# hubble v einstien

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my limited experience with relativity. tells me a photon crossing the the universe travels 0 distance in no time at all due to time dilation and length contraction. if that is the case, how can a photon have frequency?

Edited by moth
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my limited experience with relativity. tells me a photon crossing the the universe travels 0 distance in no time at all due to time dilation and length contraction. if that is the case, how can a photon have frequency?

Does a photon have frequency or does it constitute a wave together with other photons that have frequency together? A single wave can't have frequency - though it can have wavelength.

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Does a photon have frequency or does it constitute a wave together with other photons that have frequency together? A single wave can't have frequency - though it can have wavelength.

my understanding is a photon has frequency as in e=hf

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my understanding is a photon has frequency as in e=hf

Given that the speed of light is fixed, frequency and wavelength would be linked values. But frequency literally refers to the number of waves in a given distance, I think, whereas wavelength literally refers to the length of the wave. What I don't get is what the relationship between the photon and EM wave is. Is one photon = one EM wave? Is 1 photon = to a sequence of electric and magnetic fields including positive and negative oscillations? If so, I would say that each photon consists of 4 waves in total, unless you count the oscillations as peaks and troughs of the same wave, in which case it would be two waves (1 electric and 1 magnetic). I don't really get it though since it seems like the two terms are used in different contexts.

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my loose analogy of a photon is a changing electric field causes a change in the magnetic field of "space" which changes the electric charge of "space", but how can something change if no time passes?

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After writing the text below I now see that you asked for frequency, not wavelength: the statement is the same except that "wavelength" then is "frequency" and "length" is "time interval".

You can indeed not sensibly define lengths -in this case a wavelength- with a measure by which all lengths are zero. The wavelength of a photon is measured in the frame of the lab/observer, where lengths are properly defined. Note that this implies that the same photon will usually have different wavelengths for different frames of reference.

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my limited experience with relativity. tells me a photon crossing the the universe travels 0 distance in no time at all due to time dilation and length contraction.

Sort of. The trouble is that you are trying to understand "the photon's point of view". This is not really allowed in special relativity. The photon does not have an inertial frame of reference and so you have to be very careful.

if that is the case, how can a photon have frequency?

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Given that the speed of light is fixed, frequency and wavelength would be linked values. But frequency literally refers to the number of waves in a given distance, I think, whereas wavelength literally refers to the length of the wave. What I don't get is what the relationship between the photon and EM wave is. Is one photon = one EM wave? Is 1 photon = to a sequence of electric and magnetic fields including positive and negative oscillations? If so, I would say that each photon consists of 4 waves in total, unless you count the oscillations as peaks and troughs of the same wave, in which case it would be two waves (1 electric and 1 magnetic). I don't really get it though since it seems like the two terms are used in different contexts.

!

Moderator Note

Questions (if you want an answer) tangential to the OP should be asked in a new thread

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Of course, the dreaded frame mixing. Thanks for setting me straight.

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