According to space.com the universe is expanding with 75km/1Mpc/1s (megaparsec), which comes down to $\beta=2.43\times10^{-18}/s$, a relative rate per second.
To put this in perspective: The average distance between Earth and Sun is $149\,600\,000\, km$. Multiplying this by $\beta$ and one year, I get roughly $11.5\,m$, which means every year the Sun moves away from earth by over $11\,m$ on average, just because of the expansion of the universe (amazing enough as to think I messed up the orders of magnitude, so please check). But this is not the point. I would like to understand the nature of this expansion better.
Questions
- Wikipedia says the expansion could be measured in principle with a ruler, say a piece of metal of a given length. Is that really true or does the space inside the ruler expand with the same rate such that by counting how often the ruler fits between Earth and Sun, we would see no difference?
- What if we measure instead with a beam of light (ignoring relative motion for the moment) and measuring how long it takes to bounce back from Sun. Will the time be longer or is space rather like a checker board on a rubber sheet and independent how large you stretch the sheet, 8 rectangles are 8 rectangles and the light moves from rectangle to rectangle, not noticing that they are all stretched out.
- In (2) above, what would be the right way to measure time anyway? Let a beam of light bounce between two mirrors and count? Huh, but the distance between the two mirrors expands also, while one beam of light goes to the Sun and back, the bouncing one bounces always the same number of times independent of how much space is stretched between to measurements.
3 questions in one post may be a bit too much, so a general explanation how the expansion of space relates to (a) the size of physical objects, e.g. the typical diameter of atomic particles (1) above, and to (b) speed, wave length and frequency of light would be great.