Hey there!
A half-life means after a certain amount of time, half of that substance will be gone/changed after that time.
If 50%, or half, of the element remains after 4000 years, that means the half life must be 4000 years.
Hope this helps!
when carbon dioxide gas is collected down ward of water wet gas is collected by the downward displacement of water . This is used for gases that are not very soluble in water . ... In water , carbon dioxide produces a weakly acidic solution , carbonic acid .
I think it’s because from earth things may appear smaller smaller in space where in actuality in space it can be way larger
