Are You Really Rich?

Imagine that you are a billionaire. One day, you found you are left somewhere in the Antarctica continent. Here comes the question, are you still a billionaire?

You may answer, of cause I am a billionaire, see, here is my credit card; My bank account; My proof of ownership of my company; And my stock account. However, no matter how many proofs you provide, you still can’t buy a thing in Antarctica continent. You are no better than a poor wretch.

Conversely, If you are billionaire now, I am also, because I have tons of gold in Mars.