EARTH – It might seem strange, but the Earth is closer to the sun tonight than any other time of the year. January 2, 2019, according to clocks in the Americas – we reach Earth’s closest point to the sun for this entire year. That closest point comes at 11:20 p.m. CST (central U.S.) on January 2. It’ll be the morning of January 3 for Europe and Africa … later in the day January 3 for the rest of the world. Astronomers call this special point in our orbit perihelion, from the Greek roots peri meaning near and helios meaning sun.
It’s known as perihelion and the Earth is a mere 91.4 million miles away from the sun.
6 months from now, we’ll reach aphelion. At that point the Earth is about 94.5 million miles away from the sun.
We’re in what’s typically the coldest time of the year in the Quad Cities, so the distance to the sun clearly isn’t what causes our change in seasons.
The change in seasons is a result of the tilt of the Earth’s axis. The Northern hemisphere is pointing away from the sun right now, and that’s why it’s winter here and summer in the Southern hemisphere.
Come late June (when we hit our summer solstice) the Northern hemisphere will be pointing toward the sun more than any other time of the year.
In the Northern Hemisphere, the summer season (June solstice to September equinox) lasts nearly five days longer than our winter season. And, of course, the corresponding seasons in the Southern Hemisphere are opposite. Southern Hemisphere winter is nearly five days longer than Southern Hemisphere summer.
It’s all due to the shape of Earth’s orbit. The shape is an ellipse, like a circle someone sat down on and squashed. The elliptical shape of Earth’s orbit causes the variation in the length of the seasons – and brings us closest to the sun in January.