Put on your perihelion party hats

Around 4:00 p.m. CST this afternoon (20:00 Universal Time), Earth reaches perihelion.  That means we achieve our perigee around the sun, or in layman’s terms, the point in our planet’s orbit around Sol at which we are closest to the star.

Now, before any of you go apeshit and tell me I’m insane because we can’t be closest to the sun in the dead of winter, let me preempt you with a hearty “Don’t be a daft dipshit!”  Our orbit around the sun has very little to do with our seasons.  The Earth’s tilt is what causes the seasons, and right now the northern hemisphere is tilted away from all that nuclear heat.  Besides, it is summer in the southern hemisphere, so there!

Anyway, the point was to let you know we’re making our closest pass to the sun this afternoon.  We’ll actually be 1.6 million miles (2.5 million kilometers) closer than we are on average, the average being what’s called an astronomical unit (AU) representing our mean distance from the star throughout one full orbit.  An AU is equal to 92,955,808 miles (149,597,871 kilometers).

As soon as we reach perihelion, we’ll begin the slow move outward away from the star until we reach aphelion on July 7 (aphelion is the opposite or perihelion, or again in layman’s terms, when we reach the greatest distance away from the sun, after which we start moving back toward it).  All of this is easier to understand if you remember that Earth’s orbit around Sol is not a perfect circle.  It’s an ellipse that carries us closer to and then further from the star, a change that occurs every six months or halfway through our one-year orbit.

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