Today at 16:03 MST (15:03 PST or 23:03 GMT) is the Winter Solstice, when the North Pole is tilted furthest from the sun. This tilt of the Earth gives us shorter days in the Northern Hemisphere. We receive less energy from the sun because we face away from the sun and our days are shorter. However, in the Southern Hemisphere, today is their Summer Solstice! The term solstice comes from the Latin word solstitium, meaning the Sun stands still. Today is the day when the sun has stopped dropping in the Northern Hemisphere, and stopped rising in the Southern Hemisphere.
Many people in Canada call this day the start of winter, which I think is erroneous. For one thing, weather is a regional phenomenon, and we’ve had winter weather for some time here in Edmonton and most other parts of Canada. For another thing, this is the date when the days start getting longer, and each day we will be receiving more solar radiation. It would be more appropriate to call this mid-winter’s day.
In celebration of the sun, here is an image from NASA’s Solar Dynamics Observatory:
The photo was taken on a wavelength band or channel called AIA 193. This channel highlights the outer atmosphere of the Sun – called the corona – as well as hot flare plasma. The Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) is designed to provide an unprecedented view of the solar corona.