Einstein’s field equation
Measurements from distant supernovae
Measurements from galaxy cluster surveys
Cosmic microwave background radiation
Observational indications of expansion
- Three independent methods indicate agreement that the universal expansion is accelerating
Analyze growth of large scale structure over time
- More mass in the universe means it is easier for clusters, walls, voids, etc. to grow
- Higher density implies faster formation of structure – indicating less structure in the past
- Size of fluctuations at present indicate curvature of the universe
- Type 1a supernovae (standard candles)
- It appears we have an accelerating universe
- We assume there must be something working against gravity; we call it dark energy
- Adds density but not gravitational attraction
- Calculate how much energy it would take to drive the galaxies apart
- Ωo ≈ 1 – density of the universe appears to be close to critical
- We postulate that there must be something driving the galaxies apart, acting like anti-gravity. We call it dark energy.
- We calculate how much energy would be needed to drive the galaxies apart.
- It appears that the universe is made up of 5% normal matter, 20% dark matter and 75% dark energy.