Here's how it works:
* Doppler Effect: Imagine a moving ambulance. As it approaches you, the siren sounds higher pitched (higher frequency), and as it moves away, the siren sounds lower pitched (lower frequency). This is because the sound waves are compressed as the ambulance approaches and stretched as it moves away.
* Light as a Wave: Light behaves as a wave. It has a specific frequency and wavelength.
* Redshift and Blueshift: When a star moves towards Earth, the light waves are compressed, resulting in a higher frequency (shorter wavelength). This is called a blueshift. Conversely, when a star moves away from Earth, the light waves are stretched, resulting in a lower frequency (longer wavelength). This is called a redshift.
* Spectral Lines: Each element emits and absorbs light at specific wavelengths, creating unique spectral lines. When a star moves, these spectral lines are shifted towards the blue end of the spectrum (blueshift) or towards the red end (redshift).
* Measuring Velocity: By measuring the shift in the spectral lines, astronomers can determine the speed and direction of the star's motion relative to Earth. This is known as Doppler spectroscopy.
In summary: The Doppler effect explains the shift in a star's spectral lines, and this shift is directly related to the star's velocity relative to Earth.
