My own comments are in [square brackets].

Part 3

In 1998, two groups of astronomers obtained startling new evidence from supernovae seen in far-distant galaxies that the expansion of the universe is accelerating. This resurrected a long discarded term in Einstein's equations that he had put in when he thought the universe was static. It was to keep the matter out in space from collapsing together from its gravitational attraction. When Einstein found out that the universe was expanding, he called it his "greatest blunder" (because without the term, his equations predicted expansion). This additional term was quickly named the *cosmological constant*. The justification of the cosmological constant is explained as follows: Every newly created cubic centimeter of space has the same energy as all the cubic centimeters that already exist. A universe with a cosmological constant has the ability to create new energy continuously, literally from nothing. [Why does it have to be energy? Why can't it be that each cubic centimeter of ordinary vacuum has a repulsion force to the matter outside of it (force is not energy)? Vacuum has always contained the laws of the universe.]

The value of the cosmological constant is different than Einstein proposed; it is set to match the observations of the recent data. The statements in part 1 about the universe being open or closed only hold true when the cosmological constant is zero. The average density of matter in the universe (ratio of actual density to critical density) is now called Ω_{m}, and the effect of a cosmological constant is called Ω_{λ}. For a flat universe Ω_{m }+ Ω_{λ }must equal 1. Inflationary theories say that they do. One theory proposes that during the inflationary era, the universe acquired an enormous cosmological constant, which faded to zero as the universe became 10^{-30} seconds old.

Astronomers first detected *dark matter* by observing the motions of stars in galaxies and of galaxies in galaxy clusters by the *Doppler* effect. Astronomers can attempt to "weigh" a galaxy by measuring the speeds at which stars move in orbit around its center. They now believe that dark matter is about 75% of the total, and that Ω_{m} has a value of 0.2 to 0.4.

Supernovae Type Ia are used as "Standard Candles" to determine the distances to faraway galaxies. They are believed to all have very close to the same peak luminosity. During in the mid 1990s, the High-Z Supernova Search Team and the Supernova Cosmology Project have established better values. Supernova observations give us the measurement that Ω_{m }- Ω_{λ }= -0.4. Observation of redshifts and apparent brightness of Type Ia supernovae reject the possibility of a flat universe with a zero cosmological constant. A flat universe with an average density much less than the critical density is suggested. It is also based on the assumption from Inflation that Ω_{m }+ Ω_{λ} = 1. This would mean that we will never have the "Big Crunch."

Supernova data with red-shift more than about 0.2 have to be adjusted for the slowing down of time due to Einstein's special theory of relativity. The rise-time and fall-time of the apparent brightness are greater from the observer's point of view than a supernova with no red-shift. Since supernovae are never seen at the start of their cycle, this is important to calculate their start time and to determine what type of supernovae they are. When this is done, data for distant supernovae appear closer to the mean in a velocity versus distance graph (Hubble diagram).

Astronomers have admittedly incomplete theories about supernova explosions. If closer supernovae luminosity turns out to be 25% more than high redshift ones, the cosmological constant will revert back to zero. Dust in a galaxy causes reddening by absorbing more shorter wavelength light than red light. Dust is hard to estimate in far away galaxies. Interstellar dust is at such low levels it is neglected. This reddening is recognized in the spectral analysis, and can be compensated. Hypothetical "gray" dust could absorb all light colors equally. There has been discussion between cosmologists on this issue.

The cosmic background radiation can tell us the sum of Ω_{m }+ Ω_{λ} if low angular measurements (lower than COBE made) are made with sufficient accuracy. Our best measurements [2000] now imply that the sum is between 0.4 and 1.5. Generations of astronomers have employed generations of improved computers to model the universe's evolution of galaxy formation. The best that modelers can say now is that Ω_{m} lies somewhere between 0.1 and 0.5. Counting and modeling large clusters of galaxies like the Virgo cluster in a fixed volume of space over a large time period yields a value for Ω_{m} of about 0.2.

A superb verification of Einstein's General Theory of Relativity is the "Einstein Ring" or arc. A galaxy between us and another galaxy bends the light of the distant one around the in-between one. The result appears as a ring of light. This allows us to calculate Ω_{λ, }[and the mass of the in-between galaxy. See Jorrie's blog on Relativity and Cosmology]. The current results from observations of gravitational lensing show that if the sum of Ω_{m }and Ω_{λ }equals 1, then the value of Ω_{λ }almost certainly lies below 0.75, and likely lies below 0.5. [If we take this value to be 0.4, then the supernova data gives us zero for the mass of the universe, which is clearly nonsense. The point here is that there is too much uncertainty in these measurements to prove the existence of the cosmological constant.]

(Adapted from *the runaway universe* by Donald Goldsmith, copyright 2000)

[Part 4 will be a summary of recent data. Let's discuss the "gray" dust, which according to Anthony Aguirre could be rapidly rotating, elongated, roughly cylindrical graphite fibers. What about magnetic monopoles?]

1## Re: State of the Big Bang Theory - part 3