This phenomenon is called redshift. Here's why:
* Electromagnetic Spectrum: Light is a form of electromagnetic radiation. The electromagnetic spectrum encompasses various types of radiation, including visible light, which our eyes perceive as different colors. Each color has a specific wavelength: red has the longest wavelength, while violet has the shortest.
* Doppler Effect: Just like the sound of a siren changes pitch as it moves towards or away from you, the light from a star shifts in wavelength depending on its motion relative to us. When a star is moving away from us, its light waves are stretched, causing the wavelength to increase. This shift towards longer wavelengths is known as redshift.
* Observing Redshift: Astronomers use spectroscopes to analyze the light from stars. They observe a shift in the spectral lines (specific wavelengths emitted by atoms) towards the red end of the spectrum when a star is moving away from us. This redshift provides evidence for the expansion of the universe, as galaxies are generally moving away from each other.
