# Thread: Does a substance emitting light lose mass?

1. Given that a photon has mass and is emitted from a source under excitation (heat, electricity, nuclear fission), does the substance emitting the light lose mass in the form of light packets?

2.

3. Yes, in principle. But it's a teeny tiny amount, too small to measure. The reason is that the 'effective mass' of a photon is its energy divided by the velocity of light squared. The energy of a photon of yellowish light is about 2 eV (electron Volts). One ev corresponds to 1.6 10-19ergs. That number divided by c2 is 1.8 10-36 kilograms. Even though there are lots and lots of photons in a laser beam it still adds up to an unmeasurable amount. Even if you radiate a kilowatt for a day, you lose about 108 Joules of energy. That's equivalent to 10-9 kg of mass. Not a lot.

4. A photon has no mass, but since it does have energy, technically an emitting object does lose mass. (E=mc^2)

5. Err, try the first post in this thread

6. But..

The mass lost, what does that equal of particles, superstrings?

7. Originally Posted by HexHammer
But..

The mass lost, what does that equal of particles, superstrings?
Can you rephrase this question in a way that makes sense?

8. When you talk about electron flow, it is like adding electrons into a sea of electrons and they flow to complete a circuit. Could it be that light is the same; that light is created by adding energy (in whatever form) to the substance causes the light particle to leave but the net mass stays the same because it is replaced?

9. Originally Posted by jetstove
When you talk about electron flow, it is like adding electrons into a sea of electrons and they flow to complete a circuit. Could it be that light is the same; that light is created by adding energy (in whatever form) to the substance causes the light particle to leave but the net mass stays the same because it is replaced?
No. When the photon of light leaves the mass, the mass does not stay the same. It becomes lesser by the amount of m=E/C^2, where E is the energy of the photon, in accordance with Einstein's famous equation.

10. Originally Posted by Harold14370
No. When the photon of light leaves the mass, the mass does not stay the same. It becomes lesser by the amount of m=E/C^2, where E is the energy of the photon, in accordance with Einstein's famous equation.
Although ... wouldn't this depend, to some extent, on why the mass is emitting photons? If it is an object that is cooling down or undergoing radioactive decay then the loss of energy will cause a corresponding (tiny) loss of mass. But if it is something like an electric light, then the energy will come from the electricity - and so no net mass loss. (But I'm not quite sure if that is what jetstove was getting at.)

11. Yes, I may have misinterpreted the question. Going back to the original question, in the examples given (heat, electricity, nuclear fission) if you are adding heat, by electricity or some external source, so as to keep the temperature constant, then the mass lost due to photon emission would be replaced by mass added due to the heat input. Nuclear fission, though, will result in a net loss of mass from the original bomb material or reactor core.

12. It's possible for the emitting object to lose momentum/kinetic energy instead of mass, as in the case of an electron emitting a photon when it gets accelerated, and then slowing down a little bit as a result.

13. Originally Posted by kojax
It's possible for the emitting object to lose momentum/kinetic energy instead of mass, as in the case of an electron emitting a photon when it gets accelerated, and then slowing down a little bit as a result.
But remember that mass and energy are equivalent so if it loses energy it will lose mass...

14. Certain posts have been moved to to a new thread named "Electrons and energy" in New Hypotheses and Ideas.

15. Originally Posted by Harold14370
Originally Posted by HexHammer
But..

The mass lost, what does that equal of particles, superstrings?
Can you rephrase this question in a way that makes sense?
I does make sense, just get off your high horse.

Electron Capture (also called inverse beta decay) there you can theorize a new particle due to the changed mass i perspectivly Protons and Neutrons. The same goes for the substance emitting light, as it will lose weight/mass we can thereby theorize new particles. So the question is, has this been done or is it new grounds?

16. Originally Posted by HexHammer
I does make sense, just get off your high horse.
Hexhammer, I am sure what you wrote made sense to you. It made no sense to Harold and it made no sense to me. The primary responsibility for clear communication rests with the writer, not the reader. I think you may have mentioned in another thread that English is not your native language. If that is the case then you would benefit from paying attention when a native English speaker says he does not understand you. If I am mistaken and you are a native English speaker then you should certainly know better!

Your next sentence, intended to clarify, left me even more confused. What does it mean. The grammar is totally screwed up. Absence of commas to indicate where clauses begin and end isn't helping.

17. Originally Posted by HexHammer
The same goes for the substance emitting light, as it will lose weight/mass we can thereby theorize new particles. So the question is, has this been done or is it new grounds?
I'm not sure why you think this requires any "new particles"; if something loses energy, it also loses mass (e=mc2).

Apart from that, I was going to write almost exactly what John wrote. What you said wasn't clear (to others - which is the important bit).

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