# Mass and Light: Is There a Connection?

• bodhi
In summary: The speed of light is still a constant, even a century after its theoretical introduction.The speed c is fundamental, but not because it is the speed of light. Light happens to travel at that speed because photons have zero invariant mass. Other particles with zero invariant mass would also travel at speed c. If photons had nonzero invariant mass, they would not travel at speed c, but c would still be a fundamental speed in relativity.
bodhi
e=mc2
mass is same as energy along with a multiplier c2
when fusion takes place photon is lost n mass is decreased
can we then say mass is made of light,or mass is light conglomerated or saturated.

bodhi said:
e=mc2
mass is same as energy along with a multiplier c2
when fusion takes place photon is lost n mass is decreased
can we then say mass is made of light,or mass is light conglomerated or saturated.

Mass is equivalent to a certain amount of Energy according to E=mc², and can can be transformed into other forms of energy through processes like fusion. To say that mass is made of light is not quite correct.

bodhi said:
e=mc2
mass is same as energy along with a multiplier c2
Please use standard punctuation and grammar when you post on PF, not text-speak.

bodhi said:
when fusion takes place photon is lost n mass is decreased
Photons are typically emitted in nuclear fusion, but other things are emitted as well, typically neutrons.

bodhi said:
can we then say mass is made of light,or mass is light conglomerated or saturated.
It's true that a collection of photons has a nonzero rest mass. (Rest mass is not additive.) However, there is no way, for example, that you can model a proton or an electron as a collection of photons, since photons don't have charge.

Light does not play any fundamental role in relativity or in physics in general. Einstein's 1905 axiomatization of SR gives a fundamental role to light, but with 106 years worth of hindsight, that was a mistake. Light simply happened to be the only known fundamental field in 1905.

-Ben

bcrowell said:
Light does not play any fundamental role in relativity or in physics in general. Einstein's 1905 axiomatization of SR gives a fundamental role to light, but with 106 years worth of hindsight, that was a mistake. Light simply happened to be the only known fundamental field in 1905.

Could you please elaborate? The speed of light is an upper bound on the spectrum of velocities we can access, how is this not fundamental? The speed of light is still a constant, even a century after its theoretical introduction.

The speed c is fundamental, but not because it is the speed of light. Light happens to travel at that speed because photons have zero invariant mass. Other particles with zero invariant mass would also travel at speed c. If photons had nonzero invariant mass, they would not travel at speed c, but c would still be a fundamental speed in relativity.

Polyrhythmic said:
Could you please elaborate? The speed of light is an upper bound on the spectrum of velocities we can access, how is this not fundamental? The speed of light is still a constant, even a century after its theoretical introduction.

When Einstein was around, the only other field known was EM so it was postulated that nothing could travel faster than light or a photon. Now we know that this is not unique to EM or to a photon because all massless particles travel at that speed. So while the value itself is equal to that of the speed of light, it is not unique to light and in that sense the speed of light is not fundamental. I don't know if that is the subtlety you were after.

WannabeNewton said:
Now we know that this is not unique to EM or to a photon because all massless particles travel at that speed.
What other massless particles are you referring to?

Passionflower said:
What other massless particles are you referring to?

Even if they aren't all observed as free particles, all gauge bosons have no rest frame so them.

Among the gauge bosons, the W and Z have mass.

jtbell said:
Among the gauge bosons, the W and Z have mass.

Sorry I meant to say of the gauge bosons, so just the gluon and the photon.

I suppose the graviton could be included as well, although it can't be directly detected by any foreseeable technology.

-Ben

jtbell said:
The speed c is fundamental, but not because it is the speed of light. Light happens to travel at that speed because photons have zero invariant mass. Other particles with zero invariant mass would also travel at speed c. If photons had nonzero invariant mass, they would not travel at speed c, but c would still be a fundamental speed in relativity.

That is true, but when we talk about the speed of light, we mean c.

WannabeNewton said:
When Einstein was around, the only other field known was EM so it was postulated that nothing could travel faster than light or a photon. Now we know that this is not unique to EM or to a photon because all massless particles travel at that speed. So while the value itself is equal to that of the speed of light, it is not unique to light and in that sense the speed of light is not fundamental. I don't know if that is the subtlety you were after.

I know what you mean, but it's still correct to refer to that fundamental quantity as the speed of light.

bcrowell said:
I suppose the graviton could be included as well, although it can't be directly detected by any foreseeable technology.

-Ben

If you're referring to the graviton as a quantized gravitational wave, this might be correct. Gravity hasn't successfully been quantized so far though.

## 1. What is the relationship between mass and light?

The relationship between mass and light is that mass and energy are interchangeable, as described by Einstein's famous equation E=mc^2. This means that a change in mass can result in a change in energy, which includes light.

## 2. How does light interact with mass?

Light interacts with mass through the force of gravity. Mass bends the fabric of space-time, causing light to follow a curved path as it passes through. This is known as gravitational lensing.

## 3. Can mass be converted into light?

Yes, mass can be converted into light through nuclear reactions. This is the basis of nuclear fusion, where small particles are combined to form larger particles, releasing large amounts of energy in the form of light.

## 4. Is there a limit to how much mass can be converted into light?

There is no theoretical limit to how much mass can be converted into light. However, the amount of energy released is limited by the amount of mass present and the efficiency of the conversion process.

## 5. How does the speed of light relate to mass?

The speed of light is a constant, meaning it does not change regardless of the mass of the object it is passing through. However, the speed of light can be affected by the presence of mass, such as in the case of gravitational lensing.

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