Lemaître's Law

Definition

Lemaître's Law is a principle proposed by Belgian astronomer Georges Lemaître, suggesting that the universe is expanding and that this expansion can be observed through the redshift of distant galaxies. This concept laid the foundation for our understanding of cosmic expansion and relates closely to measurements obtained from the Cosmic Microwave Background (CMB), which provides critical evidence of the early universe's conditions and supports the Big Bang theory.

5 Must Know Facts For Your Next Test

1. Lemaître's Law posits that galaxies are moving away from us, which is evident in their redshift, indicating an expanding universe.
2. The observations supporting Lemaître's Law were further validated by Edwin Hubble's work on galaxy velocities and distances.
3. The CMB provides a critical test for Lemaître's Law, as its uniformity and slight anisotropies match predictions of an expanding universe post-Big Bang.
4. Georges Lemaître is often credited with being one of the first to propose that the universe has a beginning point, leading to the concept of cosmic expansion.
5. Lemaître's Law has implications for understanding the ultimate fate of the universe, as it raises questions about whether expansion will continue indefinitely or eventually reverse.

Review Questions

• How does Lemaître's Law connect to observations made through Hubble's work on galaxies?
  • Lemaître's Law indicates that galaxies are receding from each other, and this idea aligns closely with Edwin Hubble’s observations that revealed a correlation between a galaxy’s distance and its recession velocity. Hubble found that more distant galaxies appeared to move away faster, reinforcing Lemaître's assertion of an expanding universe. Together, these contributions helped establish a coherent understanding of cosmic expansion.
• Discuss the role of the Cosmic Microwave Background (CMB) in supporting Lemaître's Law and what it tells us about the early universe.
  • The Cosmic Microwave Background (CMB) serves as a crucial piece of evidence for Lemaître's Law because it represents the afterglow of the Big Bang when the universe cooled enough for atoms to form and light to travel freely. The uniformity and slight fluctuations in temperature of the CMB match predictions made by models based on an expanding universe. This supports Lemaître’s theory by showing that if the universe is expanding now, it must have been denser and hotter in the past.
• Evaluate how Lemaître's Law influences our understanding of the ultimate fate of the universe.
  • Lemaître's Law significantly impacts theories about the future evolution of the cosmos. If the universe continues to expand as suggested, it raises questions about whether this expansion will accelerate indefinitely or lead to a Big Freeze scenario. Alternatively, if gravitational forces eventually dominate, it might result in a Big Crunch. Understanding these possibilities is crucial for comprehending not only the dynamics of cosmic expansion but also fundamental questions about the nature of space and time.

Related terms

Hubble's Law: A law stating that the velocity at which a galaxy recedes from an observer is directly proportional to its distance from that observer, providing evidence for the expanding universe.

Cosmic Microwave Background (CMB): The thermal radiation filling the universe, a relic from the Big Bang, which provides a snapshot of the universe when it was just 380,000 years old.

Big Bang Theory: The prevailing cosmological model describing the origin of the universe, suggesting it began from a hot, dense state and has been expanding ever since.