Do we know what practices would be effective in resisting aliens? Wouldn't the public have to be convinced, in all countries, that there is such a threat? When have the major nations on this planet shown they can agree on any military course of action? Earthlings are already spending a trillion dollars a year on things military. Where would the money come from? Krugman seems to be suggesting more lies are what is needed. How about everybody cutting their military budgets in half and feeding people instead?