The Milky Way, The Milky Way, Schroedinger’s Cat,Schroedinger’s Cat,

and Youand You

Thursday, September 23, 2004 Astronomy 2 (ASTR –002-02) Kresge Town Hall Overview of the Universe

Raja Guha Thakurta(in collaboration with Sandra Faber)

UCO/Lick ObservatoryUniversity of California at Santa Cruz

Galaxies, the Building Blocks of the UniverseGalaxies, the Building Blocks of the Universe

Your Cosmic HistoryYour Cosmic History(an astronomer’s perspective)(an astronomer’s perspective)

You!Protein molecules:Basic building blocks of life

Earth and Sun:Home of the C,N,O atoms from which

these protein molecules were assimilated

Sun’s ancestral stars:Their nuclear fusion reactionsproduced these C,N,O atoms

Galaxy:Large familyof stars

You are here!

Relatives of the Milky Way

Milky Way

Where did the Milky Way Come From?

The Answer Will Take Us Back to the Earliest

Moments of the Universe

The Cosmic Web of Galaxies

Formation of Cosmic Structures Under the Influence of Gravity

A Computer Simulation

-

+

Points to Ponder

• Our bio-chemical history links us to Our bio-chemical history links us to galaxiesgalaxies

• The Milky Way and other galaxiesThe Milky Way and other galaxies

• Galaxies like to live near one anotherGalaxies like to live near one another

• The formation of galaxies: The growth of The formation of galaxies: The growth of primordial density fluctuationsprimordial density fluctuations under the under the influence of influence of gravitygravity

But Where Did the “Seeds” of Cosmic

Structure Come From?

Quantum Noise

Nu

mb

er o

f k

ern

els

pop

pin

g p

er m

inu

te

0

2

0

4

0

0 10 20 30 Time

N

um

ber

of

rad

iact

ive

dec

ays

per

min

ute

0

20

40

Position in Space

En

ergy

den

sity

of

the

Un

iver

se0

0

.999

95

1.0

0000

0.

9995

1.0

000

0.

995

1.0

00

0.5

1.0

Schroedinger’s CatSchroedinger’s Cat(a “thought experiment” by Erwin Schroedinger)(a “thought experiment” by Erwin Schroedinger)

…or…

???

R.I.P.

InflationInflation

A rapid and dramatic phase of expansion shortly after the Big Bang A rapid and dramatic phase of expansion shortly after the Big Bang blows up these quantum fluctuations and “freezes” them into the blows up these quantum fluctuations and “freezes” them into the fabric of the Universe. These are the seeds of cosmic structure.fabric of the Universe. These are the seeds of cosmic structure.

Points to Ponder

• The Universe is Nature’s ultimate example of The Universe is Nature’s ultimate example of Schroedinger’s catSchroedinger’s cat

• InflationInflation is a very, very brief period of extremely is a very, very brief period of extremely rapid expansion in the infancy of the Universe rapid expansion in the infancy of the Universe

• We have We have quantum mechanicsquantum mechanics and and gravitygravity to to thank for the existence of galaxies like our thank for the existence of galaxies like our Milky Way and indeed for our own existenceMilky Way and indeed for our own existence

Prediction #1

Galaxy collisions should be common and easily

visible

Computer Simulation of Colliding Galaxies

And This Is What We See…..

Prediction #2

“Infant” galaxies should look different from mature galaxies

Zooming into Deep Space, Looking Back in Time

Zooming into Deep Space, Looking Back in Time

Distant Galaxies Are Small and Ragged

Infant galaxy

Young galaxy

Mature galaxy

Deepest Image of Distant Galaxies

The Hubble Space Telescope is in orbit above the Earth’s atmosphere and so is able to take sharp pictures……but…..

A new method called “Adaptive Optics” allows us to sharpen the vision of telescopes that are on the ground, by

correcting for the blurring caused by the Earth’s atmosphere

….. it is prohibitively expensive to build telescopes that are based in space

Prediction #3

The farthest things we see should be the early

seeds of galaxies

Early Seeds: Fluctuations in the Microwave Background Radiation

Maps

Points to Ponder

• Galaxy cannibalismGalaxy cannibalism is a common phenomenon is a common phenomenon in which small serve as in which small serve as buildingbuilding blocksblocks from from which larger galaxies are assembledwhich larger galaxies are assembled

• Telescopes are Telescopes are time-machinestime-machines that enable us to that enable us to peer into the Universe’s distant pastpeer into the Universe’s distant past

• The The after-glowafter-glow from the Big Bang and early from the Big Bang and early hot phase of the Universe is visible today and hot phase of the Universe is visible today and indeed even the indeed even the wrinkleswrinkles on the face of the on the face of the early Universe are visibleearly Universe are visible

Infant galaxy Spiral galaxy

like our own

Sun’s stellar ancestors

Completing the Cycle……

Our planet & starProtein moleculeYou!