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The Cosmic Perspective of Cosmology. NOTES: Cosmological Terminology : Cosmology : the study of the large scale structure and evolution of the universe. Homogeneity : the claim the universe has the same density in all locations at the largest scale.

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slide1

The Cosmic Perspective

of Cosmology

NOTES: Cosmological Terminology:

Cosmology: the study of the large scale structure

and evolution of the universe.

Homogeneity: the claim the universe has the same density

in all locations at the largest scale.

Isotropy: the claim the universe looks the same in all directions.

slide2

Cosmology is NOT cosmetology…

though a cosmologist makes up the face of the universe.

slide3

Cosmology is the study of the large scale structure

and evolution of the universe: in space & time.

slide4

Homogeneity: the claim the universe has the same density in all locations at the largest scale. (Center for Cosmological Physics at the University of Chicago)

slide5

Cosmological redshift

z = redshift) = Δλ/λ = v/c (for small v = expansion speed)

slide6

Isotropy: the claim the universe looks the same in all directions.

Counts of distant galaxies and radio-sources appear

to provide evidence that the universe is isotropic.

slide7

Pre 1998 Cosmology

--ignoring dark energy in space:

In 1998, using Supernova Ia’s,

universe was found to be ruled

by dark energy,

making it accelerate.

We ignore this at first.

slide8

Ω (Omega)

= density of universe/critical density

critical density = 10-29 grams per cubic centimeter

slide9

Alexander Friedmann (Russian) 1920

(utilizing Einstein’s General Theory):

gave us three possible expanding universes.

slide10

With no dark energy:

Flat Universe:

Curvature = 0

Omega = 1

Destiny = barely stop expanding,

it reaches a maximum speed but

with no collapse

Closed Universe:

Curvature > 0

Omega > 1

Destiny = collapse

Open Universe:

Curvature < 0

Omega < 1

Destiny = endless

decelerating expansion

slide12

Galaxies are not flying apart through

space, they are being carried away

by the expansion of space itself

(like small marks in the surface

on an inflating balloon).

The Big Bang was not like an

explosion in a pre-existing space,

but rather an explosion of space itself.

slide13

However, there were problems with Friedmann’s universe

which resulted in the Inflationary Universe of

Andre Linde (Russia1979)

and Alan Guth (US 1980).

Guth got the Nobel Prize for a theory that didn’t work.

Later, Linde adapted his own theory to one that worked.

slide14

Three problems led to

a theory of early rapid

inflation:

1. Horizon Problem  The isotropy of the microwave background

indicates that regions A and B in the universe were very

similar to each other when the radiation we observe left them,

but there has not been enough time since the Big Bang for

them ever to have interacted physically with one another.

Why then should they look the same?

slide15

2. Flatness Problem If the universe deviates even

slightly from critical density, that deviation grows rapidly in time.

For the universe to be as close to critical as it is today,

it must have differed from the critical density in the past

by only a tiny amount.

slide16

3. Magnetic monopole problem:

Universe is believed to produces North magnetic poles

without a South, but we don’t observe any.

Friedmann’s universe didn’t expand enough to

make them far apart.

slide18

Just as ice takes up more volume than water,

space was believed to have undergone a expanded

phase change related to the Grand Unified Theory (GUT)

of elementary particles. (Guth’s Theory). However, this

meant that protons should decay and they don’t.

slide19

Chaotic Inflation: Among many parallel universes,

one expands like ours with a bubble that bursts and explains

the lumpy structure of the universe necessary to produce clusters,

galaxies, and stars. This is called Scale-free lumpiness.

Andrei Linde (now at Stanford) showed this.