_OBAFGKM_ t1_j226apu wrote
Reply to comment by TheLuminary in ELI5: If astronomers use "light-years" for interstellar distances, why do we use AU for interplanetary distances instead of "light-minutes"? by concorde77
It's not really like that, since tau and pi only differ by a factor of 2.
A useful equation is, for example d = 1/p, where distance is measured in parsecs and p is measured in arcseconds. If you used meters, it's not just a factor of 2, it's something like 3.086×10^(16) d = 1/p. With distances as big as parsecs, there's no intuition you can use to understand the size, so it really doesn't matter what unit you use. It just makes the most sense to use the natural unit instead of the arbitrary one
TheLuminary t1_j226tz5 wrote
Ah.. yes, I suppose having custom units for those specific equations where the constant is 1 would be handy.
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