Here's why:
* The Doppler Effect: The Doppler effect is a phenomenon where the frequency of waves (like light waves) changes depending on the relative motion of the source and the observer.
* Blue Shift: When a light source is moving towards an observer, the light waves are compressed, making their wavelength shorter. This shift in the spectrum towards shorter wavelengths is called a blue shift, even though the light might not actually become blue.
* Red Shift: Conversely, if a light source is moving away from an observer, the light waves are stretched, making their wavelength longer. This is called a red shift.
In summary: A blue shift in the light from a star is a sign that the star is approaching us, while a red shift indicates it is moving away. This information helps astronomers understand the movement and evolution of stars and galaxies.
