A list of technical terms or terms that are used in distinctive ways in this book.
absorption lines: Dark lines that appear when starlight is analyzed with a spectroscope; they indicate the presence of particular elements that have absorbed some of the energy of starlight and can be used to detect the motion of remote objects as the dark lines shift to the red or blue end of the spectrum.
accretion: The process by which matter in orbit around a star gathers together to form planets, moons, and asteroids.
activation energy: An initial shot of energy that initiates reactions that may generate much more energy, like a match starting a forest fire.
adaptive radiation: Periods of rapid biological evolution and diversification, often following mass-extinction episodes.
affluent foragers: Sedentary foragers such as the Natufians, usually found in regions of exceptional natural abundance.
agrarian civilizations: Communities of millions of people supported by agriculture with cities, states, bureaucracies, armies, social hierarchies, and writing.
agrarian era: The era of human history that was dominated by agricultural technologies; it started after the last ice age and ended two or three centuries ago.
agriculture: A suite of technologies that allowed humans to maximize the energy flows and resources available to them by manipulating the environment to increase production of plants and animals they found useful.
Anthropocene epoch: The most recent period of human history in which humans have become a dominant force for change in the biosphere; proposed as a new geological epoch, following on from the Holocene.
antimatter: Subatomic particles that are identical to other subatomic particles but have opposite charges, such as positrons (electrons with positive charges); when matter and antimatter meet, they obliterate each other and turn into pure energy.
arbitrage: Buying cheap on one market and selling dear on another market to make large profits.
archaea: Single-celled prokaryotic organisms; Archaea is one of the three major domains of life. See also bacteria and eukaryotes.
Archean eon: One of four major divisions in the history of planet Earth, from 4 billion years ago to 2.5 billion years ago.
astronomical standard candle: An astronomical object such as a Cepheid variable or a type 1a supernova whose distance can be determined, allowing it to be used to measure the distances to other objects.
atom: Smallest particle of ordinary matter, consisting of protons, neutrons, and electrons; atomic matter may account for only 5 percent of the mass of the universe. See also dark energy and dark matter.
ATP (adenosine triphosphate): Molecule used in all living cells to carry energy.
bacteria: Single-celled prokaryotic organisms in the domain of Eubacteria, one of the three major domains of life. See also archaea and eukaryotes.
big bang cosmology: Paradigm idea that arose in the 1960s to explain the emergence of our universe from a tiny, dense concentration of energy about 13.82 billion years ago.
biosphere: The sphere of planet Earth dominated and shaped by life and the by-products of living organisms.
black hole: A region so dense that nothing can escape its gravitational pull, not even light; often formed from the collapse of a supermassive star at the end of its life. There may be black holes at the center of all galaxies.
Cambrian explosion: The sudden proliferation of large organisms with hard body parts about 540 million years ago.
capitalism: A social system dominated by commercial activity and merchants in which governments favor commerce because much of their revenue comes from commerce.
carbon: Element 6 on the periodic table; the fundamental element in living organisms because of the virtuosity with which it links up with itself and other elements.
catalyst: A molecule (usually a protein) that facilitates particular chemical reactions by lowering the required activation energy without the molecule itself being changed by the reaction.
Cepheid variable: A star whose brightness varies in a regular pattern. There are two main types, and because the rate of variation is related to their intrinsic brightness, their distance can be estimated so they can be used as astronomical standard candles to measure astronomical distances.
chemiosmosis: The movement of ions down their concentration gradient across a membrane. In cells, ATP synthase in the cell membrane harnesses this energy to charge up ATP molecules.
collective learning: The process, unique to humans, by which information is shared among individuals with such precision and in such volume that it accumulates from generation to generation; the key to our species’ growing control of information and the biosphere.
complexity: Complex entities have more moving parts than simpler entities, and those parts are linked in precise ways that yield new emergent properties.
core: Central and densest region of Earth, dominated by iron and nickel; source of Earth’s magnetic field.
cosmic microwave background radiation (CMBR): Radiation left over from the moment, about 380,000 years after the big bang, when the first atoms formed; still detectable today and one of the crucial pieces of evidence for big bang cosmology.
cosmology: Study of the universe and its evolution.
crust: The surface layer of Earth, made mostly of lighter rocks such as granites and basalts that have cooled sufficiently to solidify; this is where most organisms live.
dark energy: Energy whose nature and source is not yet understood but which may account for the accelerating expansion of the universe and for perhaps 70 percent of the mass of the universe.
dark matter: Matter whose gravitational effects are detectable but whose exact source and form is not yet understood; accounts for perhaps 25 percent of the mass of the universe.
demographic transition: In modern times, declining mortality drove population growth, but increasing urbanization eventually drove down fertility rates, so population growth is slowing today; the demographic transition has transformed the attitudes to families and gender roles that were dominant in most peasant societies.
differentiation: The process by which the early Earth heated up, melted, and was sorted into layers of decreasing density, among them the core, the mantle, and the crust.
DNA: Deoxyribonucleic acid, the molecule that carries the genetic information of most living organisms.
domestication: Genetic modification of a species as it coevolves with another species; fundamental to agriculture.
Doppler effect: Apparent change in frequency of emitted radiation as objects move toward or away from each other; used in police speed traps and to detect the motion of stars and galaxies toward or away from Earth.
Earth: The planet we live on, with its possibly unique cargo of living organisms.
electromagnetism: One of the four fundamental forms of energy. It is powerful at small scales, comes in positive and negative forms, and is the most important form of energy in chemistry and biology.
electron: Negatively charged subatomic particle; normally orbits atomic nuclei.
element: A basic form of atomic matter. Each element is distinguished by the number of protons in its nucleus; elements are classified within the periodic table according to their distinctive properties, and there are about ninety-two stable elements.
emergence: See emergent properties.
emergent properties: New properties that emerge as existing structures are linked together to form new structures with properties that are not present in their component parts. For example, stars have properties that are not present in the atomic matter from which they are constructed.
energy: The potential for things to happen or move or change. In our universe, energy comes in four main forms—gravity, electromagnetism, and the strong and weak nuclear forces—but it also exists in the form of dark energy.
entropy: The tendency of the universe to become less structured in accordance with the second law of thermodynamics.
enzyme: A biochemical molecule that acts as a catalyst, facilitating reactions in cells that would otherwise require much larger inputs of activation energy.
eukaryotes: Members of Eukarya, one of the three domains of life, eukaryotes are made up of cells with internal organelles. The first eukaryotes evolved through mergers between organisms from the other two (prokaryotic) domains of life, the Eubacteria and Archaea; all multicellular organisms consist of eukaryotic cells. See also archaea, bacteria, prokaryotes.
Fertile Crescent: The arc of well-watered lands around Mesopotamia in which agriculture first appeared.
fire-stick farming: Paleolithic technology based on regularly firing the land so as to increase its productivity.
first law of thermodynamics: See thermodynamics.
foraging: Characteristic technologies of the Paleolithic period, based on the gathering of resources from the environment and a limited amount of processing.
fossil fuels: Buried and fossilized organic material, primarily coal, oil, and natural gas, that contains ancient stores of energy from photosynthesis; the primary energy sources for the modern world.
free energy: Energy that does not flow randomly and so can do work (for example, the energy of water flowing through a turbine).
fusion: Occurs when protons collide so violently that they overcome the repulsion of their positive electric charges and are joined together by the strong nuclear force; fusion is accompanied by a huge release of energy as some matter is turned into energy. Source of the energy of H-bombs and the energy emitted by stars.
galaxy: A collection of millions or billions of stars held together by gravity; our home galaxy is the Milky Way.
gas: A state of matter in which individual molecules or atoms are not tightly bound together.
genome: The information stored in the DNA of every cell that regulates how it functions and allows it to make accurate copies of itself.
globalization: The increasing scale of exchange networks until, after 1500 CE, they began to reach around the entire world.
Goldilocks conditions: The rare special preconditions and environments that are “just right” to allow the emergence of new forms of complexity.
gravity: One of four fundamental forms of energy, though weak, gravity operates over large scales and tends to draw together everything with mass or energy. Einstein showed that gravity works by warping the geometry of space-time.
greenhouse gases: Gases such as carbon dioxide and methane that absorb and retain energy from sunlight; in sufficiently large quantities, greenhouse gases tend to raise temperatures at Earth’s surface.
Hadean eon: One of four major divisions in the history of planet Earth; it began 4.6 billion years ago, when Earth first formed, and ended around 4 billion years ago.
half-life: The time it takes for half of a radioactive isotope to break down. Crucial concept for radiometric dating, as different half-lives allow different isotopes to be used to date events and objects at different time scales.
heat energy: The kinetic energy (or energy of motion) that drives the random jiggling of all particles of matter; only at a temperature of absolute zero does matter lose all heat energy. See temperature.
helium: Chemical element with atomic number 2 (two protons in its nucleus). Second most abundant element in the universe; chemically inert.
Hertzsprung-Russell diagram: Diagram charting the intrinsic brightness or luminosity of stars (the amount of energy they emit) against their color (or surface temperature); for astronomers, a powerful way of classifying different types of stars and the different ways in which stars evolve.
Holocene epoch: The geological epoch since the end of the last ice age, beginning about 11,700 years ago.
homeostasis: A state of equilibrium; living organisms maintain homeostasis by sensing changes in their environments and adjusting to those changes.
hominins: Bipedal apes that are ancestral to our own species and have evolved since our ancestors diverged from the evolutionary lineage leading to chimpanzees, about seven million years ago.
Homo sapiens: The species of great ape to which all readers of this book belong.
human: A member of the species Homo sapiens.
hydrogen: Chemical element with atomic number 1 (one proton in its nucleus); most abundant element in the universe.
ice ages: The era of ice ages interspersed with warmer interglacials that began about 2.6 million years ago, at the beginning of the Pleistocene epoch.
inflation: Cosmologically, a period of extremely rapid expansion of the universe early in the first second after the big bang.
information: The underlying rules that determine how change can occur. Some of these rules are universal, but living organisms need to be able to detect and react to local information, rules that work only in their immediate environment. Information can also refer to knowledge of how things work.
informavore: An entity that consumes information as carnivores consume meat; all living organisms are informavores.
isotope: Atoms of the same element with the same number of protons but different numbers of neutrons.
kelvin: Like the Celsius scale but begins at absolute zero (−273.15°C); the freezing point of water is 273.15 K and 0°C.
life: The emergent property of all living organisms. Hard to define precisely, as we only know of life on planet Earth, but its qualities include the ability to maintain homeostasis, metabolize, reproduce, and evolve.
light-year: Distance traveled by light in a vacuum during a single Earth year, approximately 9.5 trillion kilometers.
liquid: A fluid state of matter in which atoms or molecules are bound together but can flow past and around one another; liquid takes the shape of its container.
Luca: Last universal common ancestor; the inferred ancestor of all living organisms on Earth.
mantle: The semimolten layer of Earth beneath the crust and above the core, about three thousand kilometers thick.
map: In common usage, a schematic picture of a landscape or geographical region; often used here in a metaphorical sense to mean the pictures we create of space and time and of the entire universe and its history in order to identify our own place in the scheme of things.
matter: The physical “stuff” of the universe that occupies space. Einstein showed that matter consists of compressed energy and can be converted back to energy (for example, during proton fusion).
megafauna: Large mammals; many were driven to extinction late in the Paleolithic soon after the arrival of humans in Australasia, Siberia, and the Americas.
metabolism: The ability of living organisms to tap and use energy flows from their environment.
metazoans: Multicellular organisms; “big life.”
meteorite: A piece of space debris that lands on Earth; most meteorites have barely changed since the creation of the solar system so they provide information about the solar system’s formation and evolution.
Milankovitch cycles: Variations in the orbit and tilt of Earth that affect the amount of energy it receives from the sun; these variations help explain the cycle of ice ages during the Pleistocene epoch.
molecule: Several atoms bound together by chemical bonds.
moon: The planetary body that orbits Earth, formed from a collision with another planetary body soon after Earth’s formation.
multiverse: The speculative idea that there may be multiple universes, perhaps with slightly different fundamental laws and forms of energy.
Natufians: An archaeological term for “affluent foragers” who lived in the Fertile Crescent east of the Mediterranean between about 14,500 and 11,500 years ago.
natural selection: Charles Darwin’s key idea that individual organisms survive and reproduce or fail to do so depending on how well they fit into their environments; this mechanism is the fundamental driver of evolution.
neutron: Subatomic particle usually found in atomic nuclei; similar mass as a proton but no electric charge.
nucleus: The dense core of an atom, mainly populated by neutrons and protons.
order (structure): Nonrandom or patterned arrangements of matter and energy.
origin story: An account of the evolution of all of space and time based on the best knowledge available to a particular community; origin stories are embedded within all major religious and educational traditions and provide a powerful way of understanding one’s place in space and time.
oxygen: Chemical element, atomic number 8; fiercely reactive.
Paleolithic period: The era of human history from the initial appearance of our species, about two hundred thousand years ago, to the end of the last ice age and the beginning of farming, around eleven thousand years ago.
Pangaea: The supercontinent that existed from about three hundred million years ago to two hundred million years ago.
paradigm: An idea that is widely accepted by researchers in a particular field of study and that unifies information within that field; for example, big bang cosmology (astronomy), plate tectonics (geology), and natural selection (biology). Based on the work of the historian of science T. S. Kuhn.
parallax: The apparent movement of an object against its background as the observer moves; used by surveyors and astronomers to calculate distances to remote objects or nearby stars.
periodic table: Table of chemical elements, initially devised by Dmitry Mendeleyev, that groups elements with similar features.
Phanerozoic eon: One of four major divisions in the history of planet Earth, from about 540 million years ago to today; the era of large organisms or “big life.”
phase change: A change of state, such as the change from the gaseous to the liquid or solid state.
photon: A massless particle of electromagnetic energy that moves at the speed of light in a vacuum and also has wavelike qualities.
photosynthesis: Capture of energy from sunlight by plants or plantlike organisms to power their metabolism.
planet: Astronomical body formed in orbit around a chemically enriched star.
plasma: A state of matter in which temperatures are so high that subatomic particles cannot bind together to form atoms.
plate tectonics: Paradigm idea that emerged in the 1960s to explain how convection currents within Earth’s mantle, powered by heat in Earth’s core, drive the movement of tectonic plates on Earth’s surface.
Pleistocene epoch: Geological epoch from about 2.6 million years ago to about 11,700 years ago; dominated by ice ages.
prokaryotes: Single-celled organisms without nuclei, from the domains of Eubacteria and Archaea; the earliest life-forms on Earth were prokaryotes. See eukaryotes.
Proterozoic eon: One of four major divisions in the history of planet Earth, from around 2,500 million years ago to 540 million years ago.
proton: Subatomic particle with positive electrical charge found in atomic nuclei; the number of protons determines an element’s atomic number.
quantum physics: The study of phenomena at the subatomic level, where it is impossible to identify the exact position or motion of particles, so physical laws have to be formulated as probabilities.
quark: Subatomic particle from which protons and neutrons are created by the strong nuclear force.
radioactivity: The tendency of many atomic nuclei to spontaneously break down, emitting subatomic particles.
radiometric dating: Dating techniques developed in the mid-twentieth century based on the regular breakdown of radioactive isotopes; this book’s timeline could not have been constructed without radiometric dating techniques.
red giant: Dying star, such as Betelgeuse in Orion, that has expanded and has a cooler (redder) surface.
redshift: Shift of absorption lines toward the red end of the spectrum; an indication that an astronomical object is moving away from Earth. A key piece of evidence that the universe is expanding.
religion: Spiritual traditions, some highly institutionalized, all of which seem to have embedded within them some form of origin story.
respiration: The taking in of oxygen by animals; also, the use of oxygen in cells to release energy stored in sugars.
RNA: Ribonucleic acid, a close relative of DNA that is present in all cells and can both carry genetic information and do metabolic work.
science: Modern traditions of rigorous, evidence-based study of the world and the universe, developed since the seventeenth century’s scientific revolution.
second law of thermodynamics: See thermodynamics.
sedentism: Nonnomadic lifeways, in which individuals and households mostly stay near their home base in permanent dwellings. Usually associated with agriculture but sometimes with affluent foragers.
solar wind: A flow of charged subatomic particles from the sun.
solid: A state of matter in which individual atoms and molecules are so tightly bound together that they cannot easily alter their position.
space-time: Einstein argued that space and time are best understood as part of a single universal framework, which he called space-time.
spectroscope: An instrument that breaks light into distinct frequencies; used to determine the chemical composition of astronomical objects.
star: An astronomical body formed when fusion reactions begin at the center of a collapsing body of matter; stars are gathered by gravity into galaxies.
strong nuclear force: One of four fundamental forms of energy. Operates at subatomic scales, binding quarks into protons and neutrons and holding atomic nuclei together.
subatomic particles: Components of atoms, such as protons, neutrons, and electrons.
sun: Our local star, source of most of the energy that powers the biosphere.
supernova: Massive explosion at the end of the life of a large star; many new chemical elements are generated within supernovas.
symbiosis: A relation of dependence between two species that is so close that they begin to affect how each species evolves; the human relationship to domesticated plants and animals is a form of symbiosis.
temperature: In scientific use, a measure of the average kinetic energy (or energy of motion) of the atoms from which something is composed.
thermodynamics: The study of how energy flows and changes form. The first law of thermodynamics asserts that the total amount of energy in the universe is fixed or “conserved”; the second law states that energy tends toward increasingly random or chaotic forms, so the long-term tendency of the universe is toward randomness or increasing entropy. See entropy.
thresholds of increasing complexity: Moments of transition when something new and more complex appears, with new emergent properties; the story told in this book is constructed around eight major thresholds of increasing complexity.
trophic level: Level in the food chain through which photosynthetic energy is transferred from plants to herbivores to carnivores and on to elites in human societies; significant amounts of energy are lost at each level so populations at higher levels are always smaller.
type 1a supernova: A type of supernova whose intrinsic brightness is known, so it can be used as an astronomical standard candle.
universe: The totality of all things of which we have evidence-based knowledge; formed in the big bang.
weak nuclear force: One of four fundamental forms of energy; acts at subatomic scales and responsible for many forms of nuclear decay.
white dwarf: Dense, dead star that has blasted away its outer layers and will cool down over many billions of years.
work: In thermodynamic theory, the ability to generate nonrandom change.
world zones: Large regions of the inhabited world (Afro-Eurasia, Australasia, the Americas, and the Pacific) that were almost entirely disconnected from one another before 1500 CE, so history evolved in distinct ways in each world region.