Cosmological constant

Definition

The cosmological constant is a term introduced by Albert Einstein in his equations of general relativity that represents a constant energy density filling space homogeneously. It was originally added to allow for a static universe, but later interpreted as a force that counteracts gravitational attraction, leading to the accelerated expansion of the universe.

5 Must Know Facts For Your Next Test

1. The cosmological constant, denoted as Λ (lambda), was originally introduced by Einstein in 1917 when he believed the universe was static.
2. After the discovery of the expanding universe by Edwin Hubble in the 1920s, Einstein called the cosmological constant his 'greatest blunder' as it was no longer needed.
3. In the late 1990s, observations of distant supernovae suggested that the universe's expansion is accelerating, leading to the revival of interest in the cosmological constant.
4. The value of the cosmological constant is crucial for understanding cosmic phenomena such as galaxy formation and the overall fate of the universe.
5. Current measurements estimate the cosmological constant to be approximately 10^{-120} in natural units, which illustrates its incredibly small yet impactful nature.

Review Questions

• How did Einstein's introduction of the cosmological constant change our understanding of gravity and spacetime?
  • Einstein's introduction of the cosmological constant allowed for a new interpretation of gravity and its effects on spacetime. Originally meant to maintain a static universe, it led to insights about how energy density can influence spacetime curvature. This understanding paved the way for later developments in cosmology, particularly regarding how cosmic expansion could be influenced by an energy density that permeates all space.
• Discuss the relationship between the cosmological constant and dark energy in modern cosmological models.
  • In contemporary cosmology, the cosmological constant is often associated with dark energy, which constitutes about 68% of the universe's total energy density. The cosmological constant provides a simple explanation for dark energy's role in driving the accelerated expansion of the universe. As a result, both concepts are integral to current models explaining cosmic dynamics and structure formation.
• Evaluate the implications of a non-zero cosmological constant on our understanding of the fate of the universe.
  • A non-zero cosmological constant suggests that dark energy plays a significant role in cosmic evolution, leading to an accelerating expansion. This has profound implications for our understanding of the universe's ultimate fate; scenarios like the 'Big Freeze' or 'Heat Death' become more probable if dark energy continues to dominate. Analyzing these implications challenges our understanding of fundamental physics and raises questions about future cosmic structures and events.

Related terms

Einstein field equations: A set of ten interrelated differential equations that describe how matter and energy influence the curvature of spacetime, fundamental to the theory of general relativity.

Dark energy: A mysterious form of energy that makes up about 68% of the universe and is believed to be responsible for its accelerated expansion.

Friedmann equations: A set of equations derived from the Einstein field equations that govern the expansion of the universe in cosmology.