A way that I heard this described, is that what we recognize as the observable universe right now was the size of a grapefruit at the beginning of the big bang.

A way that I heard this described, is that what we recognize as the observable universe right now was the size of a grapefruit at the beginning of the big bang. The stuff that expanded due to whatever the big bang actually did, that stuff could have been just the size of a grapefruit and nothing more, or itself infinite. But the part we can access given speed of light restrictions was the part that was the size of a grapefruit. There might actually be a lot more stuff out there ... we can just never get to it.