Image distances

The movement of the planets and their distance from the Sun

In order to understand the drawing on this page, we must first begin by explaining the dynamics of our Solar System:

Each body has a mass that exercises a strong attraction on any other body with a mass. The bigger the mass of the body the stronger the attraction, but as the distance between the objects increases its strength of attraction decreases. This is a fundamental Law of Gravity, and as the Sun has a mass that is greater than all the others, its force of attraction over them is greater. On the other hand, these bodies or rather planets, satellites, asteroids, comets and meteorites were formed from a cloud of whirling gas and dust that revolved around its own centre, and where the Sun was formed. The result of the combination between this rotary movement and the solar attraction, is that all these bodies revolve around the Sun. The closed paths of each of these bodies is almost circular and is called an orbit.

Owing to lack of space only a part of the orbit that each planet makes around the Sun has been shown in the figure; these tracks are represented by circular arcs drawn one after the other.

Starting at the bottom left there are four little circular arcs that are very close to one another: these correspond to, going from left to right, the orbits of Mercury, Venus, Earth and Mars.

After Mars there are four more circular arcs that are quite evidently further away: these correspond to the orbits of Jupiter, Saturn, Uranus and Neptune.

The drawing shows the reciprocal distances between the planets which helps us to better understand the idea that the Solar System is for the most part empty. Especially if we consider that, in this scale, even the bigger planets, like Jupiter or Saturn, would be less than a millimetre, smaller than a pinhead.

The Astronomical Unit is often used by astronomers to measure the distance within the Solar System, it corresponds to the distance from the Earth to the Sun, that is about 150 million kilometres, or rather about 300 billion footsteps. The distance of the planets from the Sun goes from 0,3 Astronomical Units for Mercury, this corresponds to about 100 billion footsteps, to 30 Astronomical Units for Neptune, in other words 9000 billion footsteps.

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