The analogy of the balloon is senseless.

If it were like a balloon, there'd be a big empty space in the middle and everything would be on the outside.

Yes, after a Big Bang I can see how loads of "stuff" could appear to be like an expanding cloud heading off in all directions but it's still propelled. The force of the Big Bang propelled it all.

Propelled outwards /expansion/whatever, much would have left the "site" of the Big Bang so how fast did it travel? Some must have travelled faster than other "stuff" otherwise it'd all be at the same place in space, static/moving or whatever.

I see one of those huge mortar fireworks propelling a shell which explodes at a certain time after ignition. If it wasn't for our gravity, an exploding shell like that would propel all it's contents in all directions. On ignition of the shell itself, the solid explosive becomes an expanding gas, the pressure of which eventually causes the shell to burst scattering it's contents in all directions.

It would be interesting to set one off in Space. 🙂 Trouble is, at the moment we can't get far enough away from the gravitational effects of our Star and it's Planets.

We have theories and theorems, all need "modification" the more "they" look in to them and I don't see how they can have several versions to suit themselves while glibly trotting things out as a fact when they're clearly not a fact.

Trouble is, if you repeat something often enough it gets accepted as fact.