They say the universe is expanding. Is that the same as saying that time is contracting?

They say the universe is expanding. Is that the same as saying that time is contracting?

No.

• First, to measure time we employ means that are independent of the large scale behavior of the universe. In particular, the second, SI unit of time, is defined via the transition frequency of caesium atom and not through e.g. the duration of light-speed trip to Caelum Supercluster.

• Second, the expansion of the universe is not homogeneous on smaller distance scales. Small scale objects such as atoms or even planets and even larger gravitationally bound systems such as galaxies and galactic clusters keep their size. It is the space between galactic clusters that is expanding. See e.g. this question for the discussion.

So OP's list item 1 is true, list item 2 is false, and list item 3 is also false precisely because there are scales of time and distance that are independent of large scale cosmological behavior. As for item 4, asking questions is how we learn.

1-3 are all true.

1. If you use the most common cosmological coordinates, in which position is scaled by a factor $a(t)$ that increases with time, then the coordinate distance between galaxies is constant but the measured distance increases because of the scaling.

2. If you use conformal coordinates, in which both position and time are scaled by $a$, then the coordinate distance is constant and the coordinate speed limit (speed of light) is constant, but clocks tick faster at later times so it takes more real time to get to other galaxies.

3. Coordinates are meaningless. It takes longer, in actual measured time, to get between the galaxies at later times because they're getting farther apart, in actual measured distance. How you model this with coordinates and "scaling" has no bearing on those physical facts.

I guess 4 is also true, but you've gotta start somewhere. Understanding that coordinates are meaningless is the first step to understanding GR.