Title: Tak Kaneko, Astrophysics, Cavendish,
1The Cosmic Microwave Background Radiation
- Tak Kaneko
- Astrophysics Group, Cavendish Laboratory,
- University of Cambridge
- Amateur Astronomy Talk 5th July 2005
2CMB Situation in 1999
- From http//ulysse.iap.fr/CMB/index.htm
3CMB Situation in 2004
- From the WMAP Science Team http//lambda.gsfc.nas
a.gov/product/map/
41948 Relic of the Big Bang
- Alpher and Herman proposed that it should be
possible to detect the afterglow of the big bang
(ie. The CMB). - But their proposal was largely ignored
5CMB Spray Can Analogy
- When you spray deoderant, it feels cold.
- This is because the gas cools as it expands on
being released from the spray can. - Similarly, in the early Universe, energy was
concentrated in a small space so it was hotter.
6CMB Redshift Explanation
- The early Universe 30,000 years after the big
bang was - Hot (3000K)
- Filled with radiation.
- As the Universe expanded, the fabric of spacetime
was stretched 1,000-fold.
7CMB Redshift Explantion
- This stretches the wavelength of light
1,000-fold. - Longer wavelengths are less energetic and
colder (think X-ray vs radio). - We should be able to observe these colder light
permeating the Universe.
8The Surface of Last Scattering
- The CMB dates from 379,000 years after the big
bang and is called the surface of last
scattering. - It reaches us largely unimpeded, so it is 13
billion year old light. - We cannot see beyond the CMB using
light/radio/X-rays. The surface of last
scattering is like the surface of the sun.
9Cosmology in the Early 1960s
- By the early 1960s, cosmologists were divided
5050 between the big bang camp and the
steady-state camp.
10Renewed Interest in the CMB
- 1964-65 Robert Dicke realises it should be
possible to detect the relic of the big bang. - James Peebles calculates the necessary conditions
in the early Universe.
Dicke and Peebles.
11Dicke, Roll and Wilkinson
- Roll and Wilkinson made and instrument and before
they could get any data - Arno Penzias was told about Dicke and Peebles
work by Bernard Burke from MIT in a chance
meeting.
David Wilkinson
12Penzias and Wilson
- Penzias Wilson at the Bell Labs began
converting a communications antenna in 1963. - They were unable to account for around 10 of the
noise.
13The Excess Noise
- They checked everything Galactic and
extragalactic sources, emissions from New York
City, interference from the ground, pigeon
nesting in the antenna
14Well boys. Weve been Scooped. -Dicke
- Dicke visited Penzias Wilson and realised that
their noise was the CMB. - Penzias Wilson measured a CMB temperature of
3K, compared to Alphers prediction of 5K.
Penzias Wilson receiving the 1978 Nobel Prize.
15Post-1965
- Most cosmologists switched to the big bang camp.
- The CMB had a characteristic temperature of 3K
and uniform in all direction. - But, the early universe couldnt have been
completely uniform, otherwise we wouldnt have
structures today like galaxies and human beings.
16Part II Ripples in the Sky
17Structure Formation
- For galaxies and human beings to form, there must
have been seeds of imperfections in the early
Universe.
http//uchicago.edu/lss/filaments.html
18Ripples in the CMB
- Late 1960s Peeble Yu in Princeton and
Zeldovich Sunyaev in Russia independently
realised that the early universe would have
contained sound waves. - The sound waves (or density variation) would have
imprinted themselves on the CMB.
191992 COBE
- NASAs COBE satellite determined the CMB
temperature to 2.7K and detected structures in
the CMB to 1 part in 100,000.
20A Few Problems
- What seeded the variations in the CMB?
- Two patches of the CMB a few degree apart were
never in causal contact. So how come they have
the same temperature?
21Flatness Problem
- Mass energy in the Universe curves spacetime.
- The geometry can be inferred by measuring the
angles of a triangle. - Peculiarly, the Universe is very close to being
flat.
221981 Guth Inflation
- In the first 1000 billionth of a second, the
Universe may have undergone rapid expansion. - This solves the horizon problem and the flatness
problem. - Quantum fluctuation seeded the Universe with tiny
imperfections.
23High Resolution Imaging
CAT, Cambridge
CBI, Atacama Desert
Boomerang, Antartica
- Starting the late 1990s, a number of ground-based
instruments detected the CMB anisotropies.
242003 WMAP
- Launched in 2001
- Improved the resolution of the CMB.
25CMB Power Spectrum
26What WMAP Tells us
- The Universe is 13.7 Byrs old (to 1)
- CMB dates from 379,000 years after the big bang.
- Universe is close to being flat.
- First stars formed 200 million years after the
big bang.
27Inflation Put to the Test
- Fits the observations remarkably well.
- But requires massive extrapolation of the laws of
physics to explain why and how inflation happens. - Still open to debate. (Inc)
28Part III The Future
29CMB Polarisation
- Inflation predict that gravitational waves were
produced during the rapid expansion. - Gravitational waves would have left
characteristic (B-mode) polarisation patterns in
the CMB.
30CMB Polarisation
Simulated image from http//cosmologist.info/lensp
ix/
31CMB Polarisation Current Status
32Planck Satellite
- European Space Agencys new CMB satellite.
- Launch in 2007
33Planck Expected Sensitivity
34Summary
- The CMB has dramatically advanced our
understanding of the Cosmos. - The big bang paradigm has so far passed tests
drawn from many corners of astronomy physics
(A) - Inflation seems to fit observations so far but
requires huge extrapolation of the laws of
physics (Inc). - Other problems remain The nature of dark matter
and dark energy. - Adopted from James Peebles article in Scientific
American, The Once and Future Cosmos
35Bonus Slides
361998 Supernovae 1A Results infer accelerating
expansion
37Hubble Deep Field North South
38(No Transcript)
39Geometry of The Universe
40Horizon Problem
41DASI CMB Polarisation