Is light a type of matter and can it be affected by gravity?

[MrPotato1990]

My friend believe that light is a type of matter. He thinks that light is a matter because it can be sucked into the black hole. So, I've wondered this. Is light a type of matter, or is it just a wave. If it is a wave, how can it be sucked into the black hole. Is light effected by the gravity? How can light travels through vacuum. What is the differences between the sound wave and the light wave, apart from sound wave need medium to travel.

 

[DaveC426913]

My friend believe that light is a type of matter. He thinks that light is a matter because it can be sucked into the black hole. So, I've wondered this. Is light a type of matter, or is it just a wave. If it is a wave, how can it be sucked into the black hole. Is light effected by the gravity? How can light travels through vacuum. What is the differences between the sound wave and the light wave, apart from sound wave need medium to travel.

Your friend is wrong.

Light is energy. Energy is affected by gravity. Gravity does not suck things; what gravity does is distort space-time. Light, and all other forms of electromagnetic radiation, follows the curved paths made by distorted space-time.

 

[granpa]

light would be affected even if it was a wave.

 

[cragar]

even you and I behave as a wave and a particle , wave particle duality.
not only is light affected by gravity , it creates a gravitational field of its own.
light is energy just like "davec426913" said but light can be transformed into matter
an electron positron pair , E=mc^2

 

[ZapperZ]

My friend believe that light is a type of matter. He thinks that light is a matter because it can be sucked into the black hole. So, I've wondered this. Is light a type of matter, or is it just a wave. If it is a wave, how can it be sucked into the black hole. Is light effected by the gravity? How can light travels through vacuum. What is the differences between the sound wave and the light wave, apart from sound wave need medium to travel.

Please start by reading an entry in our FAQ thread in the General Physics forum.

Zz.

 

[cragar]

what gravity does is distort space-time.

Not to argue with you Dave but does gravity distort space-time or does mass and energy distort space-time and gravity is the affect of the distortion.

 

[Dale]

The particles we call "matter" are fermions which obey the Pauli exclusion principle. Photons are bosons and do not obey the Pauli exclusion principle.

 

[QuantumPion]

The particles we call "matter" are fermions which obey the Pauli exclusion principle. Photons are bosons and do not obey the Pauli exclusion principle.

I don't think this is correct. Matter is anything that has mass. There are bosons that have mass, such as the W and Z bosons (as well as composite particles such as mesons and helium-4).

 

[DaveC426913]

Not to argue with you Dave but does gravity distort space-time or does mass and energy distort space-time and gravity is the affect of the distortion.

Yes. My bad. I was over-simplifying. Yours is worded better.

 

[Dale]

Matter is anything that has mass.

I disagree. A pair of photons traveling in opposite directions has mass, but is not matter. A container of hot gas has more mass than an otherwise identical container of cold gas, but no more matter. Etc. I would not equate matter with mass.

The usual kind of basic definition of matter is anything that has mass and takes up space. Fermions take up space because they obey the Pauli exclusion principle. Bosons do not obey it, so they don't take up space, so they are not matter. However, you are correct that the majority of the mass of ordinary matter is due to the massive gauge bosons that mediate the strong interaction.

 

[VictorFS]

My friend believe that light is a type of matter. He thinks that light is a matter...

This is a physical and metaphysical point simultaneously. Photon reunites in itself light that has to do only with the sense of sight and therefore it is not physical but a mental sense. At the same time light is physical object because it must have a reflecting matter means.

Another way photon reunites in itself, of inseparable form, matter and energy. In their interaction photon performs like matter and energy at the same time.

 

[QuantumPion]

I disagree. A pair of photons traveling in opposite directions has mass, but is not matter. A container of hot gas has more mass than an otherwise identical container of cold gas, but no more matter. Etc. I would not equate matter with mass.

The usual kind of basic definition of matter is anything that has mass and takes up space. Fermions take up space because they obey the Pauli exclusion principle. Bosons do not obey it, so they don't take up space, so they are not matter. However, you are correct that the majority of the mass of ordinary matter is due to the massive gauge bosons that mediate the strong interaction.

I may not be a particle physics expert (just a lowly engineer ) but I think there are several problems with your statement...

 

[DaveC426913]

I disagree. A pair of photons traveling in opposite directions has mass, but is not matter.

Of this I am not aware.

A container of hot gas has more mass than an otherwise identical container of cold gas, but no more matter. Etc. I would not equate matter with mass.

Maybe so, but it does not invalidate the claim that anything with matter has mass.

 

[Hootenanny]

Maybe so, but it does not invalidate the claim that anything with matter has mass.

But that was not QuantumPion's claim.

 

[Dale]

Maybe so, but it does not invalidate the claim that anything with matter has mass.

All fermions have mass, so I agree with the claim that all matter has mass. As Hootenany mentioned, that is not what I was objecting to. I was rejecting the reverse claim that anything with mass is matter.

 

[QuantumPion]

All fermions have mass, so I agree with the claim that all matter has mass. As Hootenany mentioned, that is not what I was objecting to. I was rejecting the reverse claim that anything with mass is matter.

I don't think this is correct. Matter is anything that has mass. There are bosons that have mass, such as the W and Z bosons (as well as composite particles such as mesons and helium-4).

 

[Hootenanny]

There are two 'claims' being discussed here:

1. Anything with mass is matter
2. All matter is mass

The first of which is yours, which is what DaleSpam (and I) disagree with. Can you not see the difference between the two statements?

 

[QuantumPion]

There are two 'claims' being discussed here:

1. Anything with mass is matter
2. All matter is mass

The first of which is yours, which is what DaleSpam (and I) disagree with. Can you not see the difference between the two statements?

Perhaps I should specify rest mass? I thought the term "relativistic mass" had fallen out of use due to such confusion.

 

[Volcano]

There are two 'claims' being discussed here:
Anything with mass is matter

Above not correct is it? Then something has mass but not matter, what is it? Photon?

 

[Dale]

A pair (or more) of photons, thermal energy, the Z and W gauge bosons, etc. all have mass but are not matter. Thermal energy is probably the most clear-cut example of something with mass but not matter.

 

[Topher925]

Why is everyone arguing so much about this? Both "matter" and "mass" have several definitions, not just one. For example, just look at their wikipedia pages

http://en.wikipedia.org/wiki/Matter
http://en.wikipedia.org/wiki/Mass

Anyway, I define matter as anything that can be influenced by energy and I define mass as anything that has a gravitational field.

Flame shields up!

 

[QuantumPion]

A pair (or more) of photons, thermal energy, the Z and W gauge bosons, etc. all have mass but are not matter. Thermal energy is probably the most clear-cut example of something with mass but not matter.

I don't know where you are getting that two photons have mass, you'll have to elaborate on that.

I don't know why you say W and Z bosons are not matter. They are heavy particles which are force carriers for the weak interaction. I suppose you could make some argument to say they aren't matter because they have a short lifetime, or cannot exist as a free particle or some such; but the same properties hold true to a lesser extent for a neutron so you'll have to elaborate.

I don't think your notion that thermal energy itself has mass, and therefore not all mass is matter makes sense. There is no such thing as thermal energy except as a property OF matter. A high temperature gas may have more relativistic mass due to the molecules' kinetic energy, but you can't have thermal energy without the matter to begin with. Just because a particle's relativistic mass increases with energy doesn't mean that you can classify that increase in energy as mass on its own in the absence of matter.

 

[QuantumPion]

Why is everyone arguing so much about this? Both "matter" and "mass" have several definitions, not just one. For example, just look at their wikipedia pages

http://en.wikipedia.org/wiki/Matter
http://en.wikipedia.org/wiki/Mass

Anyway, I define matter as anything that can be influenced by energy and I define mass as anything that has a gravitational field.

Flame shields up!

I think the problem with this is that energy itself has a gravitational field, so basically you are saying that everything in the universe has mass (which might not be incorrect but its confusing). Similarly your definition of matter pretty much encompasses anything, as even empty space is influenced by energy.

As for your wiki definition of matter, I disagree with it in this context. The wiki article defines matter as anything that has mass and volume. With this definition, quarks and electrons, as we currently understand them, would not be considered matter as they are elementary point particles with no volume. But as fermions, collections of these particles DO occupy volume.

If you want to make the argument that this is the case, and that an individual quark or electron is not matter but bound quarks are, and thus some things which have mass are not matter, then I can see where you are coming from. But I still disagree because I find the definition inconsistent . I stick by my definition of matter = anything with non-zero (rest) mass.

 

[Topher925]

As for your wiki definition of matter, I disagree with it in this context. The wiki article defines matter as anything that has mass and volume. With this definition, quarks and electrons, as we currently understand them, would not be considered matter as they are elementary point particles with no volume. But as fermions, collections of these particles DO occupy volume.

Did you scroll down or just read the first paragraph? The wiki definition gives 7 definitions of matter, including one for quarks and leptons.

 

[QuantumPion]

Did you scroll down or just read the first paragraph? The wiki definition gives 7 definitions of matter, including one for quarks and leptons.

I scrolled down AND read it. It discusses what quarks and leptons are, and further defines ordinary matter as "anything composed of quarks and leptons" but basically leaves open the question of whether the elementary particles themselves, or indeed anything with mass, is matter or not.

 

[Dale]

I don't know where you are getting that two photons have mass, you'll have to elaborate on that.

Consider the anhilation of an electron and a positron both at rest. The initial four-momentum is
(.511,0,0,0) MeV/c + (.511,0,0,0) MeV/c = (1.022,0,0,0) MeV/c
which gives an initial mass for the electron-positron pair of
|(1.022,0,0,0) MeV/c|/c = 1.022 MeV/c²

After the anhilation the four-momentum of the resulting photons are
(.511,.511,0,0) MeV/c + (.511,-.511,0,0) MeV/c = (1.022,0,0,0) MeV/c
which gives a final mass for the pair of photons of
|(1.022,0,0,0) MeV/c|/c = 1.022 MeV/c²

I don't know why you say W and Z bosons are not matter.

Sorry, I thought I was clear. They do not obey the Pauli exclusion principle, i.e. they do not take up space. The usual definition of matter is anything that has mass and takes up space. All elementary fermions satisfy that definition and no elementary bosons do, so it seems like a pretty clear, easy, and reasonable separation.

I don't think your notion that thermal energy itself has mass, and therefore not all mass is matter makes sense. There is no such thing as thermal energy except as a property OF matter.

I guess this is our fundamental disagreement. Given a box of cold gas and a box of hot gas with the exact same number and types of molecules I think we both agree that the hot gas has more mass. You look at the increased mass and say therefore there is more matter, I look at the same number and types of molecules and say therefore there is the same amount of matter. The reason I disagree with your assessment is that I believe you are missing an important part of the usual definition of matter, specifically that it takes up space.

 

[QuantumPion]

Consider the anhilation of an electron and a positron both at rest. The initial four-momentum is
(.511,0,0,0) MeV/c + (.511,0,0,0) MeV/c = (1.022,0,0,0) MeV/c
which gives an initial mass for the electron-positron pair of
|(1.022,0,0,0) MeV/c|/c = 1.022 MeV/c²

After the anhilation the four-momentum of the resulting photons are
(.511,.511,0,0) MeV/c + (.511,-.511,0,0) MeV/c = (1.022,0,0,0) MeV/c
which gives a final mass for the pair of photons of
|(1.022,0,0,0) MeV/c|/c = 1.022 MeV/c²

So essentially you are saying that since an electron and a positron have mass, and they can annihilate to create two photons, those two photons have mass? I'm pretty sure this is entirely incorrect. Photons are massless. The photons do affect the gravitational field since they have energy, but I don't think you are arguing that anything that creates a gravitational field is matter.

Sorry, I thought I was clear. They do not obey the Pauli exclusion principle, i.e. they do not take up space. The usual definition of matter is anything that has mass and takes up space. All elementary fermions satisfy that definition and no elementary bosons do, so it seems like a pretty clear, easy, and reasonable separation.

And as I pointed out, a single free electron does not take up space either, since it has no volume. Furthermore, just because a particle obeys Bose-Einstein statistics does not mean it takes up no space. All it means is that the particles can occupy the same quantum states, i.e. many bosons can occupy the same space. That space isn't necessarily zero. For example, a Bose-Einstein condensate of helium atoms.

I guess this is our fundamental disagreement. Given a box of cold gas and a box of hot gas with the exact same number and types of molecules I think we both agree that the hot gas has more mass. You look at the increased mass and say therefore there is more matter, I look at the same number and types of molecules and say therefore there is the same amount of matter. The reason I disagree with your assessment is that I believe you are missing an important part of the usual definition of matter, specifically that it takes up space.

I think you are a bit confused. This is exactly what I am arguing AGAINST, and what you have been arguing in favor of until your last paragraph! I specifically stated that a hot gas does NOT have more matter then a cold gas. I stated "matter is anything that has mass". When you posited that a hot gas has greater "mass" then a cold gas as an example to disprove my definition, I pointed out that your argument was flawed because the "relativistic mass" of a hot gas is not the same as rest mass.

 

[atyy]

In general relativity lingo, the stuff that curves spacetime is often called matter. In this lingo, light is matter.

In quantum field theory lingo, interactions between fermionic matter are mediated by bosonic gauge fields. In this lingo, light which is a massless gauge boson is not matter.

 

[Hootenanny]

So essentially you are saying that since an electron and a positron have mass, and they can annihilate to create two photons, those two photons have mass? I'm pretty sure this is entirely incorrect. Photons are massless. The photons do affect the gravitational field since they have energy, but I don't think you are arguing that anything that creates a gravitational field is matter.

I'm not getting into the debate about fermionic/bosonic matter. However, I can say that DaleSpam is absolutely correct. Although photons are indeed massless, a pair of photons can have a mass, as DaleSpam has shown through conservation of four-momentum.

If you disagree with DaleSpam's analysis, can you show how the annihilation of an electron and positron can create a pair of photons with a zero mass? Alternatively, can you point out the error in DaleSpam's analysis?

 

[Volcano]

...I guess this is our fundamental disagreement. Given a box of cold gas and a box of hot gas with the exact same number and types of molecules I think we both agree that the hot gas has more mass...

I am really asking, is there such an experiment? And second question; is there something has mass but not matter, what is it?

 

[Dale]

Volcano, you already asked this in post 19 and I already answered in post 20. Stop repeating yourself.

 

[Hootenanny]

I am really asking, is there such an experiment?

I'm not sure what you're asking here. Clearly we can perform a gedanken experiment, whether or not we can perform an actual experiment is irrelevant here.

And second question; is there something has mass but not matter, what is it?

Yes, as has been said many times in this thread a photon pair resulting from the annihilation of an electron and positron pair has a non-zero mass, but is not considered matter.

Edit: DaleSpam beat me to it

 

[Dale]

So essentially you are saying that since an electron and a positron have mass, and they can annihilate to create two photons, those two photons have mass? I'm pretty sure this is entirely incorrect. Photons are massless.

This is entirely correct, individual photons are massless.
|(.511, .511,0,0) MeV/c|/c = 0 MeV/c²
|(.511,-.511,0,0) MeV/c|/c = 0 MeV/c²

But a system of photons can have mass if the photons are not traveling in the same direction.
(.511,.511,0,0) MeV/c + (.511,-.511,0,0) MeV/c = (1.022,0,0,0) MeV/c
|(1.022,0,0,0) MeV/c|/c = 1.022 MeV/c²

In general a system of particles will have a different mass than the sum of the masses of its constituent particles.

many bosons can occupy the same space. That space isn't necessarily zero. For example, a Bose-Einstein condensate of helium atoms.

You are correct. I was thinking only of elementary particles where elementary bosons do not take up space due to not obeying the Pauli exclusion principle.

I guess I would tentatively also say that any composite particle containing fermions is matter, even if the composite particle as a whole is a boson. Unfortunately, I haven't thought about it enough to catch any potential contradiction.

I think you are a bit confused. This is exactly what I am arguing AGAINST, and what you have been arguing in favor of until your last paragraph! I specifically stated that a hot gas does NOT have more matter then a cold gas. I stated "matter is anything that has mass".

If matter is anything that has mass and a hot gas has more mass than a cold gas then I don't see how you can consistently claim that a hot gas does not have more matter than a cold one.

When you posited that a hot gas has greater "mass" then a cold gas as an example to disprove my definition, I pointed out that your argument was flawed because the "relativistic mass" of a hot gas is not the same as rest mass.

I am using the usual definition of mass as being the invariant norm of the four-momentum, aka rest mass. I am certainly not talking about relativistic mass. The invariant rest mass of the hot gas is higher than that of the cold gas. A hot gas has more energy in its rest frame, it has more inertia as measured in its rest frame, and according to GR it has more gravity.

 

[QuantumPion]

This is entirely correct, individual photons are massless.
|(.511, .511,0,0) MeV/c|/c = 0 MeV/c²
|(.511,-.511,0,0) MeV/c|/c = 0 MeV/c²

But a system of photons can have mass if the photons are not traveling in the same direction.
(.511,.511,0,0) MeV/c + (.511,-.511,0,0) MeV/c = (1.022,0,0,0) MeV/c
|(1.022,0,0,0) MeV/c|/c = 1.022 MeV/c²

In general a system of particles will have a different mass than the sum of the masses of its constituent particles.,

I'll concede I don't know enough about general relativity to argue the point further. If a system of photons does have real mass then I guess my definition of matter is too broad after all.

 

[Volcano]

Sorry for two reason,

1. Couldn't distinguish DaleSpams's above reply
2. I guessed you talking about energy-mass differences. But you mean mass-matter difference.

But already want to learn thermal energy and mass relation. Please give me a link to read.

And, please think one more time before supposing someone repeating irrevelant. But, if really believe this, shortly, don't reply ;) I came here to ask, learn and share; not more.

Edit: Thought twice :)