To give an idea of the sizes involved, imagine there is a scale model of the solar system built in Melbourne.

We'll start by putting the sun at the MCG because, as the grand final proved a fortnight ago, Melbourne life revolves around football. Imagine it is a glowing orb in the centre of the ground, just a bit wider than the cricket pitch. 

The sun's surface temperature is more than 5000 degrees, so you would want to sit out in the stands to avoid getting sunburnt. Photo: Pat Scala/NASA

That means Mercury, the first planet in the solar system, is the size of a golf ball and orbits about one kilometre from the MCG. You will sometimes be able to find it rolling around the entrance of Parliament Station.

Now that Pluto has been demoted, Mercury is the smallest planet in the solar system. Photo: Google/NASA

Venus is a seething orange sphere at Crown Towers in Southbank, and about the same size as one of the light globes in the Crown logo.

Venus takes longer to rotate on its axis than it does to make a complete circuit of the sun, so its days last longer than its years. Photo: Supplied/NASA

To find our own planet, you have to travel to Melbourne University, where Earth is a soccer-ball-sized chunk of rock in a specimen case at the (fittingly enough) Earth Sciences Building.  

The Earth is not an exact sphere - it bulges slightly at the equator. Photo: Daniel Pockett/NASA

Parkville is home to Mars, a dusty grapefruit at Melbourne Zoo and the perfect size for one of the elephants to pick up and eat.

Elephants have been known to eat grapefruits by breaking them open on the ground, so Mars is doomed. Photo: Justin McManus/NASA

The first four planets are quite close together and would all be paying their local council rates to the City of Melbourne. But after braving the asteroid belt - which would just mean brushing the odd piece of hair from your shoulder between Brunswick and Essendon - you would be in for more of a road trip if you wanted to visit the gas giants.

Jupiter is easily the largest planet in the solar system but even it is easy to miss if you don't stop for some snacks at the Coles in Sunshine West. It's a dense, three-metre-wide cloud hovering above the car park.

Jupiter is so large that all the other planets in the solar system could fit inside it. Earlier this year the Hubble Telescope observed auroras at the planet's north pole. Photo: Goolge/NASA

Meanwhile, Saturn is an almost 2.4-metre-wide flower garden in the picturesque grounds of Chelsea Bicentennial Park in Melbourne's south-east.

If you then go down the coast to Sorrento and catch the ferry to Queenscliff, you may spot a green, beach-ball-sized miasma in the waters off Point Lonsdale. That's Uranus, and is enough to anyone reconsider going for a dip. 

Stargazers have known about first six planets since ancient times, but Uranus was not discovered until 1781. Photo: Supplied/NASA

Neptune is about the same size, but is luxuriating out in one of Daylesford's mineral water springs. But be warned, even though it has a cleaner image, Neptune still has a similar composition to Uranus, so it isn't exactly purifying the water out there.

Neptune is so far out that t takes almost 165 years to orbit the sun. Photo: Supplied/NASA

As for the demoted planet Pluto, you have to drive almost 120 kilometres from the MCG to Gippsland to see it and, when you get there, all you will find is partly-sucked Kool Mint lost behind a couch in Moe.

Of course, this model is a simplification. Celestial bodies are not fixed in space, and they don't orbit in perfect circles - in fact, most of them have elliptical orbits. Pluto's is the most erratic - that Kool Mint would sometimes be sneaking closer to the sun than Neptune and at its further point would be scaling Mount Buller - which is partly why the reason it had its planetary status unceremoniously revoked a decade ago.