Why is the unit light year invented?
Well, because we need to know the light year
Because in space things could go on for miles and miles, and it would be to big of a number. A light year is specifically how much light goes in a year, and light is fast. Making a long distance and you don't read a humungoes number even if it was estimated it would be 6.35 times 10 to the power of 300!
A light year is the distance that light (travelling at approximately 300,000 km/second in a vacuum) goes in one year. It's about 9.46 trillion kilometers. The light year is a convenient unit for distance in outer space because stars are extremely far apart in relation to any measurement on our planet. For example, the nearest star other than our sun is about 4.34 light years, or about 41,000,000,000,000 kilometers. It is important to remember that…
The astronomical unit is the average distance from the earth to the sun, and is 149 598 000 kilometres. A light year is the distance light will travel in a year, the speed of light is just under 300 000 kilometres per second, so light travels one astronomical unit in just over eight minutes. A light year is 9.46x1012 kilometres, or 63239.67 astronomical units.