aphelion-perihelion-earth
Before dawn this morning (from my North American longitude) the Earth reached its closest point to the sun for this year. Did you feel it?  No, but this annual event (this time at 6:36 UTC or 01:36 a.m. EST) is called perihelion from the Greek roots peri (near) and helios (sun).

Our planet gets closest to the sun every year in early January. Obviously, that doesn’t make it any warmer in the Northern Hemisphere, and we aren’t any cooler in early July when the aphelion occurs and we are farthest away from the sun. I’ll bet this confused the ancients (and some modern readers) if they knew it was occurring, though the Southern Hemisphere ancients must have thought it made perfect sense.

Earth is about 5 million kilometers (3 million miles) closer to the sun in early January than it will be in early July. That sounds like a big difference, but it’s not really significant enough to cause temperature changes across the planet and it doesn’t explain the seasons.

Mostly, it is the tilt of our planet’s axis that creates winter and summer. In winter, your hemisphere is tilted away from the sun and in summer it is tilted toward the sun. Those days of maximum tilt toward or away from the sun are the December and June solstices.

There’s a page on perihelion and aphelion and all the upcoming dates at astropixels.com if you want more information.

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