Some say it will happen soon.
Critics say it will take a long, long, time.
Many neuroscientists and philosophers think it ain't gonna happen, ever.
We're talking about building a machine that functions as the equivalent, or maybe as superior to, a human mind.
A synthetic brain doesn't have to be the exact equivalent of a human brain, but there are humans, the brilliant inventor Ray Kurzweil in particular, who hope one day to dump their minds into such a machine, boot up and go on living, disembodied, but mentally intact, forever.