The distance-redshift relationship describes how the observed redshift of light from distant galaxies correlates with their distance from Earth. This relationship is a key aspect of understanding the expansion of the universe, as galaxies moving away from us appear redshifted due to the Doppler effect, indicating that the universe itself is expanding over time.
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The distance-redshift relationship is crucial for measuring cosmic distances and understanding the rate of expansion of the universe.
A higher redshift indicates that a galaxy is moving away faster and is located further away from us.
The relationship was first empirically established by Edwin Hubble through observations of distant galaxies in the 1920s.
The redshift can be quantified using the formula $$z = \frac{\lambda_{observed} - \lambda_{emitted}}{\lambda_{emitted}}$$, where $$\lambda$$ represents the wavelength of light.
This relationship provides evidence for the Big Bang theory, as it implies an evolving universe that has expanded from a denser state.
Review Questions
How does the distance-redshift relationship support our understanding of the universe's expansion?
The distance-redshift relationship shows that galaxies are moving away from us, with their redshift being proportional to their distance. This observation suggests that the universe is expanding, as described by Hubble's Law. The more distant a galaxy is, the greater its redshift, which supports the idea that space itself is stretching over time.
In what ways did Edwin Hubble's discoveries influence our understanding of cosmology and the structure of the universe?
Edwin Hubble's work established a direct link between distance and redshift, forming the basis of Hubble's Law. His findings demonstrated that the universe is not static but rather expanding, leading to a fundamental shift in cosmology. This insight helped develop models of an evolving universe and contributed significantly to the Big Bang theory, reshaping our understanding of cosmic structure and dynamics.
Evaluate how the concepts of cosmological redshift and the Doppler effect contribute to our comprehension of cosmic distances and velocities.
Cosmological redshift arises from the expansion of space itself, stretching light waves as they travel through the universe. This effect, combined with the Doppler effect, allows astronomers to determine both distances and velocities of galaxies. By analyzing redshifts, we can infer not only how far away galaxies are but also how fast they are receding, providing crucial data for models of cosmic evolution and testing theories about dark energy and the fate of the universe.
A law stating that the recessional velocity of a galaxy is directly proportional to its distance from us, represented by the formula v = H₀d, where H₀ is the Hubble constant.
The redshift observed in light from distant galaxies that results from the expansion of the universe, causing wavelengths of light to stretch as they travel through space.
The change in frequency or wavelength of a wave in relation to an observer moving relative to the source of the wave, leading to redshift for objects moving away and blueshift for those moving closer.