From Sam Altman (from top left, clockwise) to Peter Thiel, Mark Zuckerberg, Jeff Bezos, and Sergey Brin, many of the world's wealthiest billionaires seem to be on a quest for the fountain of youth.Lucy Nicholson/Reuters/Marco Bello/Getty Images/Evan Agostini/Invision/APDrew Angerer/Getty ImagesAnadolu Agency / Getty Images