Does the Sun Look Bigger Today?

2000px-Seasons.svgIf it seems warmer than you expect for this time of year, it is not because we are closer to the Sun. Of course, you say, how could we be closer to the Sun in January? It’s Winter, so we must be farther from the Sun, right? Wrong.

Every year, the Earth makes its closest orbital "approach" to the Sun in early January. Yes, early January.

For the Northern Hemisphere, that means that the coldest weather of the year normally comes when we are significantly closer to the Sun than in Summer. This is because the Earth’s orbital path is not a perfect circle, but rather is very slightly oval. The average distance to the Sun is about 150 million km, or roughly 93 million miles. But typically it is slightly closer or slightly farther away, depending on where the planet is in the orbit.

Yesterday, January 2, Earth was a little more than 98% of that distance. In other words, we are nearly 2% closer than the yearly average. That’s about 3 million km or nearly 2 million miles closer in early January. In early July, however, we will be same amount, or about 2% farther away. The fact is, we are closer to the Sun in Winter, farther in Summer. It is not our distance from the Sun that determines our seasons.

The real reason for the seasons is the Earth’s tilt on its axis. In Winter, the Northern Hemisphere tilts back, away from the Sun. If I may be anthropomorphic for a moment, it’s almost like the planet (or more specifically, the Northern hemisphere) were repulsed in fear. This causes the Sun has a shorter path in the sky, rises to a lower altitude at noon, casts longer shadows with slightly less heat and light reaching the surface of the Earth. Barring other factors, such as global climate change and localized weather anomalies, this causes lower temperatures. In Summer, the opposite situation prevails, and the Northern hemisphere tilts sunward as if listening intently. In this arrangement, the Sun takes longer to reach a higher point in the sky, shadows are shorter, and sunlight is more intense due to less absorption in the atmosphere. The result of course is higher summer temperatures.

My point is simply that our yearly variations in distance to the Sun have very little affect on temperatures through the year. The real reason, first and foremost, is the planet’s tilt toward (Summer) and away from (Winter) the Sun. Other factors for variations in this pattern include changes in the atmosphere due to volcanic and geothermal processes, and modifications to the atmospheric content due to biologic activities including the burning of fossil fuels and increased methane due to livestock.

The odd weather some areas currently are having — whether unusually warm or unusually cold or unusually wet or unusually dry — is due to some factor other than our distance from the Sun. Whether climate change is the specific cause of all of these unexpected weather events and conditions is unknown. But it is clear that a change in climate regime — for example, from the relatively clement climate we have grown to consider normal to the warmer world envisaged by most atmospheric scientists — will entail decades or more of wild and unexpected weather events.


About Starman

Cosmic Awareness Facilitator. Astronomy, space, physics, science, planets, cosmology, reason, logic, clouds, sky phenomena, the environment, dogs and other animals, and other interesting stuff.
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