The increase in wavelength of electromagnetic radiation from an object moving away from an observer, crucial to our understanding of cosmic expansion and the nature of the universe.

Redshift

Redshift is a fundamental electromagnetic spectrum that occurs when light or other electromagnetic radiation from an object appears to shift toward longer wavelengths (toward the red end of the visible spectrum) as the object moves away from an observer. This effect is one of the most important tools in modern astronomy and cosmology.

Physical Mechanism

The redshift phenomenon operates on principles similar to the Doppler effect in sound waves. When a light-emitting object moves away from an observer:

The wavelengths of emitted light stretch out
This stretching causes the light to shift toward lower frequencies
In visible light, this appears as a shift toward the red end of the spectrum

Types of Redshift

Doppler Redshift

Caused by relative motion between source and observer
Common in observations of binary stars and other moving astronomical objects
Directly related to radial velocity

Gravitational Redshift

Results from general relativity effects
Light loses energy escaping strong gravitational fields
Observable near black holes and other massive objects

Cosmological Redshift

Caused by the expansion of universe
Described by the Hubble-Lemaître law
Key evidence for the Big Bang theory

Applications in Astronomy

Redshift measurements serve several crucial functions in astronomy:

Determining galaxy distances
Measuring cosmic expansion rates
Studying galaxy cluster dynamics
Identifying quasars

Historical Significance

The discovery and understanding of redshift, particularly by Edwin Hubble, led to several revolutionary insights:

The universe is expanding
Galaxies are moving away from each other
The concept of the Big Bang as the origin of the universe

Mathematical Expression

The redshift parameter (z) is typically expressed as:

z = (λobserved - λemitted) / λemitted

Where:

λobserved is the observed wavelength
λemitted is the wavelength at the source

Modern Applications

Contemporary uses of redshift measurements include:

dark energy research
galaxy formation studies
Large-scale structure mapping
cosmic microwave background analysis

The study of redshift continues to be central to our understanding of the universe's structure, history, and future evolution, making it one of the most important concepts in modern cosmology.