Around 1610, Johannes Kepler noticed that comet tails always point away from the Sun and imagined ships with sails catching a heavenly breeze. Centuries later, James Clerk Maxwell showed light carries momentum and Pyotr Lebedev measured its pressure in 1899 with a torsional balance. This episode walks through the physics of solar sailing, why a perfect mirror gets twice the push of a dark surface, and why an 800 by 800 meter sail near Earth produces only about 1.1 pounds of thrust yet can outrun chemical rockets over months of continuous acceleration.

From there we get into the materials and mechanics: micrometer thin aluminized Mylar and Kapton, porous carbon fiber, Eric Drexler's nanometer scale metal films, and the theoretical 20 nanometer lithium sail that could only be built in orbit. We compare square boom deployed sails to the spinni ...