* Red Shift: When light from distant galaxies is analyzed, it appears shifted towards the red end of the electromagnetic spectrum. This phenomenon is called redshift.
* Doppler Effect: Similar to how the pitch of a siren changes as it moves towards or away from you, the wavelength of light changes when the source of light is moving relative to the observer.
* Expansion of Space: The redshift observed in distant galaxies is not due to their movement through space, but rather due to the expansion of space itself. The fabric of spacetime is stretching, carrying galaxies along with it. As the universe expands, the space between galaxies increases, stretching the wavelengths of light emitted by those galaxies.
Key Points:
* Hubble's Law: The relationship between redshift and distance was first observed by Edwin Hubble and is known as Hubble's Law. It states that the recessional velocity of a galaxy is directly proportional to its distance from us.
* Evidence for Big Bang: Cosmological redshift is one of the key pieces of evidence supporting the Big Bang theory, which states that the universe began from a hot, dense state and has been expanding ever since.
In summary, cosmological redshift suggests that the universe is expanding, and that galaxies are moving away from us and from each other at speeds proportional to their distance from us.
