Is interstellar travel possible with "light sails"? Scientists say this technology is more reliable than rockets.

Is Interstellar Travel Feasible with "Light Sails"? Even Scientists Say This Tech Is More Reliable Than Rockets

Once upon a time, I always thought interstellar travel had to rely on rockets—roaring into the sky with a "boom," flames trailing behind like a firecracker. That was until I read recently that scientists say future interstellar journeys might instead rely on "light sails" to drift to other star systems, and that this technology is even more reliable than rockets. My first reaction back then was: Can this thing actually work? It feels just like the paper boats we folded as kids, carried along by the wind, doesn’t it?

In fact, the idea of light sails isn’t new—it was written about in science fiction decades ago. The principle is surprisingly simple: it uses the pressure of light to propel a craft forward, much like a sailing ship harnessing wind power. But for a long time, I thought this technology was too unrealistic—until I saw news this year showing that someone has actually turned the concept into reality. There are now light sail cruise ships on the Yangtze River: their top decks are covered with solar panels, which generate power from light energy to drive the ships. Not only is the noise much lower, but they also save a lot of fuel. All of a sudden, the idea of light sails in space no longer felt so far away.

And let me tell you—today’s light sails are nothing like the old concepts. Scientists from the U.S. and the Netherlands have just developed a new type, absurdly thin—far thinner than a human hair—with nanoscale holes covering its surface. It’s said that AI is used to design the positions of these holes, which gives the sail extremely strong light-reflecting capabilities while also reducing its weight. What’s even more amazing is that building something like this used to take over a decade; now it can be done in a single day, and the cost has dropped significantly. If we scale this up for use in space, it really gives us something to look forward to.

That said, it wouldn’t be honest to only talk about its advantages. Liu Cixin criticized Hawking’s "Breakthrough Starshot" project years ago, arguing that the light sail in that plan was simply unworkable. His points make sense: for example, how do you accelerate a light sail to one-fifth the speed of light? That would require an enormous amount of energy—so much that the sail material would probably melt on the spot. There’s also the issue of communication: after traveling for decades, how do you send signals back to Earth? Such a tiny craft might send signals that we can’t even pick up here. Even now, these problems haven’t been fully solved.

But scientists aren’t sitting idle. They’ve now developed "diffractive sails," which are different from the reflective sails of the past. These new sails have many small gratings that can change the direction of light through diffraction. It’s said they can adjust their direction without rotating the entire sail surface, making them much more flexible. In the vacuum of space, there’s no resistance—even if the thrust from light is small, the sail can keep accelerating and getting faster and faster. Rockets, by contrast, run out of power once their fuel is burned up. This is definitely an advantage over rockets: rockets have to carry so much fuel that they’re extremely heavy, making long-distance travel impossible.

I sometimes daydream about what a light sail spaceship might look like if interstellar travel with this technology actually becomes a reality. Would it be like a huge transparent film drifting through the universe, inching forward slowly as sunlight hits it? But Liu Cixin also raised a practical issue: funding. It’s said that the earlier Starshot project would have cost tens of billions—who would be willing to invest that much money in something that might not even succeed?

For now, light sail cruise ships are already operating on the Yangtze River. While this is on a completely different scale from space travel, it still validates the technical concept. Maybe a breakthrough will come suddenly one day—just like how we once thought mobile phones could never access the internet. Technology is full of surprises. Even so, when I think about it, I feel both excited (the idea is so cool!) and skeptical: if that day really comes, will ordinary people like us ever get a chance to ride a light sail spaceship?

Regardless, light sail technology definitely has more romance than rockets. It doesn’t rely on explosive fuel; it just borrows light from the sky to drift slowly toward other stars. That feeling is far more comforting than the roar of a rocket.