How many continents are there?

Come on kids, between us we can crack this. Image: Getty.

Once upon a time, “How many continents are there” was one of those questions with straightforward answers, like “How many colours are in a rainbow” or “what is the weather like in summer”. There are seven. Of course there are seven: all those picture books I had as a kid said there were seven.

Except, it turns out that, as with so many of the things we tell our children, this number owed as much to social convention as it does to objective reality. And social conventions can differ: depending on where you are in the world, there can be anywhere between four and seven continents, and you sometimes don’t have to travel very far to get a different answer.

So, to coin a phrase: what on Earth is going on?

Rules and regulations

First define your continent. The Wikipedia page on the matter contains this helpful explanation:

By convention, “continents are understood to be large, continuous, discrete masses of land, ideally separated by expanses of water”.

Which sounds simple enough. Except the very next sentence is this:

Many of the seven most commonly recognized continents identified by convention are not discrete landmasses separated completely by water.

Which feels like an unexpected piece of dry humour from an open-sourced encyclopaedia.

But it has a point: it’s the work of all of four seconds to think of vast numbers of ways in which the seven things you almost certainly think of as continents don’t fit this rule. Off the top of my head:

  • Islands like Great Britain are considered part of continents despite not being part of continuous masses of land;

  • North and South America are not discrete masses of land, they’re connected by an isthmus;

  • Neither are Africa and Asia;

  • Europe and Asia aren’t even vaguely separated, they’re quite obviously the same bloody thing;

  • If Europe gets to be a continent because it’s separated from Asia by some mountains and some inland seas, then why is India only a sub-continent?

  • If Australia is a continent why is Greenland only an island? Okay, it’s smaller, but where’s the line? What are the rules here?

And so on and so on.

Spinning plates

There is another way of dividing the Earth up into roughly continent sized bits, which has a rather more scientific basis to it: plate tectonics, the geological theory which explains mountain ranges, volcanoes, and so on by showing how bits of the Earth’s surface have been sliding about and banging into each other for the last few billion years.

In this theory, it’s quite obvious why the Americas are two continents, why Australia is one but Greenland isn’t, and why Africa is a different thing to Asia despite being attached to it. It also highlights a very good reason for considering Britain to be part of Europe: they’re part of the same continental shelf, even if part of that shelf is submerged under water. Despite Brexit, Britain will always be in Europe.

The plates. Click to expand. Image: USGS/Wikimedia Commons.

In many other ways, though, the map of the tectonic plates doesn’t look anything like the map of the continents. For one thing there are a bunch of oceanic ones, which on maps of the world are mostly just water with a few islands in them.

For another, the Middle East and India are their own plates, so aren’t part of Asia; neither is the Russian Far East, which is actually part of the North American plate. Europe, meanwhile, very clearly is part of Asia, except for Iceland, which is half Asian, half North American.

There are good reasons why plate tectonics isn’t going to get us very far in explaining why we mostly think we have seven continents. One is that it’s a surprisingly recent theory: it wasn’t widely recognised by the scientific community until the 1960s, so there are plenty of people around now whose school text books will have laughed at the idea.

Another is that the plate boundaries are often invisible or, at least at the human scale, nonsensical: any system which splits Iceland into two separate continents is not going to be a useful categorisation.


Geography is written by the victors

The real reason we count Europe as a continent and include Britain in it, treat India as a part of Asia, and so forth is (this is where we came in) social convention: we do it because we do.

More than that, we do it because the rules on this stuff were largely formulated by the Europeans who spent much of the last five hundred years or so conquering the world. That’s why Europe is a seen as a single, diverse continent but the Indian subcontinent, with its own patchwork of languages, cultures and religions, isn’t: because the former was the imperial power that conquered the latter.

A related point is that, if you ignore plate tectonics, the entire world doesn’t divide neatly up into continents at all. The reason a huge bunch of Pacific islands get bundled together with Australia as a slightly miscellaneous category called “Oceania” is as much because people wanted to make everything fit in somewhere, as it is because of any real connection between the two.

So those lengthy explanations aside, how many continents actually are there?

Counting continents

There seem to be six different systems, helpfully portrayed in this gif:

A gif of the various models. Click to expand. Image: AlexCovarrubia/Wikimedia Commons.

The seven continent system is the one you’re probably familiar with. That’s the one that’s standard in the English-speaking world, China, south Asia, and parts of western Europe. The British Empire can probably be blamed, at least in part, for its dominance.

There’s also an ultra-stripped down four continent model which divides the world into four major landmasses: Eurasia-Africa, America, Antarctica, Australia. This, best I can tell, isn’t taught anywhere; but it is the logical end point of the definition that involves big bits of land divided by water, so it’s worth including it anyway.

In between there are four other models:

  • A six-continent system in which Europe and Asia are one continent. This, the internet tells me, is the standard in Russia and Eastern Europe (which makes sense, given that the slavic world straddles the Urals), and also Japan (although, citation needed).

  • A different six-continent system treats Europe and Asia as separate, but combines North and South America. That one seems to be favoured in France, much of southern Europe and various places colonised by those countries.

  • There’s also a five continent system which combines the Americas but ignores Antarctica because, to the first approximation, nobody lives there. This is the one favoured by the UN and the International Olympic Committee (count the rings).

  • Lastly, there’s a variant five-continent system consisting of Eurasia, America, Africa, Australia and Antarctica. I can find no reference whatsoever to anyone using this one, but it’s in the gif and also this National Geographic page, so I’m including it for the sake of completism.

So, there you go. The best we can say is that the world has “some continents”. Assuming you accept the notion that continents exist at all.

I’m still really angry at those picture books which promised me snow in winter and heat in summer, incidentally.

Jonn Elledge is the editor of CityMetric. He is on Twitter as @jonnelledge and also has a Facebook page now for some reason.

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London Overground is experimenting with telling passengers which bits of the next train is busiest

There must be a better way than this: Tokyo during a 1972 rail strike. Image: Getty.

One of the most fun things to do, for those who enjoy claustrophobia and other people’s body odour, is to attempt to use a mass transit system at rush hour.

Travelling on the Central line at 6pm, for example, gives you all sorts of exciting opportunities to share a single square inch of floor space with a fellow passenger, all the while becoming intimately familiar with any personal hygiene problems they may happen to have. On some, particularly lovely days you might find you don’t even get to do this for ages, but first have to spend some exciting time enjoying it as a spectator sport, before actually being able to pack yourself into one unoccupied cranny of a train.

But fear not! Transport for London has come up with a plan: telling passengers which bits of the train have the most space on them.

Here’s the science part. Many trains include automatic train weighing systems, which do exactly what the name suggests: monitoring the downward force on any individual wheel axis in real time. The data thus gathered is used mostly to optimise the braking.

But it also serves as a good proxy for how crowded a particular carriage is. All TfL are doing here is translating that into real time information visible to passengers. It’s using the standard, traffic light colour system: green means go, yellow means “hmm, maybe not”, red means “oh dear god, no, no, no”. 

All this will, hopefully, encourage some to move down the platform to where the train is less crowded, spreading the load and reducing the number of passengers who find themselves becoming overly familiar with a total stranger’s armpit.

The system is not unique, even in London: trains on the Thameslink route, a heavy-rail line which runs north/south across town (past CityMetric towers!) has a similar system visible to passengers on board. And so far it’s only a trial, at a single station, Shoreditch High Street.

But you can, if you’re so minded, watch the information update every few seconds or so here.

Can’t see why you would, but I can’t see why I would either, and that hasn’t stopped me spending much of the day watching it, so, knock yourselves out.

Jonn Elledge is the editor of CityMetric. He is on Twitter as @jonnelledge and also has a Facebook page now for some reason. 

Want more of this stuff? Follow CityMetric on Twitter or Facebook.