: I just learned that mercury is in fact the closest planet to the earth. What is this madness and since when?
In: 3690
Hi there. I published the result you are talking about in Physics Today a few years ago. Here is a video I put together about it with diagrams that might help. Happy to answer questions. [https://youtu.be/GDgbVIqGADQ?si=OuK31xfE-HIPnUBE](https://youtu.be/GDgbVIqGADQ?si=OuK31xfE-HIPnUBE)
The ELI5 I think is this. Imagine 2 points in Mercury’s orbit relative to Earths: when it is near and when it is far. The average distance from Earth to those two points is the distance to the Sun. Imagine the same 2 points for Venus. Again, the average distance is the Sun. So if we just consider the nearest and farthest positions, it looks like Venus and Mercury have the same average distance to Earth.
Now consider two other points 90 degrees from the original two so that lines drawn between the point in Mercury’s orbit, Earth, and the Sun would form a right triangle. The distance to those points is shorter for Mercury (with its smaller orbit) than for Venus with (its larger orbit). So if we consider the average distance from Earth to all 4 points in each planet’s orbit, Mercury is closer.
As we include more and more points, the average distance becomes more and more clear – Mercury is closer on average. It has nothing to do with speed or even orbital mechanics. It’s just geometry.
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