How does light years work? How would explain light years in layman’s terms?
In: Physics
Simply put, lightyears are how far light travels in a year through a vacuum (empty space). It is not a unit of time, but a distance.
Light moves very very fast (it is the fastest thing in the universe and moves at a speed we call the “speed of light”) but space is very very big. A “light year” is how far a light beam can travel (at the speed of light) in one earth year.
A lightyear is a unit of measurement. It is the distance that light will travel in a year of our time. Light has a fixed speed, 299 792 458 meters per second. In a year, at that speed, you will have traveled a lightyear from where you started.
A light year is a measure of distance. It is the distance light travels in a vacuum in one year. Light travels at 186282 miles per second(iirc) so take that number and multiply it by how many seconds are in a year and you have the distance in miles light would have traveld in one year.
Edit: too many per seconds….not enough hoes.
So if I were to shine a beam of light from 20 light years away then it would take that beam 20 years to reach the surface of earth, right?
You could compare it to describing a city as being “two hours away”. It looks like a unit of time, but it’s really a unit of distance based on a known speed (in this case typical driving speeds).
The key difference between a light year and a “driving hour” is that the speed of light is precisely known and constant, so a light year is a well-defined distance while a “driving hour” can only ever be an approximate unit depending on traffic and the individual driver.
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