What evidence shows that the expansion of the universe is accelerating?

Answer 1

Basically, teams of astronomers observing extremely distant type Ia supernovae whose distances were already known found that they were dimmer than they should be at those distances. Based on this it was determined that the expansion rate of the universe at this time is higher than it was when the light left those supernovae.

Answer 2

by using a few facts.
1) all supernovae explode with the same brightness
2) the dimmer the supernovea appear to be, the further away it is
3) the further away it is, the older it was. since it took longer for the light to get here

by using these facts, scientists have discovered that some supernovea are older than the universe itself. this can't be true so the only explaination is that the universes expansion is accelerating and not constant

Answer 3

When astronomers look at the spectra of distant galaxies they find that the spectras are highly redshifted. This means that they are moving away from us. However, the galaxies they look have to be outside of the Local Group, within the Local Group some galaxies (like the Milky Way and Andromeda) are moving towards each other.

Answer 4

The expansion is constant.

But as the bubble generated by the Big Bang keeps expanding, the distances between the galaxies increase at a faster pace.

This is due to the simple geometrical fact that when the diameter of a sphere expands, its surface expands faster.

Too difficult with a sphere? Check with an expanding circle.

Just measure the distance between two points in the circumference (I mean the arc section between the two points) when the diameter is increased twice by the same constant amount.
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Answer 5

Some weird thing called dark energy.

Answer 6

Optical Measurements using trig & mathmatics are repeated year to year to year and the results show increased distances from year to year.