Coyote

I have issues with describing spacetime as simply "geometry". One of my favourites analogies of the Universe is the raisin cake model, in which galaxies are the raisins that are moved apart as the cake grows. But, the raisins are moving apart because the cake (which is a substance) is growing. That's how I always pictured spacetime, as some "substance" carrying the galaxies apart. Otherwise, why are the galaxies moving apart?

What would be more appropiate to say: The cosmological constant is a type of dark energy or Dark energy is a type of cosmological constant. ? I think is the first, but i'm just an aficionado.

I was reading on the creation of matter shorty after the Big Bang, and about the fact that more matter was created than antimatter. Then there was this explanation that kaons and antikaons don't decay into the same particles, and how this could explain the asymmetry between matter and antimatter. Is there any modern explanation why this kaon asymmetry occurs? I'm a layman so I'd prefer a non-technical explanation.

I find it hard to reconcile myself with this picture. Where would this extra space come from? Like it was created from nothing? It seems to me that the concept of stretching of spacetime is more intuitive, anyway how we can do experiments to see which mechanism is the correct one?

In the standard model of Cosmology, spacetime is expanding. I tend to regard spacetime as some kind of physical entity, given that it can be affected by matter to become curved. Also in the analogy of the balloon, galaxies are carried apart because they are fixed on the surface of the balloon,which is a physical thing. So I think that in the real Universe galaxies are carried apart because they interact with spacetime, which must be physical (how else would the galaxies know to move apart?) But my question is, the same way that if you inflate a balloon, if you inflate it beyond a certain limit, it will pop, then if spacetime is being stretched constantly, and even in an accelerated way, won't there be a point in which spacetime will "pop", because it has reached it's stretchability limit?