Did Einstein Say Light is Massive?

[Brian37]

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

I've been cracking jokes  in this thread as everyone  can see. But in all seriousness, that blur between particle and wave really does freak me out.

It is hard for laypeople to view particle and wave as fluid and not either/or.

It may be crude to think of it this way, but the melting villain from Terminator 2 might be a crude analogy.

But between particle and wave, that is the ultimate "Ford vs Chevy", "Cowboys vs Redskins" when the reality is "neither for or against" but both.