# A New Planet Is Now Our Closest Neighbor

Most of us learned in school that the planets are in the following order: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and (until 2006) Pluto.

As a result, you could be forgiven for thinking that our closest planetary neighbor is Venus. In some ways, you’d be correct: Venus comes closer to Earth than any other planet in the Solar System. Similarly, its orbit is closer to ours than any other. However, you would be incorrect in another sense. At least, that is the argument put forward in an article published in Physics Today.

Engineers from NASA, Los Alamos National Observatory, and the US Army’s Engineer Research Development Center created a computer simulation to calculate Earth’s average proximity to its three nearest planets (Mars, Venus, and Mercury) over a 10,000-year period. The model shows that Earth spends more time closer to Mercury than either Venus or Mars due to the way the planets align during their respective orbits.

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

It’s not just Earth, after all. Further calculations show that all seven planets (except Mercury) spend the majority of their orbits closer to “the Winged Messenger” than any other planet. Seems impossible? This is how they figured it out.

The findings are based on a technique known as the point-circle method (PCM), which is essentially a mathematical equation that takes two planets’ orbits as circular, concentric, and coplanar, and calculates the average distance between them as they orbit the sun.

“From the PCM, we noticed that the distance between two orbiting bodies is at a minimum when the inner orbit is at a minimum,” the authors explain.

“That observation results in what we call the whirly-dirly corollary (named after an episode of the cartoon Rick and Morty): For two bodies with roughly coplanar, concentric, circular orbits, the average distance between the two bodies decreases as the radius of the inner orbit decreases.”

“It’s clear from this corollary, and 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.” (AU is astronomical units, the distance between Earth and the Sun.)

They created a computer simulation that tracked the positions of all four planets over a 10,000-year period and calculated the average distance between them to test their hypothesis. The results of this simulation differed by a staggering 300 percent from traditional calculations (determined by subtracting the average radius of the inner orbit from the average radius of the outer orbit). However, they differed from the PCM calculations by a negligible 1%.

It found that the average distance between Earth and Venus was 1.136 astronomical units (0.28 on the “old method”). In comparison, the average distance between Earth and Mercury was 1.039 astronomical units (0.61 on the “old method”).

The hypothesis has yet to be submitted to a peer-reviewed paper and will no doubt be put through a thorough cross-examination by experts in the field, but the authors have already noted some possible uses for their newly-devised PCM equation.

“With the right assumptions, PCM could possibly be used to get a quick estimate of the average distance between any set of orbiting bodies,” the authors write.

“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.”

[H/T: Physics Today]

READ MORE: BepiColombo Captures Its First Stunning Images of Mercury During Close Gravity Assist Flyby

#### One Response

• Jack Bechtold says:

It seems to me that the orbital path of Earth is always closer to the orbital path of Venus. If we compare orbital paths between those four inner planets the classical distance between those four planets is as it always was.