Yes, but it’s part of the definition of a light-year, i.e. the distance light travels in a vacuum within one Julian calendar year. Using a year as reference to the distance light travels within a given timeframe is fairly arbitrary. We could just as well use light-months, or light-decades, or some entirely different timeframe as reference.
On addition, we could measure year by a different planet. To the universe, choosing the time it takes the Earth to move around the sun one time is pretty arbitrary. Why not Mars? Or why not a totally different star system?
Year is an incredibly arbitrary length
All lengths are arbitrary.
Years measure time, not distance
Yes, but it’s part of the definition of a light-year, i.e. the distance light travels in a vacuum within one Julian calendar year. Using a year as reference to the distance light travels within a given timeframe is fairly arbitrary. We could just as well use light-months, or light-decades, or some entirely different timeframe as reference.
On addition, we could measure year by a different planet. To the universe, choosing the time it takes the Earth to move around the sun one time is pretty arbitrary. Why not Mars? Or why not a totally different star system?
Speed = Distance over time.
There are no measurements of speed that won’t face that problem.