Something we know for certain about light is that it is an electromagnetic wave. Another reasonable assumption, corroborated by experimental results, is that this wave has a dual nature – it behaves as a particle wave under some circumstances, and as an energy (or pure) wave under others. The adoption of the dual theory resulted in the need to define the particles a ray of light is made of – photons.
It would not be wrong to say that photons are one of the most disturbing may-or-may-not-exist phenomena in physics, and create more problems than they solve. However, high profile scientists tend to approximate and negligate, which is what they have apparently done with the mass of the photon.
The mass of light – An inconclusive approach
Those who believe that photons are not completely massless are not entirely wrong. For if protons were indeed massless, there would have been no way for a black-hole to prevent the emission of light. As we know that the gravitational field has some sort of effect on light, it can be concluded that light cannot be entirely without mass. In addition, I have come across some foolish declarations which proclaim that though light has both energy and momentum, it does not have any mass.
I call this proclamation foolish, because I am not amused at the absurdity of light having “zero rest mass” and a negligibly small mass when it is in motion. The many people who cling to this statement believe that light is never at rest, which, if it had been true, would have made this theory absolutely impossible to disprove.
To Disprove a Theory
I hope you know of the existence of a phenomenon called “reflection”, wherein a wave of light (or any other wave) upon reaching a boundary between to media is returned into the medium from whence it came. At the moment of reflection, then, there is an instant where the wave can be said to be at rest, because the particle forming the wave is at rest, as that point is actually a node. This, then means that photons are at rest at the boundary of all media into which light attempts to enter…
Okay, there is nothing revolutionary in the above paragraph. But now, consider the theory again. The theory tells me that a particle of mass “x” upon being reflected goes to having zero mass and then back to the mass “x”. I am befuddled as to how this is possible, especially in vaccuum where there is absolutely no atmospheric energy to absorb.
The Insanity of It All
Look at the formula on the left. If we apply this to a photon – which we cannot, but, if this formula is applied to the photon, we see that the rest mass theory becomes the absurdiest one ever proposed. This is because, according to this formula, the mass of a photon is infinite.
If you would consider reflection again, you will see that there are two theoretical possibilities:
- The photon goes from infinite mass to zero, then back to infinite mass.
- The photon hits the boundary with all its infinite mass and the speed of light, which might be enough to induce nuclear fissions and whatnot.
So, we see that light cannot have a rest mass of zero because in that case, light simply would cease to exist in all ways. It is much, much better to say that the rest mass of light is undefined. Just like division by zero.
I have thus proposed that photons have mass. However, this too, is not completely true. I will leave you with a final question – if light indeed does have mass, where has all the light which has entered your eyes in your entire life gone? It cannot simply vanish as it has mass, and it cannot be “converted into energy” because this is not a nuclear reaction, and even if it was, your eyeballs would blow up along with the neighbourhood.
You have way too much time on your hands, considering the exams which looms large on ze horizon.
No, I just write fast when I’m on ze computer…
Anyways, Domain square is on the 22nd of september so you can see my disregard for studies.
I’m sure I’ll make up for the course, even if it’d be a last minute prep.
RG, you write fast when you are on the computer. But, then how do you think so fast??!! :-0 :-0
Man, this was one solid post!
Hmm, yes, Domain Square was today. Tough to handle in the beginning but later on it got fine.(Just FINE..Not great)
Let’s see what happens in the next day.
And yes, even I have been totally NOT immersed in studying.
But, I guess I’ll also make up. That is what I always do.
*on next day
We have to hold a meeting to decide when to hold round 2
Hey
Interesting post !
Though there are some flaws… !
Firstly. The rest mass of light is zero. so if u check the formula for the relative mass of light, it comes out to be zero*sumthing = 0. So indeed, light doesnot have mass as per that bit of math. However there is another sense in which , light os supposed to posess this property. E = mc^2. Photons do carry energy. This gives them a mass which can simply be calculated using m = E/c^2.
…
Interesting talking about eyeballs bursting out. But its not that photons have energy due to their mass. Photons have MASS due to their ENERGY. So it doesnt need a NUCLEAR process to convert this little bit of energy into warmth of our eyeballs!
>>>
For a more optimistic commentry … hehehe …
Photons CANT have rest mass. It contradicts with the very basics of relativity that nuthing except zero-restmass particles can travel at the speed of light !
So we don’t need standing light waves to proove things about its mass newayz. There are experiments in which a photon has been stopped ! However do they proove nething ? Even for reflection, what actually happens is not as simple as bouncing of a ball but things are governed by complex theories of QED. There’z an interaction between the matter-electrons n photons.
Newayz this comment is getting tooo long !!! Mayb I shud’ve written a comemnt.
For one more time…
… NICE POST !
TWISH
Consider the effect of gravity on light. Also, if we need massless stuff to acheive the speed of light, then only photons at rest can acheive it (according to the zero rest mass theory)….which is weird. And moving photons have kinetic energy which implies they have mass, but they still travel at the speed of light…
Interaction between photons and matter only prove my point.
And I admit nuclear reactions aren’t required to harvest the energy of a photon, but it is still impossible for photons to suddenly vanish. At least, they must slightly excite the electrons in the molecules of our retina. Perhaps photon-matter interaction is what enables us to see. Probably not, though.
Light does not need to have mass to be sucked into a black hole.
According to relativity, space-time is a fabric which can be curved by large masses. Light follows the geodesic and hence follows the curve of the fabric right into the black hole.
Hey! Nice post.
1. The photons enter our eyes and the energy is absorbed by the nerve receptors, transmitted through neural connections enabling us to see. The energy that enters our bodies always exit by other processes. Your eyeballs should not explode.
2. What Nikita above has said.
3. Matter and energy are interchangeable. 2 photons subjected to high enough temperature (early universe style) create one particle (electron/neutrino) and one antiparticle (antielectron/antineutrino).
So is a photon entirely massless? There’s a research area for you.
Good post, I enjoyed reading!
You are correct. Light does not have mass. However, I think you are missing a key piece of the argument… I propose that light has mass and is affected by gravitational force, yet does not exert a gravitational force. This is due to the arrangement of particles in light, which is only 1. In order to exert a gravitational field, you need a spinning particle orbiting in an odd orbit around another particle (at least 2 particles). It’s a shame most scientists have given in to this “religion” of light not having mass. – nostrumuva@gmail.com