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Our future, our universe, and other weighty topics

Thursday, December 26, 2013

We Do Not Understand How the Universe Came to Look This Way

From the time of the Big Bang nearly 14 billion years ago, the universe has undergone an amazing evolution. Imagine if you had been there at the beginning, to witness the hot smooth density, in which supposedly all of our universe was packed into a microscopic size. If you knew nothing about the eventual outcome, you would not have been optimistic about what would have resulted from this explosive event. Your best bet might have been a mess of disorganized space junk, with no more order than the debris resulting from a hydrogen bomb explosion.

But almost 14 billion years later, we have a universe of remarkable order. Matter is organized into superclusters of galaxies consisting of clusters of galaxies consisting of galaxies consisting of solar systems. A large fraction of the galaxies are the particularly beautiful type called spiral galaxies. Do scientists really have a firm grip on how this improbable evolution occurred?

Difficulties in Explaining the Seeds of Structure

Scientists say that the current structure of the universe evolved from what are called primordial density fluctuations. They can see tiny fluctuations in the cosmic background radiation, which is uniform to about 1 part in 100,000. But how did those fluctuations get there?

Cosmic Background Radiation

The most common explanation is that the fluctuations began as quantum fluctuations (matter popping into existence in accordance with Heisenberg's uncertainty principle), and that these quantum fluctuations were then amplified by a period of cosmic inflation (exponential expansion) that occurred for a fraction of a second when the universe was less than a second old.

The difficulties in this explanation are many. For one thing, no one has ever actually observed a quantum fluctuation that caused matter to appear out of nowhere, not even a fluctuation big enough to produce an atom. Secondly, there are currently serious credibility issues associated with the theory of cosmic inflation, issues that have been highlighted by Princeton physicist Paul Steinhardt in this review. Among those issues are what Steinhardt calls an “unlikeliness” problem, plus the problem of creating an inflation theory that both begins and ends an inflation phase while remaining consistent with observations. Cal Tech physicist Sean Carroll says here, “When perturbations are taken into account, inflation only occurs in a negligibly small fraction of cosmological histories,” and then spells that out as a fraction less than 1 in 1.000,000,000,000,000,000,000,000,000. The leading cosmologist Roger Penrose has described cosmic inflation as a thermalization process, and has stated, “There is, however, something fundamentally misconceived about trying to explain the uniformity of the early universe as resulting from a thermalization process.” He states that any thermalization process doing anything would have “been even more special before the thermalization than after” (The Road to Reality, page 755).

Third, the inflation theory requires a severe fine-tuning of its model parameters in order to perform the trick of inflating these quantum perturbations to be the right size. As one scientist puts it here:

A lumpiness of about 10-5 is essential for life to get a start. But is it easy to
arrange this amount of density contrast? The answer is most decidedly no! The
various parameters governing the inflating universe must be chosen with great
care in order to get the desired result.

In short, we do not yet have a good plausible explanation of how these “seeds of structure” appeared. The only explanations are ones that resort to extensive parameter tweaking, rather like in the graphic below.

Explaining the Growth of Structure: More Nebulous Fudge Factors

Scientists have done calculations regarding the formation of galaxies and the preservation of galactic structure, and have come up with the resounding conclusion that the gravity of visible matter is completely insufficient to explain the origin and persistence of galactic structure.

Consequently cosmologists have come up with some “fudge factors” to help explain things. The two biggest fudge factors are called dark energy and dark matter. Scientists say that dark matter is a mysterious type of matter that is invisible. Dark energy is supposed to be a mysterious unseen energy that pervades all of space. Scientists guess that the universe's mass-energy is 68% dark energy, 27% dark matter, and 5% regular matter.

Total unambiguous observations of dark matter: 0
Total unambiguous observations of dark energy: 0

It's not as if scientists haven't tried. They have spent many dollars and much time with some very fancy observation techniques, but have still come up short. But that hasn't stopped cosmologists from creating a “lambda cold dark matter” theory (called LCDM) designed to explain cosmic structure.

Besides the fact that it relies on dark matter (the existence of which has not been verified), there are problems in this LCDM theory. One of the main problems is that it predicts way too many satellite galaxies. The paper here describes the problem. According to this link the LCDM theory predicts that our galaxy should have thousands of satellite galaxies, but instead it only has about 26.

Another problem with the LCDM theory is that it predicts that almost all galaxies should have have large bulges in the center or be spherical. But between 58% and 74% of disk-shaped galaxies do not have a bulge.

Another problem with the LCDM theory is the difficulty of getting it to produce not just galaxies but a universe with as many beautiful spiral galaxies as we have in our universe.

A spiral galaxy

As this site says, "Cosmological evolution simulations do not generally produce universes containing large spiral galaxies. Rather they produce clumps of matter making up roughly spherical amorphous galaxies without anything like the broad disks and extended arms of a typical spiral galaxy." 

Strange Anomalies

In this story a scientist comments on strange findings he has discovered by studying deep space:

"The dark matter seems to 'know' how the visible matter is distributed. They seem to conspire with each other such that the gravity of the visible matter at the characteristic radius of the dark halo is always the same...It's like finding a zoo of animals of all ages and sizes miraculously having identical, say, weight in their backbones or something...It is possible that a non-gravitational fifth force is ruling the dark matter with an invisible hand, leaving the same fingerprints on all galaxies, irrespective of their ages, shapes and sizes."

Perhaps this is some strange cosmic conspiracy, or perhaps just a reason why we may need an explanation other than dark matter. Another strange finding is the discovery of a Vast Polar Structure (VPOS), which is basically about 26 dwarf galaxies above and below our galaxy, without any matching structure on the other two sides of our galaxy. This structure does not at all seem to be what we would  expect from a dark matter theory of the origin of structure (and may be hard to explain even with alternate theoretical models). If gravity alone is creating structure, why don't these companion galaxies exist in more of a sphere around our galaxy?

The limits of our understanding of cosmic structure may also have been highlighted by the recent discovery of the planet HD 106906 b, a planet 11 times the mass of Jupiter. HD 106906 b orbits its star at a distance 650 times the average distance between Earth and the Sun. That puts the planet 20 times farther away from its star than the planet Neptune is from the Sun. This finding seems to be quite incompatible with current theories of solar system formation. HD 106906 b is being called “the planet that shouldn't exist.”

Particle Physics Makes the Situation Even Worse

When we look in the world of particle physics for help with these problems in explaining large scale structure, we get no help.

The prevailing theory of large structure formation (the Lambda Cold Dark Matter theory) is based mainly on the hypothesis of dark matter, but dark matter is totally unaccounted for in the Standard Model of physics. Dark matter has no place in that model. That leaves dark matter as a kind of nebulous “some kind of something.” Do we know how many dark matter particles there are, or how much mass any dark matter particle has? We sure don't.

Modern quantum physics does predict that dark energy should exist. The problem is that quantum field theory predicts that the dark energy should be at least 1060 times (a trillion trillion trillion trillion trillion times) larger (and probably 10120 times larger) than the maximum value that it can be, according to observations. This is known as the vacuum catastrophe problem or the cosmological constant problem. Quantum field theory predicts that every cubic meter full of vacuum should contain more energy than the maximum amount that the observable universe can contain.

In light of all these considerations, the graphic below summarizes the current very shaky state of our current understanding of the formation of cosmic structure.