Dark Energy Constant: Is It Constant or Increasing?

Click For Summary

Discussion Overview

The discussion revolves around the nature of dark energy in the universe, specifically whether its amount is constant or increases as the universe expands. Participants explore the implications of dark energy's behavior on cosmic expansion, touching on concepts related to the cosmological constant and the relative densities of dark energy, matter, and radiation.

Discussion Character

  • Debate/contested

Main Points Raised

  • Some participants assert that the fraction of dark energy compared to matter and radiation increases as the universe expands.
  • Others question the meaning of "amount of dark energy," suggesting that while the density of dark energy is constant, the total quantity increases due to the expanding volume of the universe.
  • It is noted that the density of ordinary matter, dark matter, and radiation decreases as the universe expands, leading to an increasing relative density of dark energy.
  • Some participants argue that the cosmological constant, which is equivalent to the density of dark energy, remains constant despite these changes.

Areas of Agreement / Disagreement

Participants express differing views on whether the cosmological constant is truly constant, with some asserting it is while others challenge this notion based on the increasing fraction of dark energy relative to other components of the universe. The discussion remains unresolved.

Contextual Notes

Participants highlight that the density of dark energy is constant, but the increasing volume of the universe complicates the interpretation of total dark energy. The implications of changing densities of other components are also noted, but no consensus is reached on the overall interpretation.

Einstein's Cat
Messages
182
Reaction score
2
Is the amount of dark energy in the universe constant or else does it increase as the universe expands? In other words is the "anti- gravitational force" that is believed to be caused by dark energy and results in a accelerating universal expansion, a constant value or will it increase as the universe expands?
 
Space news on Phys.org
Yes, the fraction of dark energy as compared to matter and radiation in the universe increases as it expands.
 
Bandersnatch said:
Yes, the fraction of dark energy as compared to matter and radiation in the universe increases as it expands.
Doesn't that mean that the cosmological constant isn't constant?
 
Einstein's Cat said:
Is the amount of dark energy in the universe constant or else does it increase as the universe expands?

What do you mean by "amount of dark energy"? The density of dark energy is constant. But the volume of the observable universe is increasing, so multiplying the constant density by the increasing volume gives an increasing total quantity of dark energy. However, the latter quantity isn't really meaningful physically; it's the density that matters.

Also, the density of ordinary matter, dark matter, and radiation is decreasing as the universe expands, so, as Bandersnatch said, the density of dark energy relative to the other densities is increasing. But that reflects a change in the other densities, not in the density of dark energy.

Einstein's Cat said:
Doesn't that mean that the cosmological constant isn't constant?

No. The cosmological constant is equivalent to the density of dark energy, which is constant.
 

Similar threads

Undergrad Is the amount of dark matter constant in the Universe?
  • · Replies 20 ·
Replies
20
Views
4K
High School Dark energy might not be constant after all
  • · Replies 8 ·
Replies
8
Views
5K
Undergrad Hubble Constant, Dark Energy and the Expanding Universe
  • · Replies 20 ·
Replies
20
Views
5K
Undergrad Questions on the consequence of an evolving dark energy parameter
  • · Replies 1 ·
Replies
1
Views
3K
Undergrad Voids, dark energy and tidal forces...?
  • · Replies 0 ·
Replies
0
Views
2K
Undergrad Does dark-energy require a source of energy?
  • · Replies 2 ·
Replies
2
Views
3K
Undergrad Dark energy is intrinsic to the space itself
  • · Replies 5 ·
Replies
5
Views
2K
Undergrad Dark energy and the kinematic Sunyaev-Zeldovich effect?
  • · Replies 22 ·
Replies
22
Views
3K
Undergrad Dark energy contributing to, or modifying, mass estimates?
  • · Replies 1 ·
Replies
1
Views
2K
High School Expansion of the Universe
  • · Replies 9 ·
Replies
9
Views
3K