Imagine Campbelltown, NSW as the centre of the Solar System.
Mon, 27. June 2011
The Scale Of The Solar System
This is a journey through our Solar System, from the Sun to Pluto, is a long trip - but I am going to shorten it a little by scaling it down. The Sun itself is 1,392,530 km in equatorial diameter and it's mean distance from Earth is 149,492,000 km. Now, imagine a model of the Solar System reduced in size by a scale of one in a hundred million. The Sun could then be represented by an imaginary sphere (admittedly a rather hot one) with a diameter of just fourteen metres, about the height of a four storey building.
Where would the planets be located on this scale? If we place our imaginary (four storey high) Sun on the platform at Campbelltown Station (right near the footbridge) we can try to picture a journey to Pluto, using a suburban train instead of a spacecraft, making the (admittedly rare) assumption that every planet including Pluto is aligned in one direction. Mercury would be a 50mm diameter plum, located just over five hundred metres north of the station. Venus would be found in the vicinity of the bridge at Campbelltown Road and would be the size of a small grapefruit.
Moving on, Earth would be a slightly larger grapefruit, positioned well on the way to Leumeah and you would spot Mars as a kiwi fruit sized sphere as you sailed past the Campbelltown Sports Ground. The spaceship on rails would then speed through Minto (remember, you are imagining this) and Jupiter would be seen as a large beach ball (1.4 metres diameter) as the train approached the suburb of Ingleburn.
Saturn would be a slightly smaller beach ball (1.2 metres dia) but you wouldn't see it until the train reaches Glenfield Tip. So we reached Saturn whilst still remaining just inside the boundaries of the City of Campbelltown - but the rest of the journey is considerably further. Uranus and Neptune are both over-sized pumpkins (500mm), with Uranus at Riverwood. Neptune is not seen until you pass Redfern (our spaceship of the imagination is a City via Sydenham train).
That's the planets, now what about poor old Pluto? You won't see that particular ex-planet without changing at Central and catching a North Shore Line train, like I used to do daily on my way to work. Pluto is not so easy to spot. It's a mere 25mm diameter grape and you would only see it if you stayed on the train until it reaches Chatswood.
It sounds like a pretty quick trip across the City Rail network but don't forget your speed will be scaled down too. Imagining yourself travelling at the scaled down speed of light, our City Rail journey from the Sun (at Campbelltown Station) to Pluto (at Chatswood)) would take five and a half hours, covering about 3 metres per second. Sounds like the City Rail we all know and love.
Beyond Pluto, where's the Oort Cloud? On our scale of 1: 100,000,000, it is not on the City Rail Network. It's not in Brisbane or even Tokyo. In fact it's not even on this planet, it's one fifth of the way to the Moon.
So that's the Solar System in context. If the Sun is a giant ball at Campbelltown Station, then the Earth is a grapefruit at Leumeah (I just knew it - I have a grapefruit tree in my Leumeah backyard) and Pluto is a grape at Chatswood. To put the position of the Solar System itself in context, the nearest Star, Proxima Centauri would be beyond the Moon on this scale. The Apollo astronauts actually went to the Moon in about three days. At the (scaled down) speed of light, you would be crawling along at a speed of just eleven kilometres per hour for 4.2 years to get there.
(Article first published in Prime Focus, the monthly journal of Macarthur Astronomical Society)