Notes for Em


Time lapse of lightfoil in motion.I’m going to have to become some sort of physicist. Damn. I hate math.

No, actually, I don’t; I’m just a pathetic mathematician. Or, more accurately, not a mathematician at all. But that’s beside the point. Except, damn. I’m going to have to become some sort of physicist.

I suppose I shouldn’t be surprised. Some of the questions my brother and I asked thirty years ago probably astounded my father the way my daughter can absolutely befuddle me. “What,” she asked, not too long ago, “is a solar sail?”

Seven, by the way. Now eight.

Of course I told her about this far-flung idea of using a laser to push a spacecraft, and how the vessel could reach speeds near light. You know, stuff from fifteen years ago.

But I had no idea.

A BBC article brings me up to speed with lightfoil, which is a cool word despite the fact that no superhero will ever use it as a name:

Just as air causes lift on the wings of an aeroplane, light can do the same trick, researchers have said.

The effect, first shown in simulations, was proven by showing it in action on tiny glass rods.

Like the aerofoil concept of wings, the approach, published in Nature Photonics, works by making use of the radiation pressure of light.

The results are of interest for steering “solar sails”, a spacecraft propulsion based on the same force.

Each photon – or packet of light – carries its own momentum, and this “lightfoil” works by gathering the momentum of light as it passes through a material.

This radiation pressure has been considered as a fuel-free source of propulsion for long-distance space missions; a “solar sail” gathering up the momentum of the Sun’s rays can get a spacecraft up to a significant fraction of the speed of light.

But until now, no one thought to use the pressure in an analogue of an aerofoil, said Grover Swarzlander of the Rochester Institute of Technology (RIT).

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