During the Age of Sailing, ships circumnavigated the Earth on journeys of discovery and trade. That era ended in the 1800s, when coal-fired steam engines began to replace wind power. Now we may be on the cusp of a new age of navigation, but this time in space. Reversing history, a spacecraft propelled by sunlight rather than wind could replace engines and fuel with sails.
This idea is still in development, but we know it will work. Just a few weeks ago, NASA raised the sails of its most ambitious test vehicle to date, a satellite called the Advanced Composite Solar Sail System (ACS3). It has a square sail 9 meters wide and its trajectory can be adjusted.
Now, to actually go anywhere, we’ll need an even bigger sail, but NASA’s effort to build a 1,650 square meter sail was abandoned in 2022 as being unfeasible given the budget. But that’s an implementation issue that I’m sure a smart person can solve.
To be clear, this is not like putting solar panels on your roof to generate electricity. Many spacecraft and planetary rovers already use them. These are actually shiny, ultra-light sails. pushed by solar radiation. Now, you may ask: How on earth is that possible? light Do you want to move physical objects?
comet tail
Good question! After all, when someone says they were “moved” by the beauty of a sunrise, we don’t expect them to actually be shocked. But light reflecting off a surface actually exerts a physical force, no matter how small.
An example is the tail of a comet. You might think of it like the contrails that comets fly off as they hurtle through space. no. You see, comets are basically big, dirty snowballs. As it approaches the Sun, some of the ice turns into gas, releasing a cloud of dust. The sun’s rays then dislodge that dust, causing rivers to flow for millions of miles alongside the comet’s path.
By the way, a comet is approaching and may put on a spectacular show in October. It is called Tsuchinshan-ATLAS, and its tail may be visible to the naked eye.
electromagnetic waves
Now, light travels in waves, which is a kind of “moving displacement.” Look at the ocean waves. Water only moves up and down, but its vertical displacement causes it to move horizontally across the surface. Stepping into the water can definitely push you down.
However, light waves are different from ocean waves and sound waves. If you remove water from the ocean, there will be no waves to surf. The same applies to sound. If there is no atmosphere for waves to enter, there will be no waves. That’s why the universe is so strangely quiet.
On the other hand, light can pass through empty space. This is because, in a sense, light waves themselves are a medium. The reason is that it is actually configured. two Waves—There are electric field waves and magnetic field waves. That’s why we call it electromagnetic radiation.
