The Winter Solstice
The shortest day in the Northern Hemisphere is called the Winter Solstice and marks the first day of winter. It also means the day with the least amount of sunlight (only 9 hours and 8 mins to be exact)! Before we explain why it is cause to celebrate, first it's important to understand what it is exactly.
And in order to answer that question, it is important to recall two key facts that we all know. First, one calendar year means one complete revolution around the sun. See Image 1.
Image 1
And the other is that the Earth rotates on its axis and that it 'wobbles' or tilts. This tilt, more scientifically called its obliquity, is the angle (23.4 degrees) between its rotational axis and its orbital axis. See Image 2.
Image 2
The Winter Solstice (in the Northern Hemisphere) is the date in which the North Pole reaches its maximum tilt away from the sun (and its lowest point in the sky for us). The sun is directly over the Tropic of Capricorn (at 9:27PM central time, exactly) thus marking our shortest day. At the same time, in the South Hemisphere, it is their Summer Solstice and their longest day of the year. See figure below.
For us Northerners, our Summer Solstice marks our longest day (and why the sun is the highest point in the sky). It will occur for us on Thursday, June 20, 2024 at 3:50 P.M. and that's when the sun is directly over the Tropic of Cancer. See Image 3.
Image 3
So there you have it. That's what it means when today marks the day as the Winter Solstice. So why celebrate it when it is the start of winter, we're farthest away from summer, and its the shortest day of sunlight (6 hours and 6 minutes shorter than the Summer Solstice)?
The answer is that starting today, each day moving forward for us we continue to gain more and more sunlight. In other words, we're on the other side of it now and will be getting longer days of sunlight each day from now until June. And in case you were wondering how much more sunlight each day. Well that depends on which day it is. For example, tomorrow we gain (hold on)... less than 1 second of daylight. By the end of January though, we are gaining ~ 2 minutes more of sunlight each day. We keep getting more and more sunlight each day until March 19th at 10:06 PM when it hits it's apex of 2 mins and 50 seconds more sunlight and at which point the gains get smaller and smaller.
