Earth's gravity field anomalies
An entrepreneur reads about how gravity is different in different places around the world, as this animation shows, and gets a terrific idea of how to make money!
He sees that in Mexico City the gravitational acceleration is while in Helsinki it's . Why not buy gold in Mexico City, and then go to Helsinki and sell it there?
He estimates he can make about $200 profit per kg of gold, based on current gold prices. A single standard gold bar weighs about , meaning roughly $2500 profit per gold bar! He then flies out to Mexico City to put his money-making plan into action.
What's wrong with his plan, and why won't he make any money with it?
GIF animation is public domain, courtesy NASA