How exactly does energy become mass?

[DrGreg]

Let generalize the problem. Consider that a clock K' is located at the origin O' of its rest frame I'. It measures a time interval dt(0), has a mass m(0) an energy E(0), a temperature T(0) and an extension dx(0) in the direction of the x' axis. Are all of them REST, PROPER or INVARIANT physical quanties?
Measured from I they are dt, m, T and dx. Are they RELATIVISTIC physical quantities or there are better names?

I'm assuming that your first mention of I should have been I', which I have corrected in the quote above.

I can't comment on temperature, as that's not a subject I've studied under relativity.

Assuming we are measuring an object that is stationary relative to the I' frame, in Special (not General) Relativity:

- the relativistic mass relative to I' is the same as the rest/proper/invariant mass (all 3 mean the same)
- the energy relative to I' is the same as "rest-energy" or "rest-mass-energy"
- a time interval dt' is the same as proper time d\tau, provided we are talking about a single point in space (stationary relative to I')
- a distance interval dx' is the same as proper length or rest length

In the I frame, that same object is not stationary and so
- the relativistic mass relative to I is not rest mass
- the energy relative to I is not "rest-energy"
- a time interval dt is "coordinate time"
- a distance interval dx is "coordinate distance"

In general, coordinate measurements depend on a frame's synchronisation convention, whereas proper or invariant measurements do not.

In general relativity it gets more complicated.

 

[Phrak]

I just don't feel strong enough in GR formulas to answer this question.

But yes, let's imagine that we emited a super-powerful but short laser beam to infinity. It is so compact and heavy so it is a 'body' flying at v=c

The weird thing is that as gravity also moves at c, it arrives at the same time as light.

I don't quite know what you mean by this, but changes in the stress-energy tensor (gravity waves) propagate at c, for small perturbations in the stress-energy tensor from flat space. The stress-energy tensor itself (gravity) doesn't have a velocity.

So the effect of the gravitation becomes asymmetric? (like for cherenkov's particles) - bodies do not attract to the incoming mass, but they are pulled towards it when 'body' is leaving.

Like in Cherenkovs case, that laser beam should lose momentum because it passes the momentum to all bodies around trying to pull them in the same direction. It makes the light in the beam redder...

But of course we need someone with a more deep knowledge of GR to check if this is a correct pucture or not...

As I said, I don't really follow, but for a bunch of massive objects circling the sun, for example, it's the lighter bodies that, on average, get sent to higher orbits or are ejected from the solar system. This is due to the sling-shot effect, and will on average increase the angular momentum of a lighter body at the expense of a heavier body. This makes some sense, if you think of a system that reaches equilibrium when each object has nominally the same angular momentum as the next.

As far as light is concerned, that's another animal, so I really don't know if light can be equated with lighter bodies.

 

[heldervelez]

I'm late to this discussion but no one said that the conversion of energy to mass needs a energy (photons) an intervenient mass (atom/particles). This intervenient mass (oscilator) absorbs energy changing to permited levels or configurations, and the surplus energy can be packed into other particle(s) or photon(s) leaving the system.
AFAIK photons can not be packed as particles without an intervenient mass. Is there any experiment against this?
In this context how could a radiation dominated world generate particles?

In the thread a power laser was mencioned and some gravitational effects on neutrons (Ultra Cold Neutrons)
An experiment could be done, I think, to prove or disprove, the assertion that light are sources of gravity (independently of GR saying so).
The experiment could involve the extreme power lasers of today and try to bend the trajectories of UCN beam.
Does anyone know of an experiment that proves that light is source of gravitational effects ?

 

[altonhare]

Mass is bound energy they are (in GR and SR) exactly the same thing with different units.

What binds the energy? Forces? Energy exerts forces on itself?

 

[gonegahgah]

Naty, a fusion reaction is supposed to release about .1% of the energy of the hydrogen atoms I think (instead of 1%). Fission releases a lot less energy (bigger atoms broken in two parts; only small part converted).

About this topic, we can create diamonds by applying lots of pressure to coal. Wouldn't something similar occur for the creation of matter? ie Super extreme pressure applied to energy to cause it to bind in sufficient quantity to form protons, electrons and neutrons?

 

[neopolitan]

A late entry.

As far as I can tell, the particle with the smallest stable mass is the electron. Is this actually the case, or just the "popular physics" answer? (I know the neutrino is said to have a very small non-zero mass, but with a halflife of about 10 minutes, it is not quite as stable as the electron.)

Is mass possibly a consequence of so much energy being concentrated in so little space? An electron has a mass equivalent to a photon with a frequency of 123 petahertz (10¹⁵Hz). This is, interestingly enough, a little above the frequency where radiation become ionising, somewhere in the middle of the x-ray range.

This would align with what some have said here (mass is energy, so there is no such thing as "pure energy") and possibly get towards what other have tried to say, there is energy without mass, if the concentration of energy is not sufficient to create the phenomenon we call mass.

Neutrinos, with their unstable mass might just be on the border, not quite enough to make a stable mass, but enough to start exhibiting the features of mass. (Electron neutrinos, at around 2.2eV are equivalent to a photon in lower end of ultraviolet range/upper end of the visual spectrum. UV is where radiation does become ionising - admittedly pretty much in the middle of the UV range, at the frequency used in tanning booths, otherwise known as "booths of leathery death". I assume that ionising radiation is radiation which has enough energy to smash bonds, but it is interesting to think that the energies involved are also representative of the smallest masses. Note also that radiation in the visible spectrum is also suspected to cause skin cancer, so while it might not be ionising by definition, this lower energy radiation does do something more than provide a rosy glow.)

Just an idea, and maybe a hopelessly vague retelling of something already in quantum and/or string theory.

cheers,

neopolitan

 

[JANm]

Hallo Neopolitan
Ok ionisation is declarable as electric difference from one case to the other. Bound Bound, Bound free and free bound, but infrared radiation from neutral molecules? Isn't that just mass-velocity relation, so changing velocity and emitting infrared?
greetings Janm

 

[neopolitan]

Hallo Neopolitan
Ok ionisation is declarable as electric difference from one case to the other. Bound Bound, Bound free and free bound, but infrared radiation from neutral molecules? Isn't that just mass-velocity relation, so changing velocity and emitting infrared?
greetings Janm

I am trying to understand your statement - neutral molecules can be made to emit infrared by accelerating them? I'm using "accelerating" here rather than "changing velocities" - is there as difference?

I think there may be, since the idea that one velocity inherently has more energy than another velocity seems to smack of an absolute frame. But if you have a neutral molecule undergoing acceleration, that is another matter. By accelerating, by applying force to the molecule you are doing something to its energy. The force could slow it down relative to you, so that would be reducing the relative energy. But it could speed it up relative to another frame.

I could see that molecules could emit radiation as a result of being accelerated (and decelerated). The energy represented by frequency and quantity of the radiation (frequency in your frame) plus the final velocity (in your frame) will be equal to the energy represented by the initial velocity (in your frame) plus the work done by the force (in your frame).

The result would be conservation of energy in the system (irrespective of frame).

As for the actual mechanism, if that is in fact anything like how it works ... I wouldn't like to guess.

cheers,

neopolitan

 

[neopolitan]

I did think of a mechanism. When accelerated (during the acceleration), a molecule would be compressed. On release of that acceleration, the molecule would relax, perhaps one of the phases, or both, would release radiation. At the particle scale, this could be due to delocalisation of energy, resulting a litte "bound" energy escaping to become "free".

But since I don't know much about neutral molecules emitting radiation when accelerated, my comments should not be taken too seriously

cheers,

neopolitan

 

[feynmann]

When two particles fuse, such as in the heart of stars, their combined mass is greater than their separate mass.

More later.

>>their combined mass is greater than their separate mass.
Does not make sense to me

 

[Dmitry67]

No, of course.
Mass of He4 is smaller then 2 neutron + 2 proton masses.

 

[ccollins919]

You could say that energy becomes mass when the wave collapses into particle form. As for pure energy, one might say that the closest thing to this might be the primordial first field that came into being after the big bang.

 

[JANm]

You could say that energy becomes mass when the wave collapses into particle form. As for pure energy, one might say that the closest thing to this might be the primordial first field that came into being after the big bang.

Energy becomes mass in: foton + molecule = triggered molecule?
and primordial first field: backgroundradiation?

It is a pity that of changes of energy levels of one electron we don't even know how this takes place which would be part of the answer to the posed question. I do believe that the formula's are there to calculate the amount of energy change.

I think that counts also for infrared emission. Process unknown yet calculation of amount: on one side of the equation Max Planck:
hf = 2 pi f hbar = omega hbar
(sorry have to learn more about the symbol-editor)
and on the other side delta m c^2.
The delta m coming out of the mass-velocity relation.
If it is right to use any inertial system, why not use the inertial system comoving with the backgroundradiation?

greetings Janm

 

[DaveC426913]

>>their combined mass is greater than their separate mass.
Does not make sense to me

Does it have to? These aren't billiard balls here. Don't look to the classical world.

 

[Gerinski]

Approaching the question from a different angle from what has been discussed until now, wouldn't it be another type of answer to say that "energy is supposed to become mass via the Higgs mechanism"?

 

[JANm]

No, of course.
Mass of He4 is smaller then 2 neutron + 2 proton masses.

Hello Dmitry67
Isn't it more official to compare 4 hydrogen and He4 and the mass loss during that proces? Or should you not at least compare one He4 with 2 neutron + 2 proton + 2 electron masses?
greetings Janm