# Can mass be called mass without the “object”

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I need to clear up some confusion. In the beginning of the universe, before inflation ended, there were no “objects” just energy. Is it proper to refer to that energy as “mass” before it cooled enough to be converted to matter? I was under the assumption the definition of mass was: Mass of an object or body is a measure of it’s energy content.

I always thought that until the conversion to matter took place, it was just energy with the potential to be X amount of mass.

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There is no such thing as 'just energy'.

Energy is a property of Matter and Fields; it does not exist on its own.

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12 minutes ago, studiot said:

There is no such thing as 'just energy'.

Energy is a property of Matter and Fields; it does not exist on its own.

Understood, but it would be absurd to refer to those energy fields as mass until the energy was converted to matter, correct?

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In Special Relativity there are rest-mass (invariant-mass) and relativistic-mass. Massless particles like photons (light) have no rest-mass, but relativistic-mass.

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7 minutes ago, Short timer said:

Understood, but it would be absurd to refer to those energy fields as mass until the energy was converted to matter, correct?

No, not absurd, just not fitting in with the usual convention of how we use the term "mass" today.  The modern usage of "mass" tends to to refer to the invariant or "rest" mass.  The term "relativistic mass" has fallen out of favor for the most part and just included as "energy".  The upshot is that "energy" has many of the properties that used to only be associated with Mass.

So for example, if you have a solid sphere at rest, it has a certain inertia and it would take a given amount of effort to accelerate its center of mass up to a given speed.

If you were to spin that ball up around its axis, thus adding rotational kinetic energy, you would also be increasing the inertia the ball has and  it would take more effort to accelerate its center of mass up to a given speed. ( If you think that this added effort is just due to the motion of the individual particles on the sphere, you could do the same thing with a metal spring, a compressed spring storing energy would be slightly harder to accelerate than the same spring in the relaxed state.

Or to use Sensei's photon example,  If we were to convert the entire mass of the Sun into photons ( and somehow manged to contain them to the Sun's present volume),  this would have no gravitational effect on the orbiting planets.  That collection of photons would produce the same gravitational field as the Hydrogen and Helium it replaced. If you tried to move that bunched up collection of Photons, they would be just as hard to move as the Sun was in its original state.

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30 minutes ago, Janus said:

No, not absurd, just not fitting in with the usual convention of how we use the term "mass" today.  The modern usage of "mass" tends to to refer to the invariant or "rest" mass.  The term "relativistic mass" has fallen out of favor for the most part and just included as "energy".  The upshot is that "energy" has many of the properties that used to only be associated with Mass.

So for example, if you have a solid sphere at rest, it has a certain inertia and it would take a given amount of effort to accelerate its center of mass up to a given speed.

If you were to spin that ball up around its axis, thus adding rotational kinetic energy, you would also be increasing the inertia the ball has and  it would take more effort to accelerate its center of mass up to a given speed. ( If you think that this added effort is just due to the motion of the individual particles on the sphere, you could do the same thing with a metal spring, a compressed spring storing energy would be slightly harder to accelerate than the same spring in the relaxed state.

Or to use Sensei's photon example,  If we were to convert the entire mass of the Sun into photons ( and somehow manged to contain them to the Sun's present volume),  this would have no gravitational effect on the orbiting planets.  That collection of photons would produce the same gravitational field as the Hydrogen and Helium it replaced. If you tried to move that bunched up collection of Photons, they would be just as hard to move as the Sun was in its original state.

I think you cocked up here Janus.

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1 hour ago, Short timer said:

Understood, but it would be absurd to refer to those energy fields as mass until the energy was converted to matter, correct?

1 hour ago, Short timer said:

In the beginning of the universe, before inflation ended, there were no “objects” just energy.

Energy has dimensions ML2T-2

And Mass has dimensions M

So they are not the same

Furthermore 'energy' has no meaning before the 'big bang' since its definition includes Time.

There is a conversion equivalent, using a suitable constant (with suitable dimensions), just as there is a conversion equivalent between £ sterling and \$ dollars US.

But no one would suggest they are identical.

I didn't say anything about energy fields. I said Fields.

Finally 'absurd'  is a rant for the  sensationalist press, it is not a serious scientific term.

Edited by studiot

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48 minutes ago, StringJunky said:

I think you cocked up here Janus.

How so?

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1 hour ago, J.C.MacSwell said:

How so?

Statement 2 does not follow from statement 1:

1. If we were to convert the entire mass of the Sun into photons ( and somehow manged to contain them to the Sun's present volume),  this would have no gravitational effect on the orbiting planets.

2. That collection of photons would produce the same gravitational field as the Hydrogen and Helium it replaced.

I could be well wrong but I think he's trying to say that regardless of whether the sun is entirely photons or elements the planets will still orbit it but in the first statement he contradicts that by saying the photons have no effect.

Edited by StringJunky

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12 minutes ago, StringJunky said:

Statement 2 does not follow from statement 1:

1. If we were to convert the entire mass of the Sun into photons ( and somehow manged to contain them to the Sun's present volume),  this would have no gravitational effect on the orbiting planets.

2. That collection of photons would produce the same gravitational field as the Hydrogen and Helium it replaced.

I could be well wrong but I think he's trying to say that regardless of whether the sun is entirely photons or elements the planets will still orbit it but in the first statement he contradicts that by saying the photons have no effect.

I think that you have misinterpreted the (somewhat ambiguous) wording. I read 1 to mean that the change would have no effect on the planets, not that the photons would have no effect.

3 hours ago, Short timer said:

Understood, but it would be absurd to refer to those energy fields as mass until the energy was converted to matter, correct?

My understanding is that the earliest state we can describe with current physics consisted of a quark-gluon plasma. Quarks are fermions and so would generally be considered matter.

But the distinction seems rather arbitrary at that point. I'm not sure there is a definition of matter that really applies in all circumstances.

And there is certainly not a direct one-to-one correspondence between mass and matter. Nearly all of the mass of matter does not come from the mass of the particles that make it up, but from the energy binding them together.

At some point (I'm not sure when) fundamental particles would have had zero mass because the symmetry breaking that led to the Higgs field had not happened. But there would still have been energy, and this would have contributed mass to systems of particles.

Also maybe worth noting that mass does not appear at all in the equations of general relativity, only energy.

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45 minutes ago, Strange said:

I think that you have misinterpreted the (somewhat ambiguous) wording. I read 1 to mean that the change would have no effect on the planets, not that the photons would have no effect on the orbiting.

You're right, I meant no change in gravity felt by the planets and no change in their orbits,  and yes, in reading it back, it was awkwardly phrased.

Edited by Janus

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51 minutes ago, Strange said:

I think that you have misinterpreted the (somewhat ambiguous) wording. I read 1 to mean that the change would have no effect on the planets, not that the photons would have no effect.

I understand now Thanks for clarifying.

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Energy does gravitate, and in that way it is certainly equivalent to mass.

In the earliest moments of the universe, everything would have consisted of fields.
Fields which have an energy density, and therefore an equivalent 'mass'.
These scalar, vector and tensor fields underwent dissociation as energy density dropped, and it wasn't until the electroweak field dissociated into EM and weak fields that some of the previously massless field particles gained the ability to interact with the scalar Higgs field to acquire the associated property of what is now called inertial ( or rest ) mass.
Electrons, neutrinos, quarks and W/Z particles, previously massless, now had mass, and they comprise what we generally call 'matter'

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18 hours ago, Short timer said:

I always thought that until the conversion to matter took place, it was just energy with the potential to be X amount of mass.

In the way we keep the books, energy due to center-of-mass motion does not contribute to mass. Other energy does. A spinning top has more mass than when it is not rotating, and a hot cup of soup has more mass than an otherwise identical cold cup of soup. If you excite an atom or nucleus, its mass increases — this last effect has been experimentally confirmed.

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15 hours ago, MigL said:

Energy does gravitate, and in that way it is certainly equivalent to mass.

In the earliest moments of the universe, everything would have consisted of fields.
Fields which have an energy density, and therefore an equivalent 'mass'.
These scalar, vector and tensor fields underwent dissociation as energy density dropped, and it wasn't until the electroweak field dissociated into EM and weak fields that some of the previously massless field particles gained the ability to interact with the scalar Higgs field to acquire the associated property of what is now called inertial ( or rest ) mass.
Electrons, neutrinos, quarks and W/Z particles, previously massless, now had mass, and they comprise what we generally call 'matter'

Lots of good information from you guys. I have a bunch of questions to make sure my thoughts are matching up with the science and I’m not forcing the science to match my thoughts. I will focus on one at a time.

I need to clear up the definition of energy has an equivalence to mass. I always thought of equivalence as if you have X amount of mass, you would end up with X amount of energy if it was released from the matter it was associated with.

On the flip side, the side I’m interested in, if you have X amount of massless energy that was converted to matter, you would end up with X amount of mass. The energy that was converted to the “object” is now at rest in that “object”. Mass of an object is a measure of it’s energy content.

My thoughts are at the start of time, when there was no matter yet, just energy associated with fields.

I always thought it as being a hypothetical scenario, “if this occurred, this would be the end result”. Like in this experiment, I’m imagining they know exactly how much mass they will end up with if they succeed with converting massless energy into matter.

Edited by Short timer

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49 minutes ago, Short timer said:

Lots of good information from you guys. I have a bunch of questions to make sure my thoughts are matching up with the science and I’m not forcing the science to match my thoughts. I will focus on one at a time.

I need to clear up the definition of energy has an equivalence to mass. I always thought of equivalence as if you have X amount of mass, you would end up with X amount of energy if it was released from the matter it was associated with.

If there is a way to do that conversion, as with matter-antimatter annihilation, yes. e.g. an electron and positron annihilating will convert their 1.022 MeV of rest mass into that amount of photon energy (two or more photons, in order to conserve momentum)

Quote

On the flip side, the side I’m interested in, if you have X amount of massless energy that was converted to matter, you would end up with X amount of mass. The energy that was converted to the “object” is now at rest in that “object”. Mass of an object is a measure of it’s energy content.

If you have a photon of sufficient energy you can create a particle/antiparticle pair.

Quote

I always thought it as being a hypothetical scenario, “if this occurred, this would be the end result”. Like in this experiment, I’m imagining they know exactly how much mass they will end up with if they succeed with converting massless energy into matter.

One problem is knowing how much energy you start with. It could be zero. We typically only measure changes (or differences) in energy.

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1 hour ago, swansont said:

If you have a photon of sufficient energy you can create a particle/antiparticle pair.

Not on it's own though?

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3 hours ago, J.C.MacSwell said:

Not on it's own though?

No. You need something else around to recoil a tiny bit so that momentum is conserved.

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1 hour ago, swansont said:

No. You need something else around to recoil a tiny bit so that momentum is conserved.

I was also thinking something (same something) wrt which it would have sufficient energy, needing to take part.

Edited by J.C.MacSwell

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No you simply need some form of interaction. For example if you pass the photon beam through a polarizer lens you can split the original photon wavelength into two seperate beams. The two waveforms will be half the wavelength of the original beam.

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Again, this is not 'energy' becoming matter.
Both mass and energy are properties, and can be associated with particles.
Massless particles ( say photons ) don't have inertial mass, but they do have energy ( momentum >> kinetic energy ).
They can convert to an electron/positron pair where some of that energy is converted to inertial mass (accoding to conservation laws ).
Both, the initial photons ( massless and very energetic ) and final fermions ( massive but not so energetic) generate the equivalent gravitational field.

Edited by MigL

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1 hour ago, Mordred said:

No you simply need some form of interaction. For example if you pass the photon beam through a polarizer lens you can split the original photon wavelength into two seperate beams. The two waveforms will be half the wavelength of the original beam.

If nothing takes part in the interaction from a frame in which the photon's energy is sufficient, how is it that any photon would not have sufficient energy?

The argument being that as there can be no preferred frame of reference, how can any photon have insufficient energy?

I think there needs to be something participating that has a frame from which the photon measures as having sufficient energy. How can that be incorrect?

Edited by J.C.MacSwell

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3 hours ago, Mordred said:

I don't think it was very well worded. Does it make sense now?

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10 hours ago, J.C.MacSwell said:

If nothing takes part in the interaction from a frame in which the photon's energy is sufficient, how is it that any photon would not have sufficient energy?

I don’t understand. Something takes part in the interaction. You’ve had two of us state that.

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