h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Taking a lead from the thread called 'NE: Easy home experiments',
I thought it might be a good idea for a thread that lists 'Easy home analogies', which can demonstrate and/or describe complicated or just plain mind-boggling concepts in terms that young children can relate to

As our children are scattered around the world, perhaps it would be a good idea to mention figures, ratios, etc in (simple) adults terms - this might mean that the analogies can be adapted to suit 'local' terms

I have googled for "if the sun was the size of" and got over 100 hits... but many of the analogies are contradictory

So... for starters, a free to whoever can fill in the <<__gaps__>>

If the sun was the size of a
<<___________ (____m wide)>>,
the earth would be the size of
<<____________ (___mm wide)>>,
orbiting at a distance of
<<________ m>>
and the nearest star would be the size of a
<<_______(___mm wide)>>,
<<_______>> kms away

If the sun was the size of a football (0.11 m = 11 cm wide), the earth would be the size of a

small ant
hangnail
booger
hair folicle

(1 mm) wide

orbiting at a distance of 1.2 (~1) km

and the nearest star would be one of the three that make up the Alpha Centauri trinary system (http://homepage.sunrise.ch/homepage/schatzer/Alpha-Centauri.html)

one of which would be slightly larger than a football, another which is slightly smaller, and a third which is the size of a large marble (~ 2 cm).

*Even in the scaled down model*, the three would be 6.8 million km away - further away than the moon, closer than the sun.

So you have your football. 1 km away, you have your booger. 6.8 million km away, in space about a 20th of the way to the sun, you have your 2 footballs and your marble.

Fab.
I shall tell my kids. And my school kids.
XX

cool!

Another interesting analogy has less to do with just science but life in general these days ... that of understanding the difference in magnitude between, for example, a million, a billion, and a trillion. One I like to use is time. To reach the ripe old age of one million seconds, a person is (in more commonly used units) just about 11 and a half days old. To reach a billion seconds, the person would be somewhere in their 31st year. A trillion seconds, they'd have to have been born back in the time of the Neanderthals and Cro-Magnons, or a bit less than 31,700 years old. It's a common enough analogy, but one that seems to really put it into perspective.

Of course, I'm using the American version of "million, billion, and trillion" here - I can't really remember how those words are defined in the UK, but I remember it being more than what we use over here.

- JD

You're safe enough using your definition of billion, trillion etc in Britain as well.

Another "big number" analogy.

There are 6.5 billion people living on the Earth today, give or take. If you were to meet each one of these people in person and on their own for just 1 second, it would take you over 200 years to complete the entire task (assuming you don't get any sleep - this is a 7x24 task with no rest breaks). By which time you would be, er, dead a long long time.

You might get through the population of India if you were lucky though..

"Put three grains of sand inside a vast cathedral, and the cathedral will be more vastly packed with sand than space is with stars"
Sir James Jeans (1877 ~ 1946)
English Astronomer
p.28 Practical Skywatching
ISBN 1 876778 91 1