I think that's an important thing to do, to really pay attention to negative feedback, and solicit it, particularly from friends. This may sound like simple advice, but hardly anyone does that, and it's incredibly helpful.

It's important that we attempt to extend life beyond Earth now. It is the first time in the four billion-year history of Earth that it's been possible, and that window could be open for a long time - hopefully it is - or it could be open for a short time. We should err on the side of caution and do something now.

If you're trying to create a company, it's like baking a cake. You have to have all the ingredients in the right proportion.

I think the high-tech industry is used to developing new things very quickly. It's the Silicon Valley way of doing business: You either move very quickly and you work hard to improve your product technology, or you get destroyed by some other company.

People should pursue what they're passionate about. That will make them happier than pretty much anything else.

The lessons of history would suggest that civilisations move in cycles. You can track that back quite far - the Babylonians, the Sumerians, followed by the Egyptians, the Romans, China. We're obviously in a very upward cycle right now and hopefully that remains the case. But it may not.

I always invest my own money in the companies that I create. I don't believe in the whole thing of just using other people's money. I don't think that's right. I'm not going to ask other people to invest in something if I'm not prepared to do so myself.