Would it be valid to say that a light year is a ratio between the distance that light travels and the elapsing of one year?
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That ratio is $c$, the speed of light. – Angina Seng Jan 31 '19 at 20:37
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The light-year is a unit of length! https://en.wikipedia.org/wiki/Light-year – cgiovanardi Feb 01 '19 at 02:41
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No—it's the product of a time and a speed. The speed of light is one lightyear per year. A lightyear is the distance travelled.
Suppose we define a walker-hour as the distance a typical person walks in one hour, and that a typical person walks at $3$ miles per hour. Then one walker-hour is three miles, and typical walking speed is one walker-hour per hour.
Lightyears are the same idea as walker-hours, but with a much bigger speed and distance.
You're right that the speed of light, a lightyear and a year are related—but the relationship is that you multiply the speed of light (about $300,000$ km/s) by the time ($1$ year) to get the distance ($1$ lightyear).
We can also talk about lighthours and lightseconds. A fun fact is that one nanolightsecond is almost exactly one foot (it's about $11.8$ inches).
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