OK, how do they split peas?!
Answers: If you're talking about dried, split green peas, "they" don't split them open. The peas split open themselves as they dry. Pistachio nuts and a few other foodstuffs also do this.
with a knife
lol, if you cook them long enough, they will split open by themselves.
(you were kidding, right?)
In half? Thaw out a frozen pea and take the skin off...when I used to feed them to my fish and did that, the peas were already in halfs when I removed the skin.