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When moving at the speed of light time stops

by eyad-996
Tags: light, moving, speed, stops, time
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DaleSpam
#19
Dec30-12, 06:28 AM
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That seems like a good way to put it. In your reference frame you are not moving at the speed of light, you experience time, and in your frame light takes time to go from A to B. And light doesn't have a reference frame of its own.
eyad-996
#20
Dec30-12, 06:56 AM
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Thank you all, you have been a great help.
Last post puts it straight and simple.
jk22
#21
Dec30-12, 09:59 AM
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the lorentz transformation is singular for the speed of light i.e. Not defined
Moonraker
#22
Jan3-13, 02:41 PM
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What about this answer:

The time dilation formula is according to http://en.wikipedia.org/wiki/Time_dilation

T‘ = T * sqrt (1-v2/c2).


Set v=c, the proper time of light T’ will always be 0. The lorentz transformation is not defined for the speed of light, but the time dilation formula above is.

However, time is not frozen, the proper life time of a photon is zero.
ghwellsjr
#23
Jan3-13, 06:05 PM
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Quote Quote by Moonraker View Post
What about this answer:

The time dilation formula is according to http://en.wikipedia.org/wiki/Time_dilation

T‘ = T * sqrt (1-v2/c2).


Set v=c, the proper time of light T’ will always be 0. The lorentz transformation is not defined for the speed of light, but the time dilation formula above is.

However, time is not frozen, the proper life time of a photon is zero.
Here's a thread you should read:

http://www.physicsforums.com/showthread.php?t=661429
bcrowell
#24
Jan3-13, 07:32 PM
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I don't think any of the previous posts have really addressed the basic misunderstanding invoved in the OP's question. The OP asked:

(1)
Quote Quote by eyad-996 View Post
If when you're moving at the speed of light time freezes, why then does it take light 8 minutes to reach the earth from the sun?
The question shows a more basic misunderstanding of frames of reference. Suppose the OP had asked instead:

(2) "If when you're moving close to the speed of light time freezes, why then does it take neutrinos 8 minutes to reach the earth from the sun?"

The answer is that when we talk about the time taken for something to reach the earth from the sun, we're implicitly talking about the time as measured in the frame of the earth. But relativistic time dilation would relate the 8 minutes to the much longer time taken in the frame of the neutrino.

A question that didn't involve this misconception would be:

(3) If when you're moving close to the speed of light time freezes, does that mean that only a very short time passes in the frame of a neutrino that, in the earth's frane, takes 8 minutes to reach the earth?

The answer would be yes.
eyad-996
#25
Jan3-13, 11:04 PM
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Thanks, great answer!
Moonraker
#26
Jan4-13, 01:40 AM
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Quote Quote by ghwellsjr View Post
Hi ghwellsjr,
which one? are you (mistakenly?) refering to our current thread?
Moonraker
Moonraker
#27
Jan4-13, 01:48 AM
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Quote Quote by bcrowell View Post

(3) If when you're moving close to the speed of light time freezes, does that mean that only a very short time passes in the frame of a neutrino that, in the earth's frane, takes 8 minutes to reach the earth?

The answer would be yes.
I suppose that neutrino's speed in neutrino's frame is not higher than light speed because the distance sun-earth is diminishing in neutrino's frame as well? (according to Lorentz transformation)
ghwellsjr
#28
Jan4-13, 03:11 AM
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Quote Quote by Moonraker View Post
Quote Quote by ghwellsjr View Post
Hi ghwellsjr,
which one? are you (mistakenly?) refering to our current thread?
Moonraker
It was no mistake.

If you had read this thread you would have read this post:
Quote Quote by pervect View Post
You have some a notion of time, and you assume that light must have some sense of it too. And this idea is wrong.
So then why do you say:
Quote Quote by Moonraker View Post
However, time is not frozen, the proper life time of a photon is zero.
This is a wrong statement because time does not apply to a photon. It doesn't have a proper time or a life time or a proper life time or any other time. You shouldn't say that time for a photon is not frozen or frozen. You should say time doesn't apply to a photon which is different than saying that some kind of time of a photon is zero.
Moonraker
#29
Jan4-13, 04:38 AM
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Quote Quote by ghwellsjr View Post
This is a wrong statement because time does not apply to a photon. It doesn't have a proper time or a life time or a proper life time or any other time. You shouldn't say that time for a photon is not frozen or frozen. You should say time doesn't apply to a photon which is different than saying that some kind of time of a photon is zero.
I don’t agree. There is no doubt that each photon is sent and absorbed at a precise time.Temission and Tabsorption. Time applies to photons too. This is one of the very few things we know for sure about photons.
Doc Al
#30
Jan4-13, 05:09 AM
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Quote Quote by Moonraker View Post
I don’t agree. There is no doubt that each photon is sent and absorbed at a precise time.Temission and Tabsorption. Time applies to photons too.
These are not times measured from the (nonexistent) frame of a photon, they are measured from other quite ordinary frames of reference.
DaleSpam
#31
Jan4-13, 05:45 AM
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Quote Quote by Moonraker View Post
I suppose that neutrino's speed in neutrino's frame is not higher than light speed because the distance sun-earth is diminishing in neutrino's frame as well? (according to Lorentz transformation)
The neutrinos speed in the neutrinos frame is 0.
Moonraker
#32
Jan4-13, 05:47 AM
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Quote Quote by Doc Al View Post
These are not times measured from the (nonexistent) frame of a photon, they are measured from other quite ordinary frames of reference.
No, the moment of emission is the same for the observer and for the photon.
At the absorption, the clock of the observer shows 8 minutes (Sun-Earth). The “clock” of the photon shows 0 seconds, according to the above-mentioned time dilation formula:
T‘ = T * sqrt (1-v2/c2),
even if the Lorentz transformation does not apply to photons.
Moonraker
#33
Jan4-13, 05:55 AM
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Quote Quote by DaleSpam View Post
The neutrinos speed in the neutrinos frame is 0.
This would mean that the distance is 0 as well in the neutrino's frame.
Doc Al
#34
Jan4-13, 06:06 AM
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Quote Quote by Moonraker View Post
No, the moment of emission is the same for the observer and for the photon.
At the absorption, the clock of the observer shows 8 minutes (Sun-Earth). The “clock” of the photon shows 0 seconds, according to the above-mentioned time dilation formula:
T‘ = T * sqrt (1-v2/c2),
even if the Lorentz transformation does not apply to photons.
You do realize that the time dilation formula is just a special case of the Lorentz transformation, don't you? So if the LT doesn't apply, neither does the time dilation formula.
DaleSpam
#35
Jan4-13, 06:45 AM
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Quote Quote by Moonraker View Post
This would mean that the distance is 0 as well in the neutrino's frame.
The distance the neutrino travels is indeed 0 in the Neutrinos frame. Note that that is not the same as the distance between the earth and the sun.
Nugatory
#36
Jan4-13, 07:26 AM
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Quote Quote by Moonraker View Post
even if the Lorentz transformation does not apply to photons.
Be careful here... The Lorentz transforms never apply to things, be they photons moving at the speed of light in all frames, or massive particles and observers moving at less than the speed of light in all frames. They apply to the coordinate systems that we use to assign (x,t) values to events such as "the thing is at point x at time t"


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