History Channel’s The Universe: Beyond the Big Bang presents the history of the universe and the major figures such as Copernicus, Newton, and Einstein who helped to create our modern understanding of the big bang. This 1.5-hour episode of the popular television series provides a detailed overview of major events in the history of astronomy, physics, and cosmology. The development of the big bang theory is described, as well as the origins and potential fates of the earth, sun, and universe. The video also features commentary from current luminaries of science such as Brian Greene, Michio Kaku, Lawrence Krauss, Martin Rees, Max Tegmark, and Neil deGrasse Tyson as well as pioneers of the big bang such as Ralph Alpher, Robert Wilson, and Alan Guth.
The three-page, double-sided video worksheet consists of 115 multiple-choice and matching questions. I am also including a one-page, double-sided short answer worksheet which contains 14 matching and 19 short answer questions. Answer keys are included. The Zip file download contains files in both PDF and MS Word format. You will need to obtain a DVD of the video, or find a way to stream on the Internet. As of this writing, the video is posted on YouTube
History Channel’s The Universe: Beyond the Big Bang Overview
Modern astronomy has revealed a universe that had a beginning called the big bang, which occurred about 13.7 billion years ago. The original inspiration for the big bang was Einstein’s theory of general relativity, and the discovery of the expanding universe.
Today’s universe is immense. On earth, we orbit an ordinary star called the sun, which itself orbits about the center of the Milky Way Galaxy, a massive collection of about 100 billion stars which is about 100,000 light years in diameter. Our Milky Way is one of about 125 billion observable galaxies in the universe. The universe also appears to be rushing apart. Space itself is expanding, carrying galaxies along with it. The universe is larger today than it was yesterday.
To our ancient ancestors, the universe was harsh and unforgiving. Despite this, we appeared to be located at the center of everything! Objects in the sky such as stars, the sun, moon, and planets all appear to revolve overhead around our location on earth. Today we know that this is an illusion created by our rotating and revolving planet.
To seek order and understanding, the ancients imagined natural forces as gods, and sought to use the positions of the stars and planets to predict events on earth-what we today call the “dogma” of astrology. Despite these missteps, early inquiry into the universe began to provide tangible observations that could eventually be built into solid theories of our origin and place in the universe. The ancients built simple structures such as Stonehenge, and the pyramids of Egypt and Chichen Itza, in order to keep track of time and the seasons. Knowledge of the sky was important practical information which helped to predict when planting and harvesting should occur.
The first scientific theory of the universe can be traced to the 4th century BC philosopher Aristotle, who proposed a geocentric, or earth-centered universe. In Aristotle’s model, the earth lay at the center, and the moon, planets, sun, and stars were all located on the surfaces of transparent crystal spheres, which revolved about our location. Due to the work of the 1st century Greek-Egyptian astronomer Ptolemy, who added complex circular motions called epicycles, the geocentric model was held to be true for over a thousand years until Copernicus in the 16th century.
A remarkable feature of Ptolemy’s model was that it had predictive ability. It could be used to calculate the past and future positions of the planets with decent accuracy. For this reason and others, the Ptolemaic model of the universe came to be accepted as true by the Roman Catholic Church where it became dogma. Despite its utility, today we know that the Ptolemaic model has an incorrect foundation, the earth is not the center of the universe.
In 1543, Polish cleric Nicholas Copernicus published a heliocentric, or sun-centered model of the universe. With the sun at the center, the model became much less cumbersome, and most of the epicycles of Ptolemy could be removed (Kepler’s laws of planetary motion which came later would forever banish the epicycle). The distances and apparent motions of the planets were a logical outgrowth of the theory; Mercury, with its 88-day period of revolution, was the first planet and Saturn, with its 30-year period of revolution, was positioned last. The earth became another planet, located in the third position from the sun. Copernicus claimed that the earth also rotated in 24 hours, and revolved in a 365-day orbit around the sun. The apparent motions of the sky overhead were linked to these motions of the earth.
Fearing opposition form the Church, Copernicus waited until nearly dying to have his work published. Like a large stone cast into a pond, the Copernican theory rippled outward and eventually created a revolution in thought which helped to lay the groundwork for the modern big bang theory and other important scientific discoveries.
Starting from the Copernican theory, German mathematician Johannes Kepler discovered three laws that dictated the behavior of the planets. Kepler utilized the life work of Danish astronomer Tycho Brahe who had amassed years of accurate pre-telescopic observations of the positions of the stars and planets. Basing his theories on data, and the assumption of a heliocentric universe, Kepler discovered that the planets orbited the sun in ellipses, not circles as had been previously thought. The planets also appeared to speed up and slow down in their orbits, with the closest point or perihelion corresponding to the fastest motion. Kepler’s Laws provided an extremely accurate way to predict the behavior of the planets, and they also helped to support the factual basis of the Copernican theory.
Italian scientist Galileo Galilei is often considered to be the first modern scientist. His discoveries with the telescope represented observational proof that the Copernican theory was correct, and his studies of motion led the way to Isaac Newton’s theory of gravity.
Galileo was one of the first people to apply the newly invented telescope towards the study of the universe. He was quick to publish his results as The Starry Messenger in 1610. Galileo discovered that the planet Jupiter had four bright moons, which appear to orbit about the planet (not the earth), and that the planet Venus showed phases similar to our moon. The phases of Venus were direct observational proof that Venus orbited the sun. Galileo’s other discoveries with the telescope include mountains and craters on the moon, spots on the sun, and that the Milky Way in the night sky was composed of thousands of stars not visible to the unaided eye.
Galileo’s support of the Copernican theory led him to conflicts with the Roman Catholic Church, which maintained that the geocentric theory of Ptolemy was true, and that it corresponded to descriptions of the universe contained in the Bible. Due to various political reasons, Galileo was eventually forced to stand trial for heresy where he was condemned to house arrest for the duration of his life.
In his 1687 Principia, the towering figure of English scientist Isaac Newton presented the laws that govern motion and gravity. Newton described gravity as a force existing between any two objects with mass, and that gravity was the force responsible for the fall of an apple on the earth’s surface, and the orbit of the moon around the earth. The predictive ability of Newton’s laws led to our modern prosperous civilization. Newton also discovered many of the laws governing the behavior of light, and invented the reflecting telescope, a design based upon mirrors instead of lenses. The reflecting telescope offers several advantages over earlier types, and led to further discoveries in astronomy such as the existence of galaxies and the expanding universe made by Edwin Hubble in the 20th century.
Newton’s formulation of the law of gravity held sway for the next few centuries. In the early 20th century, German physicist Albert Einstein provided a different explanation for gravity as a warping of “space-time”, a fabric of the universe that can stretch and compress in the presence of mass. Gravity can also effect light due to the warping of space. This phenomenon was observed by Arthur Eddington during the 1919 total eclipse of the sun, and this observation provided the first experimental confirmation of Einstein’s theory of general relativity.
Einstein’s general relativity also generated what he considered a distasteful result; the universe as a whole should either be expanding or contracting. This finding clashed with a long-standing bias that the universe was eternal and unchanging. The idea of a beginning, a creation, seemed too “religious” to many scientists. In response, Einstein modified his theory of general relativity by the addition of a “cosmological constant”, a force that acted counter to the pull of gravity, which balanced out the contraction to result in a static, non-changing universe. After seeing evidence of the expanding universe from Edwin Hubble, Einstein later retracted his cosmological constant claiming that it was his “greatest blunder”.
Georges Lemaître, a Belgian priest and physicist, took Einstein’s results and followed them to their logical conclusion: the universe was expanding, and as a result, the universe had once been smaller. The entire universe had once been shrunk down to an object smaller than an atom, what he called the “cosmic egg” or “primeval atom”. Lemaître’s theory was the origin of what we today call the big bang theory. It implied that the universe was not eternal, and that there had been an “in the beginning”. The universe was expanding, and it is larger today than it was yesterday. Running this expansion backwards leads to the origin when the universe appeared as the unbelievably small primeval atom.
When discussing Lemaître’s conclusion, Einstein reportedly stated, “Your mathematics is correct, but your physics is abominable”. This “abomination” was later supported by the work of the celebrated American astronomer Edwin Hubble. Hubble had earlier demonstrated that the universe consisted of billions of galaxies, not just a single galaxy, our Milky Way. With this discovery, the universe grew from a single galaxy of 100,000 light years extent to one of about 125 billion galaxies that was billions of light years across. This result alone would have been a great achievement, but Hubble also discovered that nearly all of the galaxies in the universe appeared to be moving apart. The universe was expanding, just as Einstein’s general relativity had predicted!
Hubble’s measurement of distances in the universe using “standard candles” (stars of known brightness) led him to assert that the universe had an age of about two billion years. This conflicted with the known age of the earth at nearly five billion years. It was later found that Hubble’s age result had been based upon a separate class of star, and that a universe of nearly 15 billion years of age was the more likely result. Despite this, scientific skeptics led by English physicist Fred Hoyle proposed a counter theory named the steady state. With this theory, the universe was eternal and unchanging. The expansion was explained by the generation of new matter (hydrogen) when necessary to maintain the same average density.
In the 1950s, Fred Hoyle was also a radio personality and popularizer of science. Hoyle promoted the steady state theory, and it was held in wide regard by the public. He also coined the term “big bang” as a mocking label for the theory he disliked. Despite this, the term took hold and it still used today. Hoyle was a distinguished physicist, and his major contribution to science was the theory of nucleosynthesis, the discovery that most of the chemical elements in the periodic table were made by nuclear fusion in ancient stars and supernovas. The elements that make up the earth and our bodies were originally made in stars that had lived and died before the earth had even formed. As American astronomer Carl Sagan once said, we are made of star stuff!
Opposition to Hoyle, and support for Lemaître’s theory, was led by Russian physicist George Gamow and American physicist Ralph Alpher. This team used the big bang theory to predict the abundance of hydrogen and helium in the universe, which matched precisely the observed values. Gamow and Alpher correctly predicted that the original hydrogen, and most of the helium, in the universe had been generated just minutes after the big bang when the entire universe was billions of degrees in temperature. They also predicted the existence of a leftover remnant of the big bang’s original heat, what today is termed the cosmic microwave background energy (CMB). Gamow and Alpher stated that observation of the CMB would provide “smoking gun” evidence that the big bang had actually occurred, and that it would likely consist of an amount of energy emanating from all directions in space.
Evidence for the CMB was sought by Robert Dicke’s group at Princeton, who designed a radiometer to measure energy originating from space. Dicke’s group was unknowingly outdone by a pair of physicists working at the Bell Telephone lab in New Jersey. This pair, Arno Penzias and Robert Wilson, were operating a radio antenna to be used in satellite communications. They kept encountering a background static or hiss that could not be attributed to any known source. Eventually, Penzias and Wilson learned of the efforts of the Princeton group and realized that they had made the first measurements of the cosmic microwave background. The background static, emanating from all directions in space, had been generated by the creation of the universe! Both groups published results in 1965, and Penzias and Wilson were awarded the 1978 Nobel Prize in physics for their discovery.
The discovery of the CMB provided conclusive evidence of the big bang origin of the universe, and the majority of the physics community supported the theory. Observations of the CMB by the COBE and WMAP satellites provided estimates of the age of the universe and its composition. According to WMAP data, the big bang occurred 13.7 billion years ago. The WMAP mission also provided a “baby picture” of the early universe, the familiar image that resembles a robin’s egg. The speckled pattern represents slight differences in temperature, which later resulted in the overall structure of the universe, its stars, galaxies, and galaxy clusters.
Details of the theory still needed to be resolved. The temperature or smoothness problem was paramount. The universe was too large to have such a uniform temperature. Too account for this, American Physicist Alan Guth proposed an inflationary stage in the early universe. Occurring just after the big bang, the universe flew apart at an accelerated rate, faster than light itself. This enormous growth spurt spread out the uniform temperature that we see today. Despite its ad hoc nature, inflation is supported as a stage in the development of the universe by WMAP and other evidence.
Milestones in the history of the universe can now be asserted with confidence. The big bang occurred 13.7 billion years ago. At this time the universe was smaller than the smallest part of an atom. At its birth, the universe rapidly expanded and cooled. Within three minutes, protons and electrons formed, which later became the first hydrogen atoms. Some of these hydrogen atoms were fused into helium by the intense heat of the early universe, and these abundances of hydrogen and helium match what is seen in the universe today. Within one billion years of the big bang, the first stars appeared, and they began the synthesis of chemical elements higher than helium on the periodic table. Generations of stars were born, and they later died to build up the abundance of chemistry that we observe in our sun and earth.
Our sun and planets, including earth, formed 9 billion years after the big bang. They emerged inside a large nebula, a cloud of gas and dust that had been seeded with material from previous stars. Life emerged very early in earth history, and we now live in an expanding universe of billions of galaxies.
Also about 9 billion years after the big bang, the expansion of the universe began to increase-the effect of the surprise discovery of “dark energy” in the late 1990s. Dark energy is an unknown force that acts counter to gravity. If current predictions are correct, dark energy will eventually cause the entire universe to fly apart. All matter will be reduced to fundamental particles-the big rip!-which may occur billions of years in the future.
Before the demise of the universe, our sun will also reach the end of its life. About 5 billion years from now, the sun will expand to become a red giant. The inner planets Mercury and Venus will be incinerated as the sun envelopes their orbits. The earth itself will be destroyed as its oceans and atmospheric gases are denuded by the sun’s energy. Even the outer planets will be decimated as the sun ejects its outer layers to become a “planetary nebula”, an object similar to the famous Ring Nebula (M57). After sloughing off its outer layers as a planetary nebula, the sun will be reduced to a shriveled-up white dwarf, an object barely larger than the earth, which will eventually cool to become a black dwarf. This will be the sun’s ignominious end.
Despite these unwelcome predictions, and the reduction in humanity’s once apparently central place in the universe by the Copernican revolution, modern science has discovered that we are physically linked to past stars by the chemical elements that make up our earth and bodies. It is also incredible that we can attain factual knowledge of our origins and future, and we can use these discoveries to make and test predictions about the earth and universe.
Contributors: Brian Greene, Geoffrey Landis, Nima Arkani-Hamed, Michio Kaku, Alan Guth, Lawrence Krauss, Neil deGrasse Tyson, Marcelo Glieser, Charles Seife, Owen Gingerich, John Polkinghorne, Martin Rees, David Leeming, James Peebles, Simon Mitton, Ralph Alpher, Robert Wilson, Alan Guth, Max Tegmark