What shape is the Earth’s orbit around the sun and how long does it take?

Earth’s Orbit: More Like a Slightly Squashed Circle Than You Think!

Okay, so we all know the Earth goes around the Sun, right? That’s a given. But have you ever stopped to think about what shape that journey actually takes? It’s not quite as simple as a perfect circle, and the answer is actually pretty cool.

Turns out, our orbit is an ellipse. Think of it like a circle that’s been sat on – a little flattened, a little squished. Now, to get all sciency for a second, an ellipse is a curve that loops around two points called foci (plural of focus). The Sun? It’s chilling out at one of those focal points.

Eccentricity: How Squished Are We Talking?

There’s a fancy word for how squished an ellipse is: eccentricity. A perfectly round circle has an eccentricity of zero. The closer you get to 1, the more egg-shaped it becomes. Earth’s orbit? It’s got an eccentricity of about 0.0167. That’s really close to zero. Basically, it’s so slightly elliptical, you’d be forgiven for thinking it was a perfect circle! I mean, if you drew it, you’d probably just draw a circle.

Interestingly, compared to the other planets, Earth’s orbit is one of the least eccentric. Mercury, that little speed demon closest to the sun? Its orbit is way more oval-shaped. Its eccentricity is a whopping 0.2056!

Perihelion and Aphelion: Sun’s a Little Closer, Sun’s a Little Farther

Because our orbit is an ellipse, we’re not always the same distance from the Sun. Sometimes we’re a little closer (perihelion), and sometimes we’re a little farther away (aphelion).

• Perihelion: Around January 3rd, we’re closest to the Sun – about 91 million miles away. Brrr, feels counterintuitive, doesn’t it, since it’s winter in the Northern Hemisphere?
• Aphelion: Around July 4th, we’re farthest away – about 94.5 million miles away. Fireworks for being so far from the sun! (Okay, maybe not, but it’s a fun thought.)

That difference of 3 million miles might sound like a lot, but honestly, it’s only about a 3% change. It has a tiny effect on how much solar heating we get, but it’s definitely not the main reason we have seasons. That’s all down to Earth’s wonky 23.4-degree tilt on its axis.

How Long Does This Trip Take? The Year-Long Ride

One full lap around the Sun takes us about 365.256 days. That’s a sidereal year, in case you want to impress your friends at trivia night. During that time, we cover roughly 584 million miles, zipping through space at an average speed of 18.5 miles per second! Talk about a road trip!

Now, to keep our calendars lined up with the seasons (you know, so summer doesn’t end up in December), we use something called a tropical year. It’s the time from one equinox to the next, and it’s a smidge shorter than a sidereal year – about 365.242 days. That tiny difference is why we have leap years. We need that extra day every four years to keep everything in sync.

Gravity and Momentum: The Dynamic Duo Behind Our Orbit

So, what keeps us on this elliptical path? It’s a constant tug-of-war between gravity and momentum. The Sun’s gravity is constantly pulling us in, while our momentum (our tendency to keep moving in a straight line) is trying to fling us out into the cosmos. It’s the perfect balance that creates our curved, elliptical orbit.

So, there you have it! Earth’s orbit is a slightly squashed circle, a cosmic dance that takes us around the Sun in about 365.256 days. It’s not a perfect circle, but that slight squish plays a subtle role in the energy we get from our star. Pretty neat, huh?