Carbon 14 is radioactive, and decays over time. It is one of the ways we can date the age of living things long after they’ve died. The reason is because carbon 14 is generated in the atmosphere when high energy particles strike nitrogen atoms in the upper atmosphere, and living thing utilize that carbon while they are alive. Once they die the carbon 14 in them isn’t replenished, so as the carbon 14 decays it over time it gives us a measure of how long an organism has been dead.
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.
Remnant
In the constellation Sagittarius is a small, dim supernova remnant. There’s nothing particularly unusual about it until you begin to look a bit closer.
Islands in the Sky
In the 1700s, it was clear that the Messier objects such as M-31 are not stars. They are also not comets, as they they don’t move through the sky. Messier actually cataloged these objects so he wouldn’t confuse them with comets, which also look like fuzzy patches in the sky.
Space Detective
A research team studied photographic plates from the Harvard College Observatory. From the plates they were able to gather about 500 historical data points. This allowed them to prove that two supermassive black holes are orbiting each other.
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.
Pattern Recognition
Looking for patterns in data is useful because such patterns are often caused by a simple underlying principle, but this isn’t always the case. As an example, consider the story of the the Titus-Bode law.