✔ 最佳答案
The expansion of the universe is a funny thing because it isn't expanding like a regular explosion.
The expansion speed (which isn't even a regular speed of movement) of a part of the universe containing another galaxy depends on how far away from you that galaxy is. The farther away from you, the faster it is expanding away from you. So, the speed of expansion of different parts of the universe varies with the part's distance from you.
HOWEVER, this relationship between expansion speed and distance from you can still be expressed as a number (called the Hubble Constant) and that is:
"67.15 ± 1.2 (km/s)/Mpc. For every million parsecs of distance from the observer, the rate of expansion increases by about 67 kilometers per second." - see the source reference below. (A parsec is 31 trillion kilometers, or 19 trillion miles, or about 3.26 light years. A Mpc is a million parsecs.)
Unfortunately, in a way, nothing is simple about the universe, and the Hubble Constant isn't really a constant - it is slowly getting larger as the universe gets older. How fast it is getting larger isn't really known - yet.