I guess the others left this for me to do, for experience... and it was 3am for me when you requested this.
Original thread split and relevant posts moved - including splitting posts where required to retain integrity of both threads.
First of all a thank you, Serica - it's the first time that a split request i made actually succeded.
Maybe the other mods don't know how to do it?
Then:
Off topic but I thought this was interesting.
Photons dont exist.
http://www.the-phoney-photon.com/
My original thought was this: Momentum is proportional to mass. An object with no mass can produce no momentum (it also doesnt exist). Einstein invented the photon in the same way that the Greeks invented the phologiston. It was a way to explain an unknown without resorting to deification of a phenomenon.
I did some research to find out if others had come up with the same thoughts, and found the URL above as one example among many.
Photons do exist - everyone who ever had a sunburn can tell you this...
We can generate them, we can count (!) them, yes, we can even trap them!
They have no REST mass, but they have a relativistic mass, originating from their speed (you know that things get heavier when accelerated - the effect is very small in everyday physics, but if you get closer to the speed of light, the effect become eventually very large)
And the naming is whole 'nother story - if i create an object, something a human can sit on, and call it "foo", and later on we find out that what i actually meant was a "chair" - does the object cease to exist?
No, you only chose to give it a different name. Doer has pointed that out in his post already.
(and maybe watch the trainman scene from Matrix II, there is a similar discussion about what humans call "love")
It is counterintuitive that something with no mass appears to have momentum, but if you see a photon as pure energy - and then apply einsteins famous formula (e=m*c²) you will see that there is no real difference between matter (which has mass) and energy (a light quantum in our case).
And maybe let me pick up the example with ancient greeks to illustrate this further:
Their concept of "phlogiston" is now known was incorrect, yet the observed effect is still there and very real.
If you see it from a different angle, and see "phlogiston" as the "volatile matter" (the gases and matter that turns from solid into gas due to oxidation and heat) that escapes from a burning object, we have just added a more distinct, a more exact definition to their concept, but we haven't disproven it - burning objects still do lose weight.
If you chose to describe the effect (or the lost matter) with the term "foobar" doesn't really change anything.
And last but not least, that photons do have momentum is proven beyond any reasonable doubt - not only solar sails or gravitational lenses show that, but we can observe the momentum of photons with simply toys as "solar spinners"
I found no article to explain what solar spinners are, but maybe the a pic will help:
It's basically an evacuated glass orb with a windmill-like wheel inside, the paddels are painted black on one side, white (or silver) on the other... basically a very tiny solar sail.
The dark side absorbs the light, the bright side reflects it. Enough to get this toy spinning.
Another pic:
I'm shocked!
