I felt rather insignificant today as I attended my physics lecture. We were discussing dark matter and the effects it had on gravitational forces within the universe. One might feel insignificant when sized up against "small" galaxies orbiting around even larger galaxies elsewhere in space.

This, however, was not on my mind. Instead, through random discussions, the class began talking about the expansion of the universe. The universe is expanding without bound. No one knows for sure, but there seems to be no end to the universe, implying it is infinite.

Assuming the universe is infinite, and infinity is an idea rather than a physical construct, does that mean the universe is merely an idea.
Supposing the universe is an idea, and we are part of the universe, do we actually exist or is nothing real?