Was the Big Bang an Explosion?

Although the Big Bang is often described as an “explosion”, that’s a misleading image. In an explosion, fragments are flung out from a central point into a pre-existing space. If you were at the central point, you’d see all the fragments moving away from you at roughly the same speed. 

But the Big Bang wasn’t like that. It was an expansion of space itself – a concept that comes out of Einstein’s equations of general relativity but has no counterpart in the classical physics of everyday life. It means that all the distances in the universe are stretching out at the same rate. Any two galaxies separated by distance X are receding from each other at the same speed, while a galaxy at distance 2X recedes at twice that speed.