Question

in the 1920s, edwin hubble looked at the spectra of stars from distant galaxies. to his surprise, he found that all of these spectra were red - shifted, and that the more distant the galaxy, the greater the red - shift. what is a reasonable conclusion from this evidence?
the universe is expanding.
the universe a computer simulation.
the universe is contracting.
the universe is unchanging.

Explanation:

Red - shift in the spectra of distant galaxies means that the galaxies are moving away from us. The greater red - shift for more distant galaxies implies that the farther galaxies are moving away faster. This is evidence that the universe is expanding. The idea of the universe being a computer simulation is not supported by this astronomical evidence. A contracting universe would show blue - shift (objects moving towards us), and an unchanging universe would not have such a consistent red - shift pattern with distance.

Answer:

A. The universe is expanding.