Redshift Calculator
Calculate cosmological redshift and Doppler shifts for astronomical observations
Calculate Redshift Parameter (z)
Wavelength at the source
Wavelength as detected by observer
Wavelength Formula
Positive z indicates redshift (longer wavelengths)
Redshift Results
Example: Hydrogen α Line
Rest Frame
Wavelength: 656.3 nm
Frequency: 4.568 × 10¹⁴ Hz
Source: Laboratory measurement
Distant Galaxy
Observed wavelength: 721.9 nm
Redshift z: (721.9 - 656.3) / 656.3 = 0.10
Recession velocity: ~30,000 km/s
Example: Cosmic Microwave Background
At Emission (z ≈ 1100)
Temperature: ~3000 K
Peak wavelength: ~1 μm (infrared)
Universe age: ~380,000 years
Today (z = 0)
Temperature: 2.73 K
Peak wavelength: ~1.9 mm (microwave)
Redshift factor: 1 + z ≈ 1100
Causes of Redshift
Cosmological Expansion
Universe expansion stretches wavelengths
Dominant for distant galaxies
Doppler Effect
Relative motion between source and observer
Important for nearby objects
Gravitational Redshift
Light escaping strong gravitational fields
Important near massive objects
Redshift Ranges
Note: Higher z values correspond to greater distances and earlier cosmic times
Wave Properties
Speed of light = wavelength × frequency
Understanding Redshift in Astrophysics
What is Redshift?
Redshift is the phenomenon where electromagnetic radiation from astronomical objects is observed at longer wavelengths (lower frequencies) than originally emitted. The name comes from the fact that visible light shifts toward the red end of the spectrum.
The Redshift Parameter z
- •z > 0: Redshift - object moving away or expanding universe
- •z < 0: Blueshift - object approaching observer
- •z = 0: No shift - no relative motion or expansion effect
Redshift Formulas
From Wavelength
z = (λ_observed - λ_emitted) / λ_emitted
Measures the fractional change in wavelength
From Frequency
z = (f_emitted - f_observed) / f_observed
Measures the fractional change in frequency
Cosmological Significance
The discovery of redshift in distant galaxies led to the realization that the universe is expanding. Edwin Hubble's observations showed that more distant galaxies have higher redshifts, establishing Hubble's law and providing evidence for the Big Bang theory.
Today, redshift measurements are crucial for determining distances to galaxies, studying the expansion history of the universe, and understanding the evolution of cosmic structure over billions of years.