NASA was considering sending canaries into space to study them under zero gravity. The project was scrapped when someone realized that in spite of having sufficient water supplies, they could die of dehydration within a few hours. Why?
You have me today, Tomorrow you'll have more;
As your time passes, I'm not easy to store;
I don't take up space, But I'm only in one place;
I am what you saw, But not what you see. What am I?