Dear Zilva Zanga:

"Zilva Zanga" wrote in message
...
from someone with an interest but no education in this area.
If the universe is expanding, doesn't that mean that there is
a boundary to what scientists define as the universe?

There is no boundary. Sometimes the balloon model is used to
describe inflation, and substitutes a 2D+t analogy for 3D+t
spacetime. At any instant (a certain radius for the balloon),
you are free to be anywhere on the surface of the balloon.
Neglecting the filler neck, everywhere accessible to everywhere
else on the balloon... no boundary. Inward, is where you came
from, so there is no boundary there (except that you can't go
back). Outward is where you are going to, so "same song second
verse".

If yes, what's on the other side?

I'd vote for cream cheese and warm bagels. Of course, I am on a
diet...

David A. Smith