If somebody asks you where the center of the solar system is, you would probably say the sun.
The orrery shows it all.
Everything orbits around the sun (which we knew a lot earlier than most think.
Geocentric beliefs were kind of always pseudo science).
Except that its not that simple.
What is a barycenter?
A barycenter is the point in any system around which the objects in the system orbit.
So, the barycenter for the Earth and the Moon is…
…you guessed it.
Not exactly the Earth.
Now, because the Earth is considerably larger, the barycenter is inside the Earth.
Its not, however, the center of the Earth.
The moon does not orbit the Earth.
They both orbit the barycenter.
Which is, on average (because it wobbles) about 2,902 miles from the Earths center.
The Earths radius is only 3,963 miles.
So its nowherenearthe center of the Earth.
This was an easy barycenter to calculate.
You only have two things to worry about.
The fact that the barycenter isnt in the middle of the Earth causes the Earth to wobble.
Effectively, thanks to the gravity of the moon, the Earth is orbiting a point inside itself.
The forces created by the wobble balance each other.
But its important to astronomers as a way of understanding how systems work.
And the key factor here is that theMoon has a gravitational impact on the Earth.
We call it tides, but it also affects the actual course of the Earth through space.
If two objects of a similar size are orbiting each other, the barycenter will be between them.
Logical assumptions arent always correct
Calculating the solar systems barycenter isnt easy!
With the Earth and the Moon we have a two-body problem.
You might have heard the phrase three-body problem as something which cant be solved.
(And also a fascinating novel by Chinese science fiction writer Liu Cixin).
Regular math cant get past two bodies, and for three we have to rely on statistical predictions.
Well, in April, wefinally did it.
The sun is influenced by every body in the solar system, and most of all by Jupiter.
Which made it impossible to calculate.
Ive joked before that pulsars are key to interstellar navigation because they are basically beacons.
And those beacons can be used to measure things.
They can be used to measure things withridiculousaccuracy.
Scientists led by Stephen Taylor at Vanderbilt University were able to use this to find the solar systems barycenter.
So, its probably, what, a bit out from the center of the sun?
The barycenter of the solar system is a pointjust outside the sun.
We may refine this later.
