In fantastic news, President Obama has given a major speech in Prague where he called on all nations to reduce their stockpiles of nuclear weapons, saying the US would lead but only continue its reduction if other nations followed. To me, who deeply fears nuclear weapons and has spent years arguing for their reduction, this is like a dream come true.

The number one risk to humanity right now is nuclear weapons. In my opinion, the four primary foreseeable catastrophic risks threatening civilization over the next 50 years are general nuclear war, out-of-control replicators, MNT arms races, and unfriendly AI. Moving into the 21st century, we are now seeing top-level efforts to deal responsibly with one out of four. If we deal with them all, we could get our civilization to the point where the risk of doom is negligible and we can survive for millions or billions of years in happiness.