Hubble-Lemaître Law

Definition

The Hubble-Lemaître Law states that the velocity at which a galaxy is receding from an observer is directly proportional to its distance from that observer. This fundamental relationship supports the idea of an expanding universe and forms the cornerstone of modern cosmology, highlighting the connection between distance and redshift observed in galaxy surveys.

5 Must Know Facts For Your Next Test

1. The law was independently formulated by Edwin Hubble and Georges Lemaître in the 1920s, leading to the conclusion that the universe is expanding.
2. It provides a mathematical framework for understanding how distant galaxies move away from us, which can be observed through their redshifts.
3. The Hubble constant, derived from this law, quantifies the expansion rate of the universe and has significant implications for cosmology.
4. Galaxy surveys have confirmed the predictions made by the Hubble-Lemaître Law, revealing a uniform expansion across vast distances.
5. The law challenges the static universe theory and supports the Big Bang model, indicating that the universe has evolved over time.

Review Questions

• How does the Hubble-Lemaître Law support our understanding of galaxy movement and the structure of the universe?
  • The Hubble-Lemaître Law illustrates that there is a direct correlation between a galaxy's distance and its recessional velocity. This means that more distant galaxies are moving away faster than those closer to us, a pattern confirmed through extensive galaxy surveys. This relationship supports the model of an expanding universe, showing how galaxies are structured within it and providing insights into cosmic evolution.
• Discuss how the Hubble constant is determined from galaxy surveys and its significance in cosmology.
  • The Hubble constant is calculated by measuring the redshift of distant galaxies and their corresponding distances obtained through various methods like standard candles or Tying Cepheid variables. By plotting these distances against their velocities, astronomers can derive the Hubble constant. Its significance lies in defining the rate of expansion of the universe, influencing theories on its age and future dynamics.
• Evaluate the impact of galaxy surveys on refining our understanding of the Hubble-Lemaître Law and cosmic expansion.
  • Galaxy surveys have dramatically refined our understanding of the Hubble-Lemaître Law by providing extensive data on galaxy distances and velocities. As more galaxies are observed, patterns emerge that reinforce this law's predictions about cosmic expansion. Analyzing these surveys has led to improved estimates of the Hubble constant and insights into dark energy's role in accelerating this expansion, thus shaping our contemporary cosmological models.

Related terms

Redshift: The phenomenon where light from an object moving away from an observer is stretched to longer wavelengths, causing it to appear redder; it's a key indicator of the universe's expansion.

Cosmological Principle: The assumption that the universe is homogeneous and isotropic when viewed on a large scale, meaning it looks roughly the same everywhere and in every direction.

Expansion Rate: The rate at which the universe is expanding, typically expressed in kilometers per second per megaparsec, indicating how fast galaxies are moving away as a function of their distance.