Earth's Family: The Planets

Find out their names, how big they are and their distances from the Sun by looking at the stone panels set in the ground. 

Their relative sizes are also displayed. See how mighty Jupiter dwarfs tiny Earth!


A year is the time that it takes for a planet to go around the Sun. Therefore, the Earth completes one orbit once every Earth year.

However, this period of time varies according to how far from the Sun the planet is: the further out, the longer the year. As a result, an Earth year is very different in length from a year on Saturn or any other planet.

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For example:

1 "Mercury year" = 88 Earth days

1 "Pluto year" = 248 Earth years

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(If anyone ever lives on Mercury and uses a "Mercurian calendar", they will have birthday parties over four times more often than if they were on Earth!)

Squeezing Space - scaling the solar system

To fit our model Solar System into an area easy to walk around, we have had to shrink it down so that two metres - the height of a tall adult - is equal to about 20 million miles!!

But on this scale, most of the planets are too small to see, so their size has been increased by 200 times.

If you look closely, next to each planet is a small perspex cube set into the ground. In the centre of each of these is a model of the planet at the correct scale for the whole solar system. Be warned - not all are visible to the unaided eye!

When discussing distances within the solar system, astronomers cannot use metres, kilometres or even thousands of kilometres are simply far too small.

Instead, the Astronomical Unit (A.U) is used, where one of these is roughly equal to the distance from the Earth to the Sun. Hence,

1 A.U = 150 million kilometres = 93 million miles

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The Astropark's red gravel represents the asteroid belt - thousands of smaller bodies which range in size from pebbles up to small planets hundreds of miles across.

Sometimes the orbits of asteroids can take them outside this area - once in a while near to Earth. On very rare occasions they even hit the Earth, causing massive destruction.

Do not worry too much though: Earth is not a very big target. There is much much more empty space than planets for wandering asteroids.

Last Revised: 2010 January 29th