What was not so clear was how big bang worked, and to my knowledge there is no help from the engineering journals on this subject. So here goes. A couple of guys can’t push a heavy crated bike across the set-up floor, but if one or two others put a shoulder to it, all four can get it moving, after which just two can keep it going. The principle here is that static friction is greater than sliding friction. When an object sits still on a surface, there is time for the object’s weight to force its surface irregularities into intimate contact with those of the surface it is lying upon. When we push on the crate, this intimate contact increases friction, requiring a high force to set the crate in motion.