Lee was a doctoral student in biomechanics at the University of Utah five years ago when he got the call from Harvard University and the advanced robotics company Boston Dynamics to work on the BigDog project.

Five years later, the Defense Department-sponsored project is stretching the boundaries of people's perceptions of robots. BigDog is so lifelike that it makes Asimo, the cute humanoid robot Honda Motor Company made famous by its ability to perform dance routines, look like an expensive child's toy.

"It's very, very, very complex," Lee said. "Nothing comes close, really."

Lee was hired last fall to bring his expertise to the young university and to breathe new life into the small field of comparative animal biomechanics, the study of how animals move, including the evolution of those movements and how they compare to the movements of other animals.

Already he has purchased a digital radiography camera for UNLV. The camera, essentially a high-powered, real-time X-ray machine, will be only the third of its kind in the country, after those at Harvard and Brown universities, when it arrives in the fall.

But it was the BigDog robot that changed the course of Lee's career.

Early in college, Lee wanted to be a veterinarian or equine orthopedist. That interest led him to biomechanics and eventually to abandoning the idea of becoming a veterinarian.

"I realized biomechanics was way more exciting than the actual, day-to-day grind of ... warming horses, pulling teeth, dealing with the abscesses in their feet," he said.

Before he came face-to-face with BigDog, Lee knew what was wrong with it. Early videos he had seen showed BigDog with its front knees pointing forward, similar to what two men in a horse suit look like, and just about as awkward.

But there's no four-legged animal in the world that has its front knees pointing forward. Land animals evolved to have their front knees pointed backward and their back knees pointed forward.

Lee had the engineers turn the front legs around. Immediately, the robot's stability improved.

The next step was to make BigDog's legs springy, or compliant, to improve agility and speed. They added bicycle shocks to its legs and tweaked the hydraulic actuators that power them. A gasoline engine powers the actuators.

The change was drastic.

"The robot wanted to walk when it had stiff legs," Lee explained. "When we walk, our legs are stiff. When we run, we bend our knees. So we found when we put the compliance in (the legs) ... BigDog wanted to trot."

The overall effect was to make the machine more animal-like.

BigDog's mission is to traverse rough terrain and carry heavy loads for the military. About the size of a small mule and weighing 235 pounds, it can carry up to 340 pounds.

BigDog still is in the testing phase, and BostonDynamics wouldn't release the project's cost so far.

Onboard sensors control its movement, and it reacts to changes in terrain. Engineers tried to attach the camera system used on the NASA Mars rover in order to have the robot better predict changes in landscape, but the technology couldn't keep up with how fast BigDog could move.

And many people do find it creepy.

"I've heard people say they think it's scary. I think a lot of that is tied to science fiction," Lee said. "The prospect of things being as capable as people are in the artificial intelligence world, or as capable as animals are in the locomotion world, scares people."

On YouTube, the latest video of BigDog has logged more than 5 million views and nearly 9,000 comments from people amazed by it, disturbed by it or wanting to kill it.

It's become so popular that a spoof video has emerged of two people in black tights marching around like BigDog.

"I guess you've arrived when people are bothering to spoof you on YouTube," Lee said.

Lee's research has focused on the movements of animals, and his calculations on how much force goats and dogs use -- where they place their feet and where their center of balance is -- as the animals are walking, trotting and galloping went into BigDog.

BigDog is able to walk and trot, but they haven't been able to master galloping. It can move up to 4 miles per hour.

The results of Lee's research could lead to breakthroughs in treating arthritis and in joint replacement. With the high-speed radiography camera UNLV has purchased, scientists will be able to see and measure the stress on joints as the bones are in motion.

Lee hopes to be working with UNLV scientists, engineers and mathematicians on other robotic work.

He will be traveling to Boston this summer to do more work on BigDog, including building a better foot for the robot. Its current foot is just a rubber ball.

Lee plans on developing something closer to the foot of a goat, which can absorb shocks and can adjust to the environment

Eventually, BigDog will be able to do everything a goat can do: scale mountains, gallop and predict the terrain, he said.

But to Lee, BigDog is not just a hallmark in engineering and robotics, but in biology.

"To me, that's the real excitement, to understand biology well enough that you're able to build ... something from man-made materials or synthetic materials and have it work," he said.

Contact reporter Lawrence Mower at lmower@reviewjournal.com or 702-383-0440.