But what does that really mean? It's such an abstract number that it's hard to imagine it. Can you genuinely understand it beyond just being a ridiculously large number?
Just like humans find it really hard to comprehend the vastness of the universe. We know it's huge, but what does that mean? It's so many times greater than anything we know or have experienced.
German astronomer and mathematician Friedrich Bessel managed to successfully measure the distance from Earth to a star other than our sun in the 19th century. But he realized that his measurements meant nothing to people as they were. They were too abstract.
So he came up with the idea of a "light-year" to help people get a better understanding of just how far it really is. And rather than using a measurement of distance, he chose to use one of time.