Why do scientists believe the universe is still expanding? a. The further away an object is, the higher the temperature and pressure eventually become, causing nuclear fusion
b. Distant objects shift in frequency toward red on the electromagnetic spectrum, which tells us objects are moving away from us
c. Spiral galaxies spin, so they appear to be a rotating disk of stars and dust
d. Distant objects shift in frequency toward blue on the electromagnetic spectrum, which tells us objects are closer to us us