Why is the Earth closest to the sun in January?

Wait, We’re Closest to the Sun in January? Mind. Blown.

Okay, I know what you’re thinking: January? Winter? How can we be closest to the sun when it’s freezing cold outside? It sounds totally backwards, right? Well, buckle up, because it’s true! The point when Earth is closest to the sun is called perihelion, and in 2025, we’ll hit it on January 4th. We’ll be a mere 147.1 million kilometers away – which, let’s be honest, is still pretty far, but it’s as close as we get all year. On the flip side, when we’re farthest away (aphelion), it’s in early July. So what gives?

It’s All About the Oval

Forget perfect circles. Earth’s orbit around the sun is actually an oval, or an ellipse if you want to get technical. Think of it like a slightly squashed circle. Because of this shape, there’s a point where we’re closest to the sun and a point where we’re farthest. Now, the squashed-ness of our orbit isn’t super dramatic – it’s measured by something called orbital eccentricity, which is only about 0.0167. But even that tiny bit of difference is enough to make a real change in our distance from the sun throughout the year.

Tilt-a-Whirl: The Real Season Maker

Here’s the kicker: the distance thing isn’t actually what causes our seasons. Nope, that honor goes to Earth’s tilt. We’re tilted on our axis at about 23.44 degrees, and that tilt is the reason we have summer, winter, spring, and fall.

When the Northern Hemisphere is tilted away from the sun (like in January), we get less direct sunlight. Less direct sunlight equals shorter days and colder temperatures. Meanwhile, down in the Southern Hemisphere, they’re basking in the sun because they’re tilted towards it! That’s why they’re having summer while we’re shoveling snow.

Perihelion: A Tiny Tweak

Okay, so perihelion isn’t the main event, but it does play a small role. When we’re closest to the sun, we get about 7% more solar energy than when we’re farthest away. Think of it as a little extra boost. It’s not enough to cancel out the whole tilt thing, but it does mean that Southern Hemisphere summers are a tad bit toastier, and our Northern Hemisphere winters are just a smidge milder. Plus, because Earth speeds up when it’s closer to the sun (thanks, Kepler!), our winters are actually a few days shorter than our summers. Who knew, right?

The Grand Scheme of Things

And here’s one last fun fact: even the pull of other planets like Jupiter and Saturn can mess with Earth’s orbit over long periods of time. It’s like a cosmic tug-of-war that changes how elliptical our orbit is, which in turn affects how much sun we get over thousands of years. It’s all connected, this crazy universe we live in!