## Sunday, 16 November 2014

### It's a long way to 67P/Churyumov–Gerasimenko

As readers of this blog will know, I enjoy trying to find ways of getting our heads around large numbers and huge quantities. In my experience children in primary schools also find large numbers fascinating, and, with the help of a calculator and some approximate mental calculations, we can play with big numbers and do some interesting mathematics.

This last week saw the landing of 'Philae' on Comet 67P/Churyumov–Gerasimenko. The newspaper reports told us that this comet was 300 million miles away. That's a long way, I'm sure, but how can we understand a distance like this? I always try to connect these big numbers with our own experience.

So, let's imagine I start driving my car at an average speed of 45 mile per hour. How long is it going to take me to clock up 300 million miles, assuming I have a co-driver and we manage to drive night and day non-stop?

Well, let's see 45 mph is 45 × 24 miles per day, which is 1080 miles per day.

That's about 1080 × 365.25 miles per year, which looks like approximately 400,000 miles per year.

So to find how many years it will take me ... careful with all these zeros ... we need 300,000,000 divided by 400,000, which is 750 years!

So, put it like this: imagine I had started this epic drive in 1264, back in the Middle Ages, during the reign of Henry III, in the middle of the Crusades, when Marco Polo, that intrepid traveller, was 10 years old;  I would have continued on driving through all the subsequent Henrys, through the reigns of the Tudors and Stewarts, and the Civil War; I would have still been driving when Beethoven was born and when he died; and when Queen Victoria came to the throne and when she died; and still driving during the two World wars, mysteriously passing the day of my own birth, and right through to the present day, and I would be now just closing in on the 300 million miles target!!

Yes, it's a long way to Comet 67P/Churyumov–Gerasimenko!