Question: Thank you for helping so many people. Is there an educated guess by professionals about the difference between what the universe is expanding into and the universe itself? – Jay
Answer: This is going to sound very paradoxical, but the answer is that the universe is already infinitely big, so it is in fact not expanding anything. What is actually happening is that the space between everything in the universe is getting stretched, which results is out seeing all galaxies in the universe, which are not under the influence of local gravity like a cluster of galaxies, moving away from all other galaxies. Now, if you want a much more in-depth explanation of this rather odd fact, check out the Curious About Astronomy page answer to this question by my colleague Dave Rothstein.