“I knew the names of the planets in order before I went to kindergarten,” Joan Feynman, the younger sister of the famous physicist, told me. “My father was delighted by science. My brother, of course, was Richard Feynman—gifted as hell. When I was about three or four, he taught me to add numbers. I’d add them and if I got them right, he’d give me a reward. The reward was allowing me to pull his hair. As soon as I pulled his hair he’d make a terrible face.”
For thousands of years people in the northern part of the world have marveled at the spectacular and fearful displays that occasionally light up the night sky. The Norwegian scientist Kristian Birkeland, 1867-1917 was the first explain the real cause – that particles from the Sun were sparking the Northern Lights. To prove his theory—which is still valid today–he built his own small world in a glass box, electrified his model of Earth with its own magnetic field and showed how particles from the Sun could ignite auroras. The particles were captured by the Earth’s magnetic field and channeled down toward the Polar Regions.
Variations in the brightness and color of light from stars provide the key to the detection and characterization of planets orbiting other stars. As a planet crosses the disk of its star, called a transit, it causes a tiny reduction in the amount of light from the star. This tells us the size of the planet relative to the size of the star and the time between transits gives us the planet’s orbital period.
By measuring the color of the light, called a spectrum from the star and measuring pulsations of its brightness caused by waves traveling over the surface and inside the star, we can determine its size, age, temperature, and mass. From the star properties and the distance of the planet from the star we can make an estimate of the radiant heat flux at the planet. Determining the properties of a star is key to understanding the properties of the planet. We like to say that you know the planet only as well as you know the star.
Our neighboring planet, Mars, may be responsible for the literary genre of science fiction. It was after the supposed discovery of “canals” on Mars, popularized in the late 19th century first by Giovanni Schiaparelli in Europe and then by Percival Lowell in the US, that stories of aliens equipped with light sabers became popular.
In the last two decades we humans have turned the tables on the Martians with the use of lasers to explore the red planet. While the lasers used for exploration are not the heat rays envisioned in H.G. Wells’ War of the Worlds, these light beams have been used in a variety of ways.
Discovered in 1965, the cosmic microwave background (CMB) is the most ancient light record in the history of the Universe. Despite being detected as a “noise” across the sky, it did not take long for scientists to realise that this radiation is an incredibly rich source of information about the history of the cosmos, setting them on a search for more and more details in this early cosmic signal.