It is one of those unanswerable philosophical questions. It's to grade how you look at life and yourself.

It is said that those who say the glass is half full have a positive outlook on life and those who state half empty are supposed to be pessimistic about life.

Its the same idea as:

If a tree falls in the woods/forest and no one is around to hear it, does it make a sound?

Again, this is on a philosophical question to grade how you view the things and the world around you.

For me a glass half way filled is always half full, and of course the tree makes a sound when it falls. Just because no one can hear it doesnt make it not happen. Like time sound and light are linear.