Silverstein -- who was technically Google's third employee, after co-founders
Officials at Google and the Khan Academy weren't available for comment Thursday, though Khan Academy employee John Resig wrote on
Khan Academy is a nonprofit start-up in Mountain View, Calif., (where Google is also based) that produces online videos, exercises and testing materials in a bid to educate students in math, science, humanities and finance in countries where educational resources aren't widely available.
Silverstein started working on Google's search engine when it was a research project at
He eventually left Standford, where (like Page and Brin) he was working on a doctorate in computer science, to work for Google. Page, Brin and Silverstein did not complete their doctorates.
Later, Silverstein served as Google's technology director. Recently he was mentoring younger Google employees, AllThingsD said.
"Silverstein worked side by side with the founders to establish Google's distinct culture and wrote his fair share of the nascent search engine's base code," the San Jose Mercury News reported in 2010. "As Google's first employee, his net worth has been estimated somewhere north of $800 million."
In that article, Silverstein said that he felt a lot of Google's success was due to luck.
"I guess what I'm most proud of is successfully keeping the culture as well as we have, given all the success and growth that we've had," he told the Mercury News. "I'm proud of that. We haven't done perfectly, but we've done a lot better than I ever thought we would."
[Updated 3:08 p.m.: Google emailed a statement confirming Silverstein's departure from the company:
"Craig's been with Google since the early days. He was instrumental in the development of search and made numerous contributions to Google over the years. We wish him all the best at the Khan Academy and know that he will do great things to help them promote education around the world."
Shantanu Sinha, the president and COO of Khan Academy, also emailed a statement on the group's latest hire, saying:
"We are thrilled to have Craig Silverstein join our team. His deep technical knowledge and organization-building experience will be extremely valuable to us as we grow as an organization. We are excited that talented individuals like Craig believe so passionately in our mission and are willing to join us in our quest of providing a world-class education to anyone, anywhere."]