The Vernal Equinox

On March 20th, 2015, the northern hemisphere's spring season officially began. This time of year is called the vernal equinox, or spring equinox. We've discussed equinox before and we learned that equinox comes from the Latin for "equal night". It just means that there are the same number of hours when the Sun is above the horizon (day) as there are when the Sun is below (night).

We have discussed the autumnal equinox before, and we learned that this is when the Sun appears to travel from north to south along the ecliptic across the celestial equator. In this case, the vernal equinox occurs when the Sun travels across the celestial equator from south to north along the ecliptic. You should note that when the spring starts in the northern hemisphere, fall or autumn begins in the southern hemisphere.

Another fun thing to note is that on either equinox, the Sun rises due east and sets due west. At the equator, the Sun is directly overhead at noon. As the Sun travels farther north on the ecliptic and we get deeper into the northern spring, the Sun will be farther north in the sky at noon until it reaches its farthest point north at the summer solstice (which will be discussed as we approach that time of year).