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Tak Kaneko, Astrophysics, Cavendish,

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Amateur Astronomy Talk 5th July 2005. Tak Kaneko, Astrophysics, Cavendish, ... from New York City, interference from the ground, pigeon nesting in the antenna... – PowerPoint PPT presentation

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Title: Tak Kaneko, Astrophysics, Cavendish,


1
The Cosmic Microwave Background Radiation
  • Tak Kaneko
  • Astrophysics Group, Cavendish Laboratory,
  • University of Cambridge
  • Amateur Astronomy Talk 5th July 2005

2
CMB Situation in 1999
  • From http//ulysse.iap.fr/CMB/index.htm

3
CMB Situation in 2004
  • From the WMAP Science Team http//lambda.gsfc.nas
    a.gov/product/map/

4
1948 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

5
CMB 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.

6
CMB 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.

7
CMB 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.

8
The 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.

9
Cosmology in the Early 1960s
  • By the early 1960s, cosmologists were divided
    5050 between the big bang camp and the
    steady-state camp.

10
Renewed 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.
11
Dicke, 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
12
Penzias 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.

13
The Excess Noise
  • They checked everything Galactic and
    extragalactic sources, emissions from New York
    City, interference from the ground, pigeon
    nesting in the antenna

14
Well 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.
15
Post-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.

16
Part II Ripples in the Sky
17
Structure 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
18
Ripples 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.

19
1992 COBE
  • NASAs COBE satellite determined the CMB
    temperature to 2.7K and detected structures in
    the CMB to 1 part in 100,000.

20
A 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?

21
Flatness 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.

22
1981 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.

23
High Resolution Imaging
CAT, Cambridge
CBI, Atacama Desert
Boomerang, Antartica
  • Starting the late 1990s, a number of ground-based
    instruments detected the CMB anisotropies.

24
2003 WMAP
  • Launched in 2001
  • Improved the resolution of the CMB.

25
CMB Power Spectrum
26
What 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.

27
Inflation 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)

28
Part III The Future
29
CMB 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.

30
CMB Polarisation
Simulated image from http//cosmologist.info/lensp
ix/
31
CMB Polarisation Current Status
32
Planck Satellite
  • European Space Agencys new CMB satellite.
  • Launch in 2007

33
Planck Expected Sensitivity
34
Summary
  • 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

35
Bonus Slides
36
1998 Supernovae 1A Results infer accelerating
expansion
37
Hubble Deep Field North South
38
(No Transcript)
39
Geometry of The Universe
40
Horizon Problem
41
DASI CMB Polarisation
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