Earth reaches perihelion today

Today in Yurty, Siberia, it was 56F degrees below zero. And, believe it or not, they (and the rest of the Earth) are closer to the sun than they will be for the rest of the year.

It may be hard for some in the Northern Hemisphere to believe that here in early January, we are closer to the sun than in July. But it's true! This is the coldest time of year for most of the Northern Hemisphere.

In contrast, the Earth reaches aphelion in early July!

The reason this seems strange to folks in the Northern Hemisphere is the same reason we have seasons.

It is not how close you are to the sun; it is what angle do the sun's rays reach you.

You can see from the above image that the sun's rays this time of year strike the Earth at a 90-degree angle in the Southern Hemisphere near the Tropic of Capricorn. This is an imaginary line that circles the globe at 23.5 degrees south.

For each degree of latitude farther north, the sun angle is 1 degree lower. Every degree of sun angle matters. For example, when the sun is over the Tropic of Capricorn, the Bahamas get about 1/3 less energy from the sun than those near the Tropic of Capricorn.

Head further north to London, England. They see 3/4 less energy. That is, they absorb only 25% of the energy from the sun than the Tropic of Capricorn.

This figure gets infinitely shorter until you reach the Arctic Circle, where no solar energy is received.

If you are really interested, check out this graphic.

Take the cosine of the angle of the sun from directly overhead and use that to multiply the energy from the sun to get the figure at any degree of latitude.

However, the Earth does receive more energy from the sun during perihelion than during aphelion. However, it is only about 7 percent more. So, it does not make a big difference for the Northern Hemisphere winter.

Thanks for reading! Just look up! You never know what you will see!

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