The new animated film Star Wars: The Clone Wars features an army of cloned soldiers doing battle with droids on far-flung planets. For those of us who grew up watching the Star Wars movies, droids and laser blasters are almost as real as cell phones and Wi-Fi. But what in Star Wars qualifies as remotely plausible, according to our understanding of science, and what is pure fantasy? To help answer this question, spoke with Jeanne Cavelos, a science fiction writer and author of The Science of Star Wars [read excerpts from the book here]. When her book came out, researchers had spotted less than two dozen planets around other stars—that figure is now over 300—and South Korean researcher Woo Suk Hwang was five years from rocking the world with his fraudulent claims of cloning the first human cells. We asked Cavelos to update us on how George Lucas's vision has fared.

How far have would you say researchers have come with cloning in the last few years, and will we ever have clone armies like in Star Wars?
We have cloned many different animals at this point—cats, dogs, sheep—and there is very little holding us back from cloning humans except ethics and law. It's entirely conceivable that we will see humans cloned for medical or reproductive purposes in the coming decades. The link between genes and behavior has also become much better understood in recent years, and like the Imperial armies in Star Wars, human clones could probably be genetically altered to be obedient and programmable. One area of Star Wars cloning technology that is not very realistic according to today's science is the limited amount of time the clones have to grow and learn. Nevertheless, cloning technology is something in Star Wars that we will be seeing more of soon.

What do you think about all of the exoplanets that have turned up since you first wrote your book?
It's amazing that George Lucas predicted this universe full of planets and aliens. When Star Wars came out in 1977, scientists thought that planet formation was a fluke. Now they are saying that half of the stars out there may have planets.

So do you think we are getting closer to finding alien life forms?
Absolutely. It's amazing to think about all the potential life out there. And it's looking more and more likely that we might find life right here in the solar system. George Lucas came up with Star Wars before we knew about extremophiles, which are life-forms that can live in bizarre, extreme situations. We had thought that life was this fragile flower that could only develop if conditions were just right—it's the "Goldilocks" principle. But instead, we have found life-forms that can survive boiling and subzero temperatures or live deep underground with no sunlight whatsoever. These sorts of conditions probably aren't conducive to the rise of complex, intelligent life, so a lot of life out there in the universe will probably be rather primitive.

What's a possible reason for why the Star Wars universe could have so many humanoids?
It seems that the human species, or whatever its equivalent is in that faraway galaxy, either colonized all these worlds or was genetically "seeded" on many planets. This species became dominant somehow. It's unlikely though that one species could live on so many planets without some kind of respiratory assistance. Each atmosphere is a quirky mixture of ingredients found only on that planet; you wouldn't have the same mixture of oxygen and carbon dioxide as we do. It's nice to see people in Star Wars just land on any old planet and get out of their spaceships without a problem, but it's not realistic.

But one thing Lucas does do well is show a huge variety of life on these various planets. It helps you get an idea of the crazy abundance of different species, and this will probably be closer to the truth than we once imagined it would be.

Robots, or droids, as they are called in Star Wars, seem to be getting a lot more common than they were years ago. Was George Lucas right about them, too?
Well, nowadays we have the Roomba, that's the little robotic vacuum cleaner some people seem to like. Then there's the Honda Asimo robot that looks like an astronaut, which is pretty much as good as C-3PO at getting around. One of the major areas where people have brought robots into the home is with toys. There were those Furby robots from a while back that would talk to you and pick up what you say, and were banned from the Pentagon. You also see a lot of robots designed and built recently to mimic animals, like geckos and dragonflies.

NASA is now developing these softball-size robots—if you recall Luke's lightsaber training with the floating ball that shoots him in Episode IV—that float in zero gravity and maneuver with six fans. They can record temperature and pressure, can go into areas that are too dangerous for astronauts to go into, and be like a canary in a coal mine.

You also see robots fighting wars in Star Wars. We have devices like that deployed in Iraq called SWORDS that can detect roadside bombs, and now they are putting weapons on these. Then there are predator drones, too. There’s also the "Big Dog" army robot in development by DARPA [Defense Advanced Research Projects Agency]; it looks like an Imperial walker but with dog legs. This two-and-half-foot-tall machine keeps its balance even on ice, and it could serve as an equipment-carrying pack robot for soldiers.

What about robotic intelligence and emotions? What are some insights since you published your book?
Science has made huge strides in robot technology since the first Star Wars movie came out, and even just since Episode I was released in 1999. But the main thing robots still lack is intelligence and emotion—we don't have heroic robots like R2-D2 that take on risks, or skittish robots like C-3PO, either. Researchers who are developing artificial intelligence are realizing that emotions are needed to make robots rational; we usually think of these as being opposed to one another, but we need emotions to operate in a useful way. For example, people with frontal lobe disorders have trouble making decisions because, like computers, they go through every possible action before making a move. People with normal brains, though, have a feeling about a situation and that helps them to make a quick decision.

There are ideas to introduce a chemical reward system in robots similar to what humans have, or to program emotional states. If we are in a tough situation, say, stranded on the Star Wars desert planet Tatooine, we focus on survival by pushing ourselves to the limit and being more watchful of our environment. Likewise, robots could quickly "decide" to access their emergency power and shut down nonessential functions. Overall, emotions could make a robot more efficient in achieving its goal.

How practical is the transgalactic travel in the Star Wars universe?
The characters talk about moving in spaceships at "light-speed" or "making the jump into hyperspace" interchangeably, and there are some problems with that nomenclature. After all, light-speed is not very fast! If you were traveling at light-speed, it would take you over four years to reach the nearest star system, Alpha Centauri, because it is over four light-years [24 trillion miles] away.

What seems to be going on in Star Wars is that they travel through so-called wormholes. Einstein's theory of relativity tells us that we might be able to make wormholes to fold space in on itself in order to make the shortest distance between two points. All of space is warped by gravity. Think of it this way: Say space is a sheet hanging over a clothesline. If you want to get around to the other side of the sheet, you could go up to the clothesline and then down the other side, but it would be much faster just to tunnel directly between the two sides of the sheet.

Wormholes, if they exist, are probably smaller than atoms and survive for only fractions of a second. The way to make use of one theoretically is to "open" one up with a huge amount of energy and then keep it open and expand it with an exotic kind of matter. This matter would need to have negative mass or energy to exert an antigravitational force to hold the wormhole open long enough to let a spaceship pass through. This seems to be what Han Solo is doing with the Millennium Falcon when he makes [a] jump to hyperspace. You can sort of think of "light-speed" as slang in the Star Wars universe.

Obviously, we're very far away from any kind of technology that would take us rapidly to another star. NASA's new Orion spaceship, which will be out in 2014, is designed just to get us back to [the] moon and [to] Mars. But someday we could have interstellar travel like they use so frequently in Star Wars.

What about laser weapons? Are we any closer to having those, and are they realistic?
Who wouldn't want to have a blaster? They are so cool. Right now we have low-powered lasers than can blind people, or higher power ones that burn skin or clothing—kind of like a long-distance flamethrower. The most powerful lasers we have that I know of have about 2.2 megawatts of power, which can destroy enemy missiles from thousands of miles away. These are rather similar to what we see in Star Wars.

But for these lasers we need enough equipment to fill up a truck or even a building. We can't exactly fit this laser technology into a holster just yet. The best lasers are still only 30 percent efficient and the rest of their energy is lost as heat. You also have to cool the laser down to keep it working properly, plus you need to put a lot of power in to get a lot of power out.

There are wireless TASERs now about the size of a flashlight. They send out an ultraviolet laser beam that breaks up air molecules between them and the target. This releases ions, and then electricity can be sent through the air to knock someone out, or even give them a heart attack if you're not careful. It's kind of similar to when Princess Leia was stunned by the storm troopers near the beginning of the first movie [Episode IV: A New Hope]. There are also prototypes of stun grenades that superheat moisture in the air, which makes an explosive flash and bang that can stun people.

Let's talk lightsabers.
Ah, lightsabers. When I first saw Star Wars, I was 17 years old, and I thought they were laser beams. But that doesn't make any sense because a laser beam wouldn't come to a point after a few feet. Also, the laser wouldn't be visible unless there was a lot of dust in the air to scatter light and illuminate the beam. Plus, laser lightsabers would pass through each other like flashlight beams, which wouldn’t make for a very fun fight.

So I think plasma is a better candidate. This ionized gas is made by lightning, is what the sun's made out of, and is even used in plasma TVs. You can contain plasma using electric and magnetic fields, which exert inward pressure to match the plasma's outward pressure. This means you could make different shapes, like a lightsaber–esque cylinder. But there are some problems: You couldn't create a tip, and plasma would leak and vaporize the skin off Luke Skywalker's hands. And as with a laser, you couldn't fit all the necessary machinery to generate the plasma into a sword handle. Plus, the beam would need to be millions of degrees and far denser, in terms of energy, than anything we have now. But if somehow you could do all that, sure enough, the lightsaber would cut through metal and bone. The fields containing plasma would repel other lightsabers, so they would work like what you see, except it would radiate a great deal of heat, about as much of the sun. Jedi would have really bad sunburns.

How do you think "The Force" works in the Star Wars universe, and could it exist in ours?
The most difficult thing about trying to explain The Force is that it does so many different things: It can levitate objects, read others' thoughts, influence the weak-minded, reveal visions of the past and the future, detect disturbances or presences, and even allow for life after death.

The best chance we have of explaining The Force is through the midi-chlorians, which were introduced in the new trilogy. Lucas explains these midi-chlorians as organisms that live within our cells and allow us to feel The Force. The element that seems scientifically based here is the sensing of someone strong in The Force. You can compare this to creatures living in water that generate small electrical fields. Some fish generate these fields, and these can sense when other fish come into these fields as well as the strength of the field put out by the approaching fish.

Or maybe The Force is similar to magnetism. Birds sense magnetic fields with cells in their beaks and eyes, called cryptochromes. Birds may actually "see" the magnetic field, so you can imagine a similar kind of thing happening in Star Wars. If Darth Vader is standing in the next room, maybe you can see the emissions of The Force like a magnetic aura around him.