system
Given the following post, respond as if you're commenting on Reddit:
human
What are the velocities of the arms of the milky way?

I'm on a radio astronomy research team with my college, and I'm in charge of finding the velocities of the arms of the galaxy so that when we take data from telescopes we can analyze it (we're using a 40-foot national telescope). Can someone please explain how to do this? I'm having trouble knowing where to start, and my team leader is getting impatient.
gpt
Something that you need to consider here is that the arms do not spin like a pin wheel. Rather the stars orbit the center of the galaxy independently of the arms. The arms are like compression waves in a traffic jam. Measuring the speed of the stars will not tell you the speed that the traffic jam is moving.