Right Now The Earth Is Technically *Not* Orbiting The Sun

Right Now The Earth Is Technically *Not* Orbiting The Sun

Diagrams and animations showing the orbits of the planets are lying to you a little bit. Or to put it more accurately, they are simplifying the orbits of the planets so that teachers don’t have to explain barycenters to children who are still coming to grips with Earth not being the only planet that exists.

The way you are taught about the orbits of the planets generally looks something like the below video.

But this is a simplified version. Though the Sun is the largest object in the Solar System, with about about 1,048 times the mass of Jupiter, gravity is a two-way street. Just as the Earth exerts a gravitational pull on the Earth, you exert your own (far, far smaller) gravitational pull on the Earth. 

“Kepler’s third law describes the relationship between the masses of two objects mutually revolving around each other and the determination of orbital parameters,” NASA explains

“Consider a small star in orbit about a more massive one. Both stars actually revolve about a common center of mass, which is called the barycenter. This is true no matter what the size or mass of each of the objects involved. Measuring a star’s motion about its barycenter with a massive planet is one method that has been used to discover planetary systems associated with distant stars.”

For simplicity, we say that the planets orbit the Sun. However, the barycenter of the Solar System’s objects is usually near the Sun, given that it provides the most mass, but thanks to the orbits and influence of gas giants Jupiter and Saturn, it is rarely actually inside the Sun. The orbits look a little more like the below video from planetary astronomer and science communicator James O’Donoghue.

As a result, the Earth is not currently orbiting a point inside the Sun, as the barycenter is outside of it. We are orbiting that point in space, rather than the Sun.

“Planets orbit the Sun in general terms,” O’Donoghue explains on X (Twitter), “but *technically* they don’t orbit the Sun alone because the gravitational influence of (mainly) Jupiter means planets must orbit a new point in space.”

“The planets do orbit the Sun of course, we are just being pedantic about the situation,” he added. “The natural thinking is that we orbit the Sun’s center, but that very rarely happens, i.e. it’s very rare for the solar system’s center of mass to align with the Sun’s center.”

The same is true of smaller objects, such as the planets and their moons. The Earth and Moon orbit a point around 5,000 kilometers (3,100 miles) from the center of the Earth, though this changes as the Moon moves further and further away from the Earth.

Though these facts will probably have little impact on your life (assuming you are not an astrophysicist), it’s nonetheless interesting, and a reminder that just about everything is a little more complicated than you were probably taught in school.

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