A run across the Solar System

An interesting (if hot, starting at 31 degrees – so much for the cool of the evening!) run along the River Cam from Midsummer Common to Waterbeach, forming an exploration of the Solar System at a scale of 591 million to 1.

It shows the huge size of the Sun, but in particular the closeness of the inner rocky planets and, as I ran increasingly long distances, how far apart the outer gas giants are – and how tiny and insignificant the dwarf planets such as Pluto are.

The Sun, with Mercury, Venus, Earth/Moon, and Mars spread out across Midsummer Common.
Mercury, on this scale 100 metres from the Sun.
Another 80 metres on from Mercury is Venus.
Another 80 metres from Venus (180 metres from the Sun) we find the Earth and Moon.
The Earth (left) and Moon. The Moon is 400 times smaller than the Sun, and 400 times further away.
Finally of the inner rocky planets, Mars is 90 metres from Earth and 350 metres from the Sun.

From here it is 1000 metres (a kilometre) to Jupiter – no signs of the asteroid belt en route, but then they are so tiny and well-spaced I wouldn’t have expected to see anything.
We’re now 1.35km from the Sun, and Jupiter is huge compared to the inner rocky planets.
Another 1.3km on, and courtesy of the new pedestrian and cycle bridge, I cross to the other bank to find Saturn.
They’re getting further apart!
Not something you often see on a signpost.
After 2.5km from Saturn, I reach Uranus at Bates Bite Lock.
Still substantial compared to the rocky planets, but much smaller than Jupiter and Saturn.
2.6km on from Uranus to Neptune…
The evening light is fading but Neptune is well illuminated.
Finally, about 8.4km from the Sun, I have just left the Cam and entered Cow Hollow Wood on the edge of Waterbeach, and reached Pluto, the representative of the dwarf planets.
But where is it?
The pimple of Pluto with my fingernail for scale.
The run has hinted at how big and how empty the Solar System is – but as the panel at the end explains, that’s only a small part (literally) of the story.

Thanks to Lucy for dropping me at the start and collecting me at the end, giving Brindley a gentle walk while she waited for me.

Leave a Reply