Yes it’s finally here, the day so many of you look forward to all year long. No, it’s not the day the kids go back to school. It is, of course, the first day summer. It arrives at 6:34 this evening!

Meteorological summer began three weeks ago, that’s the warmest 90-day period on the calendar. Today marks the start of astronomical summer. It’s basically just a moment in time telling us that the sun’s angle has reached its maximum for the year in the northern hemisphere.

As the Earth, on its tilted axis, travels around the sun in the elliptical orbit, it causes the sun to appear in different positions and heights each day as it crosses our sky.  It’s not the sun which is actually moving rather an illusion is created by our spinning Earth whirling around in space at 1040 miles per hour.

Today also marks what many say is the ‘longest day of the year.’  This isn’t of course correct for many reasons. What would be more accurate would be to say there is more daylight today than any other day of the year in the northern hemisphere.  The opposite is true south of the equator.  While today does mark the 24-hour period with the most amount of daylight, it’s not the date on which the sunrise is the earliest or the sunset is the latest.  It is also far from the longest day of the year.  More on this shortly.

The elliptical orbit of the Earth around the Sun brings seasons to much of the globe.

The elliptical orbit of the Earth around the Sun brings seasons to much of the globe.

In this part of the world, our earliest sunrise occurred back on June 14th or 15th (depends on your exact location) and the latest sunset is about June 26th although it’s not until a few days later it flips from 8:27 to 8:26 because it’s only moving by seconds a day this time of year. In December, the earliest sunset comes about two weeks before the December solstice, and the latest sunrise happens about two weeks after.

The reason for all the discrepancies is because although we humans have our clocks set at exactly a 24-hour day, the reality is the solar day. The time between the highest position of the sun from one day to the next isn’t exactly 24 hours.  As a matter of fact, true solar days are longer than 24 hours several weeks before and after the solstices and longest around the winter solstice.  The sun’s position at and around the solstices, is very far north and south of the equator and as a result Earth must rotate farther on its axis for the sun to return to its daily noontime position each day.  The elliptical shape of the orbit makes December the period where a solar day is technically at the longest around 24 hours and 30 seconds.

So when folks start saying today is the longest day of the year, you can correct them and say that technically, the longest day of the year is in December, they’ll look at you funny, but you’ll be right.  Happy Summer!

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