During a brief stint as a secondary school teacher (ages 12 to 19 years), I came up with a couple of tricks which might be of use...
Well, it puts governmental budgets in context for me.
Take hold of a ruler, marked in millimetres. Imagine a cube one millimetre on a side. Now find or imagine a metre rule (maybe two computer-widths long). For those who haven't caught up yet, a metre is one tenth longer than a yard.
Right, there are one thousand (1,000) millimetres in a metre.
So, imagine a square, each side of which is a metre long. Cover that square with millimetre cubes. There are a million of them. (1,000 x 1,000 = 1,000,000, count the zeros!)
Now imagine a cube, each edge of which is one metre long. Fill it (probably only in your imagination) with those little millimetre cubes. There are one (American) billion of them. (1,000 x 1,000 x 1,000 = 1,000,000,000.)
At the time of writing, the human population of the Earth is about 7,000,000,000 people.
That's 7 of those metre cubes (if filled with water they weight a tonne each, which is close to the UK and USA tons).
The populations of the EU, USA and CIS added together are about one of those cubes. The other six and a quarter are... African, Chinese, Indian, South American... Check out the figures yourselves!
And back to the UK. Central London, I think of as having about 5 million, about the population of Norway. That's a 5 millimetre thick layer of one of those cubes. The entire UK is a layer about 56 millimetres thick (say 2 inches), out of a 39-inch high cube, which is itself a seventh of the world.
The last ice age ended about 10,000 years ago. That's a 1 cm WIDE layer, only one millimetre thick. All known civilisation fits in there.
Homo Sapiens Sapiens appeared in Europe 40,000 years ago. Coo, thats a full 4 cm wide shaving.
Human-like species have been around 1-3 million years (pick your definition of human-like, and your favourite paleoanthropologist), that's a shaving 1-3 millimetres thick from one of those 4 blocks.
Oh, yes, and if you took one of those metre cubes and put all of the millimetre cubes which it contains in line to form a chain, and magnified all the millimetre cubes until they were full metre cubes, then 150 of those chains would be needed to reach the Sun.
Space is big.
© M.D.Cahill, 2002 CE. (Population data corrected Dec. 2002.)