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Thread: Heavy light, is there such a thing?

  1. #31
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    closed pending moderator discussion
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  2. #32
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    Quote Originally Posted by Ken G View Post
    What's more, bear in mind that all we can really say about the photon is that the simplest model for it is to make it massless. We have no idea that the photons we already have are actually massless, we only know if they have mass, it is below our ability to detect. Indeed, it might be natural to expect the mass not to be zero, because a tiny thing is often easier to achieve than a zero thing. If so, the answer to "what would we need to do to light" would be "nothing." However, it can be assumed that what is meant is not, what could we do to light to give it mass, but rather, to give it a measurable amount of mass. To light, probably nothing, but what we might be able to do is something to our measuring techniques-- we might find a way to detect the mass of light, as was done with neutrinos.
    Ken G

    Turning this thread into yet another debate about the philosophy of science is off-topic to the question of the OP and violates our instructions as to how Q&A is to operate. And frankly, this post and the follow-ups are borderline on advocating ATM, which is particularly egregious in ATM. All of this will earn you an infraction

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    I will reopen this thread, but this entire side topic will stop now. If there is nothing more to say about the OP, that's fine, just let it drop. If anyone wishes to continue the philosophy discussion, start your own thread outside of Q&A.
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  3. #33
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    It's your forum. But I'm still going to point out that the statement "the photon is likely massless" is an unscientific statement, every time I see it. There's no more important element of "mainstream science" than protecting what science actually is, and I always will if you won't. Do what you like, I spend too much time on here anyway.
    Last edited by Ken G; 2018-Jul-02 at 03:28 AM.

  4. #34
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    Quote Originally Posted by Ken G View Post
    It's your forum. But I'm still going to point out that the statement "the photon is likely massless" is an unscientific statement, every time I see it. There's no more important element of "mainstream science" than protecting what science actually is, and I always will if you won't. Do what you like, I spend too much time on here anyway.

    Trying to get in the last word, after specifically being told not the pursue the topic anymore is not something we approve of.
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  5. #35
    Might I assist?

    The photon has no rest mass, but it has a non-zero inertial mass. Google on photon inertial mass. This is why in his 1905 E=mc paper Einstein said "radiation conveys inertia between the emitting and absorbing bodies". As such, light is "heavy", as per https://arxiv.org/abs/1508.06478. If a body were to absorb a photon, the mass of a body increases. It then weighs more. Then if the body "gives off the energy L in the form of radiation, its mass diminishes by L/c. Einstein used L instead of E in his 1905 paper.

    However there's no such thing as "heavy light" along the lines of heavy water.

  6. #36
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    I'm guessing by "forms of light" the OP means "frequencies." Light has momentum. It has greater momentum with greater frequency. If light is absorbed by mass the momentum is transferred. Often this means that the mass which absorbs the light gains energy and in effect heats up. So I looked up whether mass increases with heat. I believe the answer is yes, but not much. It's complicated. BUT. Light can also be used for cooling. Look up laser cooling if you don't think so. In that situation, the effect of light would be to reduce mass. In other words, momentum does not equate to mass. The point is that the transfer of momentum is not the transfer of mass and I don't believe it can be used to define any sort of mass to light.
    Depending on whom you ask, everything is relative.

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    Quote Originally Posted by Shaula View Post
    Thank you for Kensplaining this to me.

    Shaula, this is unnecessary personal snark, and it violates the rules of the forum. Please don't do it again. If you have a problem with a post, ask the mods to take a look.
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  8. #38
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    Don't know if this relates, but I was wondering, if in string theory, energy and momentum had a different number of dimensions.
    The moment an instant lasted forever, we were destined for the leading edge of eternity.

  9. #39
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    I remember talking with my physics professor about this in 1982. I don't really see how light can have mass. Its energy level would have to be infinite. There must be away that mass and light travel through space that cause the difference or a fundamental difference light and particles. My own opinion is that matter is a defect, but light is not.
    The moment an instant lasted forever, we were destined for the leading edge of eternity.

  10. #40
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    Quote Originally Posted by Copernicus View Post
    I remember talking with my physics professor about this in 1982. I don't really see how light can have mass. Its energy level would have to be infinite.
    I'd say this is double-dipping.

    The notion of requiring infinite energy to move something at the speed of light goes hand-in-hand with the notion of light being massless.

    You don't use one to justify the other.
    If you reject one, you are rejecting them both.

  11. #41
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    Quote Originally Posted by DaveC426913 View Post
    I'd say this is double-dipping.

    The notion of requiring infinite energy to move something at the speed of light goes hand-in-hand with the notion of light being massless.

    You don't use one to justify the other.
    If you reject one, you are rejecting them both.
    I can't tell if you agree with me or not, because I think we said the same thing.
    The moment an instant lasted forever, we were destined for the leading edge of eternity.

  12. #42
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    Hmm, interesting debates. Now I know light has momentum and this momentum is changed to heat when light strikes an object. Do all photons, regardless of source or frequency, create the same amount of heat when they strike the same material?
    I know that I know nothing, so I question everything. - Socrates/Descartes

  13. #43
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    Quote Originally Posted by DaCaptain View Post
    Hmm, interesting debates. Now I know light has momentum and this momentum is changed to heat when light strikes an object. Do all photons, regardless of source or frequency, create the same amount of heat when they strike the same material?
    No. Photons with higher frequency (shorter wavelength) have proportionally more energy. Look up the photoelectric effect; that was one of the earliest observations that led to the idea the light was composed of photons. Source does not matter, though. A photon's energy is determined entirely by its frequency.
    Conserve energy. Commute with the Hamiltonian.

  14. #44
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    Quote Originally Posted by Copernicus View Post
    Don't know if this relates, but I was wondering, if in string theory, energy and momentum had a different number of dimensions.
    Dimensions is a big word...

    As far as string theory goes, it has a couple of handy ways of making many more dimensions look just like 3+1 dimensions. Compactification (I think I spelled that right) and so on. It isn't a bug, it's a feature. Or it's a buggy feature because we have no tool to discriminate 3+1 from 3+1+more-dimensions at our disposal. Nor will we for the foreseeable future.

    I am hardly an expert so hang on while an actual expert comes on the line.

    I love string theory, but it is more a historical/educational "love" rather than a science based "love". It seems to be a good way to open up conversations about what has gone before and what the current outlook on science and math is, without really providing any sort of solutions. Brian Greene has teamed up with some wonderful film makers and collected a lot of scientists to present their honest opinions on the various subjects relating "strings". Somehow, these films come across as positive, without being an endorsement of anything other than the pursuit and enjoyment of knowledge.

    For reference, a typical script segment from a Brian Greene TV show:
    Interviewer - "What do you think of that?"
    Scientist - "SMH. Lol."
    Solfe

  15. #45
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    Quote Originally Posted by Grey View Post
    No. Photons with higher frequency (shorter wavelength) have proportionally more energy. Look up the photoelectric effect; that was one of the earliest observations that led to the idea the light was composed of photons. Source does not matter, though. A photon's energy is determined entirely by its frequency.
    Besides running into something, do photons ever loose their energy or would they travel through space forever? Do they have a lifespan?
    I know that I know nothing, so I question everything. - Socrates/Descartes

  16. #46
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    Quote Originally Posted by DaCaptain View Post
    Besides running into something, do photons ever loose their energy or would they travel through space forever? Do they have a lifespan?
    They can indeed travel forever, at least in principle. The photons in the cosmic microwave background have been traveling through space for 13.7 billion years. The expansion of space does cause them to redshift, so there is a sense in which they lose energy as they travel, but there's no lower limit to the energy of a photon, so there is no point at which a photon will cease to exist unless it is absorbed by some interaction.
    Conserve energy. Commute with the Hamiltonian.

  17. #47
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    Quote Originally Posted by Grey View Post
    They can indeed travel forever, at least in principle. The photons in the cosmic microwave background have been traveling through space for 13.7 billion years. The expansion of space does cause them to redshift, so there is a sense in which they lose energy as they travel, but there's no lower limit to the energy of a photon, so there is no point at which a photon will cease to exist unless it is absorbed by some interaction.
    So this redshift you're talking about can't be caused by photons loosing their mojo after traveling through space for 14 billion years?
    I know that I know nothing, so I question everything. - Socrates/Descartes

  18. #48
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    Quote Originally Posted by DaCaptain View Post
    So this redshift you're talking about can't be caused by photons loosing their mojo after traveling through space for 14 billion years?
    Photons can only lose energy if they interact with something. The trip per se doesn't make them weary. Various "tired light" hypotheses have been proposed over the years in an effort to explain redshift without a big bang, but they have all failed spectacularly (energy loss by interactions has testable consequences, none of which we observe).

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