concluding comments for the course cosmology fascinating past highly accomplished present (for...

Concluding Comments For the Course

Cosmology

• Fascinating Past

• Highly accomplished present (for example, the material covered in this course).

• Really exciting future

The History of the Universe Today

Galaxy Formation

Last Scattering

Nuclear & High Energy Physics

Inflation?

Extra Dimensions?

Time

High Energy & Temp

Anti-Gravity?*!


Cosmology




Past: Cosmology provided a great source of inspiration and new ideas:


Cosmology




Atomic energy levels

Emission

Absorption

Present: Deep understanding of our universe comes from

1) Application of known laws of physics


1) Application of known laws of physics


2) Collecting amazing data sets

The Keck 10m Telescopes on Mauna Kea, Hawaii

Segments of the Keck 10m Telescope Mirror

Mass inferred from lensing: Must have dark matter


3) Putting Data and physics together to get the big picture Big Bang Theory

What we know about the big picture

1) On large scales the matter in the Universe is spread out very smoothly (“Homogeneous”)

Mean density:29 310 /gram cm

2) The Universe is expanding

Hubble law: v Hr

3 / sec

100

mH

lightyears

The homogeneity of the Universe

Isotropy of the microwave background (from the “edge of the observable universe”) to one part in 100,000

Galaxy

The homogeneity of the universe

Galaxy surveys

Radial Direction

We are here

The homogeneity of the universe

Galaxy surveys

Radial Direction

We are here

From 1986

The Hubble law

v Hr3 / sec

100

mH

lightyears

v

r


Galaxy Formation

Last Scattering

Nuclear & HEP

Inflation?

Extra Dimensions?

Time

High Energy & Temp

Anti-Gravity?*!


4) Exploring and observing consequences of the Big Bang such as

CMB: The edge of the observable universe

The Edge of the Observable Universe:

As we look back in space we look back in time. We see:

Here & Now

Light traveling from far away =from distant past

Long ago (about 14 Billion years) the Universe was so hot and dense it was opaque: The edge of the observable universe

Today:• Only 2.726K above absolute Zero

• “Microwave Radiation” (The “Cosmic Microwave Background”: CMB)

• 1,000,000 times weaker than ambient radiation in a pitch dark room.

Properties of the Edge of the Observable Universe:

Here & Now

Similar to surface of Sun at time of emission

(~ 6000 )K

Today:• Only 2.726K above absolute Zero

• “Microwave Radiation” (The “Cosmic Microwave Background”: CMB)

• 1,000,000 times weaker than ambient radiation in a pitch dark room.

Properties of the Edge of the Observable Universe:

Here & Now

Similar to surface of Sun at time of emission

(~ 6000 )KCools off due to cosmic expansion

Same thing happens with stars “Oblers’ paradox” (see section 23.4)

Observing the Microwave Background, Past, present and future:

The History of the Universe Time

High Energy & Temp

New Image of the “Last Scattering Surface” from NASA’s WMAP satellite released Feb 11 2003

2009

Updated after WMAP announcement, Feb 2003

Real data

Simulated data

Real data !

1993

Maps of the microwave sky (the “edge of the observable

universe”

WMAP map of the “edge of the

observable universe”

plotted as a sphere

WMAP map of the “edge of the

observable universe”

plotted as a sphere

Note: we are really on the inside looking

out


4) Exploring and observing consequences of the Big Bang such as

Formation of Nuclei


Galaxy Formation

Last Scattering

Nuclear & High Energy Physics

Inflation?

Extra Dimensions?

Time

High Energy & Temp

Anti-Gravity?*!


5) New ideas such as cosmic inflation that seem to explain the start of the Big Bang and fit the data nicely

• Characteristic oscillations in the CMB power

Adapted from

Bennett et al Feb 11 ‘03

WMAP

“Active” models

Inflation

I.1 Successes

Tem

pera

ture

Pow

er

Angular scale

The future is exciting because of

1) Deep Mysteries

Dark Matter

Dark Energy

Cosmic acceleration (newest data)

Using supernovae (exploding stars) as cosmic “mileposts”, acceleration of the Universe has been detected.

Supernova

Preferred by modern data

Amount of gravitating matter

A

mount

of

“anti

gra

vit

y”

matt

er

“Gravitating” non accelerating matter

Here for inflation

Supernova


Amount of gravitating matter

A

mount

of

“anti

gra

vit

y”

matt

er

“Gravitating” non accelerating matter

Here for inflation

Accelerating “Dark Energy” is what makes U=1 (required to give consistency with inflation)

Acceleration or (required for inflation) is possible (+)

Dark Energy *very* poorly understood (-/+)

Dark Energy (accelerating)

70%

Dark Matter 25%

Ordinary Matter (observed in labs)

5%

95% of the cosmic matter/energy is a mystery. It has never been observed even in our best laboratories

The future is exciting because

2) Fantastic new data sets will enable us to explore these mysteries (and hopefully resolve some of them)

The future of cosmological data

•The James Webb (Next Generation) Space Telescope

Proposed Launch Date:

August 2011

http://ngst.gsfc.nasa.gov/

http://ngst.gsfc.nasa.gov/

Supernova


Amount of ordinary matter

A

mount

of

“anti

gra

vit

y”

matt

er

“Ordinary” non accelerating matter

Here for inflation

Proposed new experiment

The SNAP Satellite

The future of cosmological data

• The LSST (Large-aperture Synoptic Survey Telescope) NB: the director of LSST is Prof Tony Tyson of UCD

The future of cosmological theory

• The new data will allow us to resolve hotly contested issues

• Expect progress on:

•Can we explain/understand the beginning of the universe?

• What is accelerating the universe?

• What caused the galaxies to form?

•What is the fundamental nature of matter and gravity?

For the future:

-I hope this course has made you better able to understand new results as they are reported in the press.

-Feel free to come around to my office hours at any time in the future with questions.

- Perhaps some of you would like to make a career in cosmology research (feel free to see me & discuss that)

concluding comments for the course cosmology fascinating past highly accomplished present (for...

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