Summer comes to an end this week when the autumnal equinox arrives at 10:21 a.m. Thursday.
At the equinox, the sun’s rays hit the northern and southern hemispheres equally, because the planet’s tilted axis is pointed neither toward nor away from the sun.
As a result, the sun rises at due east and sets at due west, and is directly overhead in the center of the sky at noon (1 p.m. local time because of daylight savings time.)
The length of day and night are also equal at the equinox, but that is only precisely true at the equator. Because of Baltimore’s latitude about 39 degrees north of the equator, there will still be more daylight than nighttime here until Sept. 26.
That means this is the last week of the year during which the sun is up for most of the day. There sun is up for about 12 hours, 10 minutes on Wednesday, for example, but daylight shortens by 2 1/2 minutes with each rotation of Earth at this time of year.