: I just learned that mercury is in fact the closest planet to the earth. What is this madness and since when?
In: 3690
Remember that the planets orbit at different speeds. While the orbit of Venus and Mars may be the most adjacent to Earth’s that is just their orbital path; Mars and Venus could be on the opposite side of the Sun right now in their orbit. If Mercury is on the same side of the Sun as Earth then it can be the closest planet to Earth at the moment.
Actually right now it looks like Venus is closest, but Mercury is closer than Mars.
Mercury is closest on average. That is to say throughout the cycle around the sub for both planets, it is closer that Venus and Mars. Because at some points Venus and mars and earth orbits play out so that one planet is on the other side of the sun from earth.
We usually refer to orbits when talking about how close planets are, and generally its a much more useful category than physical proximity.
>I just learned that mercury is in fact the closest planet to the earth. What is this madness and since when?
You’re missing a pair of words.
Mercury is the closest planet to the Earth ***on average***. Mercury orbits faster, as a result of being closer to the Sun, and thus is more often on the same side of the Sun as Earth.
This doesn’t inherently mean that Mercury is *always* the closest, just that when you expand the timeframe out to significantly large timescales, Mercury *tends* to be the closest.
The other fun fact is that this isn’t something special about Earth; Mercury is, on average, the closest planet in the Solar System to *every other planet*.
The thing is that all of the planets are constantly orbiting the sun at different speeds, so at any given time the closest planet in terms of absolute distance to the Earth could either be Mars, Venus, or Mercury, depending on where all the planets are in their orbits. On average, Mercury is the closest of the three about half the time.
[Here’s a youtube video of a simulation showing it.](https://www.youtube.com/watch?v=GDgbVIqGADQ)
It’s the closest ***on average to all other planets.***
The reason is actually pretty simple if you think about it.
At some point, any two planets are at their closest distance to each other and at some other point they are at their furthest apart. There’s math involved related to the planet’s speed and what not, but you should be able to see that the ***average*** distance is at least related to those two things: (1) what’s the closest that they get and (2) what’s the furthest away that they get.
Mercury has the smallest orbit because it is the closest planet to the sun. That means that when it is ***closest*** to the other planet, the distance is basically the same as the distance from the other planet to the sun. Similarly, even when Mercury is as ***far away*** from the other planet as possible, it is only about the same as the distance from the other planet to the sun.
Now consider something like Jupiter and Saturn. Yes, when they are closest, they might be closer than say Jupiter to Mercury, but when they are farthest apart, they are ***over twice*** the distance from Jupiter to Mercury (because you go from Jupiter to the Sun, which is about the same as Mercury, back out to Jupiter’s distance, and then even further to Saturn’s distance).
Because Mercury’s orbit is the smallest, it never has this massive distance away, and that makes the ***average*** distance the smallest.
It depends on how you define close.
If you go by the minimum distance, then yes Venus is the closest planet to earth.
However, if you go by average distance, it’s actually Mercury.
This is because Venus isn’t at it’s closest position to earth all the time. Half of its orbit it’s on the opposite side of the sun to earth. The same goes for Mercury of course, but because Mercury’s own orbit is so small, the difference between being on the same or opposite side of the sun isn’t that much, and because of that the _average_ distance from mercury to earth is less than the _average_ distance between earth and venus.
And this same math doesn’t just work for Earth. By average distance, Mercury is the closest planet to **every** planet in the solar system _and_ pluto.
[removed]
[removed]
The distances between the planets are always changing because they’re all constantly orbiting around the Sun. Thus it’s important to be clear about what we mean by “closest”.
For example, at the moment this is being written, Venus is in fact the closest planet to Earth. It is also the planet where the *minimum* distance between that planet and Earth is smallest. We have, at some point, been closer to Venus than we have ever been to Mercury. The map of the solar system you learned in school also remains true. Mercury has the tightest orbit around the sun, followed by Venus, and then Earth.
So in what sense is it correct to say that “Mercury is closest”? That would be average distance. The further a planet is from the Sun, the wider its orbit, and the further away from us it can get when we are on *opposite* sides of the Sun. It turns out that having these periods of being very far away really increases average distance, so the planet with the lowest average distance is the one with the tightest orbit: Mercury. This isn’t even unique to the relationship between Mercury and Earth. When you use average distance, Mercury is closest to *every* planet.
A metaphorical way to think about it is that Earth and Venus are like a married couple. They spend a lot of time in the same house, often right next to each other, but they also have jobs on opposite sides of the city. Mercury is like the shut-in neighbor of this couple who never leaves their house. It is never particularly close to either member of the couple, but when they are at work, it is closer to the couple than they are to each other. The couple works a lot, so Mercury is closer to each on average then they are to each other.
Everyone insists on phrasing it like some weird thing. It’s just the fact that when things are orbiting something, all the orbiting bodies are closer (on average!) to the parent body (the sun) than the other orbiting bodies. And the bodies closest to the center are closer to all the other bodies than ones further out.
So mercury is closer to us (and mars and jupiter and pluto and ceres and all the other objects orbiting the sun) than any of the other planets. But THE SUN is even closer. The sun can never be “on the other side of the sun” from us, but all of the other planets, asteroids, etc could be. so on average it’s closer to everything else.
Latest Answers