A while ago a friend told me that the entire world population would theoretically fit onto the Spanish island of Mallorca - lying there on camping mats!
That incredible claim i thought was very positive, but in order to believe it, i'd have to prove it. So here's the math:
We'll multiply the number of people on earth times the area of the bounding box (average height x average width) of a human lying down flatly on the ground to get the area required for all humans on earth to lie down.
The estimated wold population in 2013 was, according to Wolfram Alpha, 7.13 billion. That's 7 130 000 000 people living on our planet.
Calculating the required area pessimistically, i'll approximate the height and width of my own body with roughly 185 x 40 cm. This should be far more than the global average.
So 0.75m² per human times 7.13 billion individuals gives us a total of 5 347 500 000m² or 5 348km² required for all people to lie down at the same time.
According to Wikipedia the area of Mallorca is around 3 600km².
So if the average person required 3/4 of a square meter to lie down, the entire world population could lie down side by side on a plane smaller than twice as big as the surface area of the island of Mallorca.
To put this into context, one could view the the relevant place on a map and zoom out a little bit to see how small this island actually is. Or one could calculate or look up the surface area of the earth (510 000 000km²) to see that we sleep on less than 0.002% of it.
Impressive, isn't it?!