Olber’s Paradox

1

2

3

Olber’s Paradox

4

The universe is expanding!

5

Hubbles Law

6

7

8

Four Main Issues

• Cosmic Microwave Background (CMB)

• Large Scale Structure

• Universal Acceleration

• Gravitational Leaks

9

10

11

12

13

14

15

Sachs-Wolfe effect

16

DARK MATTER:

•Gravity from baryons alone could not account for fluctuations.

•The ratios of the power spectrum peaks indicate relative dark matter density.

•Dark matter comprises 25% of the critical density.

17

Acceleration

• Has the universe always been accelerating?

• If not, when did it start, and what is causing it?

18

19

Repulsive Gravity?

• Matter and Energy produce gravity.

• The amount (density) of matter and energy in the universe determines the rate that it will slow down.

• GR allows for repulsive energies (Dark Energy)

20

As the universe expands, the matter density decreases.

The dark energy density remains the same. Or does it…?

21

There are theories suggesting that:

DARK ENERGY INCREASES

DARK ENERGY DECREASES

GENERAL RELATIVITY NEEDS FIXING

22

The dominant fix today is string theory:

23

24