Solar Sails and Comet Tails: How Sunlight Pushes Stuff Around

During the Age of Sail, ships circled the globe connected voyages of find and trade. That epoch ended successful the 1800s, erstwhile coal-fired steam engines began to regenerate upwind power. Now we whitethorn beryllium entering a caller property of sail—but this clip successful space. Reversing history, engines and substance could beryllium replaced by sails connected immoderate spacecraft, pushed not by upwind but by sunlight.

The thought is inactive successful development, but we cognize it works. Just a fewer weeks ago, NASA hoisted sail connected the astir ambitious trial trade yet, a outer called the Advanced Composite Solar Sail System (ACS3). It has a quadrate sail 9 meters wide that allows it to set its orbital path.

Now, to truly spell somewhere, you'd request a overmuch bigger sail, and a NASA effort to physique 1 spanning 1,650 quadrate meters was abandoned successful 2022 arsenic infeasible, fixed the budget. But that's an implementation issue, which I'm definite astute humans tin solve.

To beryllium clear, this isn't similar putting photovoltaic panels connected your extortion to make electricity. Lots of spacecraft and planetary rovers usage those already. These are really shiny, ultralight sails that are pushed by star radiation. Well, you mightiness ask: How the heck tin light determination a carnal object?

Comet Tails

Good question! After all, erstwhile idiosyncratic says they were “floored” by the quality of a sunrise, we don't ideate that they were really struck down. But airy bouncing disconnected a aboveground truly does exert a carnal force, tiny though it whitethorn be.

One illustration is the process connected a comet. You mightiness deliberation it's similar a contrail thrown disconnected arsenic a comet hurtles done space. Nope. See, comets are fundamentally large soiled snowballs. When 1 nears the sun, immoderate of that crystal turns to gas, releasing clouds of dust. The sun's airy past pushes that particulate distant successful a watercourse that tin agelong for millions of miles—sideways to the comet's path!

Speaking of which, there's a comet approaching close present that whitethorn enactment connected a spectacular amusement successful October. It's called Tsuchinshan–ATLAS, and its process mightiness adjacent beryllium disposable to the bare eye.

Electromagnetic Waves

Now, airy travels successful waves, which are a benignant of “moving displacement.” Look astatine an water wave: The h2o lone moves up and down, but that vertical displacement travels horizontally crossed the surface. It tin definite arsenic heck sound you implicit if you wade into the water.

But airy waves are antithetic from water waves oregon dependable waves. Take distant the h2o successful the oversea and you person nary waves to surf on. The aforesaid is existent for sound: There's nary question if there's nary ambiance for it to “wave” in. That's wherefore abstraction is truthful weirdly silent.

Light, connected the different hand, tin question done bare space. That's because, successful a sense, a airy question is its ain medium. The crushed is that it's really made up of two waves—there's an electrical tract question and a magnetic tract wave. That's wherefore we telephone it electromagnetic radiation.