well, i was just thinking about this....
light is said to be in particle as well as wave form. but if we take it in particle form, and apply einsteins theory which "STATES THAT THE MASS OF ANY OBJECT TRAVELLING AT THE SPEED OF LIGHT BECOMES INFINITY", well, does that mean that the mass of a photon (which is almost negligible) will become infinity? i know that the "INFINITY" is in comparison to its rest mass, but then, infinity has NO LIMITS.
eg.- if the mass of a photon is 1 x 10^-50 (just assuming), even then, we don't know how much its mass will increase!!!
Now tell me Frihosters: is my deduction correct???
but if I recall, the concept of a photon being a particle is based on the energy in light being quantizable as small packets of energy termed photons. I agree with the other reply that they are massless.
Again... long time ago that I looked at this stuff.
The waves (EM waves) I think I still understand
| The Conspirator wrote: |
| Photons are massless. |
well, they are SAID to be massless, but they are actually NOT massless!!!
if anything does not have mass, then that means it does not exist!!! just think about it. the mass of photons is NEGLIGIBLE, but not 0!!! | einstein wrote: |
| The Conspirator wrote: | | Photons are massless. |
well, they are SAID to be massless, but they are actually NOT massless!!!
if anything does not have mass, then that means it does not exist!!! just think about it. the mass of photons is NEGLIGIBLE, but not 0!!! |
No. It is massless.
What you may be misunderstanding is that a photon does have an effective mass when it interacts with massive systems, which is equal to E ũ cē. But it has no intrinsic mass.
There are lots of things that exist without mass. Electric fields don't have mass. They have momentum, but you don't need mass to have momentum (this kind of thinking is foreign to classical physics). | Quote: |
| Electric fields don't have mass |
well, FIELDS are different............but particles do have mass, don't they??? 
No. Photons don't have a rest mass, however they do carry energy and momentum.
Your original idea was right: The mass of a particle depends on which frame you measure it in. So if you're moving with respect to the particle, or it is moving with respect to you then it's mass is different to if it's not moving. We call the frame where it isn't moving "the rest frame", and it's mass in this frame is "the rest mass".
The problem with light is that, whichever frame you measure it in, it is still moving at the same speed. Think about that for a second... wierd huh? Well, don't complain about it, because that's the way the universe works! So you can never slow it down, or change its speed, or measure it's rest mass.
If photons did have rest mass (even a small one), you are right that they would require an infinite energy to accelerate them to the speed of light. But they don't. They're massless.
| einstein wrote: |
| Quote: | | Electric fields don't have mass |
well, FIELDS are different............but particles do have mass, don't they??? |
Where do you think they get their mass from?
The Higgs boson - the only elementary particle in the standard model we haven't observed yet - is what causes particles to have mass. But there are particles that are not under their influence. Bosons by default don't have mass - it is the Higgs boson that gives W and Z bosons their mass. The other bosons don't have mass.
We have observed photons and gluons so far, both bosons with no mass. If the graviton exists, it too will be a boson with no mass.I must say, I find the notion of massless particles hard to grasp but I suppose we just have to accept it as fact.
Is the Higgs boson part of the Standard Model? I thought it was a kind of "bolt-on" surmised to explain how other particles interact.
| DoctorBeaver wrote: |
I must say, I find the notion of massless particles hard to grasp but I suppose we just have to accept it as fact.
Is the Higgs boson part of the Standard Model? I thought it was a kind of "bolt-on" surmised to explain how other particles interact. |
Yes, it's the only standard model particle that we haven't observed yet. When they build the LHC, they'll probably see them. We do have some indirect evidence for it.
(Technically speaking, all of the standard model is a bit of a bolt-on. It seems pretty much internally consistent, and it's certainly had smashing success making predictions, but it doesn't really jive with the rest of physics that well. In fact the Big Quest of modern physics is trying to resolve the standard model with the rest of physics.)
The thing you have to remember is that there's really no such thing as a "particle" - at least not in the sense of a tiny little billiard ball zipping through space. "Particles" are simply coherent, localized wave packets - or bundled oscillations of space-time perturbations - or little bubbles of constructively interfering stress energy - or vibrating strings... really depends on what theory you subscribe to. But don't think of them as tiny little balls of matter. If you do, you'll start asking questions that really make no sense in context: like what is the diameter of an electron (hint: it's not really 3 femtometers).Mass is energy. Just lots of energy.
E=mc^2
No one can truly say whether all of the particles we theorize or know to exist are all that exist. What we see as massless particles now, in one hundred years when technology has progressed we might know massless particles as being something like Ultra Low Mass particles.
It seems to me that most energy and mass in the universe are directly related to the idea of sound waves where frequency/wavelength can be directly applied to the electromagnetic spectrum. And as our tech gets better we see more of this spectrum and discover more particles. This could mean that there are forms of energy we've yet to find because we can't detect them. All I'm saying is that it's great to sit around and theorize and delineate what we know to be true now, but no one should ever accept that current model of thinking as absolutely true. Certain aspects of our current physics models are obviously true. But if our knowledge was symbolized by the lit area in a dark room with a single dim light, what we would know as to be positively true would be the best lit area closest to Us (the light source) and what we don't definitely know to be true would be the areas just beyond the best lit area. There are obviously gray areas in this vast amount of space we call knowledge, and what is knowledge other than what we know to be totally true, right now, given our experiences and the way we perceive those experiences. All i'm saying is that physics/quantum physics/particle theory/quantum dynamics , or whatever else you'd like to lump in there, requires an open mind to progress. If I am wrong, then curse me out. That is what I know to be true :*).
| FunDa wrote: |
Mass is energy. Just lots of energy.
E=mc^2 |
Yes. Also, energy is quantised: E = h f (where h is Planck's constant and f is frequency, Hertz.)
So*, f = m c^2/h and it is mass that allows clocks to tick: without mass, there is no time (eternity is nothing to a photon). ed.
* See Roger Penrose, 2007, Brookhaven Labs webcast :: http://real.bnl.gov/ramgen/bnl/penrose.rm
requires real-player.Photons don't have mass. But they can free fall in a gravitation field, like a massive particle. This thing that photons can fall has to do with the universal equivalence between inertial and gravitational mass. In other words, the equivalence between a uniformly accelerated reference frame and a gravitational field. An experimenter in a closed room has NO MEANS, in not any experiment, to detect if he is in a gravitational field or a uniformly accelerated reference frame. That is the equivalence principle of Einstein.
