Sama> How should someone figure out how they should be useful?
Elon> Whatever this thing is you are trying to create.. What would be the utility delta compared to the current state of the art times how many people it would affect?
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Let me make my point in a less obtuse way. Most people make decisions about their careers based on opportunity and maximising profit. No one becomes a footballer to make the world a better place. This would all be fine as long as the capitalist market rewarded choices that make the world a better place. Obviously it does not and it's not the fault of a footballer that we as a civilisation choose to channel our available resources their way and not towards frivolous play like space exploration.
If anyone ever figures out a way to make the free market choose the greater good they will win all the Nobel prizes forever (we won't need Nobel prizes after that).