As of March 2016, the number of humans alive in the world
is at $7.4 billion people.
But what if every single last one of us, everybody watching
this video, including you, all lived together
in the same city?
How big or small would this city look like?
And how close together would we all have to live?
Let's pause and think for a moment about where we all
currently live.
60% of us live in Asia, while 16% live in Africa,
10% in Europe, 8% in North America, 5.5% in South America,
just 0.5% in Australia and Oceania, and too little people
to even register on the scale in Antarctica.
So first off, we would have to agree on which continent,
or island, we would migrate everybody in the world to.
50.5% of everybody in the world currently lives in a city,
so we would have to convince the other 49.5% of people
to come and join us.
So now assuming that we have gathered everybody together
in the same place to create our city,
let's look at some real life examples
to see what living so close together
might actually look like.
Singapore is the most densely populated country in the world
right now.
Five million 399,000 people live in the small country
of just 710 square kilometers.
That means that, for every square kilometer in size
within the country, there are 7,605 people living out
their lives on average.
But Singapore is a country the size of a city,
and there are much more densely populated cities than that
already in the world.
For reference, downtown Manhattan in New York City
has a population density of 26,939 people
every square kilometer.
That's a lot of people very close together,
but we're just scratching the surface.
The densest city in the world right
now is Manila, in the Philippines,
where you will find 41,515 people every square kilometer.
But Manila's total population is relatively low,
at just 1,780,000 people.
The density of people is just so high
because they all live together in such a small space.
The biggest concentration of people
in one place anywhere in the world
can be found here in Japan, the Tokyo metro area, home
to 36,923,000 people.
To put into perspective just how enormous Tokyo is,
I'm going to show you two examples
to illustrate the point.
First, this is an image of the United Kingdom
with the area of the greater London
metro highlighted in red.
And if you think that looks big, this
is the greater Tokyo metro area highlighted in blue.
It's truly gargantuan.
But onto the second example.
This is an image taken of downtown Tokyo.
But if we zoomed out further to here,
then the exact location of downtown
grows much harder to find.
Let's trade out this photo for a new one,
which shows the true size of Tokyo as seen from the sky.
In this one photo that you're looking at,
lives nearly the same population as all of Australia,
New Zealand, and Oceania combined, or about 0.5%
of everybody in the world, all in one city.
But we still have the other 95.5% of the human population
to think about.
And we can still fit people into a much smaller space.
Right now, in 2016, the highest concentration
of people living in a smaller place than a city
is probably within the city of Mumbai, India.
Located within the city is a slum called
Dharavi, which is an area just 2.17 square kilometers in size.
If we think about that size and compare it
to Central Park in New York City,
the Dharavi slum would only take up 64% of the same size,
or not even 2/3 of the area.
And living in that cramped tiny space
or anywhere between 700,000 to 1 million people.
Averaging out those numbers, we get 391,705 people
every square kilometer.
Now this number here is the highest number
of people in the world today that
live in a square kilometer.
As recently as the 1980s, however, there
was a place that was somehow even more frighteningly
claustrophobic.
The most densely populated place known in history
was the Kowloon Walled City, which
was located here in Hong Kong.
To get some kind of idea of what we're
going to be talking about, this image
is an aerial view of the city from 1987.
You can kind of get some scale of it
by looking at the basketball courts over here on the right,
or the trucks over here on the left.
But the overall total area of these buildings
is just 0.26 square kilometers.
Another way to possibly imagine how tiny that really is
is this way.
Here are three American football fields side by side.
The Kowloon Walled City would be just a little
bigger than them put together.
And 33,000 people were living in that tiny space.
Meaning that, if we stretched that out
to a full square kilometer, the population density
would be 1.2 million people.
Living that close together would look something like this image,
and this number is the absolute limit
that we've ever seen in the real world of how many people
can live together in such a small area.
So now let's visualize how big our hypothetical global city
would have to be according to the different population
densities that we have been discussing.
First, let's imagine something a little comfortable.
Let's take the city of New Orleans in Louisiana,
whose population density is about 784
people per square kilometer.
On that scale our global city would
be about the same size as roughly the continental United
States.
If we moved onto the density of say, Austin, Texas,
we would be looking at a city that
is about the size of Australia, with room left to spare.
But we want to get even smaller than that.
So we're going to try fitting everybody into the same density
as Chicago next.
On that scale, our city would be about the same size as Iran.
But let's get even smaller.
At the density of Singapore, we could fit the entire human race
into just the states of Texas, Oklahoma, and Louisiana--
already considerably smaller than at the New Orleans
density.
But we're going to keep on getting even smaller.
At the density of Manhattan, we would
be looking at a city about the size of Ecuador, here
in South America.
And if we had a city with the same density we see in Manila,
then everybody in the world would
fit inside the US state of Missouri.
But to get even more frightening and claustrophobic
our global city with the same density seen within the Dharavi
slum in Mumbai would be about the same size as New Jersey.
And finally, at about the absolute real world limit,
if we built our global city with the same population density
as Kowloon Walled City, we would fit every single person
in the world into an area about the same size as Palestine,
which itself is only about half the size of the Tokyo metro
area.
Let's put all of these different sizes
in a row to get possibly the best visualization.
First, we have a city with the same density of New Orleans,
followed by Austin, Chicago, Singapore, Manhattan,
Manila, the Dharavi slum, and finally
the Kowloon Walled City.
Whichever way you look at it, living together
in the same city would be both bizarre
and leave an enormous amount of empty space left in the world.
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As always, everybody, thank you so much for watching,
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