George Thomson had some big shoes to fill. His father J. J. Thomson had won the Nobel prize for the discovery of the subatomic particle now known as the electron, and George had become a physicist as well. Fortunately George Thomson did quite well for himself, and was also awarded a Nobel prize. In a way, George won his Nobel prize for proving his father wrong.
Current Events
In the late 1800s there was an interesting physics demonstration that became rather popular. Take a partially evacuated glass tube with wires embedded on either end and run a high voltage across it. When you did this, the tube would glow, somewhat like a neon light. It was clear that an electric current ran from one wire (the cathode) to the other (anode) through the tube, but it was not clear what was causing the glow. By evacuating more air out of the glass tube, it soon became clear that the light was emitting from the cathode, and so they were called cathode rays.
Gravity’s Shadow
In 1748 Georges-Louis Le Sage proposed a solution to gravity. He argued that gravity wasn’t due to a mutual attraction between masses, but rather due to the interactions of particles moving through space. This idea came to be known as shadow gravity.
Fiat Lux
In 1671, Isaac Newton submitted a letter to the the Royal Society outlining a new theory of light and color. While Newton is probably most famous for his theory of gravity—and the mythical apple—he was also deeply interested in the nature of light, and made one of the first detailed studies of the properties of light. The work he describes in this 1671 paper is so brilliantly simple you can do it at home. All you need is some sunlight and a couple of prisms.
Woman’s Work
Caroline Herschel was an astronomer in the 1700s. She was known for her observations of nebulae, which at the time included comets, galaxies, what we now call nebulae, as they all appeared “fuzzy” in telescopic observations. She was an honorary member of the Royal Astronomical Society and the Royal Irish Academy (women were not admitted as full members then), and was awarded the Gold Medal of Science by the King of Prussia.
Rose of Venus
If this image looks a little odd, that’s because it doesn’t show the path of Venus relative to the Sun, but rather relative to Earth. When you look at patterns such as this, you can see how difficult it was to accurately describe the motions of the planets.
Against the Grain
Yesterday I mentioned that Mars will sometimes reverse its direction of motion in the sky, a phenomenon known as retrograde motion. While Mars has the biggest example of retrograde motion, other planets also undergo retrograde motion. Such a strange variation in motion posed quite a challenge for early astronomers looking for a simple geometric model of the Universe.
Far and Away
If you want to determine the scale of the solar system, how do you do it? In particular, how do you do it when no one has done it before?
Stella Nova
The appearance of this new star, or stella nova as it was known in Latin, was a major discovery. The prevailing view at the time was that the stars were fixed and unchanging. Planets wander through the sky and comets appear from time to time, but the stars were eternal. Tycho’s observations demonstrated this was not the case, and it spurred a new interest in making accurate measurements of the heavens.