Wednesday, July 16, 2014

Why Does Every Manjack Think He's a Cosmology Expert?

It continues to mystify me how so many  - who likely have never even taken a basic astronomy course in their lives - believe they are qualified to write about cosmology or the universe at large, including cosmic expansion. . In the most recent example,   Lawrence Edward Bodkin, Sr. (Intertel Integra, April, pp. 10-11),   propounds a curious conjecture concerning the basis of the spectroscopic red shift as it applies to the expanding universe. While he basically gets the Doppler principle of spectral shifts correct, i.e.  “a shift to the red means an object is receding from us, a shift to the blue means it is approaching”, he falls down in a number of other areas.

First, it is incorrect to refer to “galaxies” in the context of red shifts and indeed in terms of cosmic expansion. The reason is that the recessional velocities observed  which conform  to the Hubble law, e.g.

V = Hd

Where H is the Hubble constant, and d is the distance, only apply to galaxy clusters (the exception being quasars or quasi –stellar objects).  Thus, no independent or unbound galaxies occur from which reliable redshifts z can be obtained, all are found to be members of aggregates that are themselves gravitationally bound. (The exceptions to this constitute galaxies that have been ejected from their respective groups.) Within each such cluster the galaxy members can undergo blue shifts or red shifts, depending on the reference point from which the observation is made. But it is critical to grasp that these individual galaxy spectral shifts within clusters have no bearing on cosmic expansion.

As an example, our Local Group features at least 35 distinct member galaxies which the interested reader can find listed in Table 2.1 of the excellent monograph, The Galaxies of the Local Group, by Sidney van den Bergh.  The members include: The Milky Way, M31 (Andromeda galaxy), and the Large and Small Magellanic clouds.

When one peruses the individual data for the individual members of the Local Group, one finds for example, a radial velocity for the Triangulum galaxy of (V(r) = -181 km/ sec) cf. Table 5.1, which denotes a blue shift indicating velocity of approach, born out by the negative sign of V(r)> On the other hand, when one consults the data table (6.1)  for the Large Magellanic Cloud, one finds V(r) = +275 km/ sec  indicating a recessional velocity and red shift.

Again, the point is that within a given galaxy cluster a member can have either a blue shift or red shift depending on the vantage point from which observed.  The key concept to bear in mind is that these have no bearing on the Hubble law and do not figure into cosmic expansion.

Second, Mr. Bodkin’s preoccupation with “viewing angle” only has reference to the interior of a galaxy cluster, and again, what angle the observed member galaxy occurs in relation to the point of the one doing the observation. It has no bearing from the cosmological perspective because all “viewing angles” are the same.

Since the expansion is one of space as well as time, there is no preferred reference frame for the expansion, so Earth is only one vantage point by which to arrive at the Hubble law. A fairly good analogy to invoke is that of an inflating balloon with ink dots on its surface. As you inflate the balloon each of the dots moves away from its neighbors, analogous to how galactic clusters move away from each other in the real cosmos. However, as can be seen, NO single dot can be the center of said expansion.

If special viewing angles really existed, this would not be the case and one would find different recessional velocities at differing distances, rendering the Hubble law unusable. In addition, it is conceivable that the odd blue shifts would appear which we do not observe in terms of cosmological observations.

Third, there is no evidence at all the “blue shifted galaxies have constantly depleted in number and become additions to the number of red-shifted galaxies.” From the true cosmological perspective, not a single such “change” has been detected.

Fourth, Doppler-determined speeds approaching the speed of light (c = 300,000 km/ sec) need to be treated very carefully. In general, the red shift for the Hubble law, defined as:

z = v /c

is for the non-relativistic case. Thus, if  z = 0.2 then the recessional velocity is: v = 0.2c. n other words the object is moving away at one-fifth the speed of light. If the object’s recessional velocity is nearing the speed of light,  a different expression is needed:

v =   c [(z 2 + 2z) / (z 2 + 2z + 2)]

Bodkin Sr. also argues that the perception of special viewing angles has been part of human experience for "billions of years". But the fact is humans haven't even been around that long. The most generic form of anthropoid ape probably only existed from 1.6 million years ago at most - and I warrant they'd not have been concerned with the viewing angles of distant galaxies. Modern scientific man has arguably only existed since Galileo in the 17th century and his primary focus was on Jupiter and its moons, Saturn and sunspots.

It seems to me that those like Mr. Bodkin might better use their time to learn about cosmology - a difficult sub-discipline of astronomy - before they write long tracts about it!

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