In the sentence "Rien ne peut arrêter ça." [Nothing can stop it.] the word "ne" seems to me to be doing nothing. It seems like the sentence should be "Rien peut arrêter ça."
Why doesn't "ne peut" mean "can't stop"? Why doesn't the initial sentence mean "Nothing can't stop it."? Or even "Nothing won't stop it."?
Is it because "ne" doesn't negate words with an already-negative connotation?
I am pretty new to French, sorry if this is a stupid question.