Since the discovery of the
Cosmic microwave background radiation (CMB) by
Penzias and
Robert Wilson
in 1965, most cosmologists concluded that observations were best
explained by the big bang model. Steady State theorists and other
non-standard cosmologies were then tasked with providing an explanation
for the phenomenon if they were to remain plausible.
This led to
original approaches including
integrated starlight and
cosmic iron whiskers,
which were meant to provide a source for a pervasive, all-sky microwave
background that was not due to an early universe phase transition.
Scepticism about the non-standard cosmologies' ability to explain the
CMB caused interest in the subject to wane since then, however, there
have been two periods in which interest in non-standard cosmology has
increased due to observational data which posed difficulties for the big
bang.
This idea subsequently became part of the understanding
of the big bang, although alternatives have been proposed from time to
time. The second occurred in the mid-1990s when observations of the ages
of
globular clusters and the primordial
helium
abundance, apparently disagreed with the big bang.
However, by the late
1990s, most astronomers had concluded that these observations did not
challenge the big bang and additional data from
COBE and the
WMAP, provided detailed quantitative measures which were consistent with standard cosmology.
In the 1990s, a dawning of a "golden age of cosmology" was
accompanied by a startling discovery that the expansion of the universe
was, in fact,
accelerating.
Previous to this, it had been assumed that
matter either in its visible or invisible
dark matter form was the dominant
energy density
in the universe. This "classical" big bang cosmology was overthrown
when it was discovered that nearly 70% of the energy in the universe was
tied up in a mysterious and difficult to characterize form of dark
energy.
This has led to the development of a so-called concordance
ΛCDM model
which combines detailed data obtained with new telescopes and
techniques in observational astrophysics with an expanding,
density-changing universe.
Today, it is more common to find in the
scientific literature proposals for "non-standard cosmologies" that
actually accept the basic tenets of the big bang cosmology, while
modifying parts of the concordance model.
There is no consensus about these ideas amongst cosmologists, but they are nonetheless active fields of academic inquiry.
Today, heterodox non-standard cosmologies are generally considered
unworthy of consideration by cosmologists while many of the historically
significant nonstandard cosmologies are considered to have been
falsified.
The essentials of the big bang theory have been confirmed by a wide
range of complementary and detailed observations, and no non-standard
cosmologies have reproduced the range of successes of the big bang
model.
Speculations about alternatives are not normally part of research
or pedagogical discussions, except as object lessons or for their
historical importance. An open letter started by some remaining
advocates of non-standard cosmology has affirmed that: "today, virtually
all financial and experimental resources in cosmology are devoted to
big bang studies...."
Sumber;
Wikipedia
