PhysicsChapter 9: Cosmology
Dark Energy and Accelerating Expansion
Dark energy
Definition
Dark energy is the name given to the component or effect associated with the observed accelerated expansion of the universe.
Cosmological Constant
Observations of distant Type Ia supernovae played a major historical role in revealing accelerated cosmic expansion. Modern evidence also combines: supernova measurements; CMB observations; large-scale structure; other cosmological distance measurements. One simple model of dark energy is Einstein's: **cosmological constant, Λ In the standard ΛCDM cosmological model: `Λ` represents dark-energy-like accelerated expansion. `CDM` means Cold Dark Matter**.
Formula / Key Relation
Scale factor acceleration: **ä > 0 indicates accelerated expansion. Hubble parameter: H=ȧ/a**
Exam preparation
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Review the key facts, formulas and checks before you move on.Dark Energy and Accelerating Expansion
Sticky Notes · Quick Revision
DARK ENERGY
- Expansion accelerating
- `ä > 0`
- Λ
- ΛCDM
- Not dark matter
60-second revision
- Dark energy is the term used for the phenomenon/component associated with accelerated expansion.
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