Seed is asking which invention I’d uninvent. My reflexive response is atomic weapons. I want to emphasize weapons because I think nuclear energy is going to be important, just as James Lovelock does. But if I was God who could change the world by fiat, well, atomic weapons would probably be it. Now, I say this with the convinction that I suspect more lives would be lost between 1945-2000 than in the “atomic age.” I think convential wars would be more brutal and more frequent than under the specter of the nuclear apocolypse. But, I suspect in my lifetime some idiotic small banana republic will blow up another worthless banana republic, and that’s going to cause problems.
But since Evolgen already said nuclear weapons, I will say that television is my runner up.