When you eat a sandwich in space flight, does your craft lose mass?

I have wondered many times about what energy is really.

Certainly a question that has puzzled the cleverest physicists.

Ok, it's needed in order for labor te be done. Nice definition that doesn't get me anywhere.

Actually energy is ‘the capacity to do work’, not labour. And ‘work’ is defined as the transference of mass over distance, so actually it is quite a precise definition, because although it applies only to mechanical energy, energy is easily convertible from one form to another.

EM: an electric field and a magnetic field at a 90 degree. How big are these fields? In other words what is the dimension of a photon?

This is a mixture of classical and quantum mechanics. It’s a question you can’t really ask; waves and particles are not the same thing in physical terms. If you think of a photon as a ‘light wave’ – that is, a disturbance in an electromagnetic field – then its size is the amplitude of the wave. The size of an electromagnetic field itself is not the size of the disturbances in it, any more than waves on a beach are the size of the ocean.

But that is when we think of light as a wave. If we think of it as a particle, it has no volume as such. The following discussion on ScienceForums clarifies the issue quite well.

And is there an in between fase between energy and matter?

Phase. Nope.

What if we could look at a decaying atom which was taped and then shown very slow motion?

No, that wouldn’t help at all. Even if you could.

not until you take a space dump.
lol.