# How the energy of light changes

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Can you actually measure the specific energy of something? And if so, how exactly? Because I heard somewhere that energy is relative.

Also about photons, I know about the red and blue shift, but how does that effect a photons energy? Can't photons only have specific energy in order to exist? But, the blue shift states I as I approach an object, the wavelength of light becomes more condensed, and I can calculate the energy based on wavelength, so doesn't that mean energy is purely relative and nothing has a specific defined amount of energy?

But then, if I am traveling at 10 kilometers per hour exactly, don't I have to have a specific amount of energy to do that? Also, don't electrons have to have a specific amount of energy in order to be in a specific energy level?

Edited by questionposter

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Ok I noticed no one wants to take a shot at it because people don't understand it I guess.

So you know the blue shift right? Well, it states that as I get closer to a source of frequencies, the frequency becomes greater, like with the doppler effect. But, since I can calculate the energy of a photon based on its wavelength, does that mean I could eventually accelerate towards a radio electron enough to turn it into a gamma-ray? Cause I mean, that doesn't seem right. I could eventually turn something that doesn't destroy human tissue into something that does just by eventually putting enough energy into moving towards it, but then again, I can calculate energy based on wavelength.

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If you go fast enough so that radio waves get blue shifted to gamma rays, your body will perceive them as gamma rays.

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If you go fast enough so that radio waves get blue shifted to gamma rays, your body will perceive them as gamma rays.

So for some random magical reason, just because my body "thinks" they are gamma rays, the radio waves magically destroy human tissue even if they are actually radio waves but the only thing that's changing is that I'm moving towards them? Not even quantum mechanics is as obscure as that. Furthermore, why wouldn't have scientists concluded that as evidence that all states of universe exist because of perception alone if the difference between dying from radiation poisoning and not dying from it is my point of view? That's like The Matrix basically, but so far, there is no scientific evidence to support that we can bend a spoon just by willing it to happen or that things happen because that's how our brains expect them to happen, so that description probably isn't right. Even with quantum mechanics its not because we expect things to happen, its because things have become detirmined, more like we are only viewing a snapshot out of an entire sequence.

For some reason, that's how I've heard it described, although not by real physicists, but that doesn't seem to make any sense whatsoever.

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So for some random magical reason, just because my body "thinks" they are gamma rays, the radio waves magically destroy human tissue even if they are actually radio waves but the only thing that's changing is that I'm moving towards them? Not even quantum mechanics is as obscure as that. Furthermore, why wouldn't have scientists concluded that as evidence that all states of universe exist because of perception alone if the difference between dying from radiation poisoning and not dying from it is my point of view? That's like The Matrix basically, but so far, there is no scientific evidence to support that we can bend a spoon just by willing it to happen, so that description probably isn't right.

For some reason, that's how I've heard it described, although not by real physicists, but that doesn't seem to make any sense whatsoever.

If it makes you feel any better (and even if it doesn't) if you die from radiation in one frame you die in them all.

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Can you actually measure the specific energy of something? And if so, how exactly? Because I heard somewhere that energy is relative.

Also about photons, I know about the red and blue shift, but how does that effect a photons energy? Can't photons only have specific energy in order to exist? But, the blue shift states I as I approach an object, the wavelength of light becomes more condensed, and I can calculate the energy based on wavelength, so doesn't that mean energy is purely relative and nothing has a specific defined amount of energy?

But then, if I am traveling at 10 kilometers per hour exactly, don't I have to have a specific amount of energy to do that? Also, don't electrons have to have a specific amount of energy in order to be in a specific energy level?

Energy is frame-dependent. The value you measure only has meaning in the frame you measure it.

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Energy is frame-dependent. The value you measure only has meaning in the frame you measure it.

So if there's a nuclear bomb, then to not die from the radiation, all I have to do is travel at nearly the speed of light away from the blast site just before it hits me and the gamma rays which are gamma rays to many other people will suddenly turn into radio waves which won't effect me at all and travel harmlessly through me since their wavelength will somehow be stretched out just because I'm moving away which the photon can't even know because they havn't hit me yet?

Or are you trying to say what's measured isn't actually what a physical object is?

Edited by questionposter

Yes

Yes

Yes what?

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Yes, if you sped away from a nuclear blast, you would redshift the gammas to lower energy.

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Yes, if you sped away from a nuclear blast, you would redshift the gammas to lower energy.

But how do the photons know I'm moving away from them before they hit me? And, don't the photons still have a specific energy and if I could speed away at just any speed, wouldn't that make the photons to go into impossible measurable energy states that consist of decimals rather than intervals? Because if the photons actually did go into those "in between" energy levels mathematics predicts their wave functions would have too much interference and they wouldn't exist.

I don't see why if a star super-novas and emmits a gamma rays , why in reality it would suddenly make it harmless just to move away fast. If a gamma ray hits me then it hits me, why would the speed I'm moving away form it matter?

Not only that, but if that is actually how it worked in reality, wouldn't there be a delocalization problem? Because if the photon actually DID have a lower-wavelength, then that means it should spread out more, which means other sources would also detect it as a radio wave even though they aren't moving as fast because a radio-wave as that much more delocalized.

Not only that, but we're sending particles around in a hadron colidder at nearly the speed of light, and to some frames of reference tons gamma rays should be hitting Earth since there's all sorts of other lower wavelength particles coming towards them as the particles are accelerating towards them, yet life on Earth isn't sterilized, and then to some gamma rays from gamma ray busts we detect in the sky, those should actually be radio-waves half the time since the particles in a hadron colidder are also accelerating away from those particles sometimes too.

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But how do the photons know I'm moving away from them before they hit me? And, don't the photons still have a specific energy and if I could speed away at just any speed, wouldn't that make the photons to go into impossible measurable energy states that consist of decimals rather than intervals? Because if the photons actually did go into those "in between" energy levels mathematics predicts their wave functions would have too much interference and they wouldn't exist.

I don't see why if a star super-novas and emmits a gamma rays , why in reality it would suddenly make it harmless just to move away fast. If a gamma ray hits me then it hits me, why would the speed I'm moving away form it matter?

Not only that, but if that is actually how it worked in reality, wouldn't there be a delocalization problem? Because if the photon actually DID have a lower-wavelength, then that means it should spread out more, which means other sources would also detect it as a radio wave even though they aren't moving as fast because a radio-wave as that much more delocalized.

Not only that, but we're sending particles around in a hadron colidder at nearly the speed of light, and to some frames of reference tons gamma rays should be hitting Earth since there's all sorts of other lower wavelength particles coming towards them as the particles are accelerating towards them, yet life on Earth isn't sterilized, and then to some gamma rays from gamma ray busts we detect in the sky, those should actually be radio-waves half the time since the particles in a hadron colidder are also accelerating away from those particles sometimes too.

Don't anthropomorphize the photons. They hate it when you do that.

The speed of light is a constant. When you move away from the source, the frequency of the light has to drop. The photons don't "care" about that; if they hit something stationary in the source frame, they will have their original energy. But to someone in another frame, the frequency will change, depending on the relative motion.

There is no "inherent" energy to a particle. It always depend on the frame of the observer.

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Don't anthropomorphize the photons. They hate it when you do that.

The speed of light is a constant. When you move away from the source, the frequency of the light has to drop. The photons don't "care" about that; if they hit something stationary in the source frame, they will have their original energy. But to someone in another frame, the frequency will change, depending on the relative motion.

There is no "inherent" energy to a particle. It always depend on the frame of the observer.

But if an electron jumps down exactly one energy level, can't there only be a specific amount of energy in a photon no matter who is observing it? Also, since nothing is completely stationary, we can't even say with 100% accuracy what the energy of a photon actually is? Also, why does the frequency "have" to drop? And also, your saying that the same photon can hit two different objects simultaneously as a radio wave and gamma wave at the same time? So how do we ever know what a photon actually is since we are always moving and everything else is always moving?

Edited by questionposter
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The answer to the change in frequency is the Doppler Shift. An example is the pitch of an approaching vehicle which has a higher frequency than when it is moving away from you. I am sure you can find illustrations showing this as this is an elementary physics problem.

If you think in terms of waves instead of photons you can reduce the amount questions you have.

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The answer to the change in frequency is the Doppler Shift. An example is the pitch of an approaching vehicle which has a higher frequency than when it is moving away from you. I am sure you can find illustrations showing this as this is an elementary physics problem.

If you think in terms of waves instead of photons you can reduce the amount questions you have.

So your saying that because I move further away at a greater speed, the number of wave crests of photons that hits me decreases. That makes sense, but then, what's the actual shape of a photon? Both gamma rays and radio waves are the same substance, but why does a gamma ray tend to act like a particle and act over a short distance when its just the same material as a radio waves which can effect things in a greater distance? If I send out a gamma ray, its not going to hit every cell phone, its only going to be tightly bound into mostly a single position and probably going to travel, so why can't a photon be as long as a radio wave but still have a higher wavelength? If I have a pool of water exactly 10 feet by 10 feet, I can make tighter waves resembling gamma-rays or longer waves resembling radio waves, but the dimensions of the pool stay the same which means a radio wave would effect the same amount of area as a gamma ray inside the pool and the waves travel across the same length. Why doesn't it work that way with photons? Is it because of the uncertainty principal? The uncertainty principal makes higher energy light particles tend to be measured in a more tight region?

Or is it because by adding wave-length, your using up more surface area of the photon per wavelength? Because a photon is also a particle too, so actually I think that surface area shrinkage thing makes sense too. When a photon has more energy, it has more vibrations in its waving particle surface, so more of its surface area is used up in those vibrations, like this:

Its sort of like coiling a piece of paper. Your adding more potential energy into a piece of paper, but by doing so your making it coil, and the more energy you put into it, the more it coils reducing the size between coils since the energy uses up more surface area to coil.

So when you move fast away form light like near the speed of light, fewer wave crests hit you per second, although there's still something wrong, because once you measure any part of a photon, doesn't its wave mechanics collapse? So no more wave crests would keep hitting you? But then, what would happen to the wave crests that are suppose to be hitting everything else?

Would this mean all we need to do to avoid the devastation of a nuclear bomb is to have one single giant sheet move away from the nuclear blast at nearly the speed of light when it happens so that it perceives the gamma-rays as radio-waves and then collapses their wave mechanics making it seem like the only thing that ever happened was an outburst of intense radio waves? But then, what happened to all the rest of the energy that was in the rests of the wave crests of the gamma ray once I measured it as a radio wave? Does it suddenly not exist because of the collapsing wave mechanics?

Edited by questionposter
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The distance of action of gamma rays and radio waves are the same in a vacuum. It is easier to focus "short" waves such as gamma and micro waves compared to longer radio waves which just wraps around corners and bends. The physics concept is refraction. Try putting into your pool physical blocks of matter and continue to make waves of different wavelengths and observe how these waves move past the blocks. It is the same thing for the photons.

Concerning the wave crests, I think you are measuring the distance between wave crests to determine the wavelength of the waves, you are not measuring the position of the photons (which would call the Heisenberg uncertainty principle into operation) so why does the wave want to collapse? Moving your giant sheet won't help the rest of the population, which is not moving relative to the nuclear detonation. The receding giant sheet may get a dose of radio waves but the stationary population will get their gamma rays.

In my opinion there may be some confusion on your part concerning the energy of a photon in relation to its wavelength (or frequency). I call to your attention the photoelectric effect, where the intensity (i.e. amount of photons) of the light source does not affect the ejected electrons, only the wavelength (i.e. the energy of each photon emitted) of the light source does. In classical wave mechanics, the amplitude of the wave correlates to the energy of the wave. unfortunately I do not know how to offer a solution to the last part of you post, but you sure have an interesting question there tho. I was thinking of a solution from the Poynting Vector but.....

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Concerning the wave crests, I think you are measuring the distance between wave crests to determine the wavelength of the waves, you are not measuring the position of the photons (which would call the Heisenberg uncertainty principle into operation) so why does the wave want to collapse? Moving your giant sheet won't help the rest of the population, which is not moving relative to the nuclear detonation. The receding giant sheet may get a dose of radio waves but the stationary population will get their gamma rays.

But if a photon hits you, your measuring it though right? It doesn't matter if your only measuring its wavelength or only its energy, your measuring it. Just like it doesn't matter if I'm only measuring the momentum of an electron or only the spin, I'm still measuring it and in either measurement I collapse its wave mechanics.

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But if a photon hits you, your measuring it though right? It doesn't matter if your only measuring its wavelength or only its energy, your measuring it. Just like it doesn't matter if I'm only measuring the momentum of an electron or only the spin, I'm still measuring it and in either measurement I collapse its wave mechanics.

And the energy something has is not invariant; it matters what frame of reference you are in.

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And the energy something has is not invariant; it matters what frame of reference you are in.

Ok, I'm already agreeing with that, but I'm asking about the wave mechanics collapse form one of my previous posts. If the first wavelength of a photon hits me, don't I determine the position of the photon to be that single position that I perceived it hitting me at? But then, what happens to the rest of the photon?

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Ok, I'm already agreeing with that, but I'm asking about the wave mechanics collapse form one of my previous posts. If the first wavelength of a photon hits me, don't I determine the position of the photon to be that single position that I perceived it hitting me at? But then, what happens to the rest of the photon?

What rest of the photon? You either absorb it or you don't. You can't break it down any more than that.

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What rest of the photon? You either absorb it or you don't. You can't break it down any more than that.

But a photon doesn't exist in just a single position, it's wavelength can be as big as a football field right? So it's size is as big as a football field. So if only the first tiny part of the photon hits my body, what happens to the rest of it? Or with a gamma ray, the only reason I measure it as radio-waves when traveling away from it is because less of the photon hits me per second, like with the Doppler effect, less hertz from an emitted sources hits me per second as a travel away from it. Are you saying that just by touching any part of a photon, that all of it somehow instantaneously condenses to the single point of where it touched me? But then what about radio waves? They travel through solid walls and electronics and they still exist as acres in size when doing so, they don't get determined like how you say.

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You would not be able to make that determination because of the Heisenberg Uncertainty Principle. The interaction is not instantaneous; if a 1 micron photon hits your body, the entire photon hits you, the "other side" hits you within several femtoseconds. Even a meter-long photon takes a few nanoseconds. Light is fast.

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You would not be able to make that determination because of the Heisenberg Uncertainty Principle. The interaction is not instantaneous; if a 1 micron photon hits your body, the entire photon hits you, the "other side" hits you within several femtoseconds. Even a meter-long photon takes a few nanoseconds. Light is fast.

So your saying the size of a photon isn't due to it's wave mechanics, which is why a photon will continue to be large even when it hits something? Does that mean the uncertainty principal isn't wave mechanics, but it's own thing?

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So your saying the size of a photon isn't due to it's wave mechanics, which is why a photon will continue to be large even when it hits something? Does that mean the uncertainty principal isn't wave mechanics, but it's own thing?

I'm saying that when a photon is undergoing a quantum-mechanical interaction, you don't interact with just part if a photon.

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I'm saying that when a photon is undergoing a quantum-mechanical interaction, you don't interact with just part if a photon.

So doesn't that mean I interact with all of the photon regardless of how far away I am from the actual end of the photon if I only touch the first part of it? But then how could that doppler effect work?

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