If photons have no mass, how can they have energy?
August 4, 2018 at 4:03 pm #10496
I’m sure one of the scientists here will have the answer, but here’s the question in a little more plain language detail.
Einstein’s relativity theory tells us that mass and energy aren’t two different thing but rather are one thing in two different states, so it would seem that anything having energy must also have mass and vice versa. However, if photons have no mass (and thus no energy), why do I feel warm when I stand out in sunlight? How can a beam of laser light cut metal?
What is the answer, in plain language, please?August 4, 2018 at 5:40 pm #10502
Abandon all hope of using human experience and classical physics when trying to understand why photons have energy. E=mc2 is only for the static case. It’s how your microwave oven works. Photons have the famous quantum mechanics wave/particle duality and therefore have energy e=pc where p = relativistic momentum. Some describe photons as having as “relativistic mass”.
What’s really cool is some people are thinking about harvesting energy from the unused waves that permeate our existence.August 4, 2018 at 6:00 pm #10503
What is relativistic momentum? Is there a formula for relativistic mass?August 5, 2018 at 8:20 pm #10551
Photons are just electro-magnetic wave energy, no different from radio waves except in frequency. Unlike particles, waves pass through each other. Imagine what the universe would look like if photons were particles that could collide. Star clusters would look pretty blurry, moreso than from how their dust blurs them.
But waves can still interact with mass. As double-slit experiments show, photon waves even seem to pass through both slits at once, only converging into one defined location when they convert back into a particle. And they are curved by gravity without affecting the gravity mass; as they’re travelling without mass they aren’t tugging on other mass. The big conundrum here is regarding the non-locality of a photon, which becomes even more mysterious when two photons start out entangled with each other and seem to interact instantaneously (i.e. faster than light) over large distances. They act like they’re the same particle, only temporarily split.
tldr, mass and energy are different states of “wavicles“.
Not sure why you’d think energy has mass because sunlight can warm you. Simple analogy here is a microwave oven heating up your soup. The waves interact strongly with mass, making them move faster, so making them hotter. The big question, again, is how and when do waves and matter interact.
And we haven’t even touched on how waves and matter change state from and to each other.
August 5, 2018 at 8:51 pm #10554
- This reply was modified 2 weeks, 2 days ago by PopeBeanie.
Here is an interesting article I have been giving consideration to. It looks at Einstein’s “hidden variables” you mentioned in an earlier topic recently and the Bell Test. I had been visualizing the two photons still being connected by a light wave that kept the information about their “position” instantaneously retrievable. It would not matter how far apart they were as the wave treated their state as “Local” information all the time. That would remove the “spookiness”?? (must try harder!)August 5, 2018 at 10:09 pm #10555
Thanks for link to article Reg.
That is a cool attempt to explain it but lets say two photons are entangled from one light year away and they are communicating simultaneously is the information about position retrievable because our understanding of time is incomplete?August 5, 2018 at 10:41 pm #10559
As the light-wave or photon is traveling at the speed of light (sorry), it is traveling faster than the rate of expansion of the Universe. The empty space between objects with mass is increasing. By “empty space” I mean there is “no thing” there with mass, only a quantum field of energies exists there without the effects of gravity. The light waves exist in and move though this field and all “information” is preserved. So our instinctive understanding of Time is not needed. Even grasping that photons are individual grains of light (or quanta) is difficult. It got Einstein his Nobel prize for the photoelectric effect. We need to think of it in terms of SpaceTime – because Space and Time are not separate entities from the photons point of view. It’s wave just travels though a quantum filed where “time” and “distance” are not factors.
I am not a scientist and this is just how I visualize things at present. I have not explained it very well and to me that means I don’t understand it as well as I think I do (given the adage that nobody understands QM). Must re-read this excellent book.August 5, 2018 at 11:06 pm #10563
Yeah, like love and marriage (space and time) ya can’t have one without the other. Yes, the information is preserved. Yes, expansion is or may be relevant to understanding entanglement.
But if we have allowed for or adjusted for time space so that the two photons are one light yr apart and yet they dance together how can we explain it?
Perhaps the implication is that everything that happened continues to happen and everything that will happen continues to happen all at once. We are stuck in past present and future but maybe the monkey is fooling us?August 6, 2018 at 4:56 am #10582
Thanks Reg. I remember those stories when they came out. It seems in this story Bell’s Inequality wasn’t explained correctly, but it doesn’t matter because I still lack what it takes to understand it in detail.
It made me think of another question, having to do with pilot wave testing: I have no clue, and I’m wondering if bending the path of photons in optical fiber is possible without causing loss and if so, then could a pilot wave theory be put to rest (assuming a pilot wave doesn’t also follow the fiber!).
I could use a fairy god-physicist. Over dinner maybe. On call. 🙂August 6, 2018 at 5:16 am #10583
Thanks Reg. I remember those stories when they came out. It seems in this story Bell’s Inequality wasn’t explained correctly, but it doesn’t matter because I still lack what it takes to understand it in detail. It made me think of another question, having to do with pilot wave testing: I have no clue, and I’m wondering if bending the path of photons in optical fiber is possible without causing loss and if so, then could a pilot wave theory be put to rest (assuming a pilot wave doesn’t also follow the fiber!). I could use a fairy god-physicist. Over dinner maybe. On call. 🙂
And if you were somehow to capture photons in a sealed circular optical fiber tube, would the resulting black hole fold space causing everything to be everywhere all at once?August 6, 2018 at 5:43 am #10584
LOL, just like the big bang, and we’d have to start all over again. Gives me more time to think about responding to @toms. 🙂August 6, 2018 at 1:11 pm #10589
About 15 years ago I installed a new fiber “backbone” to link 3 factory buildings in the same plant back to the data storage building. It greatly improved network speeds, especially from the furthest away plant (700m).
One of the managers, who was to pay me for the work, asked me if I could speed it up anymore, without replacing any more hardware. I replied that the “ping” rates were so fast that there was no need and explained that it was his old Windows 95 PC that was the bottleneck as the newer PCs were working as I predicted. “So you are telling me that you can’t make the transfer any faster then?” he replied in a condescending tone. This was a ploy to argue for a deduction to my bill. “Correct, I think you will find it difficult to get the fiber to transfer data faster than the speed of light. But feel free to get a second opinion”. I got paid in full 🙂
- This reply was modified 2 weeks, 1 day ago by PopeBeanie. Reason: condensing -> condescending. What, you can't spell this right?!
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