|Is Everything We Know About The Universe Wrong?
Non-standard Cosmology - A New Way of Understanding the Universe
There's something very odd going on in space –– something that shouldn't be possible.
A non-standard cosmology is any physical cosmological model of the universe that has been, or still is, proposed as an alternative to the big bang model of standard physical cosmology.
In the history of cosmology, various scientists and researchers have disputed parts or all of the big bang due to a rejection or addition of fundamental assumptions needed to develop a theoretical model of the universe.
From the 1940s to the 1960s, the astrophysical community was equally divided between supporters of the big bang theory and supporters of a rival steady state universe.
It was not until advances in observational cosmology that the big bang would eventually become the dominant theory, and today there are few active researchers who dispute it.
The term non-standard is applied to any cosmological theory that does not conform to the scientific consensus. Today it is also used to describe theories that accept a "big bang" occurred but differ as to the detailed physics of the origin and evolution of the universe.
It is as though vast swathes of the universe are being hoovered up by a vast and unseen celestial vacuum cleaner.
Sasha Kaslinsky, the scientist who discovered the phenomenon, is understandably nervous: 'It left us quite unsettled and jittery' he says, 'because this is not something we planned to find'.
The accidental discovery of what is ominously being called 'dark flow' not only has implications for the destinies of large numbers of galaxies - it also means that large numbers of scientists might have to find a new way of understanding the universe.
Dark flow is the latest in a long line of phenomena that have threatened to re-write the textbooks. Does it herald a new era of understanding, or does it simply mean that everything we know about the universe is wrong?
Dark flow is an astrophysical term describing a peculiar velocity of galaxy clusters. The actual measured velocity is the sum of the velocity predicted by Hubble's Law plus a small and unexplained (or dark) velocity flowing in a common direction.
According to standard cosmological models, the motion of galaxy clusters with respect to the cosmic microwave background should be randomly distributed in all directions.
However, analyzing the three-year WMAP data using the kinematic Sunyaev-Zel'dovich effect, the authors of the study found evidence of a "surprisingly coherent" 600–1000 km/s flow of clusters toward a 20-degree patch of sky between the constellations of Centaurus and Vela.
The authors, Alexander Kashlinsky, F. Atrio-Barandela, D. Kocevski and H. Ebeling, suggest that the motion may be a remnant of the influence of no-longer-visible regions of the universe prior to inflation.
Telescopes cannot see events earlier than about 380,000 years after the Big Bang, when the universe became transparent (the Cosmic Microwave Background); this corresponds to the particle horizon at a distance of about 46 billion (4.6×1010) light years.
Since the matter causing the net motion in this proposal is outside this range, it would in a certain sense be outside our visible universe; however, it would still be in our past light cone.
The results appeared in the October 20, 2008, issue of Astrophysical Journal Letters. Since then, the authors have extended their analysis to additional clusters and the recently released WMAP five-year data.
The dark flow was determined to be flowing in the direction of the Centaurus and Hydra constellations. This corresponds with the direction of the Great Attractor, which was a previous gravitational mystery originally discovered in 1973.
However, the source of the Great Attractor's attraction was thought to originate from a massive cluster of galaxies called the Norma cluster, situated merely between 150-250 million light-years away.
This may reveal that the source of that attraction might lie even further away, and which the Great Attractor itself is heading towards.
In a study from March 2010, Kashlinsky extended his work from 2008, by using the 5-year WMAP results rather than the 3-year results, and doubling the number of galaxy clusters observed from 700.
The team also sorted the cluster catalog into four "slices" representing different distance ranges. They then examined the preferred flow direction for the clusters within each slice.
While the size and exact position of this direction display some variation, the overall trends among the slices exhibit remarkable agreement. "We detect motion along this axis, but right now our data cannot state as strongly as we'd like whether the clusters are coming or going," Kashlinsky said.
The team has so far catalogued the effect as far out as 2.5 billion light-years, and hopes to expand its catalog out further still to twice the current distance. Astrophysicist Ned Wright posted an online response to the study arguing that its methods are flawed.
The authors of the "dark flow" study released a statement in return,
refuting three of Wright's five arguments and identifying the remaining
two as a typo and a technicality that do not affect the measurements and
A more recent statistical work done by Ryan Keisler claims to rule out
the possibility that the dark flow is a physical phenomenon because
Kashlinsky and others do not consider primary CMB anisotropies as
important as they are.
NASA's Goddard Space Center considered that this could be the effect of a
sibling universe or a region of space-time fundamentally different from
the observable universe. Data on more than 1,000 galaxy clusters have been measured, including some as distant as 3 billion light-years.
Alexander Kashlinsky claims these measurements show the universe's steady flow is clearly not a statistical fluke.
We can use physics and mathematics to understand how strongly gravity affects something if we know enough about that thing, mainly how much weight it has. This way, we can understand how objects act on Earth.
However, astrophysicists have learned that the way things in deep space behave is different. Many scientists have tried to understand why the rules are different in deep space.
One idea is that we do not really understand gravity as well as we think we do. Another idea, which many think is more likely, is that there is something called dark matter.
Kashlinsky said: "At this point we don't have enough information to see what it is, or to constrain it. We can only say with certainty that somewhere very far away the world is very different than what we see locally. Whether it's 'another universe' or a different fabric of space-time we don't know."
In physical cosmology, astronomy and celestial mechanics, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe.
Dark energy is the most accepted theory to explain recent observations that the universe appears to be expanding at an accelerating rate.
In the standard model of cosmology, dark energy currently accounts for 73% of the total mass-energy of the universe.
Two proposed forms for dark energy are the cosmological constant, a constant energy density filling space homogeneously, and scalar fields such as quintessence or moduli, dynamic quantities whose energy density can vary in time and space.
Contributions from scalar fields that are constant in space are usually also included in the cosmological constant.
The cosmological constant is physically equivalent to vacuum energy. Scalar fields which do change in space can be difficult to distinguish from a cosmological constant because the change may be extremely slow.
High-precision measurements of the expansion of the universe are required to understand how the expansion rate changes over time. In general relativity, the evolution of the expansion rate is parameterized by the cosmological equation of state (the relationship between temperature, pressure, and combined matter, energy, and vacuum energy density for any region of space).
Measuring the equation of state for dark energy is one of the biggest efforts in observational cosmology today. Adding the cosmological constant to cosmology's standard FLRW metric leads to the Lambda-CDM model, which has been referred to as the "standard model" of cosmology because of its precise agreement with observations.
Dark energy has been used as a crucial ingredient in a recent attempt to formulate a cyclic model for the universe. A recent survey of more than 200,000 galaxies appears to confirm the existence of dark energy, although the exact physics behind it remains unknown.