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Gonzalez and Richards Chapter Nine

Assumptions and implications are not the same thing

Posted Monday, August 22, 2005 by Gerald Vreeland

Chapter Nine, of The Privileged Planet is entitled “Our Place in Cosmic Time.”  Regrettably, I think this chapter will prove to be the weakest link in the chain.  It will, most probably, not be regarded as being “wrong” as much as being weak.  In a book wherein I have groused repeatedly about the copious and somewhat tedious end-noting, this chapter is rather annotatively Spartan.  Several things are taken for granted that might otherwise be necessary in a discussion at this level.  Primarily, the lack of documentation and/or explanation regarding Cepheid variables is glaring.  I want to know why these are considered “standard candles” against which to measure distance and redshift.

My theory, without researching it is as follows: using the parallax method (trigonometry using our position at opposite sides of the year, therefore knowing a side and two angles) we have arrived at a reasonably certain distance for some Cepheid variable or other.  We have determined that their periodicity (the “variable” part) is related to how bright they appear to us at that distance (a.k.a. magnitude) and then we establish what an absolute value would be to their brightness (luminosity).  Because we have studied redshifting, we are pretty sure of how much light shifts to the red side of the spectrum at whatever increasing distance.  Hence, when we deduce luminosity from periodicity (the constant) and calibrate the amount of redshift, we can slingshot out into deep space and arrive at some rather remarkable approximations at great astronomical distance.

Be that as it may, the authors begin with a shorter history of Hubble’s (and others) efforts at resolving Cepheid variables on M31 or the larger Galaxy in the constellation Andromeda in the 20’s and 30’s using what was then the new 100 inch reflecting telescope on Mt. Wilson.  Three things were demonstrated: first, the Milky Way was not all there was of the universe; second, it was demonstrated that other spiral nebulae were, in fact, distant galaxies – looking very much as ours would appear to them; third, the combination of discoveries implied that the universe, redshifted as it was, was expanding (pp. 169-70).

Up to that point it had been considered more scientific to view the universe as static.  Einstein even introduced a “fudge factor” called the “cosmological constant.”  Although mathematical models vindicated such a view, it was not to withstand the onslaught of rapidly accumulating data.  Einstein was later to call the cosmological constant, his “greatest mistake.”  This required some soul searching and a paradigm shift.  The idea of an expanding universe implied a beginning to time – since there must have been a point when time, space, matter and energy were more compact.  For children of “The Enlightenment,” such a paradigm shift seemed unscientific.  Thus was born initial inflation or what Fred Hoyle called “the Big Bang.”  The name has been around a while. . . .  The problem illustrates the point made by Thomas Kuhn in his The Structures of Scientific Revolutions because it shows how great cognitive dissonance must get before the establishment changes its collective mind.  There must come something of an intellectual crisis (p. 171).

In the southern hemisphere there are formations known as the Large and Small Magellanic Clouds.  These are the Milky Way’s largest satellite galaxies.  In studies of periodicity and luminosity conducted in the early 1900’s by Henrietta Leavitt, a standard measuring device was born.  Cepheid variables, it was discovered, despite their great distance, can be measured by the period of their variation and their absolute brightness (luminosity).  It was discovered that these stars are brighter if their variable periods are longer.  This seems to be true throughout the species.  Hence, it is presumed, if we can get a lid on those Cepheid variables whose distance we can measure trigonometrically, then we can determine the two variables, period and luminosity, for greater distances.  Hence, at distances where the trigonometric angles must be shaved too fine for accuracy, these “standard candles” will tell us the distance.  When we measured those stars in galaxies like the great Andromeda galaxy, we discovered that they were redshifted and were at distances we did not expect (p. 172).  Of course, our methods and measurements have become and will continue to become more accurate over time (p. 172). 

Another “standard candle” that has been studied over the last decade is the Type Ia supernovae (p. 173).  However, they don’t happen every day – and we can be especially thankful that they don’t happen regularly in our neighborhood.  I got a hold of a piece from the New York Times (February 18, 2005) reporting on a radiation blast from a burned out supernova that had formed a magnetar.  The radiation blast was mostly gamma rays; but it still out shined the rest of the Galaxy on December 27, 2004.  It warped our own ionosphere (which helps protect us from similar radiation from our own Sun).  Had such a blast happened on Alpha Centauri or Sirius (assuming they were collapsed neutron stars), the exposed half of the planet would have been blown away . . . the other half wouldn’t have made much difference after that. . . .  In any case, using Cepheid variables, Type Ia supernovae and Parallaxes, we work our way out on a ladder of distance and time (p. 174).  Perhaps the most disturbing thing about the gradual acquisition of data and the increasing accuracy of the method is its slowness.  At this point, we are running about 10% uncertainty with respect to the distances (pp. 174, 388, n. 10).  Of course, when you get out to your more distant quasar, at, oh, say 10 billion light years, the distance on the fudge factor becomes, well, astronomical.  But what’s a billion light years [!] between quasars and friends?  So, if you are headed that way, you had best plan for quite a lot of extra propellant and provender.

Several people proposed various ways to avoid the scientifically “repugnant” idea that the universe had a beginning.  One such way was Hoyle, et al’s so called Steady State universe.  Again, the accumulation of data overwhelmed the theory.  In 1965 some Bell Lab employees discovered the Cosmic Microwave Background Radiation.  It has turned out, in various models, to indicate the “echo” of the initial inflation of the universe (Described by Stephen Hawking, A Brief History of Time, 133-4; 136-7), or what Hoyle initially and apparently disparagingly referred to as the “Big Bang.”  This radiation is about 2.7 degrees above absolute zero (p. 174).  It is said to represent photons that were emitted some 380,000 years after the big bang:

Current models indicate that the CMB photons were liberated about 380,000 years after the Big Bang event.  It took that long for the universe to expand and cool enough for protons to combine with electrons to form neutral hydrogen.  This cosmic expansion has preserved the shape of the spectrum of the cosmic microwave background radiation – a critical clue to its origin.  This is because the universe today is far too transparent to photons for the background radiation to have been produced in its present state; in other words, the radiation is too far out of equilibrium with the matter in the present universe to account for its origin.  The present background radiation points back to a time when the universe was much denser and hotter (p. 175).

This accumulated knowledge and that already indicated helps us with what we see when we look into deep space.  I have acquired several publications that use famous shots of the so-called “Hubble Deep Field.”  It is suggested, due to confirmed expectations of redshifting, that some of the galaxies therein imaged are some 9 billion light-years away.  As such we are looking back some 9 billion years to the time of the early universe (pp. 175-6).  However, one of the questions that is never addressed is why so many of these galaxies – whose light allegedly took many billions of years to reach us – are so well developed.  We even see full-armed spiral galaxies.  Apparently galaxies form the intricate and sophisticated patterns indicated by, for example, the Milky Way and the Great Andromeda Galaxy rather more quickly than we might expect.

The authors then move on to explore three “constants” that are indicative of size, age, mass and energy in the known universe (pp. 176-7).  The first is the so-called “Hubble Constant.”  This is the present rate of expansion of the universe as determined “by measuring the distances and redshifts of galaxies” (p. 176).  The second: “The matter-energy density is basically the total amount of matter and energy in the universe . . . which we discern from its light emissions and gravitational effects” (p. 176).  Finally, “The cosmological constant, or vacuum energy . . . contain energy, which, at very large scales, can actually counteract gravitational attraction” (p. 176).  These correspond well to what we have gleaned from the Type 1a supernovae data discussed above.

In the next brief section, the authors indicate the problem with the rapid cooling of the earlier universe.  At the proposed rate, nothing really beyond Lithium on the periodic table could have been formed.  However, the theory of “nucleosynthesis” and particle physics confirmations indicate how the heavier elements could have been formed and it is concluded:

In a sense, the cosmic abundance of the light-element isotopes is a type of telescope that can peer just beyond the time when the background radiation formed.  Particle physics and cosmology merge in the moments after the Big Bang.  So we have three independent observations that all give support to the Big Bang theory: Hubble’s galaxy redshift relation, the cosmic microwave background radiation, and the relative abundances of the light-elements (p. 178).

The authors then explore “further tests of cosmological expansion” that prove to be more theoretical and, in my mind, risky.  Because of tests and predictions in the 30’s by Tolman, Sandage was able, by studying thirty four early-type galaxies, to refine the estimates of the Hubble constant.  “At the same time Sandage was able to eliminate the ‘tired light’ hypothesis, which posits that redshifts result from photons losing energy over vast distances, by showing that galaxies do not change with redshift as the hypothesis predicted.”  I am not certain that this entirely defies either the observations or the mathematical models attached to them.  But, be that as it may, studies of Type Ia supernovae, it is alleged, have light curves that are broadened due to distance.

This means that the light from a distant supernova seems to wax and wane more slowly than that from a nearby one.  According to the Big Bang standard model, this phenomenon is due to time dilation.  As the cosmos expands, it leaves behind “stretch marks” in the fabric of space-time.  This time dilation was first confirmed in 1995 from supernova light curves (p. 179).

Well, the word “seems” seems to mean that there is something of the interpretive happening here.  Secondly, one has to break into the standard model wherein “space-time” is a thing that can be referred to as “fabric.”  It is certainly not fabric in any tangible sense of the word that I know.  In fact some philosophers of time believe that time is radically different from space.  Some even posit a theory divesting time of thing-ness wherein time is a parameter rather than a coordinate.  This would mean, of course, that the observations have to be explained less in terms of the distortion of time and more in the effects of gravity and the distortion of light vectors and velocity.  Their conclusion, however, is important: the fact that we can even look at these things and develop theoretical models to explain them is only because we just happen to live in a place where we can simultaneously observe, measure and inhabit!

The farther away we get from home, the more speculative things can become, I suppose.  The authors next discuss quasars and suggest that they are indicative of conditions “shortly after matter and radiation decoupled” (p. 179).

These powerful beacons are the most luminous and distant objects in the visible universe. Quasars are believed to be galaxies in their early stages, when their central black holes were growing rapidly by accreting gas.  Before disappearing into the black hole, the gas forms a very hot, bright accretion disk around it.  It is this accretion disk that makes quasars so bright even from vast distances (p. 179).

Because of their incredible luminescence, they also tell us quite a bit about the terrain between them and observers on earth.  “Quasars emit light most strongly in the ultraviolet part of the spectrum, and the intervening gas absorbs most strongly at a distinctive spot in the electromagnetic spectrum called Lyman-alpha, due to an atomic transition in neutral hydrogen . . . the far ultraviolet” (pp. 179-81).  Everything between us and the quasars has a different redshift and so produces a Lyman-alpha absorption line at a different wavelength.  This then “presents a time-ordered . . . record of cosmic history” (p. 181).  With conditions other than our light absorption abilities and, let’s say, a contracting universe, things would be rendered invisible from our vantage point.

And so the authors move on to address the issue of “The Cosmic Habitable Age” (p. 181).  Along with the Circumstellar Habitable Zone and the Galactic Habitable Zone, it is postulated that there is a Time Zone wherein we can both be found to exist, to flourish and to observe and measure.  This section begins with the assumption: “Not all places and times around a star or within a spiral galaxy are equally habitable.  Similarly, not all ages of the universe are equally habitable” (p. 181).  The authors begin with the obvious: before the decoupling of matter and energy, life would have been impossible . . . radiation, gravity, lack of heavy elements and so on.

Unlike our present, the early universe was poor in heavy elements and rich in high-energy quasars, star births, and supernovae.  Early-forming planets in the inner regions of galaxies would have been bathed in lethal levels of gamma ray, X-ray, and particle radiation (p. 182).

There is a caveat, however: because our galaxy is larger, it would naturally accrue heavier elements more rapidly (p. 182).  But the bottom line is: “. . . the universe has been getting more habitable” (p. 182).

The authors note that this trend will gradually reverse as the long-lived radio isotopes, important to geology (tectonics), decline.  This will limit the number of habitable planets formed in the future.  Because any planet forming today will not have the same geology in 4.5 billion years (according to the authors), it will necessarily have to compensate by being larger.  That runs up against gravitational problems that militate against complex and technological life.  It will also increase the number of asteroid and comet strikes and make whatever place much more hazardous to its inhabitants’ health.  Look at the radioisotopes for heating earth-like cores:

We can’t be precise about the maximum future birth time of a habitable planet, but it’s notable that the three most important radioisotopes for heating Earth – potassium-40, uranium-238, and thorium-232 – have half-lives of 1.3, 4.5, and 14 billion years. Perhaps it’s a coincidence that their average half-life is similar to the lifetime of Sun-like stars in the main sequence.  One of these corresponds to the age of the universe, and another to the age of Earth (p. 182).

The authors then note that the “relatively narrow range of metallicity . . . translates into a narrow range of ages of the universe that are acceptable for building habitable planets.” (p. 183).  Hence, we most probably could only live not only here, but only now.  As yet there is not reason to assume that life elsewhere would or even could be radically different from life here – even if it exists.

If we combine all the relevant properties of the universe that vary over time – declining star-formation rate, declining high-energy radiation levels, increasing metals, declining radioisotopes – we begin to get a picture of the Cosmic Habitable Age.  We can easily rule out the extremes as hostile to life (p. 183).

Because any terrestrial planets formed after that time will likely revolve about white dwarfs and red dwarfs they will most probably have tidally locked rotations and they will lack necessary tectonic activity as well.  And so they conclude, reasonably: “Perhaps we must live at just this time in the history of the universe, in the sense that it is the only time compatible with our existence” (p. 183).

The authors, it must be recalled, correlate habitability and measurability.  With that in mind, there is a review of the discoveries of the 19th and 20th centuries.  Because of what we are, where we are and when we are, we are able to observe many things hitherto opaque to us in times of greater concentration of dust or radiation.  Obviously, those would be dangerous times – but they would be times of limited scientific discovery as well.  (pp. 183-6).  Things may once have been much closer together in space; but, they would also have been much more difficulty to observe and measure.  Consequently, reasonable inference would have been much more difficult and we would have known much less about the universe.

Be all that as it may, things are moving away from us at such a break-neck pace that gradually stuff will just blink out of sight.

According to the best current measurements of Type Ia supernovae light curves, dark energy is now overwhelming gravity’s tug at cosmic scales, and accelerating the universe’s expansion.  Until about six billion years ago, gravity still ruled the roost, and the cosmic expansion was decelerating.  Although this is new evidence, if the prevailing interpretation of the Type Ia supernovae observations is correct, the universe should continue to expand and even accelerate indefinitely (p. 186).

So we had best do all our looking around within the next several billion years or there will be nothing but our local galactic cluster to observe, measure and make inferences.  Because:

. . . the event horizon will begin affecting our view of the universe in twenty to thirty billion years.  After that, the amount of accessible information in the universe will start to taper off.  The first to fade from view will be the most distant parts of the universe, such as the background radiation (p. 187).

I should think that were we to re-enter some kind of dark age wherein knowledge is lost, catching up to where we are even now would be impossible.  Dubious that we’ll make it that far, I suppose. . . .

What follows is an extended discussion on the relevance of the Cosmic Microwave Background Radiation to the discussion (p. 187-8).  First the misunderstanding of Hoyle and others that it is a local phenomenon is cleared away.  “. . . it looks pretty much the same in every direction.”  This it would not do were it local.  Were we closer to the core of the galaxy, we could not observe the background radiation so readily.  In any case, the environment would have been a good front row seat to looking at the central black hole; however, that would have been the instant we were incinerated by the radiation in the dense stellar regions of the galactic center.  There are lots of black holes at a safe distance out there to look at without getting sucked into one.  From our safe vantage we can observe the background radiation and other more contemporaneous and more lethal phenomena.  Because of the kind of galaxy we live in and where we are in it, we can observe these phenomena and survive as well.  Were we in an elliptical or globular cluster, we would not be able to observe the background radiation as well.

In the early universe, particle emission was more intense and would have drowned out the background radiation.  The later universe will be more dark and dusty and the background radiation having dissipated even more than it has.

Our educated guess is that apart from the epoch just before stars began forming, the background radiation is more accessible now than it was in the past or will be in the future (this would be an interesting question for an aspiring young researcher to investigate) (p. 189).

After the background radiation, the next thing to blink out will be the most distant quasars.  It is thought, under the current accelerating paradigm, that in about 150 billion years, anything past the present distance of about 30 million light-years will fade out as it approaches the event horizon.

In addition, although we live in a time when stars are still forming, there will be fewer of the classical Cepheids and supernovae that are essential for measuring the current universe.  The authors then speculate as to what would have happened had we been around to observe about 10 billion years later.  There would have been a lot fewer of the measuring sticks that we currently use to help us determine the parameters of the known universe and its makeup (p. 190).

In sum, over the next few billion years most galaxies will be farther apart, the particle horizon father away, the cosmic microwave background radiation dimmer, cosmological standard candles and pulsars rarer, and quasars fainter.  Fewer samples of the original light-element abundances will be available, and most profoundly, once the effects of the event horizon start to become apparent in about a couple of Hubble times (a Hubble time is roughly the present age of the universe), some important diagnostics about the universe will gradually disappear.  Observers living in the “near” future will enjoy a more distant particle horizon, but at the cost of most of the astrophysical tools astronomers use today (p. 191).

Note 39 provides an interesting bit of speculation based upon current occurrences:
Of course we might survive for billions of years into the future and artificially maintain a habitable environment, but then we’re talking about our technological expertise built on the finely tuned habitability and measurability foundation of our own present age (p. 391).

And so, how is the “Paradox Solved”? (p. 191)  The paradox is what is called “Olbers’ Paradox.”  That is, if the universe is eternal and infinite, why are the night and day skies not equally bright?  There would, of course, be all the time in the world, as it were, for the skies to fill with light from a virtually infinite number of light sources.  From what we have discovered from our privileged perch:

Simply put, there’s no paradox if the universe is neither eternal nor infinite in the requisite sense.  In fact, a dark night sky is itself evidence for a beginning (p. 193).

But thanks to a darker night sky, we can both survive the barrage of radiation the universe emits and we can make reasonable observations, measurements and inferences as to the nature of the universe in which we live (p. 193).

Guillermo Gonzalez and Jay W. Richards, The Privileged Planet: How our Place in the Cosmos is Designed for Discovery (Washington, DC: Regnery, 2004).

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