Friday 31 January 2014

Planets of St Kilda

Welcome to my 300th blog post!

It was a hot summer day in the mid-30s last Sunday, so Narrelle and I decided to escape the sun by walking 5.9 billion kilometres across the solar system.

Wait - let me clarify. We actually walked 5.9 kilometres, from Melbourne's St Kilda past Middle Park and Port Melbourne to Beacon Cove. And we started at this Sun:

I'd gone years without noticing this sculpture. In 2008 a Solar System Trail was established along the Port Phillip Bay foreshore, including models of the Sun, all eight planets, and the demoted dwarf planet Pluto. Also one other interesting item I'll mention later.

What's remarkable about the work, a joint project between artists and scientists, is its attention to detail. Constructed to a 1:1 billion scale, the stars and planets are both in correct proportion to each other, and correctly spaced apart. Hence the 5.9 (billion) kilometres between the Sun and Pluto.

The foreshore walk is great fun anyway, as you pass beaches, rollerbladers and cyclists, always with the bay in view. Visiting each planet would be a bonus on a hot sunny day.

Though I was surprised at the variation in their spacing.

The inner planets were only a couple of hundred metres apart; in fact I could see most of them from my vantage point next to the Sun, opposite the corner of Marine Parade and Blessington Street, St Kilda.

Only 58 metres away was tiny Mercury:

Then 50 metres further on, comely Venus:

And then at the 150 metre mark, our dear old home Earth - complete with Moon (38.4cm from its parent world):

Finally on our tour on the inner planets, at the 228 metre mark - warlike Mars:

Well, that was easy. Now, as we approached the gas giants, the planets became further spread out.

We had to walk another 550 metres to reach mighty Jupiter, which we found next to the lawn near the St Kilda Sea Baths. As the largest planet, on a 1:1 billion scale it was about the size of a softball:

We'd covered 778 metres so far, an easy stroll. We found Saturn at almost twice the distance we'd already covered, next to Catani Gardens at 1.4 kilometres from the Sun. Sadly its marvellous rings were a little the worse for wear, probably due to vandalism:

We'd done six planets! We only had three to go! Hooray! But we'd only covered 1.4km of the 5.9km trail. Hmm. This was clearly an inconveniently designed solar system.

We then had a long stroll for another 1.5km along the Middle Park foreshore, finally locating lopsided-orbit Uranus near the corner of Beaconsfield Parade and Wright Street, at the 2.9km mark:

We were now halfway across the system, with only two planets left. Another 1.6km walking brought us to Neptune, at the 4.5km mark within sight of Port Melbourne's Station Pier and the docked cruise ship Diamond Princess:

It had been a great walk but we were very hot and tired by this point, and I was tempted to call a halt by invoking Pluto's demoted planetary status as an excuse.

However, on reflection we felt we'd come too far to give up. So we trudged on past Station Pier along the boardwalk in front of ritzy apartment buildings, a final 1.5km, to find... this:

A colossal 5.9 billion kilometres from the Sun (at least it felt like it), and that's all we got? Well, at least we'd made it all the way to everyone's favourite dwarf planet. Then we had to walk a kilometre or so back to Port Melbourne for the tram.

And the bonus astronomical object I alluded to earlier?

Back near the Sun, just a few metres away, was this model of the star Proxima Centauri:

The nearest star beyond our solar system, it's located a breathtaking 40 trillion kilometres away.

So why was it so close to the model of the Sun, if everything was in proportion? Because at the 1:1 billion scale, you'd have to place it 40,000 kilometres away - and that, coincidentally, is the circumference of the Earth.

Yep. If you started here and travelled in the entirely opposite direction around our entire planet to reach the Sun model the long way, you'd have covered the appropriate distance. And that was the closest star beyond our immediate stellar neighbourhood.

As Douglas Adams once wrote, "Space is big. Really big. You just won't believe how vastly hugely mindbogglingly big it is. I mean you may think it's a long way down the road to the chemist's, but that’s just peanuts to space."

He was right.

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