Great Gifts for Math Lovers 2024
Our annual Holiday Gift Guide is here again to help you find awesome presents for the math lovers in your life! Check out our recommendations.
Back-to-school season is upon us, and with it comes the end of summer. To make it official, today we are celebrating the Fall Equinox!
Also known as the Autumn Equinox, September 22, 2021, marks the First Day of Fall. But what does this mean?
Let’s start with some basics about Earth.
A hemisphere is half of a sphere. Earth’s hemispheres are divided by the equator, defined as a Great Circle located at 0-degrees latitude.
“An axis is an invisible line around which an object rotates (or spins). The points where an axis intersects with an object’s surface are the object’s North and South Poles.”1 Rather than spinning on a 0-degree tilt, the Earth’s axial tilt is about 23.5 degrees. Earth completes one full spin about its axis in 24 hours, giving us day when the Northern Hemisphere faces the Sun and night when facing away from the Sun.
In fact, the axial tilt determines our seasons as the Earth rotates around the Sun. Earth’s orbital period is about 365 days, during which it completes one full rotation around the Sun. We experience winter in the Northern Hemisphere when the North Pole is tilted away from the Sun (losing warmth) during this full rotation; alternatively, we experience summer in the Northern Hemisphere when the North Pole is tilted towards the Sun (gaining warmth).
All of this brings us the Equinoxes. The lengths of our days and nights are not usually equal except for two days in a year: the Spring and Fall Equinox Days. Equinox stems from the Latin words for “equal” (aequus) and “night” (nox). During the 24-hour day on the two Equinoxes, we can expect roughly half of the day (12 hours) to be day and the second half of the day (another 12 hours) to be night.
Officially, the Equinox marks the moment when the Sun is in line with the equator, representing for us an official change in season. When an Equinox happens, the dividing line between the light and dark parts of the Earth extends directly through the North and South Poles.
The answer is no. Since the Fall Equinox represents the time in the North when the Sun’s centre passes the celestial equator from north to south and the Northern Hemisphere continues to tilt away from the Sun, it likewise represents the time of year when the Southern Hemisphere continues to tilt towards the Sun. Whereas in the Northern Hemisphere we celebrate the Fall Equinox in September and the Spring Equinox in March, the Southern Hemisphere celebrates the Spring Equinox in September and the Fall Equinox in March!
How do you and your family celebrate the change in season?
Sources:
1. Caryl-Sue, National Geographic Society (2012). Axis. National Geographic: Resource Library Encyclopedic Entry. Retrieved from https://www.nationalgeographic.org/encyclopedia/axis/
2. Resnick, B. (2018). When and where fall foliage colors will peak, in one map. Vox. Retrieved from https://www.vox.com/energy-and-environment/2018/9/4/17800200/peak-fall-foliage-2018-map