Arsenic

Since time is relative to the observer, in order to measure absolute time (and observe concurrency) the observer would need to be static.

Now on earth, that's obviously not possible, the earth rotating around its axis, the sun. The solar system rotating around the center of the galaxy, the galaxy moving towards some supercluster and all.

Is there a point in space where an observer would not be in any kind of motion?

Obviously light speed is the universal speed limit (apart from hypothetical particles like Tachyons).

But we know that space itself is not bound by this limit. Do we know how fast space is expanding? How do we know this?

Without referring to time itself or offering some kind of circularity of definition (i.e. involving other quantities that are based off time, for example velocity). This is not from a philosophical standpoint, but purely from a scientific one. What exactly is time?