(July 7, 2019 at 4:01 pm)Rhondazvous Wrote: I’ve been laboring under the impression that photons are massless. But I’m now reading Einstein’s Universe by Nigel Calder in which he claims that Einstein said light is heavy
In some ways, it does seem that light must have mass. How could gravity bend light or trap light in a black hole if it had no mass? At the same time light doesn’t have the second property of matter. It doesn’t take up space. It wouldn’t be able to pass through solid objects such as glass, plastic. Or ice if it took up space. Only in intense concentration (laser) does light appear to take up space and move material objects out of its way.
So, are we making a difference between mass and matter? Between photons and light?
It helps if you think of a photon as not so much a particle, but as a package of energy in the electromagnetic field as a whole (it's both, smart people tell me). A packet of energy would necessarily have no mass, but energetic fields react to gravity.
I've probably worded this badly.
Boru
‘But it does me no injury for my neighbour to say there are twenty gods or no gods. It neither picks my pocket nor breaks my leg.’ - Thomas Jefferson