01:750:109 Chapter Notes - Chapter 14.3: Weakly Interacting Massive Particles, Cosmic Distance Ladder, White Dwarf
Evidence for Dark Energy
●Case for existence of dark energy more circumstantial, but has been growing stronger with each
passing year
What is the evidence for dark energy?
●2 major lines of evidence:
○Accelerating expansion
○Flatness of the universe
●Evidence for dark energy is based on observations of distant white dwarf supernovae that have
enabled us to probe the fate of the universe in an entirely new way
○White dwarf supernovae excellent standard candles that allow us to measure the
distances of very distant galaxies
○Therefore, we can use observations of white dwarf supernovae to determine how the
expansion rate of the universe has changed over long periods of time
The Accelerating Expansion
●Dark energy was proposed in order to explain the source of the repulsive force counteracting
gravity, so there would be no need to invoke dark energy if the expansion were not accelerating
●Accelerating model best agrees best with a model of the universe in which the expansion is
accelerating with time
●We conclude that some force must counteract gravity, providing evidence for the existence of
what we call dark energy
Flatness and Dark Energy
Document Summary
Case for existence of dark energy more circumstantial, but has been growing stronger with each passing year. Evidence for dark energy is based on observations of distant white dwarf supernovae that have enabled us to probe the fate of the universe in an entirely new way. White dwarf supernovae excellent standard candles that allow us to measure the distances of very distant galaxies. Therefore, we can use observations of white dwarf supernovae to determine how the expansion rate of the universe has changed over long periods of time. Dark energy was proposed in order to explain the source of the repulsive force counteracting gravity, so there would be no need to invoke dark energy if the expansion were not accelerating. Accelerating model best agrees best with a model of the universe in which the expansion is accelerating with time. We conclude that some force must counteract gravity, providing evidence for the existence of what we call dark energy.
