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TRANSCRIPT
The steady-state
theory of the
universe
contents
&
contexts
H. Kragh,
Centre for Science Studies,
Aarhus University
The 1950s: is cosmology a respectable science?
The choice between cosmological models remains ”a matter for aesthetic
judgment” (Ernst Öpik, 1954).
Cosmology is a field where ”personal taste will greatly influence the choice
of basic hypotheses” (Oskar Klein, 1953).
”Cosmologists have always lived in a happy state of being able to postulate
theories which had no chance of being disproved” (Martin Ryle, 1953).
“Cosmologists are often in error, but never in doubt” (Lev Landau?)
T. Gold H. Bondi F. Hoyle
The steady-state
theory of the universe
The universe expands
eternally, with continual
creation of matter securing
a constant density of mass.
The Perfect Cosmological
Principle: On a very large
scale, the universe is
uniform both in space and
time.
Wm. McCrea J. Narlikar D. Sciama
Motivations behind the steady-state model
1. The time-scale problem
2. Creation in the past is an unscientific hypothesis
3. Relativistic cosmology is not a theory, but a supermarket of
theories (lack of uniqueness; little predictive power).
4. Only a unchanging universe guarantees that the laws of
physics are constant (repeatability of experiments).
Two early examples of uniform cosmological models.
W. de Sitter, 1931
“In general relativity a very wide range of models is available … The
number of free parameters is so much larger than the number of
observational points that a fit certainly exists.” (Bondi & Gold 1948)
O. Heckmann, 1932
The cosmological controversy: Not a controversy between Gamow (big bang)
and Hoyle (steady state), but between the steady state theory and relativistic
evolution theories.
The Hot Big Bang
In 1948-53, the Big-Bang model
was revived and greatly developed
by George Gamow et al. Their
work led to a “hot”, radiation-
dominated early universe,
calculations of primordially
produced elements, and a
prediction of a cosmic microwave
background (of T ≅ 5 K).
11th Solvay Congress 1958: Structure and evolution of the universe
Although the Solvay congress meant an acknowledgment of cosmology as part of
physics, it included no speakers supporting physical (big bang) cosmology in the style
of Gamow. Of the 12 addresses, 7 were astronomical/astrophysical and 3 were given
by steady-state advocates.
IAU conference, Berkeley 1961
”We admit we are fighting an up-hill battle.”
The perfect cosmological principle
”My guiding principle is … that the Universe in its
essence has always been what it is now: matter,
energy, and life have only varied as to shape and
position in space.”
Svante Arrhenius 1908
”The universe … is not only homogeneous, but also
unchanging on the large scale.”
H. Bondi & T. Gold 1948
Space curvature k = 0 (flat space)
Exponential expansion: R ~ exp(Ht), H constant
Deceleration parameter q0 = -1
Matter density ρ = ρcrit ≈ 5 × 10-28 g cm-3
Matter creation rate = 3ρH ≈ 10-43 g s-1 cm-3
Age of universe: infinite
Average age of galaxies <t> = T/3 ≈ 6 × 108 y
(T ≡ 1/H)
2
22
0
/
RH
dtRdq
Predictions of classical steady-state theory, ca. 1950
A chapter in the history of cosmology
including instructive discussions of
philosophical aspects, and involving scientists
(H. Bondi, T. Gold, G.C. McVittie), philosophers
(R. Harré, A. Grünbaum, N. Russell Hanson), as
well as scientist-philosophers (G.J. Whitrow, H.
Dingle, M. Bunge, R. Schlegel).
The steady-state controversy
”A scientific theory, to be useful, must be testable and vulnerable”
”The steady state model is the one that can be disproved most easily by
observation. Therefore, it should take precedence over other less
disprovable ones until it has been disproved.”
Non-empirical testing:
Does the SS theory lead to consequences that are
contradictory, or highly bizarre?
Whitrow’s paradoxes
1. Infinitely many causally unconnected galaxies that at all
times are empirically unknowable.
2. Infinitely many supermassive galaxies that grow by
accretion of new matter and violate cosmological principle.
3. An infinite past contains actual infinities and is
therefore ruled out (past eternity ≠ future eternity).
Cosmological tests, ca. 1948-1966
1. Time-scale problem
2. Redshift-magnitude relationship
3. Angular diameter-redshift relationship
4. Nucleosynthesis (He and heavier elements)
5. Radio-astronomical source counts
6. Formation of galaxies
7. Cosmic microwave background
7. Logical and methodological arguments
Hubble’s constant
& the time-scale
problem
H = 500 km/s/Mpc
T = 1/H = 1.8 Gy
Lemaître 1927 H0 ≅ 625 km/s/Mpc
Hubble 1931 H0 ≅ 558 km/s/Mpc
WMAP 2010 H0 = 70.1 km/s/Mpc
Sandage et al. 1956:
q0 = 2.5 ± 1
”the steady-state
theory does not fit
the real world.”
Palomar 200-inch Hale telescope
A. Sandage, ”Cosmology: a search for two
numbers,” Physics Today 23: 34-41
Cosmological tests,
1956-64,
magnitude-redshift:
favour evolutionary models
with q0 ≈ (½ …1), but do not
unambiguosly rule out
steady-state model.
m - M ≈ 5 log(cz) + (1 – q0)z
Angular diameter-redshift test
The relation between apparent angular
diameter and redshift depends on q0 and
can therefore be used as a cosmological
test (Hoyle 1958). However, …
log N(S) = const – 1.5 log S
Radio astronomy (Cambridge; Sydney)
Ryle et al. 1955
Ryle et al. 1966
The mass gap problem
How to produce nuclei with A > 8?
Triple alpha (3 12C) not possible.
Fermi (1949): ”This theory is incapable of explaining
how the elements have been formed.”
The 1948 prediction of a cosmic microwave background
R. Alpher & R. Herman, ”Evolution of the universe,” Nature 162 (1948), 774-75.
1965: Discovery of the cosmic microwave background (predicted by R. Alpher and R. Herman in 1948, T ≈ 5 K)
A. Penzias & R. Wilson
Standard hot-big-bang cosmology (1965+)
R. Dicke
J. Peebles
Y. Zel’dovich
Ca. 1970: A new paradigm of
cosmology (hot big bang).
Growing institutionalisation
etc.
QSSC (quasi steady-state cosmology)