Summer Solstice

A beautiful sight greets early risers on the first day of summer tomorrow: a conjunction between the Moon and the planet Jupiter. Jupiter looks like a brilliant star to the upper left of the Moon. As a bonus, orange Mars is not far to their left.

Summer actually arrives at just about the same time — 4:14 a.m. Central Daylight Time. That moment is the summer solstice in the northern hemisphere. The Sun is farthest north for the entire year, so it’s the longest day of the year.

Despite all that sunlight, the solstice is not the warmest day of the year. That usually comes in July or August for most of the hemisphere. And there are a couple of reasons for that.

Since the Sun stays high in the sky long after the solstice, it continues to shine almost directly down on us. So its rays pass through a thinner layer of atmosphere than at other times of the year. That means the atmosphere doesn’t filter out much of the Sun’s energy, so things continue to heat up.

And we still have more hours of daylight than darkness, so there’s more sunlight to heat things up. It’s kind of like putting a roast in the oven at a high temperature, then turning it down a bit. The roast can keep on warming up until it reaches the same temperature as the oven. In the case of the atmosphere, it reaches that point in mid to late summer — when we’re thoroughly “baked” by the heat of the Sun.

We’ll have more about the solstice tomorrow.
 

Script by Damond Benningfield

Today's program was made possible by Mercer Caverns, in Calaveras County in California's historic Gold Country.