Mass of Light?

[Circlenaut]

This is a question thats been bothering me for a long time. If I'm correct light has some mass due to the photons and it travels at the speed of light. Now shouldn't time slow down or stop and shouldn't the mass of the photons become infinent. Just a ponder.

 

[Evadman]

Light can be both a wave and a particle. Wave = weightless. AFAIK light has no mass. It is 100% energy.

 

[Sahakiel]

Define energy.

 

[OS]

Originally posted by: shadowmind359
This is a question thats been bothering me for a long time. If I'm correct light has some mass due to the photons and it travels at the speed of light. Now shouldn't time slow down or stop and shouldn't the mass of the photons become infinent. Just a ponder.

I don't see where you are going with this, but I'll just say that according to modern physics, photons are considered massless particles.

 

[Evadman]

Originally posted by: Sahakiel
Define energy.

Oh God, please don't ask me to go there

 

[singh]

Originally posted by: Evadman

Originally posted by: Sahakiel
Define energy.

Oh God, please don't ask me to go there

LOL I believe light has no mass, but does have momentum.

 

[heliomphalodon]

A photon has zero rest mass, but it does indeed have a finite nonzero mass directly related to its frequency.
This mass may be calculated using Einstein's famous formula e = m*c*c so the more energetic the photon, the greater its mass.

 

[Circlenaut]

Thanks guys that cleared things for me.

 

[unclebabar]

I'm a little confused about the question. What does time have to do with the mass of a photon?

Here's one:

Is there such a thing as a zero-energy photon? Like are there trillions of photons (left over from the creation of the universe) in/on a tungsten light-bulb filament waiting for electricity to free them? Or are the photons spontanously created by the electricity? Is it useful to distinguish between the two possibilities?

 

[heliomphalodon]

Originally posted by: unclebabar
I'm a little confused about the question. What does time have to do with the mass of a photon?

Here's one:

Is there such a thing as a zero-energy photon? Like are there trillions of photons (left over from the creation of the universe) in/on a tungsten light-bulb filament waiting for electricity to free them? Or are the photons spontanously created by the electricity? Is it useful to distinguish between the two possibilities?

I think shadowmind359 mentioned time stopping and mass becoming infinite because he was thinking about what might happen if one attempted to accelerate a fermion (an electron, say) to the speed of light. That's impossible since infinite energy would be required to so accelerate any particle possessing nonzero rest mass.

As to your question about a "zero-energy photon" -- there's no such thing. Since a photon is emitted when an electron falls to a lower-energy state in an atom, I suppose that one could ask where the photon "comes from" -- but the answer is that it's emitted by the electron, as you suggest in your "spontaneously created" alternative.

Whether or not it's useful to distinguish between the two possibilities -- I suppose that the "zero-energy photon" idea is vaguely akin to the concept of a virtual particle, which concept is very useful indeed! Perhaps someone familiar with Feynman diagrams and virtual particle histories can enlighten us, so to speak.

 

[CTho9305]

this means light exerts a force on everything around it? if someone shines a really really really powerful light you will get sucked into the beam? (no, i'm not serious, i'm just giving an extreme example) how "effective" is the mass? is it "real"?

 

[Evadman]

Originally posted by: CTho9305
this means light exerts a force on everything around it? if someone shines a really really really powerful light you will get sucked into the beam? (no, i'm not serious, i'm just giving an extreme example) how "effective" is the mass? is it "real"?

It would have to be re-defined in some way to pure energy ( zero mass ) or the photon could not move at light speed, because any mass would equal infinate mass @ the speed of light.

 

[unclebabar]

> Perhaps someone familiar with Feynman diagrams and virtual particle histories can enlighten us, so to speak.

ha ha, very *punny*

I took "Modern" Physics way back when I was in college. I believe I scraped by with a D or D-, which would be the extent of my expertise in this subject. I still don't see how time figures into it. Assuming time to be relative, an observer of the acceleration would sinmply see the particle disappearing and hypothetically, if you were the particle, wouldn't you just see the 'observer' diappearing but otherwise, your 'time' reference would be normal? Time would be slower outside your frame, but wouldn't you be too busy whizzing past to notice, i.e. you wouldn't know or care what time the observer was experiencing? (Slower meaning that for every second you as the particle experience, multiple seconds are experienced by the 'observer').

I wonder if shadowmind359 posted his question after reading the time dilation thread (which I've yet to wade through).

 

[unclebabar]

For CTho9305: light is just energy, if someone shined a big flashlight at you, you would have more 'energy' (and no not the kind you get from eating wheaties). If the light happened to be at the resonance frequency of water, as in the 'light' of a microwave oven, you'd be cooked. Which would probably suck. You'd need more light than you can imagine for it to turn into mass. I'd imagine you'd need a containment field, too. [btw, does anyone know what frequency light the GE Advantium oven uses?]

>It would have to be re-defined in some way to pure energy ( zero mass ) or the photon could not move at light speed, >because any mass would equal infinate mass @ the speed of light.

huh? How could a photon (in a vacuum) not move at the speed of light (in a vacuum)? Since photons are carriers of electromagnetic radiation (light).

heliomphalodon mentioned above that "if one attempted to accelerate a fermion (an electron, say) to the speed of light. That's impossible since infinite energy would be required to so accelerate any particle possessing nonzero rest mass", which I can accept but I don't remember why. Something about the speed of light being the cosmic speed limit ? However, photons, according you guys have zero-rest mass and are classified a bosons in the "Standard Model". Perhaps the exemption is due to the wave/particle duality.


I better go to sleep before my head explodes.

 

[heliomphalodon]

Originally posted by: CTho9305
this means light exerts a force on everything around it? if someone shines a really really really powerful light you will get sucked into the beam? (no, i'm not serious, i'm just giving an extreme example) how "effective" is the mass? is it "real"?

That's a great question! I've been told that energy does in fact warp space according to its mass just as matter does. Theoretically, then, two laser beams that pass close to each other at right angles will actually deflect each other. Also if we have two otherwise identical objects, one hot and one cool, the hot one is more massive.

With regard to the "stopping of time" for a particle accelerated to the speed of light (as if that were possible) -- no time at all would elapse for such a particle during a finite nonzero interval measured by another observer. Thus "time is stopped" for the particle. This effect (at a large fraction of lightspeed) has in fact been measured in the laboratory.

 

[heliomphalodon]

Originally posted by: unclebabar
heliomphalodon mentioned above that "if one attempted to accelerate a fermion (an electron, say) to the speed of light. That's impossible since infinite energy would be required to so accelerate any particle possessing nonzero rest mass", which I can accept but I don't remember why. Something about the speed of light being the cosmic speed limit ? However, photons, according you guys have zero-rest mass and are classified a bosons in the "Standard Model". Perhaps the exemption is due to the wave/particle duality.


I better go to sleep before my head explodes.

The mass of a particle increases without limit as it is accelerated toward lightspeed. Hence the energy required to accelerate the ever-more-massive particle also increases without limit.

Fermions exhibit wave/particle duality just as bosons do. It seems very strange because macroscopic objects don't display such duality. As one of my professors said, "An electron exhibits some of the properties of a macroscopic particle, and some of the properties of a macroscopic wave -- but it is neither a particle nor a wave. It is an electron."

 

[Evadman]

It would have to be re-defined in some way to pure energy ( zero mass ) or the photon could not move at light speed, because any mass would equal infinate mass @ the speed of light.

huh? How could a photon (in a vacuum) not move at the speed of light (in a vacuum)? Since photons are carriers of electromagnetic radiation (light).

That's my point. It was stated by you that it had a non zero mass, which would mean at the speed of light it would have infinate mass.

My reasoning behind this is the fact that speed adds mass. if a photon had any mass it would have to have infinate mass per e=mc^2 right? Or am I thinking too hard, or not explaininng my thinking well enough? Beer = good

 

[BumJCRules]

How would speed add mass? It wouldn't.



E=MC^2

Speed is some form of constant. Light travels at slightly different speeds through various mediums. There have been experiments where photons have exceeded the speed of light. The Photons were accelerated through the test chamber and exited faster than they entered. Messed up stuff. What practical use is there for faster photons? Maybe better bombs perhaps.

So if you are using the given constant for speed in whatever medium you choose, then the conclusion is that the greater the energy level the higher the mass has to be. It is a direct relationship.

I mean rearrange the equation. M = (E/C^2)

Light, whether using particle theory or quantum theory, will have to contain some form of mass.



Another spin on that get sucked into a high powered beam of light scenario.

Cosmic rays... X-rays.... Etc. They don't push/move you... they blast right through you. One major reason for the existence of ECC memory for computers. Digits get blown away. Not frequent but it does happen. X-rays blast through you. Some of them reflect back off of really thick or hard surfaces, a.k.a. Bones, and they develop the picture. Every thing else would be fully developed. So on the negative it would be black where the dense materials are and white where the rays hit the film. Then develop it and get the reverse.

Another is infrared light. It cooks what it hits. Microwaves pass through flesh. (Cooks from the inside out.) Shall I go on?

Light changes the surrounding environment. Whether it is wave, particle, quantum mechanics or whatever other forms you wish to choose; Light, based on modern physics would have mass.

No what are you going to do with you new found knowledge?


Back to you...

 

[unclebabar]

> No what are you going to do with you new found knowledge?

Me and Evadman are going to accelerate a can of beer to light speed to create more beer until the universe is completely made of beer. Bruhahahahaha

 

[Evadman]

Originally posted by: unclebabar
> No what are you going to do with you new found knowledge?

Me and Evadman are going to accelerate a can of beer to light speed to create more beer until the universe is completely made of beer. Bruhahahahaha

Sounds good to me! Whohoo!

 

[glugglug]

E = mc^2
E = hf ............. so

mc^2 = hf
m = hf/c^2, where h is Plank's constant, ( 6.626176x10-34 J s), and f is the frequency of the photon.

momentum of the photon is then mv = mc = hf/c. And yes, this momentum is absorbed (and can be observed) when shining a bright light against one side of something sliding on a near frictionless surface.

 

[Peacekeeper100]

Originally posted by: BumJCRules
How would speed add mass? It wouldn't.



E=MC^2

Speed is some form of constant. Light travels at slightly different speeds through various mediums. There have been experiments where photons have exceeded the speed of light. The Photons were accelerated through the test chamber and exited faster than they entered. Messed up stuff. What practical use is there for faster photons? Maybe better bombs perhaps.

So if you are using the given constant for speed in whatever medium you choose, then the conclusion is that the greater the energy level the higher the mass has to be. It is a direct relationship.

I mean rearrange the equation. M = (E/C^2)

I think the problem they are talking about is you have to keep increasing the energy to approach the speed of light. So E will increase causing M to increase. Or the energy is required to cause accel.

And since this is the "technical" forum I am going to be technical about the microwave question. Light is a particular frequency range. Microwaves are outside the "light" range.

That experiment that the photon went faster then the speed of light is in question. Something about the avg speed was still at the speed of light or slower because the photon got split up. The first part of the photon reached the other side faster, but the last part was much slower. So if you take the speed of the front and back parts and avg then you don't go faster than the speed of light.

Of course who know if this is correct. Maybe light actaully isn't the speed limit. Maybe the theory is incorrect, but no one has proof to dispute it yet. Maybe there is some force or phenomenon we don't know about yet. I believe that it usually only takes 40 years to prove a theory wrong in the scientific world. But this is a good theory because it has lasted much longer.

 

[zzzz]

Light is a particular frequency range. Microwaves are outside the "light" range.

no. You mean "visible" light is a particular frequency range of the electromagnetic spectrum. microwaves are less energetic and their frequency is smaller than the visible light frequency. X-rays have frequency higher than the visible light. But there is no other difference in all these forms of "light".

 

[sash1]

"Light can be both a wave and a particle."

I always thoguht light travelled in waves, but was a particle.

Anyways, I do believe that light has mass. Of course, I'm not really one to hypothesize, I haven't taken Physics yet (Chemistry comes first and that's what I'm going to take this year, I just had Biology). But if gravity effects light, then wouldn't that mean that light has mass? And anyways, protons/neutrons/electrons/quarks all have mass, there is no denying it. And these elements make up everything in nature, thusly light must have some mass.

"It is 100% energy."

If that is true, mass and energy are interchangeable...

 

[RossGr]

Light is unique in the way that it travels through space. It appears to have mass in that it is apparently bent as it passes near massive bodies. But, another way of viewing it is that light follows universal geodesics, it is tied to the fabric of the universe so when space is curved near massive bodies, as per General Relativity, light must follow a curved path, not because it is massive but because space itself is bent.