¿Qué es la materia oscura?

The video explains the concept of dark matter, which is invisible yet more common than visible matter. It discusses how gravity holds galaxies together despite the insufficient gravitational force of visible stars. The Doppler effect is introduced as a method to measure the speed of stars in galaxies, using the analogy of a police siren's changing pitch. The video emphasizes using observable phenomena to infer the existence of unseen elements like dark matter.

What analogy is used to describe the behavior of stars in a galaxy?

How do astronomers measure the speed of stars in distant galaxies?