John Dalton

John Dalton was a chemist primarily known for his development of the modern atomic theory.  "Daltonism" is another word for color blindness because Dalton was colorblind.  In common with his brother, he confused scarlet with green and pink with blue. Dalton supposed that his vitreous humor was tinted blue, selectively absorbing longer wavelengths. He instructed that his eyes should be examined after his death, but the examination revealed that the humors were perfectly clear.

Eratosthenes

The ancient Greek mathematician and geographer Eratosthenes is credited with making the first accurate estimation of the Earth's circumference. In the third century BC, he observed that at noon on the summer solstice, the sun was directly overhead at the city of Syene (present-day Aswan, Egypt). At the same time, in the city of Alexandria, he measured the angle of the sun's rays relative to the ground and found it to be about 7.2 degrees.  Using these observations, Eratosthenes was able to calculate the Earth's circumference by assuming that the sun's rays are parallel (which is not exactly true, but close enough for his purposes) and using simple geometry. His estimate was remarkably accurate, and modern measurements have shown that it was only about 15% too high.  He was also the first to calculate Earth's axial tilt, which also proved to have remarkable accuracy.  He created the first global projection of the world, incorporating parallels and meridians based on the available geographic knowledge of his era.   He is also known for the sieve of Eratosthenes.

Noble gases

Noble gases are a group of chemical elements in the periodic table with very low reactivity. They are located in group 18 of the periodic table and include helium, (He) neon (Ne), argon (Ar), krypton, xenon (Xe), and radon (Rn).  They have also been referred to as the inert gases or aerogens.

Bryology

Brylogy is the study of mosses and liverworts.  From the Greek byron, a moss or liverwort.  Johann Hedwig is the father of bryology.

The first neon sign

The first neon sign was said to have been used in Paris in 1913 to make letters for Cinzano vermouth.  This is disputed.  Was it for a hairdresser?  Maybe a barber.

Length of a light-year

A light-year is approximately 5.8 trillion miles (or 9 trillion kilometers, if you are a scientist, or 9 trillion kilometres, if you are a British scientist).

Stone skipping

The thing I learned today is that a group of French researches discovered that the optimum angle for a stone to hit the water so it skips across the surface is 20 degrees.  Lydéric Bocquet, a physics professor at the University of Lyon, and his team found that even if other variables are changed, the stone has the best chance of skipping when hitting the water at 20 degrees, the "magic angle."This was confirmed by Japanese scientists as well.

The term "atomic bomb"

The thing I learned today is that the term "atomic bomb" was first coined in 1914 by H.G. Wells in The World Set Free, thirty-one years before "The Gadget" was first tested in New Mexico.

Point Nemo

Point Nemo is a name for tthe oceanic pole of inaccessibility, the place in the ocean that is farthest from land. It lies in the South Pacific Ocean, 1,670 miles from the nearest lands: Ducie Island (part of the Pitcairn Islands) in the north, Motu Nui (part of the Easter Islands) in the northeast, and Maher Island in the south. The area is also known as a "spacecraft cemetery" because hundreds of decommissioned satellites, space stations, and other spacecraft have been deposited there upon re-entering the atmosphere.  The space station Mir fell there in 2001.

Juan Vucetich was an Argentinian police official who was a pioneer in the science of fingerprinting, making the first positive identification of a criminal based on a bloody fingerprint in 1892. (Interestingly, the murderer was a woman.)

Minamata disease is a neurological condition brought on by severe mercury poisoning. Ataxia, numbness, paralysis, loss of senses, and muscle weakness are all symptoms. It is named after a Japanese city where the Chisso company opened a chemical plant in 1908.

Sonic Hedgehog protein

Even though this sounds ridiculous, the gene that helps determine physical structures in people, including teeth and appendages, has been named Sonic Hedgehog (SHH). Yes, after the video game character. It is one of three hedgehog homologues in mammals.

An acre is a measurement of area equal to 4,840 square yards or 43,560 square feet. That is 4046.8 square meters. It was supposedly originally defined as the amount a man could plow with an ox in one day.

A lepton is a fermion (a sub-atomic particle with 1/2 integer spin) that is opposed to a quark. An electron is a kind of lepton.

Albert Einstein (born on this date, Pi Day, 1879), was chosen as Time magazine's Person of the Century in 2000. Let's hear it for the egghead!

Hydrogen is the most abundant of the chemical elements, constituting roughly 75% of the universe's elemental mass, though estimates vary up to 90%.

first woman in space

The first woman in space, Valentina Tereshkova, blazed a trail for the many female space-goers who would follow. Tereshkova, a Soviet cosmonaut, was selected from more than 400 applicants to launch on the Vostok 6 mission on June 16, 1963.  She orbited the Earth 48 times, spent almost three days in space, is the only woman to have been on a solo space mission and is the last surviving Vostok program cosmonaut. Twenty-six years old at the time of her spaceflight, she remains the youngest woman to have flown in space under the international definition of 100 km altitude, and the youngest woman to fly in Earth orbit.

Snell's window

Snell's window is a phenomenon by which an underwater viewer sees everything above the surface through a cone of light of width of about 96 degrees.

Newspapers and other cheap papers turn yellow over time because the lignin, a dark substance found in cardboard, in them gradually reacts to oxygen to reflect a darker color.

Himalayan salt, rock salt mined primarily in Pakistan, is noted for its pink color. Large crystals of Himalayan salt are sometimes used as lamps.