These are eternal questions which our ancestors wondered about from time immemorial. In the past they have been answered primarily by religion and mythology in a symbiotic relationship. Since the emergence of science in the middle ages other answers, based on observation and test, have developed. Throughout the world there continue to be many concepts, each passionately held by its believers. Some may seem preposterous such as the woman who believed that “the world is really a flat plate supported on the back of a giant tortoise.”
I will trace the evolution of several of these cosmic concepts from the ancient Hebrews to that based on the “Big Bang.” In doing so I will relate the progression of cosmic concepts by reference to its principal personalities.
Note: The terms cosmos and universe, meaning essentially the same thing, are used interchangeably.
The image of the world as imagined by Biblical writers was very different and vastly smaller than the cosmos known today. To them there was a “firmament” in the sky in which the stars were embedded. It separated the “waters above” from the “waters below.” A flat earth floated on the lower waters. When activated a “floodgate,” allowed the “waters from above” to rain down on the earth below. In Noah’s time the floodgate stuck wide open and it became apparent that a new cosmic concept might be needed. Several thousand years, later Pythagoras provided it.
In about 500 B.C. Pythagoras, the famous Greek mathematician, proposed a cosmic concept that was based on the beauty of the theory of numbers. To him the sphere was the most perfect shape and therefore, without any experiment or observations, he concluded that the earth must be a sphere--not flat. He further postulated that the earth was at the center of the Universe about which there were seven transparent concentric shells--one on top of the other like inverted cereal bowls of increasing size. On these rested the moon, sun and planets. The seventh shell was reserved for heaven and that is the source for the expression “seventh heaven.” Pythagoras is best known to high school students for his theorem that in a right triangle the square of the hypotenuse is equal to the sum of the squares of the two opposite sides. How many of you remember that? Good--we will have a short quiz after the program.
In 340 B.C. the Greek philosopher Aristotle shared Pythagoras’ concept that the earth was round and not flat. However he based his theory on observations by noting the experience of sailors who would first see the top of the masts of sailing ships as they approached from over the horizon before seeing their hulls.
Although Aristotle’s concept of the cosmos was similar to that of Pythagoras it was much larger consisting of 55--not seven-- individual, concentric, transparent, shells centered on a stationery earth. Each shell, carrying a celestial body, rotated at a different velocity. The Moon was the first of the celestial bodies followed by Mercury, Venus, SUN, Mars, Jupiter, Saturn, the fixed stars, and finally the “Prime Mover.” The motion of the “Prime Mover” was imparted to the other shells causing each of them to rotate. To conform his theory to observations he added a complex system of “Epicycles” in which each celestial body orbited in a small circle around its position on its larger shell.
In 150 AD the Egyptian Ptolemy adopted Aristotle’s system but added Epicycles to each of Aristotle’s Epicycles. Ptolemy published his concept of the cosmos, including a catalog of the stars, in a book that became known as the “Almagest.” This very complex system, with the Earth at the center (geocentric), became known as the “Ptolemaic Universe.” It prevailed as authoritative for more than a thousand years. Very important, the Earth being privileged at the center of the system placed man and his God there. It was embraced by the Catholic Church and became part of its dogma.
A thousand years later, Nikolai Kopernik, better known as Copernicus was born in 1473 in Poland. He studied mathematics and medicine and received a doctorate in canon law. Through the influence of his uncle he was appointed a canon of the Church; in addition to his ecclesiastical duties he practiced medicine. During his spare time he made astronomical observations with the “naked eye” since the telescope had not yet been invented. He then wrote the book, “On the Revolutions of the Heavenly Spheres.” When published in 1543 it completely revised the Earth centered (geocentric) cosmos of Ptolemy. Instead, as you know, Copernicus proposed a Sun centered (heliocentric) system in which the Earth together with the other planets revolved in orbits around the Sun. This is what he wrote:
“Finally we shall place the Sun himself at the center of the Universe. All this is suggested by the systematic procession of events and the harmony of the whole Universe, if only we face the facts, as they say, ‘with both eyes open’.”
Although Copernicus conceived of the planets revolving in orbits around the Sun he was puzzled as to what it was that held them together. He did not know.
Fearing the Church’s possible reaction Copernicus didn’t publish his book until close to his death in 1543 in fact it is reported that he received a copy of the book only on his death bed. His apprehension was justified since by removing the Earth and man from the special position in the center of the Universe, the book contradicted the scriptures of the Church which had adopted the Ptolemaic Universe. It was banned in 1616 and not restored for another two hundred years.
Galileo, a Professor of Mathematics at the University of Pisa, is regarded as the founder of modern experimental science. He is perhaps best known for his use of the telescope which had recently been invented by a Dutch lens maker. In particular he noted that four moons circled the planet Jupiter. From such observations he reasoned that if those moons could circle Jupiter then not all heavenly bodies were constrained to revolve around the earth. Accordingly he concluded that Copernicus’s concept of a heliocentric cosmos was correct and invited Church officials to look through the telescope to confirm what he had seen. They refused to do so because they considered the telescope to be an instrument of Satan. As expected, Galileo’s strong support of Copernicus incurred the wrath of the Inquisition. After a trial for heresy Galileo was condemned to lifetime house arrest. It wasn’t until 350 years after Galileo’s death, that Pope John Paul II, in 1992, endorsed a commission’s finding that the church had made a mistake in condemning Galileo.
By introducing his laws of gravity in 1665 Newton provided the answer to solve Copernicus’s puzzle of what bound the planets and Sun together. But that created another problem. What kept the stars by means of their mutual gravitational attraction from falling inward toward each other?
Newton’s answer was that there was an infinite number of stars in the universe and consequently they remained static in space. He argued that since there is an equal number of stars on each side of any star the force of gravity on one side would be offset by gravity on the opposite side.
Einstein agreed with Newton that the universe of stars was static but disagreed that there was an infinite number of them. Instead into his equations of 1919 he arbitrarily introduced a “cosmological constant” which had the effect of negative gravity and theoretically made the stars to stand still.
But in 1922, Alexander Friedman, an obscure Russian mathematician, using a simplification of Einstein's own equations calculated that the Universe was dynamic and not static and could either be expanding or contracting.
Until Edwin Hubble made his observations in 1927 most astronomers believed that the Milky Way galaxy was alone in the cosmos; it was the cosmos. Hubble trained the 100 inch diameter Mt. Wilson telescope on what is a small “fuzzy blur” that can be seen with the naked eye in the Andromeda constellation and saw it to be a galaxy of stars similar to the Milky Way. He then realized that the Milky Way was not the only galaxy in the Cosmos.
He subsequently discovered more than 100 galaxies, measured their distances from Earth and found that the further away they were the faster they receded from each other at very high speed. These observations confirmed Friedman’s analysis that the universe was dynamic and expanding. Hubble’s discovery of the expanding universe was the forerunner of what later became known as the “Big Bang.” In great embarrassment, Einstein then declared that the insertion of a “cosmological constant” into his equations which was intended to keep the stars static in space was “the greatest blunder of my life.”
In 1927 the Belgian priest and astronomer Abbe Georges Lemaitre used Alexander Friedman type solutions to formulate a model for the beginning of the Cosmos. He wrote that there was a “Cosmic Egg” which exploded.
In 1940 George Gamow, a Professor at George Washington University, predicted that the explosion described by Lemaitre would produce a background of microwave radiation that could be detected. In 1964 while conducting test on satellite communication, Arno Penzias and Robert Wilson of Bell Telephone Laboratories inadvertently detected the predicted radiation. Because it was the first experimental confirmation of the Big Bang theory they were awarded the Nobel Prize.
Scientists transformed Lemaitre’s “Cosmic Egg” into a “singularity,” of infinite temperature, and density. When it exploded 13.7 billion years ago it created space that expanded at extremely high velocity carrying time, sub atomic particles and radiation with it.
For 400,000 years after the Big Bang, the cosmic soup of subatomic particles and radiation was so hot and dense that no light could come through; during that period there was darkness on the face of the universe. After 400,000 years the cosmic soup had thinned out sufficiently to allow light to escape. That was the background radiation observed by Penzias and Wilson.
As the universe expanded huge clouds of hydrogen formed and dispersed. In time, as they continued to cool, and compressed by gravity, the hydrogen clouds condensed into 100 billion galaxies, each with about 100 billion stars and us.
That is apparently what we do know and its a lot, but there is much more that we don't know. In particular we don’t know the nature of “dark matter” and “dark energy.”
Stars in a galaxy revolve around a center just as planets revolve around the Sun. In accordance with Newton’s laws, the outer stars in the galaxy should orbit at a slower velocity than the inner stars. In 1970, Dr. Vera Rubin of the Carnegie Institution of Washington found that was not the case. The outer stars were orbiting just as fast as those closer to the center. She then reasoned that unless there was additional mass in the galaxy to hold them, the outer stars would spin away just like a skater on the end of the line in the game of “crack the whip.” As a consequence of her findings, and that of other astronomers, cosmologists believe there is additional “dark matter,” invisible to normal observations, that is holding the outer stars in their orbits. It is estimated that “dark matter” accounts for 23% of all the matter in the Universe.
In 1999 physicists from Princeton University and Lawrence National Laboratory, after surveying a wide range of evidence of the explosion of massive stars (Supernova) in many galaxies, wrote that “it is forcing us to consider the possibility that some cosmic ‘dark energy’ exists that opposes the self-attraction of matter and causes the expansion of the Universe to accelerate.” That would be negative gravity. Although astronomers know what the effects of “dark energy” are, they do not know what it is even though it represents 73% of all that exists in the Universe. Einstein may have been right after all. “Dark Energy” may be the reincarnation of his “cosmological constant.”
The universe is enormously greater than that of the ancient Hebrews and almost beyond comprehension. The current concept of the cosmos is that it consists of three major component parts; “matter,” “dark matter” and “dark energy.” “Matter” is the stuff with which we are generally familiar. It includes more than 100 billion galaxies each with about 100 billion stars, planets, comets, oceans, trees, mountains--and us. But that accounts for only 4% of all that exists in the cosmos. “Dark matter” accounts for 23% and “dark energy” for 73% .
It is ironic that much more is known about the smallest component of the cosmos and least is known about the largest. Understandably, Cosmologists are expending much effort in attempting to learn the nature of “Dark Matter” and “Dark Energy.” When in the future that is known the concept of the cosmos at that time is likely to be very different from today’s.
In summary. Cosmic concepts have evolved from a “firmament” and flat earth to--inverted transparent shells and a geocentric spherical earth to--a heliocentric system--to an infinity of fixed stars and a static universe--to a dynamic expanding universe--to a vast universe expanding at an accelerating rate with billions of galaxies and stars and us--to “dark matter” and “dark energy.”
To some this may all seem overwhelming and incomprehensible. Perhaps the concept of a flat earth resting on a giant tortoise may be more plausible.