Hubble's Law

Definition

Hubble's Law states that the velocity at which a galaxy is receding from an observer is directly proportional to its distance from that observer. This relationship implies that the universe is expanding, providing crucial evidence for the Big Bang theory and showing how galaxies move away from each other over time.

5 Must Know Facts For Your Next Test

1. Hubble's Law was formulated by Edwin Hubble in 1929, based on observations of distant galaxies and their redshifts.
2. The law is often expressed as $$v = H_0 imes d$$, where $$v$$ is the recession velocity, $$d$$ is the distance to the galaxy, and $$H_0$$ is the Hubble constant.
3. The value of the Hubble constant has been refined over time, with current estimates around 70 km/s/Mpc, indicating how quickly galaxies are moving away per megaparsec of distance.
4. Hubble's Law supports the idea that the universe is not static but expanding, influencing theories about the origins and fate of the cosmos.
5. The observation of distant supernovae has provided additional evidence for Hubble's Law, demonstrating accelerated expansion of the universe due to dark energy.

Review Questions

• How does Hubble's Law relate to the concept of redshift and what does this signify about the motion of galaxies?
  • Hubble's Law directly connects to redshift as it describes how galaxies appear to be moving away from us, which causes their light to shift towards longer wavelengths. This redshift indicates that these galaxies are receding due to the expansion of the universe. As distance increases, so does velocity, illustrating that more distant galaxies move away faster than those closer to us.
• Discuss how Hubble's Law provides evidence for the Big Bang theory and influences our understanding of cosmology.
  • Hubble's Law supports the Big Bang theory by demonstrating that the universe is expanding from an initial singular point. As galaxies recede from each other, it suggests they were once much closer together. This expansion implies a dynamic universe that has evolved over time, shaping our understanding of cosmic history and leading to models about its future evolution.
• Evaluate the implications of Hubble's Law on our perception of space and time in the context of modern cosmology.
  • Hubble's Law significantly alters our perception of space and time by suggesting that space itself is expanding, which affects how we understand distances and interactions between galaxies. This concept implies that as time progresses, galaxies are not just moving through space but are creating more space between them. Consequently, this challenges traditional notions of static spatial relationships and introduces a framework in which both space and time are interconnected in a dynamic cosmic environment.

Related terms

Redshift: A phenomenon where light from an object moving away from an observer is shifted to longer wavelengths, indicating that the object is receding.

Cosmological Redshift: The redshift that occurs due to the expansion of space itself, affecting the light emitted by distant galaxies as they move away from us.

Expansion of the Universe: The ongoing process whereby the distances between galaxies increase over time, a fundamental observation in modern cosmology.