Galaxies and the UniversePage 2

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Large-Scale Structure of the Universe to 500 m.l.y.

Slide 20

Travel to the Stars?

Kinetic Energy = 1/2 Mv2

What does it take to get a 1000-ton spaceship to 10% of the speed of light? (43 years to Alpha Centauri)

M=106 kg, v = 3 x 107 m/sec

KE = 1/2 x 106 x 9 x 1014 = 4.5 x 1020 joules

Equals U.S. Energy Production for 4.5 years

Once you get there, you have to stop.

Slide 21

Slide 22

Relativity

Speed of Light is Independent of Source

Michelson and Morley, 1887 - Speed of Light Independent of Observer

“One of the Most Unexpected Results in the History of Science” - Isaac Asimov

Conclusion: Speed of Light is the Same for All Observers

Implication: Space and Time Must Change to Keep Speed of Light Constant

Slide 23

Why the Speed of Light is a Speed Limit

Energy of a Moving Object in Relativity: E = mc2 -------------------------------------------------------------------------------  1 - v2/c2

One consequence: as v approaches c, Energy goes to infinity

Also, as we approach c, Energy goes up very fast

Slide 24

Slide 25

Fuel Economy of a Starship

At 0.1 c, energy is 0.7% greater than Newtonian formula

At 0.5 c, 24% greater

At 0.9 c, 3 x greater

At 0.99 c, 12 x greater

At 0.999 c, 43 x greater

Each extra 9 more than triples the energy

Getting our 1000 ton ship to 0.9 c takes 1.1 x 1023 joules = U.S. energy use for 1100 years

Slide 26

Another Consequence of Relativity- Gravitational Lenses

Slide 27

What Does The Universe Look Like?

Slide 28

What Does The Universe Look Like?

Slide 29

“The Big Bang”

Edwin Hubble, Recession of Galaxies, 1929

Red-shift increases with distance

Cosmic Microwave Background, 1965

Estimated Age of Universe: 12-15 b.y.

“Big Bang” originally a derisive term, coined by Fred Hoyle

Slide 30

As Far Out as We Can See - Ten Days With the Hubble Telescope

Slide 31

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