When you want, you can say electromagnetic waves are the fifth aggregat state.

It must possible that you can compress it or think anyone other?

The solution is ready for it. 

When you have a hollow ball that reflects waves to hundred percent, then must be the waves thicker and thicker or not? Naturally you must send more and more waves in it.

At an example you put the ball on a libra and maessure the weight.

Edited December 25, 20187 yr by Phantom5

Superposition (adding waves, which is what I assume you mean by "thicker") happens. Such a ball would indeed have a greater mass.

What do you man by "compress"? 

 

The same as when you compress maybe air or other gases or plasma.

19 minutes ago, Phantom5 said:

The same as when you compress maybe air or other gases or plasma.

Light doesn't "compress" the same way. Light in a cavity is not typically going to behave like a gas.

Yes but what is when you put more and more in a ball?

 

After plasma comes waves.

Edited December 25, 20187 yr by Phantom5

Just now, Phantom5 said:

Yes but what is when you put more and more in a ball?

Photons are reflected from ball surface less efficiently than 100%. Remaining amount is absorbed by material. After absorption, material is heated, and loses reflective properties. e.g. heat metal and it will start emitting photons in MW, IR then visible spectrum (thermal radiation). Search net for reflectivity on graph, how it changes with temperature.

 

And when you take other wavelength the reflectivity is then better. What is then?

https://en.m.wikipedia.org/wiki/Reflectance

Or at an other way you put more photons in the ball that them lost.

I must correct me, more photons as them lost.

3 hours ago, Phantom5 said:

Yes but what is when you put more and more in a ball?

Photons are bosons. There is no theoretical limit to how many you can have. Only practical limitations. You have to have them in an allowed mode of the cavity. It won't behave like an ideal gas.

 

3 hours ago, Phantom5 said:

After plasma comes waves.

What plasma? You have light.