## Our little companion, the moon

Credit: bartoCredit: barto

## Have you ever wondered how far away the moons is?

### Can you grasp a big number?

Sometimes, at night I look outside my window wondering how far away the moon is. I grab a lexicon to find out that the moon is between 363 and 405 thousand kilometres away. Wow, what are huge numbers! But what does it actually mean, 400 000 kilometres. Could I walk it? How long would it take? Lets try to grasp this huge number by making some down to earth comparisons.

## Lets Walk!

The average walking speed of a grown up is around 5 kilometres per hour. Walking the distance to the moon would take you 80 000 hours or 3333 days or around 9 years. And that all without resting or sleeping. Quite a while, hmm?

Lets assume you could keep up to walk 8 hours per day. Then, it would take you a bit more than 27 years to reach the moon. I think it is doable and if there was a road, I bet people would do it.

## A bit faster

Now, let us take a little ride to the moon. I promise we will have a nice view. The best thing is, it will only take us a bit more than three and a half months with an average speed of 150 kilometres per hour. 111 days, not that much anymore. I start to like this idea more and more. We should build a road! With an average fuel consumption of two gallons (7.5 litres) per 100 kilometres and a price of 3 dollar per gallon it costs 24000 dollar to drive up to the moon. If we are four that is just 6000 dollar per person.

## Still got some Lego blocks at home?

A standard Lego piece has a height of 9.6 mm. If we build a simple Lego tower that would reach up to the moon, how many blocks would we need? At least 41.7 billion Lego pieces. That is funny, because the Lego Group has estimated that it has produced some 400 billion Lego blocks in the last five decades. So, we really have enough blocks to do it. Lets gather!

In the beginning I said that the moon is between 363 and 405 thousand kilometres away from earth.

That is because the orbit of the moon is not a circle but an ellipse. The shortest distance between the centre, the earth and the ellipse, the moon, is called periapsis. The farthest distance is called apoapsis.

## Final thoughts

I think the moon isn't that far away. We could walk up to it in a lifetime and if we were four we could drive for just 6000 dollar. We even have enough Lego blocks to build a tower that reaches up to our little companion. Have a look at the moon tonight and sleep well!