- #36
Quantum_Grid
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DaveC426913 said:The OP simply wishes to understand the process by which energy is converted to mass.
Thank you, at least a FEW of you understood! ;)
DaveC426913 said:The OP simply wishes to understand the process by which energy is converted to mass.
Clearly, matter and energy are two different things, in that we percieve them, measure them and treat them in definably different ways (even [if] they are, at their core, the same thing)
Fuse barium and krypton to get uranium, you will actually gain mass.
I picked those two because they are the byproducts of uranium fission. So, you could reverse the process.Naty1 said:This can't actually be done, right? or can it?? In other words, is this a theoretical statement or a practical one as well??
? Are you saying you can't have energy without matter??malawi_glenn said:Maybe this helps you: Think of energy as a property of matter, not an entity itself.
DaveC426913 said:? Are you saying you can't have energy without matter??
kev said:The only form of mass that is officially recogised is rest mass. A single photon has no rest mass, because it can not be identified with an inertial rest frame.
/QUOTE]
Photons indeed have no restmass, but not for that reason. GR and ST both concur that all physics within an inertial frame are the same. They move with velocity c with respect to any such frame, so there cannot be an inertial comoving frame for photons.
Always thought that the term inertial rest frame was used for the one derived from the backgroundradiation.
"How exactly does energy become mass?"
Can this be answered exactly? There is potential energy, kinetic energy, heat energy, the energy of a particle as a function of wavelength made uncertain by it's bandwidth, gravitational potential energy, static electric potential energy, whatever it is from the weak and strong forces... Can one answer exactly cover them all?
Rubbish. How many rest frames do you need with this kind of physics?kev said:Some individual particles that had the property of rest mass before the explosion, now have the property of being able to travel at the speed of light and not having an identifiable rest frame as an individual particle.
Quantum_Grid said:Re: How exactly does energy "become" mass?
DaveC426913 said:When two particles fuse, such as in the heart of stars, their combined mass is greater than their separate mass.
More later.
What do you mean with inertial mass of a photon?Phrak said:This is not inconsistant with particle physics, nor energy in transit as photons. Measure the photons on a scale, they have inertial mass.
feynmann said:Isn't that true their combined mass is Less than their separate mass. e.g. mass of helium atom is less than the sum of 2 neutrons and 2 protons.
It's called mass defect, extra mass is converted to energy
lightarrow said:What do you mean with inertial mass of a photon?
This has to do with momentum, not mass.Phrak said:You've heard of light sails, right? Photons have inertia. They exert a force on the sail. I turn, the sail changes the momentum of the photon. Bounce enough light off a scale, it will measure an applied force.
lightarrow said:This has to do with momentum, not mass.
But it doesn't interest me, I answered to your claim that a light sail works because of photons inertial mass. Photons don't have mass.Phrak said:No. The OP asked about energy and mass as defined in this: [tex]E=mc^2[/tex].This has to do with momentum, not mass.
Physis is an experimental science. How do you measure this mass, m
?[tex]m=\frac{E}{c^2}[/tex]
No, because a photon's mass is zero, but its energy is not, so that equation is wrong. The correct one (always valid, in a flat spacetime) is:Dmitry67 said:
What you call rest mass is better called invariant mass and this is the only meaningful concept of mass in SR.Photons are 'massless' because they do not have rest mass, but the do carry mass when threy move.
Yes, but only because in this case p = 0 (or you can always find a ref. frame where it's 0). For a *single* photon that's false and the mass is exactly zero.Dmitry67 said:lightarrow, again, depending on what you call a mass.
I have 1kg of matter and 1kg of antimatter.
I annihilate them and get a huge flash of light.
There is no hardronic matter left.
(lets forget about the neutrino) do you agree that the total mass of light flash is 2kg?
There is only one kind of mass in SR.Phrak said:Tomatoes and Potatoes
[tex]E^{2} = m_{p}\!^{2} c^{4} + c^{2}p^{2}[/tex]
[tex]E = m_{i}c^2[/tex]
[tex]m_{i}[/tex]
and
[tex]m_{p}[/tex]
are not the same vegetable.
lol. And I suppose you wish to assert that it is the "rest" kind, rather than the "relativistic" kind?lightarrow said:There is only one kind of mass in SR.
just a few posts before (n.59) I said it's better called "invariant" mass.cesiumfrog said:lol. And I suppose you wish to assert that it is the "rest" kind, rather than the "relativistic" kind?
You said it, but that doesn't make it so.lightarrow said:I said ..
DrGreg said:I think it's necessary to remind some participants that there is more than one definition of "mass" in relativity.
- invariant mass, or rest mass, or proper mass, which excludes the kinetic energy of the object's centre of momentum
- relativistic mass, sometimes called inertial mass, which includes the kinetic energy of the object's centre of momentum.
Be sure you know which sort of mass is being talked about.
Most modern physicists use "mass" to mean "invariant mass" but some people use "mass" to mean "relativistic mass".
Photons have zero invariant mass, but non-zero relativistic mass. The quoted Wikipedia article on the photon refers only to invariant mass, which is described simply as "mass", consistent with modern usage.
Whichever definition you choose, mass is a form of energy, like other forms such as kinetic energy, potential energy, heat energy, sound energy, etc. So mass doesn't get converted into energy, but it can be transformed from mass-energy to some other form of energy. The total energy from all sources (as measured by a single observer) remains constant.
Phrak said:You've heard of light sails, right? Photons have inertia. They exert a force on the sail. I turn, the sail changes the momentum of the photon. Bounce enough light off a scale, it will measure an applied force.lightarrow said:What do you mean with inertial mass of a photon?Phrak said:This is not inconsistant with particle physics, nor energy in transit as photons. Measure the photons on a scale, they have inertial mass.
Yes, several photons and *not traveling in the same direction*. If he talks about light sails, it's more about photons traveling in the same direction than the other way round.jostpuur said:The response to lightarrow should have been, that the comment was about inertial mass of several photons, not of a single photon.