Neil deGrasse Tyson -- Gravity-Defying MLB Helmet Incident ... Isn't Gravity Defying

You know that crazy clip of Indians shortstop Jose Ramirez kicking his helmet backwards ... only for it to magically reappear and smack him back in the head??

Turns out, it's not really that magical ... it's physics -- so says astrophysicist Neil deGrasse Tyson.

The science whiz joined the guys on the "TMZ Sports" TV show (airs tonight on FS1) -- and explained why the helmet returned to Ramirez like Yondu's whistle arrow in "Guardians of the Galaxy."