If You Think You Know Which Planet Is Closest To Earth, Think Again

If you’re a person of a certain age, you’ve probably realized by now that there are more than a few “facts” we learned in school that are now outdated.

The order of the planets hasn’t changed (I’m pretty sure), though, so how could we be wrong in guessing that Venus is Earth’s closest neighbor?

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Well, listen up and I’ll tell you.

In some ways, the old knowledge rings true. Venus comes closer to Earth in orbit than any other planet, and our orbits are also the closest together – but according to this article published in Physics Today, there’s another way of looking at things, too.

Engineers affiliated with NASA, Los Alamos National Observatory, and the US Army’s Engineer Research Development Center built a computer simulation to calculate how far we actually are from neighboring planets – and over the past 10,000 years Earth has spent more time closer to Mercury than either Venus or Mars.

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Huh.

“In other words, Mercury is closer to Earth, on average, than Venus is because it orbits the Sun more closely.”

And actually, all of the planets spend more time near Mercury than any other celestial body.

To get to this conclusion they used the point-circle method, which is a mathematical equation that takes the orbits of two planets as circular, concentric, and coplanar and calculates the average distance between them as the circle the sun.

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“From the PCM, we noticed that the distance between two orbiting bodies is at a minimum when the inner orbit is at a minimum… It’s clear from the table that Mercury (average orbital radius of 0.39 AU), not Venus (average radius of 0.72 AU) is the closest planet to Earth on average.”

Their hypothesis, while tested, has not been submitted to a peer-reviewed paper or journal, so don’t start changing your homeschooling plans just yet.

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That said, the study’s authors believe their calculations are not only correct, but could be useful in ways other than just sparking interesting debates at trivia night.

“Perhaps it can be useful for quickly estimating satellite communication relays, for which signal strength falls off with the square of distance. In any case, at least we know now that Venus is not our closest neighbor – and that Mercury is everybody’s.”