Anything that grows exponentially is a bubble. The only question is when it stops growing because it has run out of space. A simple example is that if Caesar

Anything that grows exponentially is a bubble. The only question is when it stops growing because it has run out of space. A simple example is that if Caesar had invested one gram of gold after the conquest of Gaul at 3% compound interest today it would be worth 2.64e24 dollars. Or a trillion times larger than the world economy today.