Scientists around the world have seen the prize, and hundreds of millions are going into start-up companies. There is a nice twist to this line of investment. Despite the ups and downs, the long-term trend for the price of oil is up. That means the size of the prize for replacing oil is going up, while the size of the challenge is going down. Replacing $20-a-barrel oil would be difficult, but replacing $100-a-barrel oil is much easier.