Here's a remarkable coincidence. The number of inches in a mile is 63360 : the number of astronomical units in a light year is 63367.31...
I'm using a tropical year of 365 days 5 hours 48 minutes & 45 seconds. Other measurements of the year will obviously give a slightly different result.
I also admit this would be way more impressive if the two numbers had been identical, but still, only a difference of seven and a bit between the two is impressive to me.
But what's the use of this tittle of trivia?
It's a wonderful way of visualising the scale of the universe for anybody who knows what an inch and a mile are.
Imagine a circle two inches in diameter. That's the orbit of the Earth round the sun. The Alpha Centauri system, our nearest neighbour, is over four miles away. Sirius is six miles away. The centre of the Galaxy is about a tenth of the way towards the moon.
At this scale, even a snail would be travelling at several times the speed of light.
The one thing that bugs me about Astronomical units is the fact that they're only 498 light seconds long. Make them 500 light seconds long! Countless astronauts of the future will bless us for making their calculations simpler.
I know the AU is the distance from the Sun to the Earth, but do we have to be so Geocentric? After all, G, the acceleration due to gravity, is not 10 meters per second squared, but slightly less. Now is the time to make the change before we get out into the Galaxy and start measuring it.