There are certain things we learn from boys and we take for granted the rest of our lives. For example, the order of the planets.
The most memorable can remember how they come: first, next to the Sun, is Mercury, then Venus and then us, followed by Mars, Jupiter, Saturn, Uranus and Neptune.
They also teach us which planet is closest to Earth. Do you remember what it was?
Maybe that does not come to mind, but you certainly know the answer is one that you learned in school.
TheWas it Mars? OR Venus?
Test for yourself: how much do you know about the planets and the solar system?
What are the true colors of the planets?
Well, if it was that simple, we would have nothing to tell you!
It turns out – in addition to what you were told as a child – there is not a single answer to the question, because the distances between the planets are changing.
In fact, although Mars and Venus are always attracted like our neighbors – one on each side – sometimes none of them are the closest to Earth.
This was recently revealed by BBC Radio 4's "More or Less" radio program, which analyzes numbers and statistics of daily life. *
It was a listener who wrote asking to clarify the issue, after watching a BBC television show, where it was said that Mars was our nearest neighbor..
"It's certainly a mistake," said Graham Sherman, convinced that the correct answer was Venus.
The truth is that each planet has a different rhythm of orbit, the path of the planets around the Sun.
This implies that the distances between them are changing.
To calculate which planet actually spends the most time near Earth, you have to have an average.
That's exactly what "More or Less" did, with the help of statistics expert Oliver Hawkins.
Hawkins was able to estimate which one the planet was closer of our every day of the last 50 years.
So he managed to figure out which, on average, was the one who spent most of the time as our nearest neighbor.
The answer will amaze you …
How is this possible? You ask.
To understand this, the BBC sought out David A. Rothery, a professor of planetary geosciences at the Open University.
A matter of time
"The order of the planets, of the Sun, is: Mercury, Venus and then Earth, but when Venus is on the other side of the Sun, it is very far from us," Rothery explained.
So while the orbit of Venus makes that planet be the one that can best get close to us, followed – secondly – by the orbit of Mars, sometimes the red planet is very close to Earth, while the distance with Venus is enormous.
"And although Mars is the second potentially closest to us, among all, the planet that spends most time near the Earth is Mercury"he confirmed.
Statistics prove this clearly: in the last half century, the smallest planet – and closest to the Sun – was the closest to Earth on Earth. 46% of the time.
Venus came in second place: 36% of time as our closest neighbor.
On the other hand, the red planet, which many suppose to be the closest to Earth, was in that place only 18% of time.
Why the confusion?
Perhaps the confusion about the proximity of Mars has to do with huge interest which spawned this planet in recent years among space agencies, especially American NASA.
Why is there so much talk about making visits to Mars if Venus is in fact a shorter distance and Mercury ends up spending more time on our side?
The reason, explains Rothery, has nothing to do with distances, but with the characteristics of each planet.
"Mars is a place that could shelter life and is not too hot on its surface. A spacecraft could operate there for a long time, "he said.
"On the other hand, if you land on Venus, it is very hot because the dense atmosphere holds the heat."
Mercury, the next challenge
As for Mercury – the unexpected winner of the best neighbor award – is the most complicated. And not because it's the hottest (actually, Venus is warmer, though it's farther from the Sun).
"It is the most difficult planet to reach because when you go to Mercury you approach the Sun and you are taking speed … which makes it more complicated to enter your orbit, "said the expert.
Only two space missions have achieved so far: Mariner 10 in 1974/75 and MESSENGER, released in 2004 – both from NASA – making Mercury the least-explored planet in our solar system.
But Rothery is part of a group of experts in search of a third exploratory voyage to little Mercury.
Last October, space agencies in Europe and Japan launched a the third mission of the history for this planet: the BepiColombo.
The ambitious mission that goes to the "pizza oven" of Mercury, the great unknown of the Solar System
It is estimated that the probe it's gonna take a while 7 years in being able to enter the orbit of Mercury, due to the problems of acceleration mentioned by the expert.
Maybe then we can finally learn more about our enigmatic and unsuspecting neighbor.
* You can listen to BBC Radio 4's "More or Less" program in English, on here