Can someone patiently explain time dilation to me?
d = 5 396 264 244 000 or 5.4 billion kilometers
takes light 5 hours from our perspective to travel that distance
from the perspective of the light, it happens in less than a minute
If a clock were mounted to a particle of light, the mechanism of the clock - each atomic component of the clock - would register less than a minute passing as the light traveled that distance.
Why?
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Anonymous2008-01-28 14:41
Because as experienced by the clock, the distance traveled would be much shorter due to length contraction?
In fact, seen from the particle of light, I think the journey may be instantaneous, as the universe would essentially be flat.
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Anonymous2008-01-28 17:46
So, a clock attached to a photon would never experience time passing while that photon moved through a vacuum? In a vacuum of infinite distance, the time the clock would record as having passed as the photon reached the opposite side (traveling the infinite distance) would be 0?
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Anonymous2008-01-28 19:28
I understand why a beam of light mounted on a space firing at a reflective surface would appear to travel a greater distance to a stationary observer while moving at the same speed from both perspectives, that makes complete sense to me since apparently our understanding of physics requires that light always move at the same speed in vacuum regardless of how fast whatever emits it is moving.
However, if it were a foosball being launched at a surface, the ball WOULD have the additional velocity of the spacecraft added to it - it would appear to be covering a greater distance to the observer, but to the observer the speed would also be greater.
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Anonymous2008-01-28 20:28
>>3
The problem would be that your clock would need a rest mass of 0, otherwise its effective mass will be infinite at the speed of light.
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Anonymous2008-01-28 21:17
>>5
The clock rest mass is 0. Just an example to help me with the concept.
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Anonymous2008-01-29 15:03
shouldn't time stop completely while travelling at the speed of light?
lorentz contraction looks like this: d = d_0 * sqrt( 1 - (v/c)^2 ), so with v = c, any given distance becomes 0.
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Anonymous2008-01-29 15:15
Supposedly time does stop completely, and that's why traveling backwards through time suddenly became less of an impossibility. Perhaps.
From what I've read, there are particles that travel faster than light, but nothing below lightspeed can accelerate to that speed or beyond.
Particles can travel faster than light does in substances. Water, for instance. I think light travels something like .75 c in water.
>>8
Time dilation and the like refers to the speed of light in a vacuum, or 299,792,458 metres per second. It may be sloppy to omit it, but everyone who isn't a total dumbass (or getting their physics from Star Trek) understands that.
There are plenty of examples of particles moving faster in a given medium than light does in that medium (most famously, Cherenkov radiation), but that's completely irrelevant, since the speed of light in that medium refers to the light beam as a whole, not individual photons, which do still move at 299,792,458 metres per second (as anything with 0 rest mass must). The effective slowing down of light beams in other media than vacuum is due to scattering.
Basically, the observed speed of a beam of light isn't necessarily constant, but the observed speed of individual photons is. Neither is particularly relevant to backward time travel.
>>14 >>16
Are you trying to say that you'd need infinite energy to move backwards through time?
We know.
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Anonymous2008-02-02 22:30
>>17
You'd need infinite energy to stop time. You'd need more to move backwards.
But >>14,16 was just making a crap joke about how we're all moving forwards through time unless we're moving at the speed of light, so it doesn't particularly matter.
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Anonymous2008-02-03 20:05
Cock. Just one.
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Anonymous2008-02-04 18:18
>>19
Haha! Cocks! Hilarious! Now say something REALLY crazy like BOOBIES! LMAO!
>>29
No, it was at the top already when I posted. COCKS COCKS COCKS COCKS
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4tran2008-02-12 18:26
>>8
Travelling backwards in time is nonsense in SR.
Tachyons have never been observed.
Light speed doesn't change in a substance. It seems to change because the light interacts with the substance. There is frequent absorption and emission of photons. Particles going faster than this "observed light speed" results Čerenkov radiation.