ÐÓ°ÉÔ­´´

Questions of origin have always been the most difficult ones to answer. But
perhaps the most fundamental of all questions concerns the origin of the
Universe. Many astronomers and physicists today feel they have found the
answer. They believe that the Universe was created at one instant in a hot
explosion, called the big bang, and that the basic structure of matter was
decided in the first billion-billion-billion-billionth part of a second (10
^-36). But this hypothesis has serious deficiencies,
which the results from the satellite COBE have only served to highlight.

According to the big bang theory, in those early epochs of high energy
activity, particles of matter and radiation interacted closely, leading to
the formation of light atomic nuclei by the time the Universe was barely
three minutes old. Matter and radiation separated after about a hundred
thousand years. These primordial ‘seeds’ of matter grew to form the galaxies
and larger structures that astronomers observe today, while the radiation
cooled to give a microwave background radiation of some 2.7 kelvin.

This picture received considerable support in the mid-1960s when Arno
Penzias and Robert Wilson first detected the microwave background and
astronomical surveys began to reveal abundances of light nuclei close to
those predicted by the hot big bang theory. Over the years belief in the big
bang has strengthened. Last year, COBE reported temperature fluctuations in
the background, the imprint of seeds of what have now become large-scale
structures of matter. Surely, this should have convinced any doubting
Thomases.

Far from it. The COBE results have ruled out a large number of contending
theories of galaxy formation, some of which had enjoyed wide popularity –
for example, those based on pure hot dark matter and on pure cold dark
matter (see ‘Beyond cosmic ripples’, New ÐÓ°ÉÔ­´´, 1 May). The surviving
theories must not only explain the COBE results but also relate them to
other data on large-scale structure, such as the motion of galaxies on the
largest scale. COBE has made life for big bang cosmology more difficult than
anyone expected.

There are three major problems with the big bang model. First, as a theory
of physics, it breaks a cardinal rule by violating the law of conservation
of matter and energy. At the instant of the big bang the entire Universe is
created in what is known as a singular event, or ‘singularity’. Physics is
believed to apply only after this instant. Secondly, the microwave
background is believed to be the strongest evidence for the big bang. Yet
such a fundamental feature of the radiation as its temperature cannot be
deduced from any calculations of the early Universe. Its value is assumed.

The third problem is that big bang cosmology is supposed to explain the
origin of most light nuclei. But although it can with some success explain
the formation of helium and deuterium, it runs into problems with other
nuclei such as lithium, beryllium and boron. Even with deuterium it places
such stringent upper limits on how much baryonic matter (‘ordinary’ matter,
in the form of neutrons and protons) is allowed in the Universe that it
forces astronomers to suggest that the ‘dark’ matter thought to make up most
of the mass is in some exotic form.

Furthermore, the most popular version of the big bang model, that involving
inflation, implies a total age for the Universe that is uncomfortably small
compared with the ages of our Galaxy, of globular clusters and of other
galaxies.

The knots into which big bang theorists have tied themselves in the
post-COBE era convinced Fred Hoyle, Geoffrey Burbidge and myself that we
should seriously explore an alternative theoretical framework for cosmology.
In this framework, which we call ‘quasi-steady state cosmology’ (QSSC),
matter and energy are created by routine methods of theoretical physics.
Using the model, we can estimate correctly the present temperature of the
microwave background, explain the formation of light nuclei in the right
quantities without requiring non-baryonic dark matter, and avoid the ‘age
difficulty’. Our theory attempts to link the large-scale features of the
Universe with the phenomena of high-energy astrophysics. Before coming to
cosmology, let us look at these astronomical events.

Driving force of the Sun

By 1960, it was becoming clear that the process of nuclear fusion that
works well in explaining stellar energy, from Sun-like stars to red giants
and supernovae, proves either inadequate for or inapplicable to a wide
variety of more violent phenomena. Today, these include binary X-ray
sources, the nucleus of our Galaxy, extragalactic radio sources,
quasi-stellar objects (QSOs) and active galactic nuclei (AGNs). By 1964, the
team of astrophysicists that had earlier carried out seminal work on the
synthesis of nuclei in stars – Hoyle, Geoffrey and Margaret Burbidge and
William Fowler – had come to the conclusion that the clue to the energy of
many of these objects lay in gravity rather than in nuclear physics, as the
energy in such sources is being generated in compact regions where gravity
is very large and dominates all other known forces.

Today the popular version of that scenario envisages a massive spinning
black hole at the centre of the object, which pulls in matter to form a
thick, hot ‘accretion disc’ around it. Much of the observed radiation from
these objects is believed to come from this hot disc. Over the years this
basic idea has been expanded to accommodate more recent observations – but
in a way that is reminiscent of the ancient Greeks’ practice of grafting
extra epicycles to their model of planetary motion.

In a typical double-lobed radio source, for example, the two lobes, several
hundred thousand light years apart, are ‘activated’ by the bombardment of
jets from the central region, which is believed to contain a massive black
hole. The black hole pulls in surrounding matter into an accretion disc
which somehow makes long, narrow jets. These jets, which emerge in opposite
directions, are thought to contain plasma travelling at near the speed of
light. But neither the black hole, nor the accretion disc, has been
directly observed. It is not clear how accretion is possible, despite the
strong outward pressure of radiation from the object. In a typical
astrophysical process energy is converted to a more useful form (radiation
or dynamical motion) very inefficiently, usually with an efficiency of below
1 per cent. In the Sun, for example, only 0.7 per cent of the matter is
converted into radiation. But the black hole accretion process requires
between 10 and 30 per cent of the gravitational energy to be converted to
X-rays and other radiation. Finally, the circumstantial evidence claimed for
the existence of a black hole stops far short of explaining its theoretical
radius.

Far from matter falling into a black hole, the evidence shows matter and
radiation pouring out of compact regions, as emphasised by the Armenian
astrophysicist Viktor Amazaspovich Ambartsumian in the early 1960s and
conjectured even earlier by James Jeans, back in 1929. But these ideas have
found little support among theoreticians, mainly because they are perceived
to violate the law of conservation of matter and energy. The idea of a
single, ancient explosion as found in the big bang cosmology did not look
too bad until the discovery of QSOs, AGNs, radio sources and so on, which
are phenomena indicative of ongoing explosive activity. Today it looks
inadequate to explain the continuing occurrence of such violent events.
Somehow, cosmology has to come to terms with these without sacrificing the
conservation law.

Our attempt to do this is based on a model in which a series of ‘minibangs’
replaces the single big bang. These ‘minibangs’ begin with a physical
process that resembles the way matter falls into a classical black hole. But
instead of everything being gobbled up indefinitely, at some critical point
defined by the size of a repulsive ‘field’, the material is pushed out with
tremendous force, rather like an explosion. Unlike the big bang, which is
spontaneous and causeless, these smaller creation events are part of an
ongoing process. The idea that matter is being created continuously – the
so-called steady state model – was put forward by Hermann Bondi and Thomas
Gold in 1948, and by Hoyle, who also tried to reconcile the creation of
matter with the theory of relativity.

Creation great and small

We now propose a model in which the Universe passes through alternate phases
of ‘large’ and ‘small’ creation. In large creation more matter is created by
means of more frequent or larger explosions than in small creation. Large
creation therefore accelerates the expansion of the Universe as the matter
flies apart. But this acceleration simultaneously reduces the strength of
the repulsive field responsible for creating matter. The expansion process
slows down until, at some point, more and more explosions occur and the
whole process repeats itself. The overall picture is one in which slow and
steady exponential expansion over the order of a thousand billion years is
combined with short-term ‘wiggles’ of between 20 and 40 billion years.

Today’s measurements give a range of values between 50 and 100 kilometres
per second per megaparsec for the Hubble constant, H, which relates the
speed of recession of a galaxy to its distance from us. That is, a galaxy at
a distance of 1 megaparsec is typically moving away from us at a speed of
between 50 and 100 kilometres per second. The constant has the dimensions of
the reciprocal of time, with 1/H between 10 and 20 billion years. We suggest
that the Hubble constant is a measure of the short-term ‘wiggles’ in our
model.

Large-scale surveys of the Universe, using radio and optical astronomy,
should eventually show whether the idea of these two timescales is correct.
Meanwhile, the QSSC model will be judged largely by its ability to explain
the origin of light nuclei and the microwave background radiation.

In big bang cosmology the process of nucleosynthesis in the early Universe
is able to account for the quantities of deuterium observed in the Universe
– provided there is a strict upper limit (about 10 ^-30il 24
per cubic centimetre) on the density of baryonic matter in the Universe.
This leaves the problem of deciding what the dark matter in the Universe is
made of. For if we add in dark matter to the matter density, we exceed this
upper limit. This has led big bang cosmologists to suggest that dark matter
must be in an exotic, non-baryonic form which does not take part in the
synthesis of deuterium.

In the QSSC model the entire process of synthesis of nuclei is different, so
in the production of deuterium there is no upper limit on the density of
ordinary matter. In the QSSC the first particle to be created is the
so-called Planck particle, whose mass is determined by the three fundamental
constants of physics, the speed of light, Planck’s constant and the constant
of gravitation. This mass is a few tens of micrograms, but its lifetime is
extremely short, about 10 ^-43. So the particle
decays into less massive but more stable particles: the neutron and the
proton and six other, less stable baryons. Since the creation process is
continuous, it works in favour of the existing mass – one generation of
masses are made of matter, so the next one continues to be made of matter.

In big bang cosmology, there was no initial distinction between matter and
antimatter; both were treated on a par. Physicists therefore have a puzzle
on their hands as to how the Universe today seems to be made predominantly
of matter. Moreover, big bang cosmology has not explained why the particles
of light (photons) in the radiation background outnumber particles of
matter, baryons, by about a billion to one.

In the QSSC model, baryons and radiation are both end prod-ucts of the decay
of the Planck particle. The two baryons familiar to us, the neutron and the
proton, form part of an octet that makes up the baryon family. Of these, the
remaining six particles are very short-lived and decay into protons which
form the nuclei of hydrogen atoms we see today. The original neutron and
proton pairs, on the other hand, combine to form the nuclei of helium atoms.
So we would expect about 25 per cent of the mass in the Universe to be
helium and the rest hydrogen. More detailed calculations lower the helium
fraction to about 23 per cent, while calculations for light nuclei like
deuterium, tritium, lithium-6, lithium-7, beryllium-8 and boron-11 all agree
well with estimates of primordial abundances based on their observed
abundances today. The model also allows small quantities of elements such as
carbon, oxygen and iron to be formed.

Now for the microwave background radiation. In big bang cosmology the
background radiation is seen as the relic of an early hot beginning. In the
QSSC there is no beginning, so we have to show how the existing steady
background is continually replenished as the Universe expands. We suggest
that it works mainly by starlight being absorbed by matter and re-radiated
as energy, a process called thermalisation. In this picture, the source of
the microwave background radiation is starlight left over from previous
wiggles. By calculating the amount of starlight produced in the present
wiggle so far – that is, since the last minimum phase of the oscillation –
we can infer the amount of starlight being carried over from one cycle to
the next, and thereby estimate the temperature of the background radiation.
We find that this thermalised starlight should indeed have a temperature of
about 2.7 kelvin.

Having got the temperature right (an achievement as yet denied to the big
bang scenario) we next have to explain how the background radiation produces
a spectrum of the perfect ‘black body’ shape that is observed. A black body
spectrum arises whenever the radiation has passed through a series of
absorption/re-emission sequences. In the QSSC model, we suggest that the
radiation from previous wiggles is continually absorbed and re-emitted by
needle-shaped dust, mainly at the minima of oscillations (thermalisation is
a continuous process but acts more strongly at the minima because of their
high densities). Iron needles about a millimetre long and about 0.01
micrometres across are needed to bring this about. Laboratory experiments
show that metallic vapours do tend to condense into whisker-like shapes.
Such iron vapour would have been produced in supernovae, as well as in the
nucleosynthesis process of a minibang, and only a tiny fraction of the
estimated cosmic abundance of iron would be needed for thermalisation to
work. This process would have gone on long enough to produce a perfect black
body spectrum, and a near perfect isotropy (sameness in all directions).
The tiny fluctuations detected by COBE in its isotropy are then simply the
marks of imperfect processing since the last wiggle.

The QSSC model also has implications for astrophysics. In the QSSC, the
dark matter believed to be present in large quantities in spiral galaxies
(including our own) would simply be remnants of burnt out stars. The
estimated mass of the Galaxy could be built up to its present value through
several cycles of matter creation, some as long as 200 billion years, and
this would be long enough for some star clusters to be too faint to be seen.
A similar argument applies to dark matter in clusters of galaxies. In the
QSSC, the timescales are also sufficiently long to allow clusters to merge
into superclusters.

Several types of future observation might support the model. For example,
the search for gravity waves now being planned might be one way of detecting
minibangs if they exist, since such minibangs would generate gravity waves.
For this to happen, the explosions would have to be irregular in shape and
their intensity and duration would be such that they can be distinguished
from other gravity wave sources like exploding stars and shrinking binary
neutron stars. The gravity wave background may also be detectable through
its effect on the precise timing mechanism of millisecond pulsars; pulsar
measurements are not yet sensitive enough to detect such a background.

The framework described here serves only as a starting point. Unlike the
big bang model, it is not presented as the definitive theory of cosmology,
but as one theory. We hope it will at least provoke some debate.

Jayant Narlikar is director of the Inter-University Centre for Astronomy and
Astrophysics at Pune, India. Further reading: ‘A quasi-steady state
cosmo-logical model with creation of matter’, Astrophysical Journal, 20 June
1993.