A typical analogy explaining redshift involves a siren or a train whistle. So how do we know the same phenomenon works with light?

Question

A typical analogy explaining redshift involves a siren or a train whistle. So how do we know the same phenomenon works with light?

In: 2

Answer 1

We can measure it, an example you’ve likely heard the name of is “doppler radar”. Radio waves are just low frequency light, we can measure the shift in frequency based on how fast an object is moving towards or away from the radar, and we can measure the speed of that object with some other method to check that we’re measuring what we think we’re measuring.