Underwood, with a close second by Bo Bice....shoot me...please.

Well, let's blow up France at least for starters!


[[[smoke]]]

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Originally posted by DrUg_Tit0 Not really. You see, that's the funny side of relativity. Regardless of the reference frame it will always take a minimum of 1600 years for two objects that are 1600 light years apart to reach each other. If we take a spot that's right in between those two objects (the Earth and the hole), they will both seem to move towards that point at the speed of light, but their speed relative to each other will also be equivalent to the speed of light. Sounds impossible, but that's the way it is, because every reference frame is equally valid and in each reference frame no object can go faster than light.

forgive my ignorance, but i'm still at a loss to understand how this is possible... two objects simultaneously moving towards eachother can never exceed the speed of light..

So the light from one Alpha Centauri (or however you spell it) takes 4.35 years to reach earth.. and the light from the sun 4.35 years to reach Alpha Centauri... now, wouldnt the light from either star intersect at a point 2.175 light years from earth as it travels through space?????

That makes more sense to me, but I'm an science/physics noob..

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A witty saying proves nothing.
-Voltaire

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Originally posted by Dupz forgive my ignorance, but i'm still at a loss to understand how this is possible... two objects simultaneously moving towards eachother can never exceed the speed of light.. So the light from one Alpha Centauri (or however you spell it) takes 4.35 years to reach earth.. and the light from the sun 4.35 years to reach Alpha Centauri... now, wouldnt the light from either star intersect at a point 2.175 light years from earth as it travels through space????? That makes more sense to me, but I'm an science/physics noob..

They can't exceed the speed of light because it is constant in every reference frame. You see, if I move towards you at 0.9 the speed of light, and emit a lightwave (like turning on a flashlight), the lightwave won't move towards you at 1.9c, but at c. It will also move away from me at c. Basically it's because relatively accelerated reference frames have time flowing differently than those which are nonaccelerated. In other words, if I sped up to nearly the speed of light, time would flow slower for me, thus making it seem from my position that light is traveling faster than it seems when viewed from your position.

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1+1=10

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Originally posted by DrUg_Tit0 They can't exceed the speed of light because it is constant in every reference frame. You see, if I move towards you at 0.9 the speed of light, and emit a lightwave (like turning on a flashlight), the lightwave won't move towards you at 1.9c, but at c. It will also move away from me at c. Basically it's because relatively accelerated reference frames have time flowing differently than those which are nonaccelerated. In other words, if I sped up to nearly the speed of light, time would flow slower for me, thus making it seem from my position that light is traveling faster than it seems when viewed from your position.

Right, but doesn't that only reflect the relative velocities with respect to an observer on either object or an independant observer not in motion? As in if both objects are moving at .9c, The light eminating from both objects wouldn't be 1.9c but c. However, both objects are still travelling at velocities of .9c and regardless of how they "look" they are still moving across an equivalent distance of space given their velocities? Hmmm am I making sense?

Edit: In other words, relativivity only dictates the measured and observed speed of light for every reference frame. If we were both driving cars towards each other at .6c, it wouldn't look like you were approaching me at 1.2c. However, I am still moving at .6c and you are still moving at .6c, and we still cover the distance proscribed by that speed independant of one another.

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Retro ...

Last edited by occrider on Jun-07-2005 at 19:06

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Originally posted by occrider Right, but doesn't that only reflect the relative velocities with respect to an observer on either object or an independant observer not in motion? As in if both objects are moving at .9c, The light eminating from both objects wouldn't be 1.9c but c. However, both objects are still travelling at velocities of .9c and regardless of how they "look" they are still moving across an equivalent distance of space given their velocities? Hmmm am I making sense? Edit: In other words, relativivity only dictates the measured and observed speed of light for every reference frame. If we were both driving cars towards each other at .6c, it wouldn't look like you were approaching me at 1.2c. However, I am still moving at .6c and you are still moving at .6c, and we still cover the distance proscribed by that speed independant of one another.

Umm, well, if we're both moving towards each other at .6c, it would look to each of us like we're moving towards each other at something like .8c or .9c. An independant observer would see us both traveling towards each other at .6c, thus our combined speed would seem to him to be 1.2c.

Now, what I've confused myself with just now is that if we're both driving towards each other at .6c therefore meaning that I'm driving towards you at about .9c and towards an independent observer at .6c, to me it would seem that I didn't meet up with the observer and you at the same time. Obviously this shouldn't be the case, but I can't really pinpoint why...

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1+1=10

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Originally posted by DrUg_Tit0 Now, what I've confused myself with just now is that if we're both driving towards each other at .6c therefore meaning that I'm driving towards you at about .9c and towards an independent observer at .6c, to me it would seem that I didn't meet up with the observer and you at the same time. Obviously this shouldn't be the case, but I can't really pinpoint why...

Ah, I got it explained now. So the path I traveled is not s=v/t, but it's s=(s-vt)/sqrt(1-(v/c)^2). IOW the object is moving towards me at 0.6c, but the virtual distance between us is greater than if we were both standing still. I suppose this makes sense now.

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1+1=10