At the outset of this Section the writer (N.M. Short) wishes to let the reader know that I am not an astronomer or cosmologist by profession. But as a geologist I do have enough background in Science to have taught myself nearly everything you will encounter in this Section. There are probably errors or misconceptions - if you discover any, I'd appreciate your contacting me through my email.
Preparing this Section has been a revelation - almost a life-changing experience. It has given me a profound philosophic comprehension of the most intimate nature of existence itself. I am now constantly revising my understanding of what all beings, life, and myself are all about. Night after night, as I prepare for sleep, I keep asking myself two deep questions: How do we fit into this vast Universe, and why is it there at all? As I approach my end (at this writing 82 and in poor health), I am discovering renewed hope that answers will be found in an afterlife. For those who read through the Section, I trust you will re-examine your outlook based on realizing your place in the grand scheme of things.
More than 10 years after I began this Section, I purchased a Cosmology DVD course available from The Teaching Company, which specializes in providing college level courses covering almost all areas of knowledge. The course is conducted by Dr. Mark Whittle, a Professor at the University of Virginia. It is an extraordinary offering which thoroughly and clearly surveys the entire field. It is my hope to be able to incorporate ideas and material from this course into this Section, thereby revising it by modifying and expanding the content.
Note: 1) Most of the pages in this Section are image-intensive, so that the large number of illustrations can lead to a lengthy download time for those using modems connected to telephone lines; 2) Some parts or ideas presented in this Section may seem repetitious, i.e., are stated more than once; some of this reiteration is deliberate - much of the topics covered tend to be complex and unfamiliar to the non-specialist reader (those who are not astronomers, cosmologists, physicists), so that repeating is a helpful aid in reminding one of these previously developed ideas and tying them (making them relevant) to the other subjects where they later appear.
There will be no individual page summaries in Section 20 which deals with Cosmology: The Origin, Composition, Structure, Development, and History of the Universe (or Universes, if there are more than one). This is largely because of the complexity and wide range of ideas on each page: this does not lend itself easily to synopsize. The reader instead should work through the knowledge imparted on each page without the aid of a preview or reduction to a simplified digest. If the field is new to you, several readings of this Section may be needed to facilitate mastery of this ultimate subject: the Origin of Everything. Also, if a novice, you should profit from working through the excellent online "textbook" in Astronomy prepared by Dr. J. Schombert at the University of Oregon, which have been referenced in the Preface . In keeping with the Overview and the 20 Sections that have followed, every illustration will be accompanied by a synoptic caption.Despite this absence of page summaries, we will attempt to abridge the overall ideas underlying Astronomy and Cosmology in this synopsis shown in green:
ASTRONOMY deals mainly with the description of the objects, materials, structure, and distribution of everything that appears to exist beyond the Earth itself. COSMOLOGY deals with the origin, development, and future expectations of/for the Universe Thus, Astronomy is mostly concerned with the "what" and "where" whereas Cosmology is more concerned on the "how" and "why". Both focus on the subjects of stars, galaxies, interstellar/intergalactic gases, and the void called "space", but from differing perspectives.
Astronomy as an observing "science" traces its roots to early civilizations such as the pre-Christian era Babylonians, Egyptians, Greeks, and Chinese and the Mayans and Aztecs in the New World. Star groupings, the constellations, were established and became involved in myths that suggested deity controls of how the World (i.e., the Universe) is able to function. ,.
Ideas of an Earth-centered Universe began in early times, with both myths and theological explanations for the meaning and cause(s) of the physical (natural) World (including and beyond the Earth) gradually being supplanted by scientifically-based observations. Key ideas that provide this basis include the postulates by such Greek philosophers as Pythagoras, Euxodus, and Aristotle (the latter proposed the Earth as the center of the Universe, with the Moon, Sun, and stars being embedded in crystal spheres that rotated around Earth) and the later (ca. 140 BCE) Ptolemaic description of epicyclic "heavenly" motions; these persisted largely as philosophical musings until the advent of Copernicus in the 16th Century CE who posited the heliocentric theory for the Solar System (but that had been suggested - and discounted - by Aristarchus in 280 BCE), followed by important contributions from Tycho Brahe (detailed measurements of motions of celestial bodies) and Johannes Kepler (Laws of planetary movements) soon thereafter. Galileo was the first to use the telecope for astronomical observations; his observations confirmed Copernicus's revolutionary idea that the Earth was not the center of the Universe nor the Solar System. Isaac Newton provided the foundation for the movements of stars and planets with his Laws of Gravity and Motion. William Herschel in the late 1700s CE provided the first proof that the Milky Way, in which the Sun is located. is an "Island Universe", namely a huge cluster of stars comprising a galaxy; Herschel surmised that other such galaxies must exist. This led to the beginning of the modern era of Cosmology stemming for work by Edwin Hubble and others in the 1920s, who showed that there were many galaxies beyond the Milky Way and some of these were located at huge distances from Earth. Hubble also confirmed the idea of expansion from a Big Bang that had been put forth by the Abbe Lemaitre in the early 1920s. Of great importance to cosmologists was the new framework for a proper understanding of the Universe and of the laws of physics that affect it that was established by Albert Einstein's theories of Special and General Relativity (see Preface).
Before the beginning of this (there may be more than one) finite Universe there was (at least for those within it) no time nor space, no energy (in the discrete forms we know) nor matter - at least in the sense that we perceive these fundamental "qualities". What may have existed is some as yet undefined quantum state in an endless void in which fluctuations in the "emptiness" - the void - led to extremely fleeting "particles" containing the essence to grow into a Universe. Essentially all such evanescent moments ended with the disappearance of these particles (still unidentified entities: energetic virtual (potential non-yet existing particles which may be those constituting the Dark energy that dominates the Universe [see this page and Pages 20-8 and 20-9] have been proposed). But the potential was there for one such particle to spring to existence at a moment (the singularity) that witnessed "creation of space and matter" from when our Universe sprang. This diagram may help as you work through the next three paragraphs (variations will appear later on this page):
The singularity particle was so unstable that it "exploded" into what is known colloquially as the "Big Bang". That took place some 13.7 billion (+/- 200 million) years ago (see page 20-9 for a discussion as to how this value has been reached and has changed several times in recent years). What actually happened is not a true explosion but a process that is described as the creation of "space" which has been expanding ever since. The first minute of Universe time was the critical stage leading to the state of the Universe we observe today. We can trace theoretically events during the minute back to 10-43 sec(onds) - an instant known as the Planck time - when the Universe was infinitesimally small. (Experimentally, astrophysicists can actually reconstruct the sequence and verify the essential physics of the Universe�s early conditions back to 10-12 seconds and to particle sizes as small as 10-17 meters; better yet, a significant number (most?) of the particles and forces [and fields through which they interact] have now been defined and all but a few actually found and identified under laboratory conditions.) Initially, the fundamental forces (strong; weak; electromagnetic; gravity) were unified (as may be explained through one new theory in physics called "superstrings"). But, they quickly separated systematically into the individual four prime forces. Although expansion was rapid, at about 10-35 seconds, there was a one-time only extreme acceleration of this minute Universe through a process called Inflation. Inflation may be responsible for the likelihood that the Universe is much larger than the 13.7 billion light year limit of the observable Universe imposed by the speed of light.
Thereafter, in this first minute as expansion continued and the proto-Universe cooled to lower energy levels, the fermions (matter), controlled by the appropriate bosons (force), began to organize into the protons and neutrons (both composed of quarks), electrons, mesons, neutrinos, and others of the myriads of particles continually being discovered in high energy accelerator experiment in physics labs.
As the first minute ended, some particles began to associate with others (while probably all the anti-matter that should have been created was destroyed). In the first few minutes, particles began to organize into nuclei that were part of a plasma state in which the mix included electrons, photons, neutrinos and others. In the next 380,000 years or so, this particle-radiation state witnessed the beginnings of organization into atoms, mostly of Hydrogen and some helium. After that time the Universe became "transparent" so that communication through photon (light) radiation was possible between segments of the Universe close enough to exchange information at the speed of light. The Universe was almost completely homogeneous and isotropic on a grand scale but locally tiny fluctuations in the state of matter (mostly H and He), as appear in the irregularities in the Cosmic Background Radiation (greatly cooled Big Bang "afterglow' that pervades the Universe and marks its observable edge), led to gravitational clumping (into nebulas) that grew simply because these slight increases in density continued to increase the organization through the force of gravitational attraction. From this eventually, in the first billion years, stars began to form and to arrange in clusters called galaxies. These adopt specific shapes, such as spiral, elliptical, or irregular. This diagram, a classification of forms first put forth by Edwin Hubble, shows the range of shapes (note: it is not an evolutionary chain ):
A star is defined as a massive, spherical astronomical body that is undergoing (or has undergone) burning of nuclear fuels (initially Hydrogen and, if hot enough, Helium); as it evolves elements of greater atomic number are consumed as well) so as to release energy in large amounts of both luminous and non-luminous radiation (over a wide range of the EM spectrum); stars eventually change significantly in mass, size, and luminous output with some finally surviving only as very dense cores (neutron stars) of minimal luminosity. Stars burn their Hydrogen at high temperatures, during which (depending on their size) they convert this fuel to heavier elements (largest ones can produce elements up to iron in the Periodic Table). Large stars die out rapidly (a few hundred thousand to one or more billion years); small stars can persist for times that are comparable to the total life of the Universe. During their stable lifetimes, the stars hold together by a fine balance between inward contraction under gravity, involving internal heating up, and the outward pressure of the radiation produced by nuclear processes. Many stars can explode as supernovae. Various types of stars evolve over time through distinct pathways; among these are Red Giants; White Dwarfs; Brown Dwarfs, and Neutron Stars. Black Holes are another, perhaps widespread, constituent of space. As a star forms out of nebular material - gases mainly of some Hydrogen and helium, and other elements in various forms, including particulate dust), some of this material not drawn into the growing star may collect in clots that would form planetary bodies - rocks and gas balls - similar to those making up our Solar System.
The composition of the Universe has only recently been determined fairly precisely. Ordinary matter, making up the stars, galaxies, gas/dust clouds and a small fraction of the so-called empty space, accounts for about 4% (most of that is Hydrogen and some Helium). The rest is present in Dark Matter (undetected directly by any technique so far; includes the WIMPS and MACHOs discussed on page 20-9) which seemingly increases around galaxies, and makes up about 23% of a Universe and Dark Energy (about 73%), tied to a still mysterious force that seems to act like the anti-gravity force first postulated by Einstein,which he called the Cosmological Constant, and is the prime candidate for causing the recent observation that the Universe now is once again expanding after slowing down for the first seven or so billion years.
The fate of the Universe depends ultimately on how much mass (and its convertible form, energy) it has. If that number is high the Universe�s expansion may slow down and eventually reverse (contract) so that all matter and energy collect again at a superdense point which may undergo another Big Bang. Or the matter/energy is insufficient to slow expansion and the Universe enlarges forever. The shape of the Universe will depend on the nature of the expansion; recent evidence indicates that it may be "flat". At large scales the Universe is subject to the laws of Relativity (but equally as important is the role of matter/energy at the smallest - quantum - scales). Recent information favors endless expansion and the possibility that the rate of expansion is now increasing.
Add to all of this the theoretical (quantum-driven) possibility that there may be multiple universes, unable to communicate with one another, with new ones forming at various times and perhaps old ones dying in some way. The mind boggles at this point. But even more amazing is the realization that there is something we humans recognize as "mind" - our most valuable property and objectively the most powerful entity so far discovered in the Universe. Our minds have identified the ways in which planets form, including those suited to hosting living creatures, and the very nature of life itself.
Humankind has in the last 400 years, and especially the last 50 years, developed the skills and the will to explore our Universe. We now obtain data of great explanatory/interpretive value using telescopes that gather in radiation from all parts of the EM spectrum. Thus, there are now specialized observing systems that sample in the gamma-ray, x-ray, ultraviolet, visible, near and far infrared, and radio wavelength regions of the spectrum. Astronomy is probably the prime user of nearly all segments of that spectrum, as it gathers its information almost exclusively by remote sensing methods.
The big advance during the last 50 years has been to place astronomical telescopes into space, in orbits above the Earth's atmosphere. The most famed of these is the Hubble Space Telescope (HST) which has dazzled astronomers, other scientists, and the world public with its abundance of extraordinary images. There have been other great space observatories; we mention most of the best known in this Overview: the Compton Gamma-Ray Observatory (CGRO); the Chandra X-Ray Telescope; XMM-Newton; Extreme Ultraviolet Explorer (EUVE); the International Ultraviolet Explorer (IUE); the Far Ultraviolet Explorer (FUSE); the Galaxy Evolution Explorer (GALEX); the Infrared Astronomical Satellite (IRAS); the Infrared Space Observatory (ISO); the Space InfraRed Telescope Facity (SIRTF; renamed the Spitzer Space Telescope. Only two radio telescopes have yet been orbited but plans are underway for more. A pictorial overview of the major space observatories is presented in this illustration:
THIS IS A GOOD PLACE, IN THIS SYNOPSIS, TO MENTION SOME OF THE MAJOR INDIVIDUALS OF THE 20TH CENTURY AND THEIR CONTRIBUTIONS TO COSMOLOGY (MORE DETAILS WILL FOLLOW ON THIS AND LATER PAGES):
MAX PLANCK: THE ORIGINATOR OF SOME OF THE IDEAS THAT LED TO QUANTUM PHYSICS.
VESTO SLIPHER: DISCOVERED THE "RED SHIFT" OF STELLAR SPECTRA, INDICATING GALAXIES WERE MOVING AWAY FROM THE EARTH AS AN OBSERVING PLATFORM.
ALBERT EINSTEIN: THE "GIANT INTELLECT" WHOSE CONCEPTS OF RELATIVITY CHANGED PHYSICS AND RECAST OUR UNDERSTANDING OF THE UNIVERSE; STATED THE NOTION OF SPACETIME AND DEVISED NEW CONCEPT OF GRAVITY; HE BELIEVED IN A STEADY STATE UNIVERSE.
WILLEM DE SITTER:FROM HIS SOLUTION OF EINSTEIN'S GENERAL THEORY OF RELATIVITY EQUATIONS, CONCLUDED THE UNIVERSE WAS EXPANDING.
ALEXANDER FRIEDMANN: THE RUSSIAN MATHEMATICIANT WHO CONFIRMEDED THE POSSIBILITY OF AN EXPANDING, FINITE UNIVERSE.
GEORGES LEMAITRE: THE BELGIAN PRIEST WHO CONCEIVED OF THE UNIVERSE'S EXPANSION FROM A VERY SMALL VOLUME (THE PRIMORIDAL ATOM; SIZE ROUGHLY THAT OF THE SOLAR SYSTEM) THAT "EXPLODED" AT THE BEGINNING OF TIME (SINGULARITY)".
EDWIN HUBBLE: THE ASTRONOMER WHO DISCOVERED GALAXIES BEYOND THE MILKY WAY AND PRESENTED EVIDENCE FOR EXPANSION.
GEORGE GAMOW: THE PHYSICIST WHO EXPLAINED HOW STARS FORM AND BURN THEIR HYDROGEN FUEL.
FRED HOYLE: THE ASTRONOMER WHO EXPLAINED HOW ELEMENTS HEAVIER THAN HELIUM ARE PRODUCED BY FUSION IN STARS; HE ALSO COINED THE TERM "BIG BANG" (AS A DERISION OF EXPANSION CONCEPTS) AND CHAMPIONED A STEADY STATE UNIVERSE.
BRANDON CARTER: THE PHYSICIST WHO PROPOSED THE MODERN CONCEPT OF "THE ANTHROPIC PRINCIPLE" - THE UNIVERSE HAS JUST THE RIGHT SET OF PROPERTIES TO ALLOW LIFE TO DEVELOP WITHIN IT AT SOME EVOLUTIONARY STAGE (AND REQUIRES INTELLIGENT LIFE TO REALIZE THAT IT EXISTS).
ALAN GUTH: THE COSMOLOGIST WHO PROPOSED THE IDEA OF THE BRIEF SUPEREXPANSION KNOWN AS INFLATION THAT BEST ACCOUNTS FOR THE UNIVERSE'S SIZE AND PROPERTIES.
ARNO PENSIAS AND ROBERT WILSON: THE TWO ENGINEERS WHO FORTUITOUSLY DISCOVERED THE COSMIC BACKGROUND RADIATION (BEING SOUGHT THEN BY ROBERT DICKE'S GROUP AT PRINCETON UNIVERSITY); PREDICTED BY EINSTEIN, THIS RADIATION IS STRONG EVIDENCE FOR THE BIG BANG AND IT HELPS TO ESTABLISH THE "TRUE" AGE OF THE UNIVERSE (IN TERMS OF EARTH YEARS).
We close this Overview summary with a map that shows the main features of the Observed Universe; other kinds of maps are possible and several will appear later in the Section.