Earth reaches its closest point to the sun on a frigid Minnesota day

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On January 4th, Earth reached its closest point to the sun on its orbital journey.  Long forgotten by many, Earth’s orbit is not a perfect circle, but shaped more like an egg.  Therefore there is a point along the way where Earth is at its closest point and furthest point away.  The closest point, called the perihelion, occurs during the first week of January where the Earth is roughly 91 million miles from the sun.  The aphelion is when the Earth is at its further point away from the sun during the first week of July, and it’s roughly 3 million miles further.  So, if the Earth is closer to the sun during our winter here in the Northern Hemisphere, why is it so cold and wouldn’t our winter be warmer than our summer?

Well, this is a good reminder that the seasons here on Earth are not because of the change in distance from the sun.  We have seasons because the Earth is tilted on its axis giving each hemisphere lopsided amounts of sunshine during the course of the year.  When we have more sun in the summer, it’s warmer… when we have less sun in the winter, its cooler.

Now, you may have known all of this information already, or maybe not, but here are a couple of fun facts that many of us don’t know:

Many scientists believe that if the timing of Earth’s perihelion and Aphelion were reversed (we are closest to the sun in the Northern Hemisphere summer and further in the winter), we would have even more extreme temperatures on our planet.  Land heats and cools far more efficiently than water… this is why it takes so long to boil a pot of water on the stove, it just takes more energy.  Well, the Northern Hemisphere has an enormous amount of land, while the Southern Hemisphere is mostly water.  So, if we were closer to our heat source by a good 3% when there is more land directly facing the sun, our summer could very well be even hotter than it is now.  But the opposite could be said about the winter with the Earth further away and more water facing the direct sunlight, the Northern Hemisphere could very well be cooler than our current winter.

The other fun fact is that our winter is ALWAYS shorter than our summer.  The overall speed of Earth through the universe changes very little over time, but the speed at which we pass around the sun changes depending on our distance.  Because we are closer to the Sun in the winter, we are actually passing by it faster than we are in the summer.  While it’s not a huge difference, it does change the overall seasonal calendar by nearly 5 days.  So we actually have 5 more days of summer than winter in the Northern Hemisphere.

This may make you think twice when you say we have really short summers in Minnesota, when in reality, we have shorter winters.