Cosmological constant

Definition

The cosmological constant is a term introduced by Einstein in his equations of General Relativity, representing a constant energy density that fills space homogeneously. It was originally proposed to allow for a static universe, but later became associated with the accelerated expansion of the universe, linking it to dark energy and influencing our understanding of cosmic evolution.

5 Must Know Facts For Your Next Test

1. Einstein originally introduced the cosmological constant to counteract gravitational attraction and achieve a static universe, which he later referred to as his 'greatest blunder' after discovering the universe is expanding.
2. In modern cosmology, the cosmological constant is associated with dark energy, which accounts for the observed acceleration in the universe's expansion.
3. The value of the cosmological constant is extremely small but has significant implications for the large-scale structure and fate of the universe.
4. Cosmologists use observations from supernovae, cosmic microwave background radiation, and large-scale structure to measure the effects of the cosmological constant.
5. The cosmological constant remains a critical component in our understanding of cosmic inflation and theories regarding the ultimate fate of the universe.

Review Questions

• How did Einstein's introduction of the cosmological constant influence early concepts of the universe?
  • Einstein introduced the cosmological constant to support a static universe in his General Relativity framework. This move allowed him to balance gravitational forces, as he believed that a static cosmos was essential. However, once it was discovered that the universe is actually expanding, Einstein referred to this addition as his 'greatest blunder', highlighting how it initially misled early concepts about cosmic dynamics.
• Discuss how observations related to supernovae have contributed to our understanding of the cosmological constant.
  • Observations of distant supernovae have shown that they are fainter than expected if the universe were only filled with matter. This discrepancy indicated that some form of energy, now understood as dark energy linked to the cosmological constant, must be causing the acceleration of the universe's expansion. These findings provided key evidence for incorporating the cosmological constant into modern cosmological models.
• Evaluate the implications of a non-zero cosmological constant on theories regarding the fate of the universe.
  • A non-zero cosmological constant implies that dark energy plays a significant role in governing cosmic dynamics, leading to an accelerated expansion of the universe. This has profound implications for theories about its ultimate fate, suggesting scenarios such as a 'Big Freeze', where galaxies drift apart forever as expansion outpaces gravitational attraction. Understanding this concept helps scientists explore various models, such as Lambda-CDM, and challenges traditional views on cosmic evolution.

Related terms

dark energy: A mysterious form of energy that makes up about 68% of the universe, driving its accelerated expansion.

Einstein field equations: A set of ten interrelated differential equations that describe how matter and energy in the universe influence the curvature of spacetime.

Lambda-CDM model:

The standard model of cosmology that incorporates the cosmological constant (Lambda) and cold dark matter to explain the large-scale structure and evolution of the universe.