These things are predicted from Einstein's math, and are well supported by experiment.
The term particle, I should think, has mass
built into it by definition. But if you will
consider the wave/particle duality of
matter, does a wave have mass?
When I was a boy, forty years ago, an atheist had some pretty firm ground to stand on. Really it was already too late for him but your average atheist's concept of the cosmos was not all that fantastic or limitless. Oh yeah, we had heard by then that the universe was 'infinite' but who amoung us had even the tiniest inkling of infinite?
Then along came guys like Carl Sagan (bless his pagan soul even though he was a godless piker) and the Hubbel telescope. Now we have pictures of galaxies scattered thicker than the stars we can see with earthbound telescopes in every direction and we know that each one of them is akin in size to our own and we know that we cannot even really grasp the enormity of our own one little galaxy. But we have an inkling.
We know enough to realize that the universe we can SEE is an impossiblity. It's just impossibly big. The situation we find ourselves in is just ...... impossible. It's almost as impossible believing there is an intelligence, a being, a God who willed the whole thing into being. It's as impossible the scientifically supported 'near fact' that at the moment of the big bang .... nothing became everything Hubble can see at our moment in time. It's all impossible. It's all just too fantastic to grasp.
So the poor atheist today just knows too much. He no longer has a nice neat little scientific universe to postulate as a more creditable alternative to a God created universe. Each idea is equally absurd to our enfeebled little minds. BUT one is now trully free to place his faith with confidence for logic recoils from everything we know as fact now so why fear the decision to have faith in God? One is in an impossible pickle anyway. Ya might as well take the safe bet.
The strong and weak nuclear forces? Electron shielding? Gluon attraction? Too bad Physicist isn't here, I'm in over my head..
What do you think of the recent stories of the 5th dimension that may be measured in the lab within 3 years? 95% of the mass of the universe is said to be dark matter and dark energy, and resides in this 5th dimension. This 5th dimension is not thought to be almost immeasurably small like the rest of the superstring dimensions, but of the order of millimeters in size. Bigger than neuronal complexes in the brain. Bigger than the amount clipped off the nail with nail clippers. Heard of that? There have been a couple 5th dimension threads on FR recently.
How about neutrinos with imaginary mass?
This particle has a zero rest mass, however, light has relativistic mass (since its traveling at the speed of light “C”) and can be acted on by gravity.
This is the answer to your objection to photons being massless. They have zero rest mass, but they're never at rest. The photoelectric effect (subject of the paper for which Einstein did get a Nobel; he didn't for either special or general relativity) results when photons splat into metal foil like little rocks with enough momentum to knock loose electrons, thereby ionizing and charging the metal.
Photon mass equivalence has tripped me up, too. I once thought I figured out that, if you threw enough mass into a black hole, eventually even the quarks "cook off" and it all turns into photons. Excitedly, I explained to Physicist--do you see the presumption here?--that the mass gravitationally binding the black hole disappears and you get--Tah Dah!--a BIG BANG. So I sat back and waited for him to recommend me for a Nobel.
Instead, he simply told me that mass and energy are equivalent. Photons have energy, so photons have mass. Photons don't just bend under gravity, photons make gravity. A black hole will always be a black hole.
RA, thanks for the ping!