Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization
© 1975-1979, 2008 Robert A. Freitas Jr. All Rights Reserved.
Robert A. Freitas Jr., Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization, First Edition, Xenology Research Institute, Sacramento, CA, 1979; http://www.xenology.info/Xeno.htm
4.1 The Universe
On a dark, clear evening the human eye can distinguish several thousand distant suns, all of which lie in the Milky Way (our home galaxy). Floating freely in Earth orbit our senses would be assaulted by the light of nearly six times as many stars. The Palomar 200" optical telescope -- now the second largest in the world -- has the light-gathering power of a million human eye balls and extends our vision to several billion celestial objects in this galaxy alone. And about ten billion galaxies are observable with present-day astronomical equipment, the farthest (3C 123) lying eight billion light-years distant.1952
How big is the universe? An important clue was uncovered by the American astronomer Edwin Hubble back in the early 1920’s, when he was measuring the atomic spectra emitted by various galaxies. The farther away the object, he found, the more its spectral lines appeared to be displaced towards the lower frequencies of light. This curious phenomenon, which became known as the "redshift," was interpreted to be a kind of Doppler effect for photons.
Much the same as a receding siren seems to be putting out lower and lower pitched sounds as it passes by, so do galaxies seem to emit redder light as they travel away from us. Since the most distant objects are seen to possess the greatest redshifts, the simplest explanation is that they are receding from Earth at velocities approaching the speed of light. Nearby galaxies are moving at a far more leisurely pace. Conclusion: The universe is slowly expanding.
This is not to say that Earth has the extraordinary good fortune to lie at the exact geometric center of all creation, simply because most all astronomical objects appear to be heading away from us. More correctly, our galaxy is like a spot of India ink on the surface of a spherical balloon. We are surrounded by billions of similar spots. As the balloon inflates, every point on its surface moves away from all adjacent points. From the chauvinistic viewpoint of each galaxy, all others will look like they’re flying away at various speeds depending on distance. Each will view itself as the "center" of the universe! This idea that the cosmos will appear roughly the same from any position is called the Cosmological Principle.
The latest measurements of galactic redshifts seem to indicate that the speed of recession increases about fifty-five kilometers per second for each megaparsec* of distance from Earth.1953 (This number is called the Hubble Constant.) Since the maximum velocity of recession which can be detected is the speed of light, then the outermost shell of the swelling universe should lie about eighteen billion light-years from Earth.
Of course, if the "balloon" deflates, points on its surface will rush together again. Using our value of the Hubble Constant, we can mathematically run time backwards and extrapolate to Time Zero -- the creation event. The inverse of the Hubble Constant is in units of time and represents the age of the universe assuming a constant rate of expansion. This works out to a period of eighteen eons!**
But scientists believe that the expansion of the universe has not been constant; on the contrary, it has probably decreased with the passage of time because of gravity. Taking this into account, the true age of the universe will not be quite so large, and is now usually set at about sixteen billion years.1953,1983 Our estimate of the radius of the universe, likewise corrected, drops down, to sixteen billion light-years.
Any theory of cosmology that purports to explain the mechanics of the cosmos must, at the bare minimum, be able to account for Hubble’s redshift phenomenon. The one proposal which has been most successful in this regard is the Big Bang hypothesis.
According to this leading view of cosmic evolution, the universe began as a highly compact fireball of pure energy and infinite density. After perhaps a millionth of a second this density dropped off to nuclear values as the ylem or "cosmic egg" exploded outward.2062 The overall temperature may then still have exceeded 1013 K.1192 The stuff of the universe started to change from pure energy into matter, primarily neutrons.
When half an hour had passed most of the neutrons were gone, replaced by a mixture of 60% hydrogen ions and 40% helium ions (by mass), as well as a smattering of deuterium (heavy hydrogen).1813
Using this model, it can be calculated that at the one hour mark, the temperature was down to about 250 million degrees; after the passage of a quarter of a million years, it had fallen off to the present temperature at the surface of Sol. And 170 K was reached after 250 million years following the big bang.
This turned out to be a red-letter date in the evolution of the universe, because for the first time in history the density of matter became greater than the mass density of radiant energy. Protons and electrons must have coalesced into de-ionized H, He, and D atoms, leaving no more than 0.1% still in the plasma state.1192 This signaled a dramatic change in the behavior of material. No longer was matter incessantly sloshed and stirred by the overpowering radiation field, which had kept it permanently osterized in a thin, gaseous form. Once radiation refrained from dominating the scene, matter was free to gravitationally condense into relatively huge, massive aggregates -- supergalaxies, galaxies, and stars.1813
There are two variations of the Big Bang scenario upon which most discussion has focused. The first of these is known as the closed, or pulsating universe model. According to this thesis the universe is a gravitationally "bound" system. That is, some thirty eons or so from now the fragments from the original ylem explosion will cease their outward rushing and commence to fall back together again like the dots on the surface of a deflating balloon. Cosmic evolution occurs in a series of alternate expansions and contractions. At the very end, the Final Moment, everything is destroyed, the slate wiped clean in preparation for the beginning of the next eighty-billion-year cycle.
Besides giving rise to philosophical nihilism, this has interesting consequences for the development of life. During an expansion phase light is redshifted to the relatively harmless lower frequencies. However, during the contraction phase the intensity of dangerous high frequency radiation might become unbearable -- due to a blueshift effect. If the pulsating model is correct, then we are lucky to be alive during the half of the cycle most likely to be hospitable to life. In the second half, the development and expansion of biology would be severely restricted. Are we, asks Carl Sagan, "trapped in a vast cycle of cosmic deaths and rebirths?"20
The second variant of the Big Bang theory is the open, or expanding universe model, which suggests that the cosmos will never stop enlarging and ultimately will disperse to infinity. In this view, all matter reached the "escape velocity" of the universe at the time of the ylem explosion: The cosmic radius increases indefinitely. This is in sharp contrast to the pulsating model, in which the radius oscillates between some maximum value and zero.
There is evidence to support the Big Bang theories. For instance, it will be recalled that the fireball cooled rather rapidly as it expanded. If this rate is extrapolated from the Bang to the present, sixteen eons later, the temperature should be down around a few degrees above absolute zero. This early prediction from evolutionary cosmology was verified in 1965 with the discovery of microwave radiation which fills the entire universe perfectly isotropically. The energy corresponds to a constant, uniform temperature of 2.7 K. This actual relic of the primeval ylem superexplosion strongly affirms the Big Bang theories, and appears to verify the Cosmological Principle mentioned earlier.
How can we decide whether the universe is open or closed? It turns out that if the mean density of the cosmos is less than about 5 x 10-30 gm/cm3 (only about three atoms per cubic meter -- intergalactic space is very nearly empty), then there is insufficient mass to hang onto the galaxies gravitationally. The universe would be open and must disperse to infinity.
Measurements of the actual density are difficult to make. However, based on the latest data, revised Hubble Constant, and such parameters as the observed density of galaxy-clusters locally and the abundance of deuterium in space,1959 astronomers have reached a tentative conclusion: The universe is open.1953
Another class of cosmological theories which has persisted for decades in various forms is the steady-state model, which suggests that the universe is not thinning out at all despite the apparent recession of galaxies. According to a typical model of this variety, neutrons appear suddenly out of nowhere in the interstellar void, roughly one particle per cubic meter every few eons or so. The local density is thus maintained at a constant level, the outflowing mass exactly balanced by the spontaneously generation of matter within the included volume.
The most recent attempt to forge a more plausible steady-state model is the Hoyle-Narlikar cosmology (Figure 4.1).1956 This is based on the concept of a "mass field," which is such that the mass of a chunk of matter is dependent upon its spatial and temporal location in space-time. The universe consists of a checkerboard pattern of normal and reversed mass fields. While mass never becomes negative, its value does vary from zero at a boundary to some maximum value defined by the field. Einstein’s relativistic cosmology is said to represent a special case,1955 valid near a boundary but not across it or very far away from it. Astronomer Hoyle infers that we are close to such a boundary.
Figure 4.1 The Hoyle-Narlikar cosmology1956
If mass has been steadily increasing since we crossed the border some sixteen billion years ago, then galaxies we passed along the way -- which lie nearer the boundary -- should have older, less massive atoms. If less massive atoms also have less massive electrons, these electrons should lie in larger atomic orbits and generally emit spectral lines of lower frequency. That is, the spectra should be redshifted. The observed redshift of galaxies is explained, not by their headlong flight, but because the electrons comprising their atoms are lighter in weight.1954
Hoyle also has an explanation for the 2.7 K background radiation. It is known that light is most efficiently scattered by particles of low mass. Hence, the boundary at Time Zero (where mass goes to zero) must completely scatter all radiation coming from previous cells. The background is just the smeared out starlight emitted by galaxies on the other side of the border. Hoyle calculates that such galaxies still exist prior to Time Zero as far back as 150 eons.1956
Figure 4.2 The Local Universe399,1985
Many other unusual theories have been proposed from time to time, including the Klein-Alfvén matter-antimatter cosmology,1192 the universe-as-a-black-hole idea1963 (and black holes as accretion nuclei for elliptical653 and spira1964 galaxies), the Everett-Wheeler "splitting universe" scheme1982,3683 and other multiple universe ("multiverse") theories.1512,1957,1958 The cosmological problem has not yet lent itself to a definitive solution. Perhaps it never will until we are able to ask ETs, situated elsewhere in distant space, for their observations and ideas.
* 1 megaparsec(Mpc) = 103 kiloparsecs(kpc) = 106 parsecs(pc) = 3.26 x 106 light-years(ly) = 3.07 x 1022 meters(m).
** An eon is one billion (109) years.
Last updated on 6 December 2008