LightSail 2 is the latest demonstration of solar sail technology, which uses the gentle pressure of photons — the particles of light — on a lightweight, reflective surface to propel a craft through space, similar to the way the wind pushes a sailing ship across the ocean.

Have you ever noticed," asked Anne reflectively, "that when people say it is their duty to tell you a certain thing you may prepare for something disagreeable? Why is it that they never seem to think it a duty to tell you the pleasant things they hear about you?"

The Daguerreotype process involved combining metal particles and chemicals on a silver-covered piece of copper to reflect, or give back, images of light. This reflective process was able to produce sharp, colorless pictures.

The tyre wall is coated with a reflective material to provide extra visibility in the dark.