Cosmos: A Spacetime Odyssey

The Earth's location within the Virgo Supercluster

Tyson opens the episode to reflect on the importance of Sagan's original Cosmos, and the goals of this series. He introduces the viewer to the "Ship of the Imagination", the show's narrative device to explore the universe's past, present, and future. Tyson takes the viewer to show where Earth sits in the scope of the known universe, defining the Earth's "address" within the Virgo Supercluster. Tyson explains how humanity has not always seen the universe in this manner, and describes the hardships and persecution of Renaissance Italian Giordano Bruno in challenging the prevailing geocentric model held by the Catholic Church. To show Bruno's vision of the cosmic order he uses an animated adaptation of the Flammarion engraving, a 19th century illustration that has now become a common meme for the revealing of the mysteries of the Universe.

The diversity of species as shown via the Tree of Life.

The episode covers several facets of the origin of life and evolution. Tyson describes both artificial selection via selective breeding, using the example of humankind's domestication of wolves into dogs, and natural selection that created species like polar bears. Tyson uses the Ship of the Imagination to show how DNA, genes, and mutation work, and how these led to the diversity of species as represented by the Tree of life, including how complex organs such as the eye came about as a common element.

The first page of Isaac Newton's 1687 Philosophiæ Naturalis Principia Mathematica

Tyson then relates the collaboration between Edmond Halley and Isaac Newton in the last part of the 17th century in Cambridge. The collaboration would result in the publication of Philosophiæ Naturalis Principia Mathematica, the first major work to describe the laws of physics in mathematical terms, despite objections and claims of plagiarism from Robert Hooke and financial difficulties of the Royal Society of London. Tyson explains how this work challenged the prevailing notion that God had planned out the heavens, but would end up influencing many factors of modern life, including space flight.

An artist's concept of a black hole's accretion disk.

Tyson begins the episode by explaining the nature of the speed of light and how much of what is seen of the observable universe is from light emanated from billions of years in the past. Tyson further explains how modern astronomy has used such analyses via deep time to identify the Big Bang event and the age of the universe.

Tyson proceeds to describe how the work of Isaac Newton, William Herschel, Michael Faraday, and James Clerk Maxwell contributed to understanding the nature of electromagnetic waves and gravitational force, and how this work led towards Albert Einstein's Theory of Relativity, that the speed of light is a fundamental constant of the universe and gravity can be seen as distortion of the fabric of space-time. Tyson describes the concept of dark stars as postulated by John Michell which are not visible but detectable by tracking other stars trapped within their gravity wells, an idea Herschel used to discover binary stars.

Tyson then describes the nature of black holes, their enormous gravitational forces that can even capture light, and their discovery via X-ray sources such as Cygnus X-1. Tyson uses the Ship of Imagination to provide a postulate of the warping of spacetime and time dilation as one enters the event horizon of the black hole, and the possibility that these may lead to other points within our universe or others, or even time travel. Tyson ends on noting that Herschel's son, John would be inspired by his father to continue to document the known stars as well as contributions towards photography that play on the same nature of deep time used by astronomers.

Representative Fraunhofer lines used in astronomical spectroscopy to determine the composition of distant stellar objects

This episode explores the wave theory of light as studied by humankind, noting that light has played an important role in scientific progress, with such early experiments from over 2000 years ago involving the camera obscura by the Chinese philosopher Mozi. Tyson describes the work of the 11th century Arabic scientist Ibn al-Haytham, considered to be one of the first to postulate on the nature of light and optics leading to the concept of the telescope, as well as one of the first researchers to use the scientific method.

Supernova SN 1987A demonstrated the existence of neutrinos.

This episode looks to the nature of the cosmos on the micro and atomic scales, using the Ship of the Imagination to explore these realms. Tyson describes some of the micro-organisms that live within a dew drop, demonstrating parameciums and tardigrades. He proceeds to discuss how plants use photosynthesis via their chloroplasts to convert sunlight into chemical reactions that convert carbon dioxide and water into oxygen and energy-rich sugars. Tyson then discusses the nature of molecules and atoms and how they relate to the evolution of species. He uses the example set forth by Charles Darwin postulating the existence of the long-tongued Morgan's sphinx moth based on the nature of the comet orchid with pollen far within the flower. He further demonstrates that scents from flowers are used to trigger olfactory centers in the brain, stimulating the mind to threats as to aid in the survival of the species.

Meteor fragments from Meteor Crater in Arizona were used to estimate the age of the Earth and other materials in the Solar System.

This episode is centered around how science, in particular the work of Clair Patterson (voiced in animated sequences by Richard Gere[24]) in the middle of the 20th century, was able to determine the age of the Earth. Tyson first describes how the Earth was formed from the coalescence of matter some millions of years after the formation of the Sun, and while scientists can examine the formations in rock stratum to date some geological events, these can only trace back millions of years. Instead, scientists have used the debris from meteor impacts, such as the Meteor Crater in Arizona, knowing that the material from such meteors coming from the asteroid belt would have been made at the same time as the Earth.

Tyson then outlines the work Patterson did as a graduate under his adviser Harrison Brown to provide an accurate count of lead in zircon particles from Meteor Crater, and to work with similar results being collected by George Tilton on uranium counts; with the established half-life of uranium's radioactive decay to lead, this would be used to estimate the age of the Earth. Patterson found that his results were contaminated by lead from the ambient environment, compared to Tilton's results, and required the construction of the first ultra-high cleanroom to remove all traces of environmental lead. With these clean results, Patterson was able to estimate the age of the Earth to 4.5 billion years.

The Harvard Computers that helped to classify the types of stars

This episode provides an overview of the composition of stars, and their fate in billions of years. Tyson describes how early humans would identify stars via the use of constellations that tied in with various myths and beliefs, such as the Pleiades. Tyson describes the work of Edward Charles Pickering to capture the spectra of multiple stars simultaneously, and the work of the Harvard Computers or "Pickering's Harem", a team of women researchers under Pickering's mentorship, to catalog the spectra. This team included Annie Jump Cannon, who developed the stellar classification system, and Henrietta Swan Leavitt, who discovered the means to measure the distance from a star to the Earth by its spectra, later used to identify other galaxies in the universe. Later, this team included Cecilia Payne, who would develop a good friendship with Cannon; Payne's thesis based on her work with Cannon was able to determine the composition and temperature of the stars, collaborating with Cannon's classification system.

A map of Earth's tectonic plates

This episode explores the palaeogeography of Earth over millions of years, and its impact on the development of life on the planet. Tyson starts by explaining that the lignin-rich trees evolved in the Carboniferous period about 300 million years ago, were not edible by species at the time and would instead fall over and become carbon-rich coal. Some 50 million years later, near the end of the Permian period, volcanic activity would burn the carbonaceous matter, releasing carbon dioxide and acidic components, creating a sudden greenhouse gas effect that warmed the oceans and released methane from the ocean beds, all leading towards the Permian–Triassic extinction event, killing 90% of the species on Earth.

Tyson then explains the nature of plate tectonics that would shape the landmasses of the world. Tyson explains how scientists like Abraham Ortelius hypothesized the idea that land masses may have been connected in the past, Alfred Wegener who hypothesized the idea of a super-continent Pangaea and continental drift despite the prevailing idea of flooded land-bridges at the time, and Bruce C. Heezen and Marie Tharp who discovered the Mid-Atlantic Ridge that supported the theory of plate tectonics. Tyson describes how the landmasses of the Earth lay atop the mantle, which moves due to the motion and heat of the Earth's outer and inner core.

Michael Faraday presenting his experiments with electromagnetism at a Christmas Lecture, 1856

This episode provides an overview of the nature of electromagnetism, as discovered through the work of Michael Faraday. Tyson explains how the idea of another force of nature, similar to gravitational forces, had been postulated by Isaac Newton before. Tyson continues on Faraday, coming from poor beginnings, would end up becoming interested in studying electricity after reading books and seeing lectures by Humphry Davy at the Royal Institution. Davy would hire Faraday after seeing extensive notes he had taken to act as his secretary and lab assistant.

After Davy and chemist William Hyde Wollaston unsuccessfully tried to build on Hans Christian Ørsted's discovery of the electromagnetic phenomena to harness the ability to create motion from electricity, Faraday was able to create his own device to create the first electric motor by applying electricity aligned along a magnet. Davy, bitter over Faraday's breakthrough, put Faraday on the task of improving the quality of high-quality optical glass, preventing Faraday from continuing his research. Faraday, undeterred, continued to work in the Royal Institution, and created the Christmas Lectures designed to teach science to children. Following Davy's death, Faraday returned to full time efforts studying electromagnetism, creating the first electrical generator by inserting a magnet in a coil of wires.

This episode covers how life may have developed on Earth and the possibility of life on other planets. Tyson begins by explaining how the human development of writing systems enabled the transfer of information through generations, describing how Princess Enheduanna ca. 2280 BC would be one of the first to sign her name to her works, and how Gilgamesh collected stories, including that of Utnapishtim documenting a great flood comparable to the story of Noah's Ark. Tyson explains how DNA similarly records information to propagate life, and postulates theories of how DNA originated on Earth, including evolution from a shallow tide pool, or from the ejecta of meteor collisions from other planets. In the latter case, Tyson explains how comparing the composition of the Nakhla meteorite in 1911 to results collected by the Viking program demonstrated that material from Mars could transit to Earth, and the ability of some microbes to survive the harsh conditions of space. With the motions of solar systems through the galaxy over billions of years, life could conceivably propagate from planet to planet in the same manner.

The increase in surface temperatures on Earth due to global warming

This episode explores the nature of the greenhouse effect (discovered by Joseph Fourier and Svante Arrhenius), and the evidence demonstrating the existence of global warming from humanity's influence. Tyson begins by describing the long-term history of the planet Venus; based on readings from the Venera series of probes to the planet, the planet once had an ocean and an atmosphere, but due to the release of carbon dioxide from volcanic eruptions, the runaway greenhouse effect on Venus caused the surface temperatures to increase and boiled away the oceans.

Tyson then notes the delicate nature of the amount of carbon dioxide in the atmosphere can influence Earth's climate due to the greenhouse effect, and that levels of carbon dioxide have been increasing since the start of the 20th century. Evidence has shown this to be from humankind's consumption of oil, coal, and gas instead of from volcanic eruptions due to the isotopic signature of the carbon dioxide. The increase in carbon dioxide has led to an increase in temperatures, in turn leading to positive feedback loops of the melting polar ice caps and dethawing of the permafrost to increase carbon dioxide levels.

Earth as a pale blue dot in the middle of the band of light, taken by Voyager I from outside the orbit of Neptune

Tyson begins the episode by noting how the destruction of the Library of Alexandria lost much of humanity's knowledge to that point. He then contrasts on the strive for humanity to continue to discover new facts about the universe and the need to not close off further discovery.

Tyson then proceeds to describe the discovery of cosmic rays by Victor Hess through high-altitude balloon trips, where radiation increased the farther one was from the surface. Swiss Astronomer Fritz Zwicky, in studying supernovae, postulated that these cosmic rays originated from these events instead of electromagnetic radiation. Zwicky would continue to study supernovae, and by looking at standard candles that they emitted, estimated the movement of the galaxies in the universe. His calculations suggested that there must be more mass in the universe than those apparent in the observable galaxies, and called this dark matter. Initially forgotten, Zwicky's theory was confirmed by the work of Vera Rubin, who observed that the rotation of stars at the edges of observable galaxies did not follow expected rotational behavior without considering dark matter. This further led to the proposal of dark energy as a viable theory to account for the universe's increasing rate of expansion.

Tyson then describes the interstellar travel, using the two Voyager probes. Besides the abilities to identify several features on the planets of the Solar System, Voyager I was able to recently demonstrate the existence of the Sun's variable heliosphere which helps buffer the Solar System from interstellar winds. Tyson describes Carl Sagan's role in the Voyager program, including creating the Voyager Golden Record to encapsulate humanity and Earth's position in the universe, and convincing the program directors to have Voyager I to take a picture of Earth from beyond the orbit of Neptune, creating the image of the Pale Blue Dot. Tyson concludes the series by emphasizing Sagan's message on the human condition in the vastness of the cosmos, and to encourage viewers to continue to explore and discover what else the universe has to offer.