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if photons had mass


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One of the fundamental issues is modern physics is that we actually do not know if Photons have mass or not. It has not been shown with current technology that they have mass, and all indications are that they do not, but this could be a limitation of our technology.

It's a very long time since I did anything along these lines, but one thing that intrigues me is that is all photons are travelling at the same speed (exactly), what determines their energy? I understand that atomic level reactions to the cause of this energy, ie, a gamma ray photon gets emitted when, for example, a high energy proton collides with either another proton or an atomic nucleus, but if the photon leaves the nucleus at the exact same speed as the visible light photon also produced, then what is the cause of the energy difference...is it that they do not leave at the exact same speed, perhaps billionths of a meter per second difference, or do they in fact have different masses that have so far remained undetermined due to their low level...or will we discover something even more fundamental out about sub-atomic particles that has so far remained elusive...

A photon's energy is determined by its frequency. A gamma ray photon has much higher frequency than a visible light photo, so it's far more energetic. Photons don't have mass, but they have momentum which is what drives solar sails.

The energy of a photon is E=hv where v is the frequency and h is the reduced plack constant

The momentum is p = hv/c where c is the speed of light

Variable speed of light is an active area of research, but for all we know they all travel at the same speed through the same region of vacuum.

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Photons may have some relativistic mass and do have momentum as stated above (which is why a box full of photons would weight infinitesimally more than the same box containing nothing at all) but they have zero rest mass. The speed of light itself is only constant and absolute in a vacuum - it can be as slow as 60kph in sodium cooled to within a small fraction of absolute zero. If you've ever seen the eerie blue glow in spent fuel ponds in nuclear power stations, then that's caused by cherenkov radiation where particles exceed the speed of light in the local medium. :)

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A photon's energy is determined by its frequency. A gamma ray photon has much higher frequency than a visible light photo, so it's far more energetic. Photons don't have mass, but they have momentum which is what drives solar sails.

The energy of a photon is E=hv where v is the frequency and h is the reduced plack constant

The momentum is p = hv/c where c is the speed of light

Variable speed of light is an active area of research, but for all we know they all travel at the same speed through the same region of vacuum.

Keith, I understand that, but as frequency and energy are interlinked, there has to be another influence on the determination of the frequency to make the energies different across the Electromagnetic spectrum if al their speeds are the same, ie C. I can do all the maths till I am blue in the face, but call me cynical, i simply feel we are missing something..

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Photons may have some relativistic mass and do have momentum as stated above (which is why a box full of photons would weight infinitesimally more than the same box containing nothing at all) but they have zero rest mass. The speed of light itself is only constant and absolute in a vacuum - it can be as slow as 60kph in sodium cooled to within a small fraction of absolute zero. If you've ever seen the eerie blue glow in spent fuel ponds in nuclear power stations, then that's caused by cherenkov radiation where particles exceed the speed of light in the local medium. :)

But momentum is a product of the mass and velocity/acceleration of a body, if the photon has absolutely no mass at all, then we must conclude that there is an influence that has an impact on determining all the properties of photons and thus their respective energy levels....

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Keith, I understand that, but as frequency and energy are interlinked, there has to be another influence on the determination of the frequency to make the energies different across the Electromagnetic spectrum if al their speeds are the same, ie C. I can do all the maths till I am blue in the face, but call me cynical, i simply feel we are missing something..

Try this example

Consider yourself a photon and assume you have one of those shaker torch

You can shake the torch quickly to produce a lot of energy or shake it slowly to produce less (torch frequency)

If you get into a car and drive while shaking the torch (speed of torch), how fast you drive should have no influence on how much energy you are producing for the torch. That depends only on how fast you shake it.

High frequency = more energy, low frequency = less energy.

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i read an artical a while back (or may have been on a documentory) that it has been detected that the speed of light can vary according to frequency, although only a tiny amount detected over several million light years so e=mc2 may need a bit of a rethink, although close enough, i`ve always thought that light probably does have mass and may be the ultimate fundamental partical, that said even a bucky ball can behave as a wave producing interference patterns with the 2 slit experiement, exhibiting the same behaviour as in the quantum world, it`s a very strange world and the boundrys of quantum and classical physics are sometimes not as clear cut as we may like, leaving hope to be able to unite the 2 best bet at the moment being m theorys ...that said of course theres me with no more than a gcse in physics although i do read a lot about it as it fascinates me.

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But momentum is a product of the mass and velocity/acceleration of a body, if the photon has absolutely no mass at all, then we must conclude that there is an influence that has an impact on determining all the properties of photons and thus their respective energy levels....

You are thinking in three dimension, but this is a 4 dimension problem. Momentum is a product of mass, velocity, energy and speed of light.

http://en.wikipedia....i/Four-momentum

I don't know the details of the variable speed of light theory, and it is an area of ongoing research way beyond my understanding of physics. However, if any researcher managed to proof speed of light is not constant then he will definitely win the Nobel price.

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But momentum is a product of the mass and velocity/acceleration of a body, if the photon has absolutely no mass at all, then we must conclude that there is an influence that has an impact on determining all the properties of photons and thus their respective energy levels....

Hence they may have relativistic mass... :)

Having said that, you can't always apply classical physics at quantum levels - there may be special rules that apply here.

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Keith, I understand that, but as frequency and energy are interlinked, there has to be another influence on the determination of the frequency to make the energies different across the Electromagnetic spectrum if al their speeds are the same, ie C. I can do all the maths till I am blue in the face, but call me cynical, i simply feel we are missing something..

The energy and hence frequency of the photon/em wave is produced by the energy transferred by the particle that caused the emission of the photon in the first place.

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Try this example

Consider yourself a photon and assume you have one of those shaker torch

You can shake the torch quickly to produce a lot of energy or shake it slowly to produce less (torch frequency)

If you get into a car and drive while shaking the torch (speed of torch), how fast you drive should have no influence on how much energy you are producing for the torch. That depends only on how fast you shake it.

High frequency = more energy, low frequency = less energy.

Thanks for that, sadly when speaking of photons that analogy falls over, The frequency is dependent on the energy and vice versa, clearly this is the majority of the "problem", but this does not actually solve all the issues at quantum levels...hence the ongoing research into the many of these aspects...Remember, that the intrinsic properties of photons, charge, mass and spin are determined by the properties of Gauge Symmetry..I am also aware that the current understanding of the photon has allowed us to produce Lasers, Masers, develop theoretical physics dealing with Bose-Einstein Condensates and even Quantum Field Theory, so i do not think it is wrong, just we are missing something that may turn out to be important, and for me, that is one of two things, either a very low level mass (or something like it) or that the speed of the electromagnetic spectrum is variable as very high degrees of measurement..

In 1972 a team at NBC Boulder measured the speed of light as 299,792,456.2±1.1 m/s and this was accepted by the 15th CGPM in 1975, being rounded to 299,792,458 m/s, there were discrepancies caused by the lack of accuracy or the indeterminate nature of the length of the meter. In 1983 this was set at the 17th meeting of the CGPM as

The metre is the length of the path traveled by light in vacuum during a time interval of 1/299 792 458 of a second

This determined that the speed of light was thus settled on 299,792,458 m/s (299,792.458 km/s)

However this has inbuilt inaccuracies and thus the speed of light, as far as I am concerned, is only accurate to within a few percent of accuracy at best, thus that leaves the field wide open to gaps in our knowledge.

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However this has inbuilt inaccuracies and thus the speed of light, as far as I am concerned, is only accurate to within a few percent of accuracy at best, thus that leaves the field wide open to gaps in our knowledge.

Can you let me know where you found this information? I'm very surprise how there could be a few percent of inaccuracy in c. As far as we know a few neutrinos thought to have arrived a few nanoseconds early was sufficient to create a major event in the physics community. If speed of light was not constant, the theory of relativity will collapse, but so far it has stood up to all attempts to disprove it. The 'error' you suggested was cause my the inaccuracy of the meter and the second rather than c. The metre and second were redefined using speed of light because speed of light was constant. Time is variable depending on the altitude (gravitational time dilation) and speed (relative speed time dilation).

If there is a different in speed of light, then a microwave photon should be slower than a gamma ray photos, but there is no evidence for that.

I don't understand why you think there is a problem with frequency being proportional to energy. For me there isn't any problem with this. In fact I think there will be a problem if frequency is independent of energy.

Why do you need mass and speed in the equation?

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Keith, maybe a few percent is stretching things a bit, but the fact that the accepted speed of c has been tailored to a human defined measure that is based on the very speed your defining, thus they are interdependent so defining one based on the other is mistake, the speed of c has been rounded down, thus it is inaccurate. Will post better thoughts on this later.

Sent from my GT-P5110 using Tapatalk 2

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