Friday March 20th is an equinox day. This means that for those in the northern hemisphere winter is ending and spring has ‘sprung’ (starts). For our counterparts south of the equator summer is ending and fall is beginning. From a geographical perspective we would describe the Sun as being over the Earth’s equator, and as this graphic shows there would be an equal amount of daylight and night on our planet as a result.
At mid-day on the equator the sun is directly overhead and from that latitude you have no shadow, just a ‘blob-like’ shadow at your feet as this picture of my feet taken at mid-day in Quito Ecuador shows.
Northern hemisphere spring officially (well at least astronomically) begins at 22:45 UT (4:45 pm CST) on the 20th when the Sun reaches the celestial coordinates of 0 hours and 0 degrees as it moves northward along the ecliptic crossing the celestial equator. At this location the Sun is within the constellation of Pisces the Fishes and not just entering Aries the Ram as the pseudoscience of astrology would have you believe.
To learn more about the celestial coordinates click here to read a previous post about seasons and the equinox.
The time of this equinox is about 13 hours after a new Moon phase and a solar eclipse. This picture shows the shadow of the Moon cast on the Earth during a solar eclipse as seen from the International Space Station.
Click here to see the online world sunlight map used to make the day/night graphic at the top of the page.
Click here to go to the NASA Sun-Earth Days web site.
Here is a short series of hourly pictures taken during the day on the September equinox on the equator in Quito Ecuador at Collegio Menor San Francisco de Quito, a private school that I visited and did the SunShIP project with (Sun Shadow Investigation Project).
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.