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sqljunkey
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What field of physics deals with what a photon experiences as far as it comes to time and such. Like two photons traveling side by side, or having some kind of interaction. Is that the realm of quantum mechanics?
No field of physics deals with what a photon experiences or with two photons traveling side by side, for the same reason that no field of biochemistry deals with the metabolism of pink unicorns - these concepts make no sense.sqljunkey said:What field of physics deals with what a photon experiences as far as it comes to time and such. Like two photons traveling side by side, or having some kind of interaction. Is that the realm of quantum mechanics?
sqljunkey said:What field of physics deals with what a photon experiences as far as it comes to time and such.
The reference system of the “fast” object Measures a velocity c respect to the photon. It’s time is relented only if watched by another reference system, but it’s own time “proper time” is unchanged and its “perceptions” are unchanged. Given that a photon don’t have a reference system, we can’t say anything about the time flow in the life of a photon.Dale said:Well, fundamental particles don’t really experience anything. However, the time that human beings experience (and clocks and other animals and ...) is called “proper time”, and photons do not have any proper time.
Chris Miller said:The Lorentz equations cannot be applied to photons.
If you were traveling near the speed of light time would be just fine, your clocks running, to an observer you'd be literally glowing and no way to read out the clock at that speed!sqljunkey said:So if I was traveling at the speed of light my clock would not be moving relative to me? I would be frozen in time? I wouldn't notice it but to others that's how it looks like?
YesTom Atkinson said:If you were traveling near the speed of light time would be just fine, your clocks running...
If you are approaching the observer, yes. But not if you were moving away, then Doppler would red-shift the light coming from you.to an observer you'd be literally glowing
Notwithstanding the very valid issues already posted, it is possible to answer this question in the spirit in which it was asked.Young physicist said:As far as I know, a object will experience time slower when its speed is close to the speed of light.
But photons themselves moves at the speed of light, does that mean that they experience no time?
Is there any online reference that explains this equation in more detail? What is ##\tau##, x##\mu##, and x##\mu##? Thanks.vanhees71 said:The proper time is well-defined for worldlines of massive particles, which are time-like. Then it's the affine parameter ##\tau## which is defined uniquely by the equation
$$\frac{\mathrm{d} x^{\mu}}{\mathrm{d} \tau} \frac{\mathrm{d} x_{\mu}}{\mathrm{d} \tau}=c^2.$$
.Scott said:and your mass would have increased enormously.
.Scott said:Second, from the photons perspective
The sentence started "From an Earth-bound observer". I don't need to explicitly say "relativistic".weirdoguy said:Relativistic mass which is not what is meant nowadays when physicists say 'mass' (as been pointed out zilion times, even in this thread...).
And my point is that we can still look at the situation as the limit is approached. I think I did a very good job in explaining some of the problems with the notion of the "photon's perspective".weirdoguy said:This whole thread is about the fact that there is no such thing as "photons perspective", so why you write things like this?
If you say "mass" and mean "relativistic mass" then yes, you do need to say "relativistic mass". Or, better yet, rephrase what you are saying in terms of invariant mass, momentum or energy..Scott said:The sentence started "From an Earth-bound observer". I don't need to explicitly say "relativistic".
You should find this in any textbook on relativity. It's very basic when you treat relativistic dynamics. My attempt to explain relativity can be found here (Chpt. 2):kurt101 said:Is there any online reference that explains this equation in more detail? What is ##\tau##, x##\mu##, and x##\mu##? Thanks.
.Scott said:The sentence started "From an Earth-bound observer". I don't need to explicitly say "relativistic".
weirdoguy said:Relativistic mass which is not what is meant nowadays when physicists say 'mass'
jbriggs444 said:If you say "mass" and mean "relativistic mass" then yes, you do need to say "relativistic mass".
.Scott said:from the photons perspective, the starting and ending points are coincident
Certainly as one approaches c (relative to everything else), the universe will appear to contract in the direction of travel. So wouldn't it be correct to say that as v approaches c, the apparent distance between your starting and ending points approaches zero? Then from there, as a limit, the distance would be zero?PeterDonis said:It has already been pointed out that a photon does not have a "perspective" in the sense of an inertial frame. However, even if we choose a coordinate chart in which the photon has three out of four coordinates constant (which is possible, although such a chart will not correspond to any inertial frame), it is not the case that "the starting and ending points are coincident".
There isn't a limit here. At any time you will see light passing you at c, and still have 300,000km/s to make up to catch up to it..Scott said:Then from there, as a limit, the distance would be zero?
Of course it's ok to have the question. Just like it's ok to ask which way is north from the north pole. The answer, though, is going to be that the question doesn't make sense because it's based on assumptions about arc length that don't apply to null paths..Scott said:It is okay to have the question - badly worded or otherwise.
.Scott said:wouldn't it be correct to say that as v approaches c, the apparent distance between your starting and ending points approaches zero?
.Scott said:Then from there, as a limit, the distance would be zero?
That's right. The limit in velocity is only seen be the Earth-bound people. The limits seen be the traveler is with the velocity of the universe rushing by (approaching c), the limit of the distance between the start and end point (approaching zero), and the travel time (also approaching zero).Ibix said:There isn't a limit here. At any time you will see light passing you at c, and still have 300,000km/s to make up to catch up to it.
Mathematically, being poorly defined at the limit value doesn't invalidate the process of taking limit of a function. If anything, it could suggest that a different answer could be derived if the limit was taken differently.PeterDonis said:No, because the limit you are trying to take is not well-defined.
No, but it does invalidate any attempt to equate the value as we approach the point at which the function is poorly defined with "the value at that point" (scare-quotes because of course that value doesn't exist - if it did it wouldn't be poorly defined). There is no mathematically sound way of getting from "the separation in an inertial frame approaches zero as the relative velocity approaches ##c##" to "the separation is zero in the inertial frame in which the relative velocity is ##c##"..Scott said:Mathematically, being poorly defined at the limit value doesn't invalidate the process of taking limit of a function.
Nugatory said:It is somewhat unfortunate that setting ##v=c## in the time dilation, length contraction, and relativistic mass formulas yields such a convincinghand-wavingheuristic argument for the speed of light limit, because taking that argument seriously leads to some misunderstandings later.
vanhees71 said:Is this the same Don Lincoln from Fermi Lab who writes great articles in The Physics Teacher?
.Scott said:Certainly as one approaches c (relative to everything else), the universe will appear to contract in the direction of travel.
I needed to say relative to something. Since I was looking to approach the limit, saying "relative to everything else" works.Mister T said:But it makes no sense to say your speed approaches ##c## relative to everything else. Protons in the Large Hadron Collider have speeds that approach ##c## relative to the laboratory, but relative to each other they have speeds that approach zero.
The only thing that makes any sense here is along the lines of "relative to something that was stationary before I went off, and stayed stationary"..Scott said:I needed to say relative to something. Since I was looking to approach the limit, saying "relative to everything else" works.
Alternatively, I could have said, "relative to even the fastest cosmic rays".
I'm pretty sure my pot belly sitting in my office chair is traveling close to ##c## relative to the fastest cosmic rays..Scott said:Alternatively, I could have said, "relative to even the fastest cosmic rays".
.Scott said:I needed to say relative to something. Since I was looking to approach the limit, saying "relative to everything else" works. Alternatively, I could have said, "relative to even the fastest cosmic rays".