How Big is the Universe?

Really big!The Sun is 8 light minutes away.

There are 1011 stars in our galaxy.

COBE/DIRBE satellite image

The center of our Galaxy is 25,000 light years away.

The Milky Way in infrared emission.

From Hubble

STScI/NASA Field & Levay1011 Galaxies in Observable Universe

The Universe is ExpandingHubble observed that the further away a galaxy is the faster it is moving away.

Us Galaxy

We are not (that!) special, all observers see the same. A neighbor

We should think about this as “making space” since the Big Bang, not as an explosion in a preexisting space. The Universe appears the same from all vantages.

The Universe is Infinite. We live in a “Hubble Patch”

Diameter set by:

2 (speed of light) x (age of universe)

Observable Universe or Hubble Patch

“Edge” of the observable universe

Ignore the expansion and imagine being able to go anywhere in the “whole universe” instantaneously

Because the Speed of Light is Finite, Telescopes Are Like Time Machines

We see distant objects as they were when they were younger.

“Edge” of the observable universe

Still ignoring the expansion

Younger

Now Add The Expansion

Light from the “edge” was emitted when the universe was much more compact.

The expansion of space stretches wavelengths.

“Edge” of the observable universe

Younger

The Standard Model of Cosmology

Surface of last scattering at “decoupling.”

“Reionization”

Decoupling of the CMB

The universe expands and cools from its fiery beginning.

When the temperature of the Universe is roughly half the temperature of the Sun, atoms of hydrogen can form.

This is called the epoch of decoupling and it occurred 379,000 years after the Big Bang.

-e

-e -e-e

Neutral atomsIonized

plasma

Universe cools CMBproton

The Standard Cosmological Model

Surface of last scattering at “decoupling.”

“Reionization”

Mark Subbarao & SDSS Collaboration

How Do We Measure the CMB?

With the expansion of the universe, the CMB has cooled to -270 oC, or 2.725 oC above absolute zero.

The CMB is about 1000 times cooler than the Sun and so “shines” in the microwave regime.

TV Channel 69 broadcasts at 800 MHz

CMB approx 1% of TV noise!

You’ve all detected the CMB!

(COBE announcement, 4/92)

Dave Wilkinson

Wilkinson Microwave Anisotropy Probe.

UBCMark Halpern

JPLOlivier Dore

NASA/GSFCBob Hill Gary Hinshaw Al KogutNils OdegardJanet WeilandEd Wollack

PrincetonNorm Jarosik Lyman PageKendrick SmithDavid Spergel

ChicagoStephan MeyerHiranya Peiris

BrownGreg Tucker

UCLANed Wright

Science Team:

WMAPA partnership between NASA/GSFC and Princeton

Johns HopkinsChuck Bennett (PI)Ben GoldDavid Larson

CornellRachel Bean

MicrosoftChris Barnes

CITAMike Nolta

ICELicia Verde

UT AustinEiichiro Komatsu

OxfordJo Dunkley

ColumbiaMichele Limon

K Band, 22 GHz, 1.4 cm

Ka Band, 33 GHz, 1 cm

Q Band, 41 GHz, 0.7 cm

V Band, 61 GHz, 0.5 cm

W Band, 94 GHz, 0.3 cm

5º

How do we get hot and cold patches?

Gravitational landscape--just like hills and valleys.

ColderColder

Hotter

Spot size = [speed plasma ( ) travels]x[age of universe at decoupling]

1 degree in angle

W. Hu

The “fundamental mode” acts as a fundamental “footprint” or yardstick at the edge of the observable universe.

This allows us to determine the size of the observable universe.

Us

(12,000 stacked hot spots.)

deg

Cosmic Paleontology

From the standard yardstick, we can deduce the distance to the edge of the universe.

Knowing this distance, and the speed of light, we deduce that the age of the universe is:

tU=13.75 +/- 0.13 Gyr

Basic model (with only six parameters) agrees with virtually all cosmological measurements.

Parameters of the Model

4.6%22.6% 72.8%

The “dark energy” has no foundation in any fundamental theory of nature.

It is as though the vacuum has an energy associated with it that drives the universe apart, like antigravity.

Most feel that “dark energy” represents a missing piece of theory as opposed to a substance.

The Standard Cosmological ModelAt a very early time a “quantum field” impressed on the universe a gravitational landscape. We measure characteristics of this field.

Abbreviated

This is a picture of a quantum field from the birth of the universe.

Matter fell into the valleys to form eventually “structure.” But only 1/6 of this matter is familiar to us.

The dynamics of the universe is now driven not so much by the matter but by an apparent