Is it possible to place all the planets of the solar system between the Earth and the Moon?


The phrase that all the planets of the solar system can be freely placed between the Earth and the Moon wanders from one cognitive or pseudo-scientific VKontakte public to another and sometimes raises questions from my readers, such as the following:

Well, let’s sort it out together. First, let’s do what my reader tried to do. Google tells us that the distance from the Earth to the Moon is 384,400 kilometers.

The radii of the planets can be taken, for example, in Wikipedia. In order not to bore you with calculations, I made a visual picture — the relative sizes of the planets are observed.

Suddenly it turns out that Neptune does not fit between the Earth and the Moon after all the other planets have been placed. Can VKontakte publics from the «Encyclopedia of Facts» series lie?

The point is, the publics are right. But with a little caveat. It would be correct to say that all the planets of the solar system can be placed between the Earth and the Moon ONLY when the Moon is at the farthest distance from the Earth.

In many textbooks and popular science books, and on the Internet, the orbits of planets and satellites are drawn in circular for clarity, although in fact the orbits of all celestial bodies are ellipses (the orbit of Venus is closest to an ideal circle).

So the difference between the apogee and perigee of the Moon’s orbit (i.e. the points of greatest distance and approach to the Earth) is more than 40,000 kilometers, and this is a minute larger than the diameters of such planets as Earth, Venus, Mars and Mercury combined!

What did Google give us? He gave us the value of the semi-major axis of the ellipse of the Moon’s orbit, the value of which is often used for simplicity as the average distance from the Earth to the Moon. In this case, of course, in any important astronomical and astrometric calculations, one should use the exact values of the distance at a certain point in time.

PS. For the sake of simplicity, this article does not take into account the fact that the planets do not have the shape of perfect balls, and in particular for giant planets, the difference between the equatorial and polar radii reaches several percent, but in general this does not significantly affect the result.