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Mercury -- Not Venus -- is the Closest Planet To Earth on Average, New Research Finds (gizmodo.com)

Posted by msmash on from the how-about-that dept.

That's the finding presented by a team of scientists who have published their results this week in an article in the magazine Physics Today. From a report: They explain that our methods of calculating which planet is "the closest" oversimplifies the matter. But that's not all. "Further, Mercury is the closest neighbor, on average, to each of the other seven planets in the solar system," they write. Wait -- what?

Our misconceptions about how close the planets are to one another comes from the way we usually estimate the distances to other planets. Normally, we calculate the average distance from the planet to the Sun. The Earth's average distance is 1 astronomical unit (AU), while Venus' is around 0.72 AU. If you subtract one from the other, you calculate the average distance from Earth to Venus as 0.28 AU, the smallest distance for any pair of planets. But a trio of researchers realized that this isn't an accurate way to calculate the distances to planets. After all, Earth spends just as much time on the opposite side of its orbit from Venus, placing it 1.72 AU away.

One must instead average the distance between every point along one planet's orbit and every point along the other planet's orbit. The researchers ran a simulation based on two assumptions: that the planets' orbits were approximately circular, and that their orbits weren't at an angle relative to one another.

5 of 177 comments (clear)

  1. Link to the Physics Today Article by mykepredko · · Score: 4, Interesting

    https://physicstoday.scitation...

    Interesting work with the best message to get out of this; don't rely on what's obvious, test what you think is true.

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    1. Re:Link to the Physics Today Article by MachineShedFred · · Score: 4, Interesting

      Anybody that understands that all the planets aren't always in a single synchronized line could have inferred this - all the planets do not have the same orbital period, so there will always be a distribution around the Sun. This means that some of them may be on the opposite side of the Sun from us, and even though their average distance from the Sun is close to Earth's average distance from the Sun, they are not close to each other at that point in time.

      I didn't know there was opportunity for publishing papers that spell out common sense and grade school two-dimensional geometry, though.

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  2. Obvious to anyone who observes them by jfdavis668 · · Score: 4, Interesting

    Amatuer astronomers love to observe Mars. The problem is Mars is on a close, but outside orbit. Unlike Jupiter and Saturn, which the Earth passes every year in thier orbits, it is a different story with Mars. It is only really close for two months every 2 years. It spends most of its time on the far side of its orbit until the Earth can chase it down again, and then quickly races away. Even though you can view it through most of its orbit, it is small and normally far away. Venus, even when near the far side of its orbit, it is fairly easy to observe. At least once it rises far enough out of the Sun's glare. Mercury would be even better, but due to the small orbit it doesn't get far from the Sun from our point of view before it dives back down into the glare.

  3. So, pre-Kepler? by Actually,+I+do+RTFA · · Score: 1, Interesting

    It's not "research". They ran a simulation and reported the results. Which isn't interesting because the simulation was stupid.

    p>They assumed a fucking circular orbit (because the extra 1 parameter for an ellipse was too damn much). Which is something that Kepler disproved in the 1600s (and became an immortal name because of it.)

    Also, this assumes planets are co-planar (they aren't)

    Also, it's meaningless. When people talk about "our closest neighbor", they mean the one easiest to get to. So we want to know the closest point of approach, not "average". Making up a useless measure and publishing it isn't science.

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  4. Re:I call bullsht by abies · · Score: 3, Interesting

    If perfectly circular, average distance from any planet to any planet should be equal to the center of their path circle, which is, drum roll please, the center of the sun.

    No? Planet A at 1AU orbit and Planet B at 2AU orbit have distance between 1AU and 3AU. Planet C at 1000AU has distance to planet A between 999AU and 1001AU. Whatever are their periods, some average of 1-3 won't get anywhere close to average of 999-1001.

    So, Earth-Mercury average distance shares the first place with any other of 45 planet pair combinations.

    Not sure how you came up with number 45. 8 planets give 28 combinations, so it should be 'any other of 27 combinations'. Even if you didn't get memo from 2006 about Pluto, it would be 36-1=35 combinations.