Eddington ryle and hoyle
Sponsored Links
This presentation is the property of its rightful owner.
1 / 30

Eddington, Ryle and Hoyle PowerPoint PPT Presentation

  • Uploaded on
  • Presentation posted in: General

Eddington, Ryle and Hoyle. Jasper Wall. How a major 20th Century discovery was lost in noise and confusion. What were the great surprise discoveries of the 20th century?. Richard Ellis, arXiv:0701024:. Cosmic expansion (Slipher and Hubble 1917-1925)

Download Presentation

Eddington, Ryle and Hoyle

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript

Eddington, Ryle and Hoyle

Jasper Wall

  • How a major 20th Century discovery

  • was lost in noise and confusion

What were the great surprise discoveries of the 20th century?

Richard Ellis, arXiv:0701024:

  • Cosmic expansion (Slipher and Hubble 1917-1925)

  • The Hot Big Bang (Penzias and Wilson 1965)

  • Dark Matter (Zwicky 1933; Rubin et al 1976; Blumenthal et al 1984)

  • Cosmic acceleration (Riess et al 1998, Perlmutter et al 1999) => Dark Energy

Other Candidates?

  • Synchrotron emission and the Galactic Centre and background (1935-1950)

  • EG Radio sources / X-ray sources => Quasars => Black Holes (1947-1970), AGNs

  • Pulsars (1968) => neutron stars

  • GRBs ~1986

  • Sub-millimetre galaxies (1997)

  • Evolution of star-formation rate (1994-1996)

Missing from any list?

  • The discovery that objects in the Universe undergo dramatic cosmic evolution in luminosity or density (1955-1960)

Sir Martin Ryle 1918 - 1984

Radar pioneer, 1939-1945

Ryle and Vonberg 1946 - first

interferometric radio astronomy

First sky surveys 38 - 159 MHz, 1950 - 55

Ryle and Hewish 1960 - Aperture synthesis

Ryle and Neville (Anne Gower) 1962 -

‘deep’ synthesis map at NCP

Gold medal of the RAS 1966

Nobel prize 1974 (with Tony Hewish - aperture synthesis / pulsars)

Ryle 1955, the Halley Lecture; Ryle and Scheuer 1955

1. The number-intensity distribution of the observed radio stars shows that they cannot be interpreted

in terms of a homogeneous distribution of sources - there is an apparent increase in the spatial density

or absolute luminosity of distant sources.

2. This increase is, within rather small statistical errors, independent of direction. It appears that the solar

system is situated at the centre of a spherical region in which the spatial density or luminosity

of the sources increases with distance, uniformly in all directions.3. It is impossible to explain the results in terms of sources situated within the galaxy, or by irregular

clustering of extra-galactic sources.

4. From limits to the integrated radiation, the minimum radius of the spherical region is comparable with that of

the optically observable universe.

5. We suggest that the observed features are due to effects on a cosmical scale; there seems every reason to

suppose that they might be explained in terms of an evolutionary theory.

6. A general explanation of the observations seems possible if it is supposed that the majority of radio stars

belong to an excessively rare class of object, having a local spatial density of about 2 × 10-26 pc-3, and an absolute

luminosity comparable with that of the intense radio source in Cygnus.

7. On this interpretation, the difficulty of identifying radio stars with optical objects finds a natural explanation;

only some tens of the main class of radio star would be within reach of the 200 in. telescope.

The notorious 2C Survey source count

The slope of this integral count was ~ -2.7,

c.f. initial slope for uniformly filled universe of -1.5

1906 sources in 2C; the majority of them would prove to be false


1. Eddington bias

2. Confusion

Sir Arthur Eddington 1882 - 1944

  • astrophysicist (Eddington limit)

  • astronomer (1919 eclipse expedition = > GR is right)

  • cosmologist (General Relativity)

  • mathematician (Clifford algebra, Dirac law of large numbers)

  • popularist (brilliant expositor of GR on all levels, very well known to the British public)

A little paper in 1913 MNRAS by Eddington: On a formula for correcting statistics for the effects of a known error of observation

Eddington bias rediscovered by

Submm Galaxy researchers

Eddington bias: a simulation

Left: Red points show a source count (number of sources on the `sky' per interval of 2 units in flux) from a toy Euclidean universe. The green line is the theoretical power law of slope -5/2. The blue points represent the distorted source count resulting from Eddington bias assuming a Gaussian flux measurement error of σ = 5 units. Black crosses represent the analytical calculation N’(S)=∫N(S)p(S)dS.

Right: plots of the integrand N(S)p(S) for apparent flux densities of 15, 20, 30 and 40 units (3σ, 4σ, 6σ, 8σ) given an underlying law of slope -5/2 and Gaussian errors ofσ= 5 units.

3σ is hopeless; 4σ is still seriously biased


A (double) 2.7-GHz sky integration to the confusion limit

Second integration: all features are duplicated

  • NB - dual-beam differencing feed system, HPBW 8’

  • - only believe sources at level of > 30 beam-areas per source

    • - perhaps the 4 largest deflections represent real sources

  • - confusion is highly non-Gaussian

  • Sir Fred Hoyle (1915 - 2001)

    Yet another radar pioneer (1939-45)

    (Developed the Lloyd’s mirror height

    measurement technique for aircraft)

    Marvellous radio presenter and publicist, wrote good SF

    Brilliant theorist, physicist, cosmologist

    - Tidal torques / galaxy angular momentum

    - B2FH (1957) - why we exist

    - Steady-State theory 1948 (with Bondi and Gold)

    - Primordial He abundance in HBB (with Tayler, 1966)

    - panspermia, viruses from comets drive our evolution ...

    - non-cosmological redshifts, quasi-Steady State (1993)...

    Gold medal of the RAS 1968

    What had Hoyle and Ryle in common?

    • Radar developers 1939 - 1945

    • Left wing socialists (who both accepted knighthoods!)

    • Anti-war

    • Brilliant, lightning-fast, lateral-thinking minds

    • Environmental activists before the days of global warming

    • Cambridge - Hoyle founded IoA, Ryle founded Mullard Radio Astronomy Observatory of the Cavendish Lab

    How did they interact?

    • Fought at every opportunity like cats and dogs.

    • Different research leadership philosophies; Ryle built his institute with his group; Hoyle built his with funds to attract visits from the best.

    • 1948 - First public argument over the nature of solar radio bursts; they were both wrong.

    • 1951 - Ryle claimed radio stars were local (Galactic); Hoyle claimed no evidence one way or the other; Gold ventured that they might be some strange galaxies, like Seyferts. He was attacked from all sides for 30 min.

    • 1955 “Ryle and Hoyle again went after each other like mongoose and cobra” (Sullivan, `Cosmic Noise’)

    After 2C - What happened?

    • Scheuer P(D) 1957, Hewish: true slope is -1.7

    • Mills ~1957; true slope is -1.8 or maybe -1.65, and the 2C catalogue is mostly garbage (overlap survey with a pencil beam)

    • Paris IAU 1958: radio astronomy in disarray

    MSH: slope -1.8

    P(D) and confusion again:

    And then?

    • QSOs (quasars) 1960-1965; 3C273 in 1963, z=0.16

    • Additional sky surveys at Cambridge, Parkes > initial slope was -1.7 or -1.8

    • Hoyle, Burbidge, Arp: non cosmological redshifts, to make counts and Steady-State compatible; but also to solve the Compton catastrophy

    • 1965 CMB Penzias & Wilson => HBB. Who cares about source counts?

    • 1968 Schmidt V/Vmax test on 35 3CR QSOs: evolution taken seriously in the USA!

    The Parkes 2.7-GHz survey

    Wall et al. 1971, et seq => 1976

    At last a decent pencil beam survey at a ‘high’ frequency!

    2.7 GHz, 11cm

    Twin beams 8.0 arcmin FWHM

    > 30 beam areas per source

    Most of southern sky up to dec +15o

    From the first 0.4 sterad (Shimmins et al 1968)

    • 40% of the objects had ‘flat’ radio spectra

    • most of these identified with BSOs => QSOs

    • source count slope almost exactly -1.5

    • markedly flatter than counts from the low frequency (178 MHz) Cambridge surveys (from which we now believed the results)

    • Long discussions with Hoyle and Bolton

    Shimmins, Bolton and Wall 1968 Nature

    Short intermission: the Apollo 11 moon walk

    20 July 1969

    Parkes 210-ft (64m) dish

    My first cosmo calculations: 1969-70

    The radio ‘m - log π diagram’

    following Sandage’s suggestion

    My first cosmo calculations: 1970 results

    Shimmins, Bolton and Wall 1968 Nature

    Wall thesis 1970

    No uniformly-filled relativistic universe count remotely resembles the observed count

    1974 - 1979 JVW

    • 1974 - JVW to Cavendish Lab, MRAO (with a little help from Malcolm Longair and Martin Ryle)

    • Sums done properly with Malcolm Longair and Tim Pearson (Wall Pearson & Longair 1976/7 et seq.)

    • 1976 `Radio Astronomy and Cosmology’ IAU 74 - Ryle and Burbidge were still arguing.

    1 chance in 1080

    1 chance in 10960

    Ryle and Hoyle 1974 =>

    • Ryle became ill ~1978, but had already drawn away from radio astronomy towards alternate (green) sources of energy. Strange propellers (windfarm prototypes) were emerging from the radio astronomy workshop. He kept his promise to me - he never went to a conference after the 1976 IAU.

    • Hoyle stuck to Steady State and with Burbidge and Narlikar pursued `Quasi-Steady-State’, non cosmological redshifts, CMB produced by reflecting needles in the ionosphere. See A Different Approach to Cosmology: from a Static Universe through the Big Bang towards Reality (2000; CUP). See also Home is Where the Wind Blows (CUP 1994), Hoyle’s autobiography. He continued to publish on dust grains, comets, life from space, non-cosmological redshifts, etc up to his death in 2001.

    What were the great surprise discoveries of the 20th century?

    Richard Ellis, arXiv:0701024: + JVW

    • Cosmic expansion (Slipher and Hubble 1917-1925)

    • Cosmic evolution of a population of galaxies (Ryle and Scheuer 1955)

    • The Hot Big Bang (Penzias and Wilson 1965)

    • Dark Matter (Zwicky 1933; Rubin et al 1976; Blumenthal et al 1984)

    • Cosmic acceleration (Riess et al 1998, Perlmutter et al 1999) => Dark Energy

    Modern radio-source counts

    150 MHz

    1.4 GHz

    408 MHz

    610 MHz

    5.0 GHz

    8.4 GHz

    15-20 GHz

    The original arguments concerned the counts in the small boxed area, 150 MHz.

    Galaxy evolution accepted 1980 ->

    e.g. galaxy evolution via number-magnitude counts

    Shanks et al. 1984



    Evolution discovered in star-formation rateLilly-Madau (1996) diagram: a modern version:

    Hopkins 2007

    An ‘AGN epoch’ accepted; similar in form to SFR

    Wall, Pope & Scott 2008

    Radio QSOs, X-ray QSOs, SMGs

    Radio QSOs, Star-formation rate

    Semi-analytic galaxy formation

    Croton et al. 2006, Bower et al. 2006:

    To effect cosmic downsizing, invoke a radio AGN phase to blast the cool gas out of the galaxy =>

    Galaxy-makers have found a use for radio AGN at last!

    Springel et al. 2005


    • Personal sadness to see two giants of science place

      themselves in such a situation. Why could they not

      collaborate? e.g. Penzias & Wilson / Dicke, Peebles et al.......

    • Hoyle and Ryle were both seriously affected.

    • The course of cosmology/galaxy formation should have been

      altered. It took years.....

    • Competitiveness is essential; perspective even more so.

    • Perhaps some results come ahead of their time? e.g. DM,

      Zwicky 1933.

  • Login