I went to Pittsburgh to talk to a man about robots. Once a dirty coal and steel town, it is now a centre of finance, medicine and learning.
I went there to meet a remarkable academic whose predictions may make your flesh creep.
In fact, Hans Moravec is the most amiable of men. He has been building robots since he was 10. Talked about for so long, now, he thinks, their time has come.
Mr Moravec's thesis is that some time in the next 50 years, machines like these are going to become more intelligent than we are. It is, he says, the way the world is evolving.
Brain power
Currently, he says, men can create machines such as the ones negotiating his corridors with the calculating powers of insects. But with computer power doubling every year, or year and a half, robots will evolve from insects to animals to human intelligence - at breakneck speed.
By around 2050, predicts Hans Moravec, a computer costing only a few hundred pounds will have the capacity of the human mind. After that, it will start exceeding it.
It may sound like pure science fiction, but it is serious academic stuff. Sometimes we non-scientists glimpse the details of it.
The American computer chip maker Gordon Moore enunciated what is now known as Moore's Law 30 years ago, when he noticed that the power and pace of computing was doubling every 18 months or so.
But the roboteer Hans Moravec thinks the evolving change we are now experiencing in computing has in fact been going for centuries in human evolution.
When machines have more intelligence than men, they will be able to do the things we do better and faster than we do.
Taking over
For Hans Moravec - and he keeps a straight face here - that means they will start taking over from us. It is not, he insists, a frightening prospect.
These super-intelligent machines will be our children, says Mr Moravec. Each generation of humans eventually learns to accept the idea of handing over continuing existence to its own offspring.
Well, the abiding faith in technological progress has long been one of the defining features of American life - it is a mainspring of the country's current extraordinary optimism. But even some Americans see a dark lining to the silver cloud.
Last year when I saw him in his think-tank hideaway in Aspen, the ski resort in the Rocky Mountains, he was still one of the optimists.
But now Bill Joy is having second thoughts, about things such as the advances in robotics that Mr Moravec is predicting.
Plagues
Add to them the human genome project, and nanotechnology, the new ability to build minute machines that can replicate themselves, too small for the human eye to see.
The result, says Bill Joy, is the possibility of electronic and biological plagues which could threaten the future of the human race.
In the networked computer world he has been instrumental in creating, knowledge about all these things is now readily available to everyone - for good uses or bad.
With genetic codes now cracked by computers, people will soon be able to choose desirable attributes for their babies.
The smallpox genome may soon become very easy for anyone to get hold of. Bill Joy's message to his fellow scientists is: stop and think.
He is so concerned about the misuse of knowledge that he is urging restraint - limits, voluntary or imposed, on where scientists should tread, and what science should do.
Forging ahead
But most of the technology experts dismiss out of hand the idea of reining themselves in.
Nevertheless, we have been warned.
A few days later on my summer trip criss-crossing America, I saw one of the wittiest advertisements I've ever seen.
A billboard sign just outside Philadelphia said in huge letters: "Go Ahead. Pick Your Nose". The message was followed in small print by the name of the advertiser: Gehry's Cosmetic Surgery.
It won't be long before we're picking more than just our noses. And within a few decades, it is just possible that our noses may be picking us.