In 30 or 40 years, we'll have microscopic machines traveling through our bodies, repairing damaged cells and organs, effectively wiping out diseases. The nanotechnology will also be used to back up our memories and personalities.

In an interview with Computerworld, author and futurist Ray Kurzweil said that anyone alive come 2040 or 2050 could be close to immortal. The quickening advance of nanotechnology means that the human condition will shift into more of a collaboration of man and machine, as nanobots flow through human blood streams and eventually even replace biological blood, he added.

That may sound like something out of a sci-fi movie, but Kurzweil, a member of the Inventor's Hall of Fame and a recipient of the National Medal of Technology, says that research well underway today is leading to a time when a combination of nanotechnology and biotechnology will wipe out cancer, Alzheimer's disease, obesity and diabetes.

It'll also be a time when humans will augment their natural cognitive powers and add years to their lives, Kurzweil said.

"It's radical life extension," Kurzweil said. "The full realization of nanobots will basically eliminate biological disease and aging. I think we'll see widespread use in 20 years of [nanotech] devices that perform certain functions for us. In 30 or 40 years, we will overcome disease and aging. The nanobots will scout out organs and cells that need repairs and simply fix them. It will lead to profound extensions of our health and longevity."

Of course, people will still be struck by lightning or hit by a bus, but much more trauma will be repairable. If nanobots swim in, or even replace, biological blood, then wounds could be healed almost instantly. Limbs could be regrown. Backed up memories and personalities could be accessed after a head trauma.

Today, researchers at MIT already are using nanoparticles to deliver killer genes that battle late-stage cancer. The university reported just last month the nano-based treatment killed ovarian cancer, which is considered to be one of the most deadly cancers, in mice.

And earlier this year, scientists at the University of London reported using nanotechnology to blast cancer cells in mice with "tumor busting" genes, giving new hope to patients with inoperable tumors. So far, tests have shown that the new technique leaves healthy cells undamaged.

With this kind of work going on now, Kurzweil says that by 2024 we'll be adding a year to our life expectancy with every year that passes. "The sense of time will be running in and not running out," he added. "Within 15 years, we will reverse this loss of remaining life expectancy. We will be adding more time than is going by."

And in 35 to 40 years, we basically will be immortal, according to the man who wrote The Age of Spiritual Machines and The Singularity is Near: When Humans Transcend Biology.

Kurzweil also maintains that adding microscopic machines to our bodies won't make us any less human than we are today or were 500 years ago.

"The definition of human is that we are the species that goes beyond our limitations and changes who we are," he said. "If that wasn't the case, you and I wouldn't be around because at one point life expectancy was 23. We've extended ourselves in many ways. This is an extension of who we are. Ever since we picked up a stick to reach a higher branch, we've extended who we are through tools. It's the nature of human beings to change who we are."

But that doesn't mean there aren't parts of this future that don't worry him. With nanotechnology so advanced that it can travel through our bodies and affect great change on them, come dangers as well as benefits.

The nanobots, he explained, will be self-replicating and engineers will have to harness and contain that replication.

"You could have some self-replicating nanobot that could create copies of itself... and ultimately, within 90 replications, it could devour the body it's in or all humans if it becomes a non-biological plague," said Kurzweil. "Technology is not a utopia. It's a double-edged sword and always has been since we first had fire."