23. Why would an astronomical unit not be
used to measure distances on Earth?

Here is your answer : )

One Astronomical Unit is the distance between the Earth and the Sun, this acts as a sort of a cosmic metre stick. Astronomers don't and cannot measure distances. Distances are merely inferred from what actually has been measured, such as an angle, a relative luminosity, a time period, etc..

Hope it helps

that would be because of both gravity and friction. so     c