What is a UK Nautical Mile?
The UK nautical mile was based on one minute of latitude, ie 1/60th of a degree. The Earth is not a perfect sphere, so a minute of latitude varies slightly with latitude, which is why a fixed length had to be chosen.
The UK nautical mile, also called the Admiralty mile, was fixed at 6,080 feet, which is 1,853.184 meters. That is 1.184 meters longer than the international nautical mile of 1,852 meters (6,076.11549 feet), which the UK adopted in 1970.
What is a lightyear?
A lightyear is a unit of measurement used in astronomy to describe vast distances in space. It represents the distance that light travels in one year, which is approximately 5.88 trillion miles or 9.46 trillion kilometers. The term "lightyear" is derived from the fact that light, which travels at a speed of about 186,282 miles per second (299,792 kilometers per second), can cover an incredible distance in the span of a year.
Light has a finite speed, so a galaxy a billion lightyears away is seen as it was a billion years ago. That is how astronomers look back at the early universe – the farther the galaxy, the older the picture.