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.

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.

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