What to say when somebody asks about the big bang

[wiploc]

... WHY the evidence that supports the big bang makes sense to you.

Basically, the detection of cosmic radiation coupled with the fact that all galaxies,

Galactic clusters

to this day, are still moving away from one another, suggests that at one point everything that exists expanded from one point and is still expanding today. ...

If cluster A is three times as far away as cluster B, then cluster A is receding at three times the speed as cluster B.  That is, not only did they come from the same place, but, they left here at the same time.