Cosmological Redshift

Definition

Cosmological redshift is the shift in the wavelength of light from distant galaxies or other celestial objects, caused by the expansion of the universe. This phenomenon is a crucial piece of evidence supporting the Big Bang theory and the concept of an expanding universe.

5 Must Know Facts For Your Next Test

1. Cosmological redshift is caused by the stretching of the wavelength of light as it travels through the expanding space between the source and the observer.
2. The greater the distance to a celestial object, the greater its cosmological redshift, as the light has traveled through more of the expanding universe.
3. Cosmological redshift is distinct from the Doppler shift, which is caused by the relative motion between the source and the observer.
4. Hubble's law, which relates the recessional velocity of a galaxy to its distance, is derived from the observed cosmological redshift of distant galaxies.
5. Cosmological redshift provides strong evidence for the Big Bang theory, as it confirms the overall expansion of the universe over time.

Review Questions

• Explain how the cosmological redshift of distant galaxies supports the concept of an expanding universe.
  • The observed cosmological redshift of light from distant galaxies is a direct consequence of the expansion of the universe. As the space between the galaxy and the observer expands, the wavelength of the light is stretched, resulting in a shift towards longer, redder wavelengths. The greater the distance to the galaxy, the greater the observed redshift, as the light has traveled through more of the expanding universe. This relationship, known as Hubble's law, provides strong evidence that the universe is indeed expanding, a key prediction of the Big Bang theory.
• Distinguish between the cosmological redshift and the Doppler shift, and explain how each relates to the expansion of the universe.
  • The cosmological redshift is caused by the expansion of the universe, which stretches the wavelength of light from distant galaxies. In contrast, the Doppler shift is caused by the relative motion between the source and the observer, where the wavelength is shifted due to the approaching or receding motion. While the Doppler shift can be observed for objects within our own galaxy, the cosmological redshift is a consequence of the overall expansion of the universe over time. The cosmological redshift, as observed in the light from distant galaxies, provides direct evidence for the expansion of the universe, a fundamental prediction of the Big Bang theory.
• Analyze how the cosmological redshift, Hubble's law, and the Big Bang theory are interconnected in our understanding of the universe's evolution.
  • The cosmological redshift of light from distant galaxies is a crucial piece of evidence that supports the Big Bang theory and the concept of an expanding universe. The observed relationship between the redshift and the distance to a galaxy, known as Hubble's law, demonstrates that the universe is expanding, with more distant galaxies receding at faster speeds. This expansion is a direct consequence of the Big Bang, the initial state of the universe from which all matter and energy originated. The cosmological redshift, as a direct observation of this expansion, provides strong validation for the Big Bang theory and our understanding of the universe's evolution over time. The interconnectedness of these concepts has been instrumental in shaping our modern cosmological model and our place within the ever-expanding universe.

Related terms

Doppler Effect: The Doppler effect is the change in the observed frequency or wavelength of a wave due to the relative motion between the source and the observer.

Hubble's Law: Hubble's law states that the recessional velocity of a galaxy is proportional to its distance from the observer, providing a way to measure the expansion of the universe.

Expanding Universe: The expanding universe is the observed increase in the distance between galaxies over time, a key prediction of the Big Bang theory.