The Science of 'Star Trek': How Close Are We?

Cruising across the galaxy faster than the speed of light. Getting "beamed up" from the surface of a planet to the deck of a spaceship. Battling aliens from far-flung worlds.

Those ideas from the beloved "Star Trek" series have captured the public's imagination for nearly two generations. They've also grabbed the attention of leading physicists and astronomers who study the science that underlies much science fiction.

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Lawrence Krauss, a theoretical physicist and author of the "Physics of Star Trek," and Seth Shostak, senior astronomer at the SETI Institute (Search for Extraterrestrial Intelligence) in Mountain View, Calif., were in New York last week to probe the science of "Star Trek" at the World Science Festival. They also answered a few questions on the topic for

Want to know if time travel or warp speed is possible? Or if Scotty could ever "beam" you up? Take a look below.

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Warp Speed

Albert Einstein said that objects with mass can't travel faster than a beam of light. But on the Starship Enterprise, Captain Kirk only had to give the order and the massive ship could zoom off to places light-years away, at speeds many times the speed of light.

To make it possible, Krauss said you'd have to "arrange for the space between you and the nearest star to catastrophically collapse and the space between you and the Earth to catastrophically expand. And then you're looking out and you're 300 miles from the nearest star and four light years away from Earth so you turn your engines on and go the rest of the way."

"It sounds good, but it also sounds ridiculous," he said.

According to the theory of general relativity, he said space can expand and contract, so the idea is possible, at least in principle, he said.

But, he said, the problem is that in order to make space expand, you need to fill it up with "negative energy," a special kind of energy that Krauss said is only known to exist in the real world at microscopic levels.

"We don't know if you can create negative energy configurations at large scales," he said.

Not only would negative energy be needed for warp drive, he said, the amount of energy required for one spacecraft to travel that fast is greater than the amount of mass in the entire galaxy.

"This is really an academic question," he said. "We're not going to be traveling with warp drive in the near future."

Time Travel

Believe it or not, wormholes -- or shortcuts through space -- are possible, at least in principle, Krauss said.

Krauss said that if space were a piece of paper and you were an ant that had to get from one end to the other, a wormhole would be a kind of tunnel made by curling the piece of paper and then cutting a hole through it. It would give you a faster way across.

Similar to warp drive, wormholes are possible in principle under the laws of general relativity, but also need negative energy to make them stable, Krauss said.

Still, he said, if wormholes are possible, then time travel is possible.

Stephen Hawking, Kraus said, famously countered the idea of time travel with the argument that "if time travel were possible, we'd already be inundated by tourists from the future."

Kraus had a response: "They all went back to the 1960s and no one noticed."

He said that if time travel were possible, there are many questions.

For example, there is the "grandmother paradox:" What happens if you go back in time and kill you grandmother before your mother is born? If you killed your grandmother before your mother was born, then you shouldn't have been able to go back in time and kill your grandmother in the first place.

"The world of time travel seems to be a world where the laws of cause and effect get screwed up," said Kraus. "But we learned throughout the 20th century that just because things seem crazy doesn't mean they don't happen, it just may mean that we have to think about them slightly differently."

"While it's highly unlikely that any of it is possible, at least we can say that it isn't impossible," he said.

The Transporter

The transporter system on the Enterprise gave rise to one of the most popular phrases in pop culture ("Beam me up, Scotty!") and was the thing that inspired Krauss' book on "Star Trek."

"The thing that sort of seduced me into thinking about this in the first place was the transporter. ?I travel on a lot of planes [and] it would be wonderful to not have to go through security, among other things," he deadpanned.

According to the television show's writers, the transporter worked by vaporizing a person into a matter stream, moving his atoms to his destination and then putting the atoms back together again.

But, Krauss said, not only is moving atoms difficult, but in order to vaporize a person, you'd have to heat him to 100,000 degrees. And he said the amount of energy released would be about 1,000 hundred-megaton nuclear weapons.

"So it's sort of a little dangerous," he said.

He also said that according to the laws of quantum mechanics, and the Heisenberg Uncertainty Principle, it's not possible to know where every atom in a body is and what it's doing at the same time.

The writers of "Star Trek," aware of the principle, gave their characters "Heisenberg compensators" to address the issue. But we're not as lucky in real life, Krauss said.

"That is one thing, even though it's the thing that seduced me into it, that I believe is impossible," he said.

Alien Encounters

Creative interpretations of alien life forms were as much a part of "Star Trek" as the high technology that let Enterprise crew members search the galaxy.

But, SETI's Seth Shostak said that the one thing Hollywood always gets wrong is that the aliens always look too much like humans.

"That's, of course, unlikely to be the case," he said. "All you have to do is go to the Bronx Zoo and see that we share a lot of DNA with those critters and they don't look like us. The idea that aliens would look like us really doesn't make any sense."

He also said that it's unlikely that they'd be at our level of technology.

Shostak said that any aliens humans encounter won't be less advanced, because they wouldn't be sending out any detectable signals (such as radio or television waves).

"If you get in touch with someone, they're at least at your level and, statistically, the chance that they'd be even within a thousand years of the same level is almost zero," he said. 'They're going to be way ahead of us. If there really were battles, if Bambi meets Godzilla, we're Bambi."

And though he said it's possible that humans could encounter aliens, he doubts it'll happen the way "Star Trek" proposes.

Given how vast the universe is and how long it would take to reach any planet with intelligent life, he said it's unlikely that humans will encounter aliens face to face in space.

He also said that since humans only started leaking radio and television broadcasts into space since World War II, it's unlikely that aliens know we even exist.

Searching for Extraterrestrial Intelligence

But he said that it's possible humans could encounter artifacts left by aliens billions of years ago, before humans had evolved.

"They might have left a message in a jar -- a time capsule," he said. In the movie "2001: A Space Odyssey," for example, the message was left on the moon.

He also said it's possible, although highly unlikely, that aliens might visit randomly.

"I think that's unlikely because, again, they don't know we're here, so it would be extraordinary if they visited now," he said.

A more plausible scenario, he said, is that SETI, which uses radio telescopes and optical telescopes to listen for signals of technology from extraterrestrial life, could detect life on another planet.

So far, after more than 40 years, there has not been a peep. But SETI's technology is advanced enough that it can detect signals from up to 1,000 light-years away, which includes a zone with about one million stars. A signal could have been sent 1,000 years ago, before that civilization had any knowledge of Earth.

"The idea of aliens, that's an old idea. I'm sure every society has had some people that look up at the sky and gaze and wonder if there's someone looking back this way," Shostak said.

Even though we're not at a point in history when we could surf the galaxy and search for aliens, he said, "What we are able to do now is actually maybe find them, to at least know that they're out there."