Is Light Matter?

Is light a physical thing, in other words, is it matter?

Light is another name for electromagnetic radiation, which is the transmission of energy. It is energy. Einstein's equation shows that energy and matter are the same concept, so in a way, it is.

Is light a physical thing, in other words, is it matter?

Light is a flow of a huge number of particles - photons. Photons have zero mass, but this doesn't make them any "less" matter than electrons or protons.

Eugene.

Claude Bile
Einstein's equation shows that energy and matter are the same concept, so in a way, it is.
E = mc^2 is the equivalence of mass and energy, not matter and energy.

Matter is traditionally regarded as stuff with rest mass, i.e. protons, neutrons, electrons and so forth, and is distinct from inertial mass.

Claude.

DaveC426913
Gold Member
this doesn't make them any "less" matter than electrons or protons.

Eugene.
In fact, it does.

Light is not matter. Light is energy. This is not a point of debate.

In fact, it does.

Light is not matter. Light is energy. This is not a point of debate.

I agree, but I think there are plenty who will debate this (I hope). Not being smart, just trying to learn,

DaveC426913
Gold Member
I agree, but I think there are plenty who will debate this (I hope). Not being smart, just trying to learn,
You agree, but you're looking for debate? Are you just looking to stir a pot or something?

Really. There's no debate. It's not open to interpretation.

Light is energy.
But such a statement does not distinguish it from matter. Nonetheless, distinction from radiation is a practical meaning for modern use of the term "matter".

On the other hand, language is fluid: "Space-time tells matter how to move".

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My purpose is not to stir. There are many people who argue that light is matter, and I would like to learn what their argument is and how credible it is. One of the hardest things with learning modern science is that there seems to be so many conflicting conclusions, it's hard to know which to believe.

Swerdna, are you sure those people weren't merely asserting that light has (relativistic) mass?

castlegates
Matter to me is localized energy. In this instance light is matter. Thats my take anyway.

Swerdna, are you sure those people weren't merely asserting that light has (relativistic) mass?
If they are, they aren’t making that point clear. Does that light has “relativistic mass” mean it is matter?

This argument has been put to me . . .

If E = mc^2, and light = E, then light = mc^2. Therefore light is matter.

Given, as Claude Bile stated (post #4), “E = mc^2 is the equivalence of mass and energy, not matter and energy”, I guess they are saying that because light has relativistic mass it is matter.

Matter to me is localized energy. In this instance light is matter. Thats my take anyway.
Matter contains energy, but how does that make energy matter? A sponge can contain water, but that doesn't make the sponge water.

prasannapakkiam
While we are on the topic. Does this prove that light cannot have mass?:

m=m0*(Gamma)

ZapperZ
Staff Emeritus
My purpose is not to stir. There are many people who argue that light is matter, and I would like to learn what their argument is and how credible it is. One of the hardest things with learning modern science is that there seems to be so many conflicting conclusions, it's hard to know which to believe.

Can you point out who "these people" are? I mean, if you're referring to crackpots who barely know physics, then we're wasting out time here, aren't we?

There is a FAQ in here that addresses the misuse of that Einstein equation. You may want to start with that. After you've done that, then maybe you should then proceed with defining what you mean by "matter". Only after you do these two, then maybe we can use that criteria of what "matter" is to see if light has such a property. I think this is the only sensible way to approach such a thing, using valid definitions and a clear understanding of what we are talking about. The way this thread has proceeded appears to be more of a "make it up as I go along" type.

Zz.

DaveC426913
Gold Member
Matter to me is localized energy. In this instance light is matter. Thats my take anyway.
Algebraically, this is what you've said:
A = Matter
B = Energy
c = localized (a modifier)

Since A = cB, therefore B=A. (Where did the c go?)

Because matter is localized energy does not make light matter. Not the least reason of which is because light is not localized; it moves at c. And If it didn't, it wouldn't be light.

castlegates
Because matter is localized energy does not make light matter.
Thats exactly what it makes it .... if true.
Not the least reason of which is because light is not localized; it moves at c.
Didn't say that light does not move at C, only that if it is localized, it can take on the characteristics of matter. A solor sail for instance one could consider as a situation where light is very briefly localized, by which light takes on a characteristic of mass by which a sail can be pushed.

Light could be said to move in a straight line, but what if it follows an orbital pattern. I.E. localization.

DaveC426913
Gold Member
Thats exactly what it makes it .... if true.
No. It does not. This claim holds no water.

Didn't say that light does not move at C, only that if it is localized, it can take on the characteristics of matter. A solor sail for instance one could consider as a situation where light is very briefly localized
One can "consider" all one wants. One can consider faeries, but that doesn't make them exist.

Light could be said to move in a straight line, but what if it follows an orbital pattern. I.E. localization.
You are making up definitions as you go. This has nothing to do with reality. Science is not a form of poetry.

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Algebraically, this is what you've said:
A = Matter
B = Energy
c = localized (a modifier)

Since A = cB, therefore B=A. (Where did the c go?)

Because matter is localized energy does not make light matter. Not the least reason of which is because light is not localized; it moves at c. And If it didn't, it wouldn't be light.

Mathematically speaking, c is a constant, however, it is possible for light to be slowed down in a Bose-Einstein condensate.

Lene Hau (Harvard University and Rowland Institute)

The latest results from the Bose-Einstein condensation experiment at the Rowland Institute presented using a combination of laser and evaporative cooling to create Bose-Einstein condensates of sodium atoms in a '4D' magnetic bottle. We have succeeded in reducing the light speed in a Bose condensate to the speed of a bicycle by using the effect of electromagnetically induced transparency. Most recently we have brought light to a complete standstill. The results have implications for quantum information processing, for probing and manipulation of Bose-Einstein condensates, and for nonlinear optics.

Light affects matter, like sun rays evaporating water, therefore is physical. Einstein's famous equation, E=mc2, shows that (light) energy cannot exist without (matter) mass, and contrariwise. Furthermore, both light and matter can exist as particle or wave, according to de Broglie. The property of mass is mediated by a physical entity, the Higgs potential.

Light has a wave-particle duality. In other words, the higher you go in frequency, the more light begins to look and act like a (massless) particle, with "probability amplitudes," or quanta. I think this is more or less the direction the OP was heading. Matter has definite distinction when examining light-matter interactions, so I would venture to say that no, light is not matter.

Edit: Bah, you beat me to it Loren Booda, although you failed to mention that the Higgs boson is still a purely theoretical conjecture.

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In other words, the higher you go in the spectrum of wave length/frequency, the more light begins to look and act like a (mass less) particle, with "probability amplitudes," or quanta.

I would have thought the contrary :

$$E=mc^2$$ (einstein)
$$E=h\nu$$ (Planck, where $$\nu$$ is the frequence of the wave)
thus, m = $$\frac{h\nu}{c²}$$.

so the higher you "go in the spectrum of wave length/frequency", the bigger the mass of the photon, and then the more it acts like a massy particle.

I would have thought the contrary :

$$E=mc^2$$ (einstein)
$$E=h\nu$$ (Planck, where $$\nu$$ is the frequence of the wave)
thus, m = $$\frac{h\nu}{c²}$$.

so the higher you "go in the spectrum of wave length/frequency", the bigger the mass of the photon, and then the more it acts like a massy particle.

Goddamn E=mc^2 !!! If only people would learn why that is they'd stop applying it to things outside of its applicability! The full formula:

$$E^2 - p^2 c^2 = m^2 c^4$$

E=mc^2 only holds when p=0 -- for a stationary particle. Is a photon ever stationary? Furthermore, m=0 for a photon, so the energy and momentum is tightly linked: E = pc. Add to that, $$E = \hbar \nu$$ and $$p = \frac{\hbar}{\lambda}$$ and you've got everything. Thus higher energy gives higher momentum, which gives *lower* wavelength, thus a high energy photon is better localised in space, behaving more like a particle.

I was right in principle, at least. Just take out "wavelength" save frequency and it all makes perfect sense.