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Olber’s Paradox

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The universe is expanding!

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Hubbles Law

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Four Main Issues

• Cosmic Microwave Background (CMB)

• Large Scale Structure

• Universal Acceleration

• Gravitational Leaks

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Sachs-Wolfe effect

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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.

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Acceleration

• Has the universe always been accelerating?

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

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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)

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As the universe expands, the matter density decreases.

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

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There are theories suggesting that:

DARK ENERGY INCREASES

DARK ENERGY DECREASES

GENERAL RELATIVITY NEEDS FIXING

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The dominant fix today is string theory:

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