Raj: Do you understand we're talking about dark matter colliding in outer space?
Sheldon: Of course I understand. And who are you to tell me about outer space?
Raj: I'm the astrophysicist! "Astro" means "space"!
Sheldon: "Astro" means "star".
Raj: OK, well let me just tell you, if we were having this argument in my native language, I'd be kicking your butt!
Sheldon: English is your native language.
The Hindi for "astrophysics" is खगोल भौतिकी khagol bhautikī - composed of khagol "the vault or sphere of the heavens" and bhautik "existing, material, real, of this world" (according to my Oxford Hindi-English Dictionary).
So Raj is right that the Hindi word for "astrophysics" contains the word for "space". The writers have done their research. (But he's wrong that the etymology of the word, in any language, is relevant to his argument.)
Hindi भौतिक bhautik is of course related to English physics. It's borrowed from Sanskrit bhautika "anything elemental or material", from bhū "to be" - from Proto-Indo-European *bheuH- "to be, exist, grow". This is the source of Greek φυσικός phusikos "natural, physical" (English physics), Latin futūrus "that is to be" (English future), and Welsh bod "to be" (combining with eistedd "to sit" to form Eisteddfod).
Concerning Sheldon's comment about Raj's native language, I suppose it's possible that Raj, who comes from an educated family in Delhi - has two native languages - Hindi and English.