Weird notions come into my mind and I like to ponder on them and see to where they take me.
Universe expanding with the speed of light, as is mentioned here too, space expanding.
Outer space? The space between galaxies and stars or all space? Even to the space we occupy ourselves. Blowing up, expanding like balloons in all three dimensions.
It is space itself that expands, is found in NASA's Imagine the universe website,
".. but actually it is space itself that is expanding faster than the speed of light, driving objects further apart at an increasing rate."
The example of raisins in a cake as it is baked and raised up, the raisins on the surface grow distant from one another, but the raisins themselves are built on space, the concept of space is not limited only to the space observed by an individual, but includes as well the space the individual itself occupies, the raisins themselves occupy, even the space their atoms occupy.
The atom built by protons and neutrons enclosed in the nucleus and far far away, in relative terms, the electrons orbiting, an enormous amount of space included and include the point-like entities of electrons, protons and neutrons, attributed with mass equals energy, that space that lies within objects expands too, and expands with the speed of light, or, as it is claimed faster than the speed of light, in order to compensate for the ultimate speed, the speed of light, the limit all objects in the universe can be accelerated to.
We ourselves, as objects of this universe expand in space, or the space that our atoms occupy expand with or faster than the speed of light.
And all done equally, we are none the wiser. The only thing that changes is the distribution of energy in space. Which in a sense is diluted. How this notion would accommodate all what we think about what mass is? Inertial mass, rest mass of a body for zero speed; at any other speed the inertial mass is greater.
According to the equations of special relativity the mass of a body increases as it is gaining speed, it is about three times as much of the inertial mass for speeds at 0.95 of the speed of light and the graphs point to infinite mass as it gets nearer and nearer to the speed of light, asymptotic curve that never touches the y axis as the speed increases to ridiculous decimal increments to the speed of light.
What if space, all around the universe environs expands at the same time? Would an infinite mass postulate still hold? Would the beginnings of the universe from a singularity, an infinitesimal point of infinite energy be more plausible? Energy and space fundamental entities that combining the two together to produce mass? Mass an emergent entity, an entity that becomes apparent only if it is looked at from above a threshold, a macro-threshold, our familiar macro-world loosing completely that attribute when it is looked at from a point below that threshold. Mass concept becomes meaningless from the standpoint of the micro-world, the quantum realm, being only extremely concentrated foci of enormous amounts of energy kept apart by even greater distances of empty space?
What difference would that make if we take the point that this space expands at the speed of light in the same way that the universe itself expands at the speed of light.