1. Light as a Wave: Light behaves like a wave. It has a specific wavelength, which determines its color.
2. The Doppler Effect: Just like the sound of a siren changes pitch as it moves towards or away from you, the wavelength of light changes when the source of the light is moving.
3. Redshift and Blueshift:
- Redshift: If a star is moving away from Earth, its light waves are stretched out, making them appear more red (longer wavelength).
- Blueshift: If a star is moving towards Earth, its light waves are compressed, making them appear more blue (shorter wavelength).
4. Spectrographs: Scientists use instruments called spectrographs to analyze the light from stars. Spectrographs break down the light into its component wavelengths, creating a spectrum.
5. Measuring the Shift: By comparing the spectrum of a star to a known reference spectrum, astronomers can measure how much the wavelengths have shifted (either red or blue). This shift tells them the star's speed and direction relative to Earth.
In short: The Doppler Shift allows us to determine a star's movement by observing the change in its light wavelength. Redshift indicates movement away, and blueshift indicates movement towards Earth.
