I had this exact same thought a few years ago without any research. I was just thinking, one day, that the world was infinite, in a way. Because a circle is infinite. Meaning, it had no end. Then, I put the concept together with my theory of space being infinite. And the only way I really see something as being 'infinite' in a linear way is if it just goes in a straight line forever. Hmm. To me, this seemed less likely because it's hard to imagine something going on forever in a straight line. So, I went "What if this universe is a sphere inside of another universe?"
And the process could go on and on. We could all be little bubbles inside of larger universes which are bubbles inside of even larger ones. I bet we are a speck, on another speck, on another speck, on another speck.
And the process could go on and on. We could all be little bubbles inside of larger universes which are bubbles inside of even larger ones. I bet we are a speck, on another speck, on another speck, on another speck.