How the Universe got its Spots

1
How the Universe got its Spots

• Edmund Bertschinger
• MIT Department of Physics

2
Outline

• Introduction the Big Bang
• Cosmic Microwave Background Radiation
• A sonogram of the early universe
• What have we learned?
• Outstanding questions

3
NASA/WMAP Science Team
4
(No Transcript)
5
The Big Bang

• The Universe as we know it began 13.7 billion
  years ago in an explosion so powerful that space
  itself was propelled outwards.
• Even atoms could not exist in this hot fireball.
• 380,000 years after the bang, H atoms formed
• 200 Million years later, the first stars formed
• How do we know?

6
Measuring the Afterglow of the Big Bang
Wilkinson Microwave Anisotropy Probe (WMAP) Launc
hed Summer, 2001 (NASA/WMAP Science Team)
7
The Cosmic Microwave Background Radiation From
COBE (1994) to WMAP (2003)
NASA/WMAP Science Team
8
What is the Microwave Background?
The cosmic microwave background radiation is the
thermal (blackbody) radiation emitted by the hot
dense gas formed in the Big Bang. It was
discovered by Penzias and Wilson in 1965 they
received the Nobel Prize in 1978. Animation
9
WMAP Actual Sky Maps
Our View Before WMAP
Top Foregrounds removed. Bottom 41 GHz
NASA/WMAP Science Team
10
A cosmic sonogram

• The Big Bang began with a burst of
  near-exponential expansion cosmic inflation
• Quantum mechanical fluctuations in energy made
  ripples in the gasAnimation
• Fluctuations in radiation Sound waves!
• Light as sound?! Yes!
• Cosmic redshift Doppler shift in an expanding
  universe

11
The Sonogram in NumbersAngular Power
SpectrumTop Temperature fluctuations vs.
angular scaleBottom Cross-correlation of
temperature and linear polarizationvs. angular
scale
12
What have we learned from these spectra?

• Age, size, and curvature of the universe
• 13.7 Billion yr, consistent with infinite
  Euclidean space on scales of 50 Billion lt-yr
• Contents of the universe bizarre!
• 4 atoms (almost all Hydrogen and Helium)
• 23 cold dark matter (elementary particles as yet
  undiscovered on Earth) detected by its attractive
  gravity
• 73 mysterious dark energy (were not even sure
  of the physics of this substance!) detected by
  its repulsive gravity causing the cosmic
  expansion to accelerate
• Hydrogen was re-ionized about 200 Myr after BB

13
We are not made of the same type of matter as
most of the Universe!
14
The WMAP results greatly improve our estimates of
cosmic parameters. Four years ago, cosmologists
proposed an accelerating universe. WMAP (in
green) strongly confirms this.
15
We have seen the seeds of cosmic structure
animation
NASA/WMAP Science Team
16
(No Transcript)
17
Outstanding questions

• What is the dark energy?
• Is it the cosmological constant?
• What new physics acts on cosmic scales to produce
  this substance?
• What is the dark matter?
• Can we now fully understand the formation of
  galaxies?