The Early Universe
as seen by the Cosmic Microwave Background
The Early Universe
as seen by the Cosmic Microwave Background
Eiichiro Komatsu
University of Texas at Austin TAMEST Meeting, January 4,
2007
Eiichiro Komatsu
University of Texas at Austin TAMEST Meeting, January 4,
2007
Our Universe Is Old Our Universe Is Old
The latest determination of the age of our Uni verse is:
13.730.16 billion years
How was it determined?
In essence, (time) = (distance)/c was used.
“Distance” to what??
It must be a distance to the farthest place we could reac h. The Rule: “Farthest Place” = “Earliest Epoch”
For the errorbar to make sense, obviously it must be ear
The latest determination of the age of our Uni verse is:
13.730.16 billion years
How was it determined?
In essence, (time) = (distance)/c was used.
“Distance” to what??
It must be a distance to the farthest place we could reac h. The Rule: “Farthest Place” = “Earliest Epoch”
For the errorbar to make sense, obviously it must be ear
The Most Distant Galaxy?
The Most Distant Galaxy?
Going Farther…
Going Farther…
QuickTime™ and a YUV420 codec decompressor are needed to see this picture.
How far have we reached?
How far have we reached?
Our Universe is 13 billion 730 million y ears old.
The most distant g alaxy currently kno wn is seen at 800 million years after t he Big Bang.
1/17 of the age of t he Universe today
Our Universe is 13 billion 730 million y ears old.
The most distant g alaxy currently kno wn is seen at 800 million years after t he Big Bang.
1/17 of the age of t he Universe today
How far can we reach?
How far can we reach?
Galaxies cannot be used to determine the age o f the Universe accurately.
Distant galaxies are very faint and difficult to find.
Fundamental “flaw” in this method: galaxies can not be as old as the Universe itself --- after all, it takes some time (~hundreds of millions of year s) to form galaxies.
So, is 800 million years after the Big Bang th e farthest place we can ever reach?
Galaxies cannot be used to determine the age o f the Universe accurately.
Distant galaxies are very faint and difficult to find.
Fundamental “flaw” in this method: galaxies can not be as old as the Universe itself --- after all, it takes some time (~hundreds of millions of year s) to form galaxies.
So, is 800 million years after the Big Bang th e farthest place we can ever reach?
NO!
Night Sky in Optical (~0.5nm) Night Sky in Optical (~0.5nm)
Night Sky in Microwave (~1mm) Night Sky in Microwave (~1mm)
Full Sky Microwave Map Full Sky Microwave Map
Penzias & Wilson, 1965
Uniform, “Fossil” Light from the Big Bang
-Isotropic (2.7 K everywhere) -Unpolarized
Galactic Center
Galactic Anti- center
A. Penzias & R. Wilson, 1965 A. Penzias & R. Wilson, 1965
CMB
T = 2.73 K
Helium Supe rfluidity T = 2.17 K
QuickTime™ and a Sorenson Video decompressor are needed to see this picture.
COBE/DMR, 1992 COBE/DMR, 1992
Isotropic?
CMB is anisotropic! (at th e 1/100,000 level)
COBE to WMAP COBE to WMAP
COBE
WMAP
COBE 1989
WMAP 2001
[COBE’s] measurements als o marked the inception of co smology as a precise science . It was not long before it was followed up, for instanc e by the WMAP satellite, whi ch yielded even clearer imag es of the background radiati on.
Press Release from th e Nobel Foundation
CMB: The Most Distant Light CMB: The Most Distant Light
Use Ripples in CMB to Measure Composition of the Universe
Use Ripples in CMB to Measure Composition of the Universe
The Basic Idea: Hit it and listen to the sound.
Analogy: Brass and iron can be discriminated by hitting them and liste ning to the sound created by them.
We can use sound waves to determine composition
When CMB was emitted the Universe was a dense and hot so up of photons, electrons, protons, Helium nuclei, and dark mat ter particles.
Ripples in CMB propagate in the cosmic soup: the pattern of the rippl es, the cosmic sound wave, can be used to determine composition of the Universe!
The Basic Idea: Hit it and listen to the sound.
Analogy: Brass and iron can be discriminated by hitting them and liste ning to the sound created by them.
We can use sound waves to determine composition
When CMB was emitted the Universe was a dense and hot so up of photons, electrons, protons, Helium nuclei, and dark mat ter particles.
Ripples in CMB propagate in the cosmic soup: the pattern of the rippl es, the cosmic sound wave, can be used to determine composition of the Universe!
QuickTime™ and a
Sorenson Video decompressor are needed to see this picture.
Composition of Our Universe Determined by WMAP
Composition of Our Universe Determined by WMAP
Dark Energy
Ordinary Matter Dark
Matter
76%
20%
4%
Mysterious “Dark Energy”
occupies 75.93.4% of the total energy of the Universe.
A Big, Big Challenge A Big, Big Challenge
Let’s face it: “WMAP has done a great job in determ ining composition of our Universe very accurately, b ut…”
We don’t really understand the nature of dark energy or d ark matter. They occupy 96% of the total energy in our U niverse!
Even the most optimistic cosmologists would not dare to say, “we understand our Universe”. Definitely not.
The next frontier: What is the nature of dark energy and dark matter?
Let’s face it: “WMAP has done a great job in determ ining composition of our Universe very accurately, b ut…”
We don’t really understand the nature of dark energy or d ark matter. They occupy 96% of the total energy in our U niverse!
Even the most optimistic cosmologists would not dare to say, “we understand our Universe”. Definitely not.
The next frontier: What is the nature of dark energy and dark matter?
A Holy Grail: Go Even Farther Back…
A Holy Grail: Go Even Farther Back…
We cannot use CMB to probe the epoch earlier t han 380,000 years after the Big Bang directly.
Photons were scattered by electrons so frequently tha t the Universe was literally “foggy” to photons.
We would need to stop relying on photons (EM waves). What else?
Neutrinos can probe the epoch as early as a second a fter the Big Bang.
Gravity Waves: the ultimate probe of the earliest mom ent of the Universe.
We cannot use CMB to probe the epoch earlier t han 380,000 years after the Big Bang directly.
Photons were scattered by electrons so frequently tha t the Universe was literally “foggy” to photons.
We would need to stop relying on photons (EM waves). What else?
Neutrinos can probe the epoch as early as a second a fter the Big Bang.
Gravity Waves: the ultimate probe of the earliest mom ent of the Universe.
Go Farther!
Go Farther!
CMB
Neutrino
Gravity Wave
Summary & Conclusions Summary & Conclusions
CMB offers the earliest and most precise picture of the Universe that we have today.
A wealth of cosmological information, e.g.
The age of the Universe = 13.73 billion years
Composition: DE (76%), DM (20%), Ordinary Mat. (4%)
CMB has limitations.
It does not tell us much about the nature of the most dominant energy comp onents in the Universe: Dark Energy (DE) and Dark Matter (DM)
Expect some news on DM from the Large Hadron Collider (LHC) next year.
DE is harder to do. (So we need to fund HETDEX.)
Go beyond CMB.
Neutrinos! (Very low energy: 1.94K -> hard to detect)
Gravity waves! The ultimate cosmological probe.
CMB offers the earliest and most precise picture of the Universe that we have today.
A wealth of cosmological information, e.g.
The age of the Universe = 13.73 billion years
Composition: DE (76%), DM (20%), Ordinary Mat. (4%)
CMB has limitations.
It does not tell us much about the nature of the most dominant energy comp onents in the Universe: Dark Energy (DE) and Dark Matter (DM)
Expect some news on DM from the Large Hadron Collider (LHC) next year.
DE is harder to do. (So we need to fund HETDEX.)
Go beyond CMB.
Neutrinos! (Very low energy: 1.94K -> hard to detect)
Gravity waves! The ultimate cosmological probe.
