radio astronomy especially. our field uses CGS instead of SI units, for one.
CGS stands for centimeters, grams, and seconds, which are the base units in astronomy. For comparison, SI uses meters, kilograms, and seconds.
Let's look at my least favorite unit, for energy. In SI, the rest of the physical sciences, energy is given in Joules. You've almost certainly heard of this unit before, though maybe not the definition - 1 joule is the amount of energy you'd need to push 1 kilogram a distance of 1 meter with a 1 newton force. Easy stuff, nice units.
(technically that definition is for work but work and energy are basically the same thing it's fine)
Now, you'd think "oh, astronomy deals with huge objects and vast distances, surely their units would be bigger to match, right?"
Astronomy uses ergs for energy. 1 erg is 100 nanojoules. you'd need 10 million ergs to get a joule. It's absurd.
We don't even have a proper unit for power! SI has watts, right? You've definitely heard of a watt before. It's 1 joule per second. Astronomy doesn't have an equivalent! We measure power output of stars in erg/s and I hate it.
Why does the field dealing in distances of parsecs use centimeters as our base unit of distance?
Astronomy is one of the oldest sciences, and so we carry a lot of traditions and conventions that other branches don't.
The brightness of stars, for example. In ancient Greece, Hipparchus (you may have heard of him) took a survey of the night sky. He looked at a whooole bunch of stars and sorted them based on their apparent brightness. Ptolemy (you may have heard of him) organized this list on a six-point scale and called it Magnitude.
It's backwards.
The brightest stars were class 1, and the dimmest were class 6.
We still use this. Magnitude is a fairly standard way of quantifying star brightness, and it's backwards.
I love this field. Genuinely. Astronomy is a little rough sometimes, but it just... it really makes you feel that whole "standing on the shoulders of giants" aspect of science.
So, yeah. We've got some weird conventions and odd unit choices, but it's a product of where we came from. Keeping those traditions may make things difficult sometimes, but I'm really glad my field respects our history like this.
