I was watching "The Big Bang theory" S7 E9. And I couldn't understand the meaning of "tip a cow". Please also explain the remaining conversation too. I am an Asian and not good at English. Here is the full conversation:


    Lenord: The math is all there. It's not real.
    Penny: Yes, it is.
    Sheldon: Yeah... uh, look. It is scientifically impossible for a person to tip a cow. Even you, with your stocky build and lumberjack shoulders, you couldn't do it.
    raj: It's horrible. Why would you push a cow over? They're sacred.
    Penny: Oh, stop it. I've seen you eat, like, a million hamburgers.
    Raj: Hey, an animal can be both sacred and delicious.
    Penny: Look, I'm telling you I've done it, okay? I clearly remember the cow standing up and then the cow on its side.
    Lenord: Were you drunk?
    Penny: I was 16 in Nebraska. What do you think?
    Lenord:I think you're the one who fell over.
    Penny: That would explain why the sky was also on its side.