Suppose you are standing 5 feet (1.5 m) away from me. Then I move 10 feet (3.0 m) further away. Now you are at 15 feet (4.5 m) distance from me.
You say I moved. I say no; the space between us has expanded. You can point me to other things around you that are still at same distance from you. You say if the space has expanded then those things must have also moved away from you.
You are right of course.
If somebody say that there isn't any expansion of space. It's just objects, heavenly bodies whatever that move away from each other. Like when a bomb explode fragments of its shell move away from the center. That’s what’s going on since the Big Bang. What’s wrong in that explanation?
It does go against the well-established claim that nothing that has mass can reach the speed of light. Heavenly bodies—stars, planets, etc.—have mass, so they cannot reach the speed of light given that they start from a lower than light speed.
How can we distinguish the eexpansion of space from objects just moving away from each other? If we plot the expansion backward in time, we see all the objects getting closer to each other and also to a center point so much so that at the very start, the Big Bang, they all converge to a point.
What’s wrong in saying that the Big Bang is an explosion that’s still happening, the heavenly bodies are moving away from the center and therefore also moving away from each other, and that since we see them moving away faster and faster till they reach speed of light and thus we stop seeing them, we can safely deduce that they have reached speed of light and may have gone even beyond?
Why would we say, opposite of what we deduce on basis of observation, and nothing that we observe go against the deduction, that it’s the space that expands, not the object reaching lightspeed and then become even faster?
Is there something in observation that can be pointed out to distinguish between space expansion and heavenly bodies moving away from each other and a center point? If there is nothing in observation to distinguish that then is there something in deduction about it? Like in the thought experiment at the top of this question where you pointed other objects to proof your point that the space didn't expand between us, its I who moved?