5 July 26

Isaac Newton's revolutionary book "Principia" was first published on 5 July 1687. "No work was more seminal in the development of modern physics and astronomy than Newton's 'Principia.' Its conclusion that the force retaining the planets in their orbits is one in kind with terrestrial gravity ended forever the view dating back at least to Aristotle that the celestial realm calls for one science and the sublunar realm, another." In other words, Newton proved that the force of gravity is the same everywhere in the universe. (Albert Einstein introduced general relativity 228 years later!) My tie shows some of Newton's equations, along with the legendary apple that triggered Newton's experiments and calculations.

5 July 23

Isaac Newton's revolutionary book "Principia" was first published on 5 July 1687. "No work was more seminal in the development of modern physics and astronomy than Newton's 'Principia.' Its conclusion that the force retaining the planets in their orbits is one in kind with terrestrial gravity ended forever the view dating back at least to Aristotle that the celestial realm calls for one science and the sublunar realm, another." In other words, Newton proved that the force of gravity is the same everywhere in the universe. (Albert Einstein introduced general relativity 228 years later!) My tie shows some of Newton's equations, along with the legendary apple that triggered Newton's experiments and calculations.

8 September 21

The eighth of September, 9-8, is honored as Gravity Day by those who know that the gravitational constant on the surface of Earth is 9.8 m/sec².  I know of no connection for this day to the life of Isaac Newton, but I'm wearing my tie that shows some of his equations regarding gravity! Albert Einstein completely changed our understanding of how gravity works, but Newton's equations are still very useful, even guiding all of the calculations for aviation and lunar and interplanetary exploration.

4 January 21

Isaac Newton was born on Christmas Day in 1642, but today's date -- the 11th Day of Christmas -- is now recognized as his birthday. In 1750, 23 years after Newton's death, Britain adopted the Gregorian calendar, resulting in a "loss" of eleven days, and a great deal of confusion about reconciling dates from the past. You may see the letters "OS" and "NS" (for Old Style and New Style) attached to many date references in the 1600s and 1700s. My tie shows many of Newton's equations for mechanics and gravitation, and the apples refer to the apocryphal story (legend) that he "discovered" gravity after observing an apple falling from a tree.

4 February 20

Thursday this week marks 348 years since Isaac Newton presented his first paper to the Royal Society. It was his "New Theory about Light and Colours," describing early experiments to define and measure what we call the electromagnetic spectrum. My very colourful tie features some of Newton's equations related to gravity, first published 15 years later (1687).

8 September 19

Stomp your feet today for gravity! Today's date can be written 9-8, which makes it Gravity Day on some calendars -- because the gravitational acceleration near the Earth's surface is 9.8 m/s². The newest tie in my collection (a birthday present from Mom Wollenweber) features many of Isaac Newton's equations of motion and gravitation. Albert Einstein completely changed our understanding of how gravity works, but Newton's equations are still very useful, even guiding all of the calculations for aviation and lunar and interplanetary exploration.