In the 1800s, ships sailed the world powered by the wind, until steam engines took over. Now, we might be on the brink of a new “age of sail,” but this time, it’s happening in space. Instead of wind, futuristic spacecraft may rely on sunlight to propel them through the cosmos. This revolutionary concept of using solar sails is gaining traction as a way to push spacecraft on deep-space missions without relying on traditional engines or fuel.
The science behind solar sails is still in its early stages, but there’s proof that it works. NASA recently launched a satellite called the Advanced Composite Solar Sail System (ACS3) to test the technology. The satellite is equipped with a 9-meter-wide sail that uses sunlight to adjust its orbit, showing the potential of this futuristic propulsion method.
To explore the vastness of space, however, much larger sails will be needed. NASA had been working on a project to develop a 1,650-square-meter solar sail but scrapped it in 2022 due to budget constraints. Yet, the fundamental technology is sound, and with ongoing advancements, solar sails could soon become a viable tool for space exploration.
But how exactly does sunlight push spacecraft? Unlike solar panels that generate electricity, solar sails use a different kind of force. When sunlight strikes the sail’s surface, the light particles—photons—bounce off, creating a small but real physical push. This is the same phenomenon that creates comet tails.
Comet Tails: Proof of Light’s Power
Comets are often seen streaking through the night sky with glowing tails trailing behind them. These tails are not contrails like those left by airplanes but are actually made of dust pushed away by sunlight. Comets are massive chunks of ice and rock, and as they approach the sun, some of the ice vaporizes, releasing dust. Sunlight then pushes that dust outward, forming the iconic tail that can stretch for millions of miles, demonstrating the force of light in action.
Speaking of comets, keep an eye out for Tsuchinshan–ATLAS, a comet that will make its closest approach in October. If conditions are right, its tail could be visible to the naked eye, offering a cosmic reminder of how light can physically move matter.
Light as an Electromagnetic Wave
To understand how light can push spacecraft or dust, we need to dive into the nature of light itself. Unlike ocean or sound waves, which need water or air to move through, light is a type of electromagnetic radiation that can travel through the vacuum of space. It’s made up of two waves—one electric and one magnetic—working together. These waves don’t need a physical medium, like air or water, to travel. That’s why light can move through empty space and why solar sails could one day harness this energy to propel spacecraft to distant worlds.
The idea of solar sailing opens up new possibilities for space exploration, offering a way to travel vast distances without traditional engines or fuel. Though the technology is still in its infancy, the potential for solar sails to power a new generation of spacecraft could mark the beginning of an exciting new era in space travel.
Read more at Wired.
