How do planetesimal form?

They don't. Living beings are believed to have evolved much later.

Accretion

Then there's nothing there.

These are contact arrangements that can be found on switches and relays. The form designation is fairly old and rarely used now. Form A: a single, normally open contact that closes upon...

This will only occur if the alpha carbon to the carbonyl group can be protonated. The keto form of acetone (for example), would be a -CH2COCH3. The alpha carbon has lost a hydrogen and is negatively...