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Vacuum Energy in the Universe. Scott Dodelson April 5, 2000. A long time ago in a galaxy far, far away. Einstein and General Relativity. Idea: Matter affects the structure of Space-Time. E.g. A massive star attracts nearby objects by distorting space.

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Vacuum Energy in the Universe

Scott Dodelson

April 5, 2000

A long time ago in a

galaxy far, far away...

Einstein and General Relativity

Idea: Matter affects the

structure of Space-Time

E.g. A massive star

attracts nearby objects

by distorting space

In 1919, Eddington led expedition to observe solar eclipse ...

Leading to confirmation of Einstein's theory ...

And widespread adulation ...

London Times Nov 8, 1919

The Revolution in Science:

Einstein vs. Newton

Expanding Sphere ...

Energy = Kinetic Energy + Gravitational Energy

0 = (½) m v2 - G m M(r)/ r

Einstein's Static Universe ...

How did Einstein make the universe static?

0 = (½) m v2 - G m M(r)/r

Changed the energy to be negative

Introduced vacuum energy. Ordinary matter: M(r) = constant Vacuum energy: M(r) ~ r3

Aleksandr Aleksandrovich Friedmann ...

Born: June 1888, St. Petersburgh, Russia

Died: September 1925, St. Petersburgh

Published paper on Bernoulli Numbers at age 17.

WWI: Join volunteer aviation detachment.

Used mathematical tools to improve bombing: ...

I have recently had a chance to verify my ideas

during a flight over Przemysl; the bombs turned

out to be falling almost the way the theory predicts.

To have conclusive proof of the theory I'm going to

fly again in a few days.

Letter from Friedmann, Feb 28, 1915

Expansion of the Universe ...

June 29, 1922: Friedmann introduces the expanding universe, abandoning the vacuum energy Einstein put in by hand.

September 18, 1992: Einstein publishes a comment on Friedmann's paper: result ``seems suspect to me'', ``solutions do not appear compatible''

May 31, 1923: Einstein retracts his criticism: ``My objection rested on a calculational error.''

BUT ... ...

M(r) = r v2 / 2G



Galaxies, clusters,


of gal



``Arrogant Theorists''


``Ignorant Observers’’


Ugly theory

Vacuum Energy in

the Universe !

Supernovae are standard candles reaches Earth

The apparent brightness of a supernova is therefore a measure of its distance from us.

Can get Hubble relation for very distant objects!

Since M remains reaches Earth

constant, expansion

slows, like a rocket

leaving Earth

Since M increases

with R, universe is driven to expand

faster and faster

Fainter -> reaches Earth

Far Away ->

Scale Factor (redshift)

What are we up to now? reaches Earth

We are observing

Measuring the distribution of galaxies

Measuring anisotropies in the cosmic radiation

Sending up satellites to observe more supernovae

Searching for exotic, dark matter

First light from the Sloan Digital Sky Survey, will map reaches Earth

a million galaxies on the sky

Satellites will map cosmic radiation reaches Earth

Photo of the universe when it was very young

Dark Matter searches continue ... reaches Earth

February 26, 2000

Deep, profound questions remain reaches Earth

  • What is the vacuum energy?

  • How is it related to the rest of physics?

  • Is it testable?

  • Could it be useful?

  • What are the ramifications for the future?



We are thinking ..

Large extra dimensions?

Cosmological constant?

What should we make of Einstein? reaches Earth

The Man of the Century…

• Missed the expansion

• Almost suppressed it

• Blundered into vacuum energy

Even Einstein’s Greatest Blunder ... reaches Earth

teaches us about the importance of tackling big problems. Even though Einstein was wrong, his audacity laid the groundwork for future work.