Semi-major and semi-minor axes
Okay kiddo, imagine that you have a big round cookie. Now, imagine cutting that cookie in half, but not straight down the middle. You cut it in a way that makes one side bigger than the other. The bigger side is called the semi-major axis, and the smaller side is called the semi-minor axis.
Now, let's think about planets. Planets are big spheres floating in space. But they're not perfect spheres, they're a bit squished. Scientists call that squished shape an ellipse. An ellipse is like a stretched-out circle.
The semi-major axis of an ellipse is the distance from the center of the ellipse to the farthest point on the ellipse. The semi-minor axis is the distance from the center to the closest point on the ellipse.
How about we use an example? Take a look at this picture of Earth's orbit around the sun. Do you see the yellow line that goes around in a circle? That's Earth's path around the sun, but it's not a perfect circle. It's an ellipse. The blue line in the middle is Earth's axis, or its imaginary spinny line.
The distance from the sun to the farthest point on Earth's path (the semi-major axis) is about 94.5 million miles. The distance from the center of Earth's path to the closest point (the semi-minor axis) is about 91.4 million miles. See how one is bigger than the other?
So, semi-major and semi-minor axes are like half of a cookie, or the distances in an ellipse from the center to the farthest point and the closest point. They're important because they help scientists understand the shape of things like planets or the paths that they orbit around the sun.
Now, let's think about planets. Planets are big spheres floating in space. But they're not perfect spheres, they're a bit squished. Scientists call that squished shape an ellipse. An ellipse is like a stretched-out circle.
The semi-major axis of an ellipse is the distance from the center of the ellipse to the farthest point on the ellipse. The semi-minor axis is the distance from the center to the closest point on the ellipse.
How about we use an example? Take a look at this picture of Earth's orbit around the sun. Do you see the yellow line that goes around in a circle? That's Earth's path around the sun, but it's not a perfect circle. It's an ellipse. The blue line in the middle is Earth's axis, or its imaginary spinny line.
The distance from the sun to the farthest point on Earth's path (the semi-major axis) is about 94.5 million miles. The distance from the center of Earth's path to the closest point (the semi-minor axis) is about 91.4 million miles. See how one is bigger than the other?
So, semi-major and semi-minor axes are like half of a cookie, or the distances in an ellipse from the center to the farthest point and the closest point. They're important because they help scientists understand the shape of things like planets or the paths that they orbit around the sun.