Wednesday, 10 October 2012

Categories, Labels and Astronomy

Space moderators, you need to sort out your admin and classifications.

This morning a ‘science’ page on Facebook posted a thing saying there are 13 planets in our solar system, including 4 ‘dwarf planets’. But that’s misleading and shows a failure to grasp the basics of astronomy. This is roughly how the categories go -
Planets (8)
They’re big and round. They fall into 2 subgroups:
Rocky (4) - Mercury, Venus, Earth, Mars.
Gas Giants (4) - Jupiter, Saturn, Neptune, Uranus.

Moons (lots)
They go round planets and minor planets.

Minor Planets (innumerable)
They’re NOT planets so it’s a very stupid name, and there are sub-groups which make it even more confusing:
Dwarf Planets, NOT planets, also known as Plutoids because a lot of people for no good reason are upset that Pluto isn’t classified as a planet anymore (do they own property there or something? Wtf?), (5) - Eris, Ceres, Pluto, Haumea, Makemake
Asteroids (millions)
Trojans (loads and loads and loads), it’s complex and all about their orbit.
Centaurs (around 44,000), unstable and behave like both comets and asteroids.
Kuiper Belt Objects (over 100,000 with diameter >100km, and far, far more smaller ones)
More info on 'minor planets' here.

Saying “There are 13 planets” is wrong and misinformed. Ceres is a tiny little thing, much smaller than our moon. Like a Malteser next to a melon.

Just to confuse things further, outside the solar system there are Brown Dwarf stars that are like huge gas giant planets not quite massive enough to ignite and become a star. They’re a link between gas planets and stars and the only real difference is how much stuff is inside them.

Stars themselves are categorised as one family because they’re all on fire, but the differences between them are huge. 

Have a look at this image showing the difference in size between our local star and CY Canis Majoris.

Here’s a chart of star types by colour...

...and the same star types (minus the tiniest two types) by size.

The categories will never be right and never be fixed because the universe is not here for our convenience. It is not ours to define, only to stick temporary labels on. In time those labels will fall off although nothing has changed except our perception. Why mention this at all? Because when we label something we stop thinking about it. We give it a name and a pigeonhole and we leave it there. Labels change the physical nature of our brain and shape how we think. The more fixed our categories the more stagnant our thinking.

“If our small minds, for some convenience, divide this universe into parts -- physics, biology, geology, astronomy, psychology, and so on -- remember that nature does not know it!”
Richard Feynman

“[The] obsession with order is contrary to the nature of ideas, and the world. Without constant reminders that categories are malleable inventions of convenience and not manifest in the world itself, the possibility of free thinking and progress is denied.”
Scott Berkun

“However much we divide, count, sort or classify [things] into particular things and events, this is no more than a way of thinking about the world: it is never actually divided.”
Alan Watts


  1. It's an honor to be quoted anywhere near those two fellows. Thanks.


    1. You're most welcome, Mr Berkun. Thanks for commenting. Between the three of you, those words summed up perfectly the matter I was meandering around.

      And may I say your blog, which I discovered by chance while looking for quotes to use above, is very good. I very much enjoyed what I read and saw plenty more I'm looking forward to reading in the future (link below for those interested).