Like, you know those rocks that make some kinds of other rocks stick to them? No?.. well those are magnets and then if you spin them around in with metal somehow... Well if you stick some copper in a lemon and then put it on a light bulb, oh right we don't have those yet...
As a programmer it would suck for me to travel back in time. People would ask me what do I do in the future and I'll have a hard time explaining it to them. I would look for a job in the past, I don't think there's a job there that remotely close to sitting 8 hours a day clicking and clacking.