# The Naked Scientists Forum

### Author Topic: Does light have mass?  (Read 77660 times)

#### lightarrow

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##### does light have mass?
« Reply #25 on: 19/07/2007 18:40:05 »
Last time I checked mass and energy were equivalent; doesn't that mean that light, which clearly has energy, must have mass?
Bored Chemist is RIGHT!
Even through we will never be able to mesure it as it allways moves @ C because if we say that it doesn't mass then we are saying than E=MC2 is totally wrong.
I donn't think anyone here is going to think that E=MC2 is  Totally Wrong !!!!!!
Ed
Probably you have missed my post of 19.06.2007. Read it well.

#### lightarrow

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##### does light have mass?
« Reply #26 on: 19/07/2007 18:51:54 »
If light has no mass, how would you explain the working of a solar sail?
Light has momentum p even if it has no mass: p = E/c.
The electric and magnetic field of an EM radiation make a force which is orthogonal to the surface, to the material's electric charges. This force pushes the sail.
Sorry, I must dissagree, EM forces has nothing to do with solar sails.

It is the fact that the solar sail is highly reflective...

1.Have you ever asked yourself why and how light can be reflected? Ok, I tell you: because light is an electromagnetic wave and when hits a surface, it puts in motion the electrons of the surface, making them oscillate, so they, in turn, generate an EM radiation because of their accelerated motion, and this is the light which comes out of the surface. Do you see strong or weak nuclear forces, or gravitational forces in this process?
2.There would be a push on the sail even if it was completely absorbing.

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##### does light have mass?
« Reply #27 on: 19/07/2007 20:13:52 »
I remember having as a child what looked like an upside down glass light bulb.

It had a small set of sails inside that were white on one side and black on the other and they rotated in sunlight or from a strong beam of light. Cant remember what it was called though.

I think that a photon is a particle that does have mass and its the gravitational force (wave) that propels it. I don't believe in the theory of any strong or weak forces.

#### paul.fr

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##### does light have mass?
« Reply #28 on: 19/07/2007 20:36:47 »
I remember having as a child what looked like an upside down glass light bulb.

It had a small set of sails inside that were white on one side and black on the other and they rotated in sunlight or from a strong beam of light. Cant remember what it was called though.

I think that a photon is a particle that does have mass and its the gravitational force (wave) that propels it. I don't believe in the theory of any strong or weak forces.

They still sell them, but i too forget what they are called.

#### lightarrow

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##### does light have mass?
« Reply #29 on: 20/07/2007 13:28:19 »
I remember having as a child what looked like an upside down glass light bulb.
It had a small set of sails inside that were white on one side and black on the other and they rotated in sunlight or from a strong beam of light. Cant remember what it was called though.
I think that a photon is a particle that does have mass and its the gravitational force (wave) that propels it. I don't believe in the theory of any strong or weak forces.

If your theory is right, why then the toy rotates in the opposite sense to what you would think?

Answer: the toy is not perfect, some air remains inside even if they try to make the void there. So, the black side of the "flags" is heated from the light more than the reflecting (or white) side; this heats the air molecules near the black side more than the air mol. on the other side, and for reaction they are thrown away, pushing ahead the black side.

If there was complete void, the rotation would be in the opposite sense: the momentum that the reflecting side receives from the light is twicw that received from the black one (theorically, for a total absorbing and total reflecting case), so the reflecting side would be pushed more.

In presence of air, the first effect prevails on the second, and the black side is pushed more than the other.

If you think that light has mass, you can try to prove it. Unfortunately, physics will prove to you the opposite, so I don't think you would be easily able to prove your theory.
« Last Edit: 20/07/2007 13:32:59 by lightarrow »

#### G-1 Theory

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##### does light have mass?
« Reply #30 on: 20/07/2007 14:10:23 »
If light has no mass, how would you explain the working of a solar sail?
Light has momentum p even if it has no mass: p = E/c.
The electric and magnetic field of an EM radiation make a force which is orthogonal to the surface, to the material's electric charges. This force pushes the sail.
Sorry, I must dissagree, EM forces has nothing to do with solar sails.

It is the fact that the solar sail is highly reflective...

1.Have you ever asked yourself why and how light can be reflected? Ok, I tell you: because light is an electromagnetic wave and when hits a surface, it puts in motion the electrons of the surface, making them oscillate, so they, in turn, generate an EM radiation because of their accelerated motion, and this is the light which comes out of the surface. Do you see strong or weak nuclear forces, or gravitational forces in this process?
2.There would be a push on the sail even if it was completely absorbing.

Dear Lightarrow;

You are right that electromagnetic waves are in the light spectrum and you have a concept here that makes very good conscience.

And I truly do like how you worded it, for it really makes sense to me.
This is a concept that has not crossed my mind, and I like it.

Do you see strong or weak nuclear forces, or gravitational forces in this process?

Well; Yes I do see “ The weak nuclear force here.” Because a good friend and mentor of mine here at UT has proven that,  “The weak nuclear force and the electromagnetic force are one and the same, and he has a Nobel for his work on this. his Name is, Steven Weindberg.

Ed

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##### does light have mass?
« Reply #31 on: 20/07/2007 19:30:52 »
Thanks for that explanation Light Arrow.

If I remember the vanes in the glass bulb were in a semi vacuum.

Yes I still think light has mass and I also think that gravity is a wave and not produced by mass.

Time it does take and as there are many many gaps and assumptions in our current theories of mass, gravity and light that I think a unified field theory is hard to construct without taking a different approach.

#### lightarrow

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##### does light have mass?
« Reply #32 on: 20/07/2007 22:18:21 »
Dear Lightarrow;

You are right that electromagnetic waves are in the light spectrum and you have a concept here that makes very good conscience.

And I truly do like how you worded it, for it really makes sense to me.
This is a concept that has not crossed my mind, and I like it.

Do you see strong or weak nuclear forces, or gravitational forces in this process?

Well; Yes I do see “ The weak nuclear force here.” Because a good friend and mentor of mine here at UT has proven that,  “The weak nuclear force and the electromagnetic force are one and the same, and he has a Nobel for his work on this. his Name is, Steven Weindberg.

Ed

Yes, you're right.

#### lightarrow

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##### does light have mass?
« Reply #33 on: 20/07/2007 22:20:09 »
Thanks for that explanation Light Arrow.

If I remember the vanes in the glass bulb were in a semi vacuum.

Yes I still think light has mass and I also think that gravity is a wave and not produced by mass.

Time it does take and as there are many many gaps and assumptions in our current theories of mass, gravity and light that I think a unified field theory is hard to construct without taking a different approach.

I agree with your last sentence.

#### marklee

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##### does light have mass?
« Reply #34 on: 19/01/2008 07:34:32 »
i feel that since light has a push on objects such as solar-sail-equipped satellites, it should have mass. and for electronic waves, they should not have an extra push against a mirror. but sunlight does. shouldn't that mean that the light itself has mass?

#### lightarrow

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##### does light have mass?
« Reply #35 on: 19/01/2008 08:43:22 »
i feel that since light has a push on objects such as solar-sail-equipped satellites, it should have mass. and for electronic waves, they should not have an extra push against a mirror. but sunlight does. shouldn't that mean that the light itself has mass?

Momentum is not m*v, in general. For example, is not m*v for photons and for light in general. For light momentum p = E/c where E = energy. So, there is no need to have mass to have momentum.

#### Supercryptid

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##### does light have mass?
« Reply #36 on: 21/01/2008 20:42:18 »
Here's an idea for an experiment. Build two lasers that, ideally, would be perfectly parallel to one another and would project laser beams that are also perfectly parallel to one another and do not spread out as they travel (or spread out negligably for the purposes of this experiment).

Take these parallel lasers in into an area of outer space where outside interferences are negligably small (gravity, dust, gas, etc.). Build a detector and put it some distance away, perhaps several million miles. Now activate the lasers simultaneously. The distance apart that the two laser beams are at the moment they are fired is labeled "x", and the distance apart that the two laser beams are when they arrive at the detector is labeled "y". The detector is designed to measure "y".

If the laser beams generate their own gravitational fields, then they should be mutually attracted to one another as they travel through space. If this is the case, then "x" will be greater than "y". If the beams do not gravitationally attract one another, then "x" should equal "y".

Therefore, if the detector finds that "x" > "y", then the laser beams generated their own gravitational fields and therefore had mass. If the detector finds that "x" = "y", then the laser beams did not generate their own gravitational fields and therefore did not have mass (according to my understanding, at least).

#### lightarrow

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##### does light have mass?
« Reply #37 on: 22/01/2008 13:12:12 »
Here's an idea for an experiment. Build two lasers that, ideally, would be perfectly parallel to one another and would project laser beams that are also perfectly parallel to one another and do not spread out as they travel (or spread out negligably for the purposes of this experiment).

Take these parallel lasers in into an area of outer space where outside interferences are negligably small (gravity, dust, gas, etc.). Build a detector and put it some distance away, perhaps several million miles. Now activate the lasers simultaneously. The distance apart that the two laser beams are at the moment they are fired is labeled "x", and the distance apart that the two laser beams are when they arrive at the detector is labeled "y". The detector is designed to measure "y".

If the laser beams generate their own gravitational fields, then they should be mutually attracted to one another as they travel through space. If this is the case, then "x" will be greater than "y". If the beams do not gravitationally attract one another, then "x" should equal "y".

Therefore, if the detector finds that "x" > "y", then the laser beams generated their own gravitational fields and therefore had mass. If the detector finds that "x" = "y", then the laser beams did not generate their own gravitational fields and therefore did not have mass (according to my understanding, at least).

1. They do attract each other (no need of experiment, Einstein's equation
Gμν = (8πG/c4)Tμν says it).

2. This doesn't mean light has mass. The Einstein's equation written up contains the tensor Tμν which depends on mass AND on energy. The equation essentially says that space-time curvature (expressed by the tensor Gμν) is given by mass and energy (expressed in Tμν).

3. The fact two (stationary) laser beams attract each other doesn't mean the same thing happens with photons (you haven't said it but in case someone could think it).
« Last Edit: 22/01/2008 13:15:05 by lightarrow »

#### Ian Scott

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##### Does light have mass?
« Reply #38 on: 21/07/2008 23:29:55 »
Light and other electromagnetic radiation interests me.

Does light have finite "rest mass" I believe we can only know to an uncertainty. Lets say light travels a little bit less than "c" - no worries here as light velocity is slower in glass than a vacuum.

So could light have a finite rest mass? If light etc traveled just less than "c" this would be plausible would it not? After all "c" is just a number based on magnetism and electrostatic forces. Permeability is a defined number and other constants are made in relation to it.

Why should light not be stoppable?

Some people I read use a resonant helium "soup" to slow light to the passage of a day in a small chamber. It must have energy still. I guess it has information.

Anyway such lasers aside ...

#### Ian Scott

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##### Does light have mass?
« Reply #39 on: 22/07/2008 11:06:42 »
My guess for what it's worth is that light has a momentum but could have a rest mass > 0 so that its speed "c" is just a bit less. Will anyone here have the brain space to understand this?

Or maybe such people choose to obscure simple ideas

#### lyner

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##### Does light have mass?
« Reply #40 on: 22/07/2008 13:21:18 »
It's a wonder that you bother to post on these forums if you opinion of other contributors is so low.

Do you think that this has not all been discussed before?

Perhaps you should put us all to shame and publish a complete and mathematically consistent paper on your theory. Obviously Albert wasn't up to much as a Scientist.
« Last Edit: 22/07/2008 13:24:01 by sophiecentaur »

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##### Does light have mass?
« Reply #41 on: 22/07/2008 22:43:16 »

take 2 base element; how about H and O;

isolate them

in BEC cold state

weigh them separately

combine them; allow to sit to room temperature

now weight them again combined

will the combined weigh more than the 2 added separately?

Energy has mass

#### lyner

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##### Does light have mass?
« Reply #42 on: 22/07/2008 22:55:10 »
But photons do not have 'Rest Mass'. There is a serious distinction there.

And why bother to read through a thread? It might interfere with one's opinions.
« Last Edit: 22/07/2008 22:56:51 by sophiecentaur »

#### lightarrow

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##### Does light have mass?
« Reply #43 on: 23/07/2008 00:45:55 »
My guess for what it's worth is that light has a momentum but could have a rest mass > 0 so that its speed "c" is just a bit less. Will anyone here have the brain space to understand this?

Or maybe such people choose to obscure simple ideas

By Jove! You don't even accept that people could be on holiday? Slow down and wait a little!

Yes, photons could have mass, and in this case they would go slightly slower than c. Furthermore, their speed would depend on their frequency. Maxwell's equations should be substituted with Proca equations.
http://en.wikipedia.org/wiki/Variable_speed_of_light
Quote
Varying c in classical physics

The photon, the particle of light which mediates the electromagnetic force is believed to be massless. The so-called Proca action describes a theory of a massive photon.[1] Classically, it is possible to have a photon which is extremely light but nonetheless has a tiny mass, like the neutrino. These photons would propagate at less than the speed of light defined by special relativity and have three directions of polarization. However, in quantum field theory, the photon mass is not consistent with gauge invariance or renormalizability and so is usually ignored. However, a quantum theory of the massive photon can be considered in the Wilsonian effective field theory approach to quantum field theory, where, depending on whether the photon mass is generated by a Higgs mechanism or is inserted in an ad hoc way in the Proca Lagrangian, the limits implied by various observations/experiments may be different.[2]

However, "could have mass" doesn't mean that we are not able to measure it, it means that "if" they have, its value is under the experimental limits, that is < ~ 10-52 kg.

Anyway, the photon's mass would NOT be E/c2, but an incredibly smaller value (and independent from the energy E).
« Last Edit: 23/07/2008 01:02:44 by lightarrow »

#### lightarrow

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##### Does light have mass?
« Reply #44 on: 23/07/2008 00:53:29 »
But If you had done it..... you would have found what exactly your statement means and what doesn't mean.
Quote
take 2 base element; how about H and O;

isolate them

in BEC cold state

weigh them separately

combine them; allow to sit to room temperature

now weight them again combined

will the combined weigh more than the 2 added separately?

Energy has mass

You don't need such complicated way to show that giving energy to a body AT REST increases its mass: heat a piece of iron and you increases its mass; spin it and you increases its mass, ecc, ecc.
Not only: while a single photon has NO mass, a system of two photons travelling in two different directions DO have mass!

If you want to know a bit more:
http://www.thenakedscientists.com/forum/index.php?topic=14606.msg174225#msg174225
« Last Edit: 23/07/2008 01:27:26 by lightarrow »

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##### Does light have mass?
« Reply #45 on: 23/07/2008 01:17:52 »
But photons do not have 'Rest Mass'. There is a serious distinction there.
every single atom that increases a state or even combines with another atom to form a molecule is em or simply a per se photon; at rest if you will.

energy itself is simply a line item of the em spectrum

Quote

And why bother to read through a thread? It might interfere with one's opinions.
i did my homework decades ago.....

by 10 quadratics, parabola.... by 16 a thesis on the human brain;

designed a gyro for navigation and even how to build a firecracker....

an opinion from you after our last thread is not worth much

Quote
You don't need such complicated way to show that giving energy to a body AT REST increases its mass: heat a piece of iron and you increases its mass; spin it and you increases its mass, ecc, ecc.
Hey a thinker....

Quote

Not only: while a single photon has NO mass,
ooops...

i disagree, that is a math error, not reality

« Last Edit: 23/07/2008 01:21:05 by Bishadi »

#### lightarrow

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##### Does light have mass?
« Reply #46 on: 23/07/2008 01:33:54 »
Quote

Not only: while a single photon has NO mass,
ooops...

i disagree, that is a math error, not reality

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##### Does light have mass?
« Reply #47 on: 23/07/2008 01:55:38 »

now do you see why Virial is so messed up?

All that energy and simply land locked and now you can see why the data from the spiraling galaxies do not meet the math of Virial; because of the exact statment you just made.

i.e... if i told you you won the lotterey; would you have more potential than if i told you you just lost your job.

simple exchanges of energy and a huge variation of potential

The energy upon mass has far more affect/potential than most comprehend.

#### Andrew K Fletcher

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##### Does light have mass?
« Reply #48 on: 23/07/2008 09:35:17 »
I agree!

I remember having as a child what looked like an upside down glass light bulb.

It had a small set of sails inside that were white on one side and black on the other and they rotated in sunlight or from a strong beam of light. Cant remember what it was called though.

I think that a photon is a particle that does have mass and its the gravitational force (wave) that propels it. I don't believe in the theory of any strong or weak forces.

#### Andrew K Fletcher

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##### Does light have mass?
« Reply #49 on: 23/07/2008 09:40:07 »
Now I disagree as the mass holds my feet on the ground.
Thanks for that explanation Light Arrow.

If I remember the vanes in the glass bulb were in a semi vacuum.

Yes I still think light has mass and I also think that gravity is a wave and not produced by mass.

Time it does take and as there are many many gaps and assumptions in our current theories of mass, gravity and light that I think a unified field theory is hard to construct without taking a different approach.

The Crookes radiometer is well known to the physics student and in science shops as a fascinating toy (Figure 13). It is a rotator with vanes polished on one side and black on the other. These are placed on a free shaft in a glass bulb which has been evacuated to a pressure of 10-3 to 10-4 atmospheres. It was the first demonstration of the conversion of light into mechanical energy. There was vigorous debate in the 1870’s over how it worked1.  The traditional explanation involves collision of air molecules with the hot black surface causing it to recoil, but this is incorrect2.  Reynolds and Maxwell proposed an explanation involving ‘thermal transpiration’ but even today there is still no complete explanation of how this little toy works.

The vanes rotate very rapidly in bright sunlight making several thousand revolutions per minute. Crookes3 measured the ‘radiometer force’ and found it to be several orders of magnitude greater than the ‘light pressure’ anticipated by Maxwell. There has been no attempt to harness the rotational energy to measure the efficiency of conversion but I suspect that solar is converted into rotational energy with very high efficiency in the radiometer.
http://www.kbescientific.com.sg/science_demonstration.htm

http://www.genuineideas.com/HallofInventions/SolarFerrisWheel/solarferriswheel.html

« Last Edit: 23/07/2008 11:26:17 by Andrew K Fletcher »

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##### Does light have mass?
« Reply #49 on: 23/07/2008 09:40:07 »