I would develop neuroscience to the point where I could enhance my brain, make myself super-smart, then I'd solve most of the big problems.

I'd build space elevators and move most of the big cities into space because there's just no point in having them on Earth. I'd try to get as many people off of Earth as I could.

I'd be able to afford to pay lots of child support so I'd make sure my genetic material was thoroughly mixed into the human genome (probably assuring the future fall of mankind... ).

I would turn Mars into a robot reservation. No humans allowed. You can drop all the robots onto the planet that you'd like but they'll have to survive on their own.

I would build interstellar slow-boats filled with every imaginable bacteria in pods that could be launched at any planet encountered along the way to pollute the interstellar neighborhood with life just in case humans self-destruct.

I would take a vacation and read Wikipedia from front to back.

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The only way of finding the limits of the possible is by going beyond them into the impossible.

Arthur C. Clarke

The Brain Science Podcast