Absolute zero – The theoretical temperature at which all motion stops, even at the atomic level, and the substance has no heat energy. According to the laws of physics, it is not possible for a substance to reach absolute zero.
Accelerating expansion of the universe – It is a scientific fact that the expansion of the universe is accelerating. The farther away a galaxy is from us, the faster it is accelerating away from us. In fact, the acceleration of the farthest-away galaxies appears to exceed the speed of light. Modern science believes that it is space that is expanding faster than the speed of light, which makes it appear that the galaxies themselves are accelerating faster than the speed of light. No law of physics prevents space from expanding faster than the speed of light.
Acceleration – The change in velocity (speed) of an object over a specific time.
Advanced aliens – This refers to intelligent extraterrestrial life that is scientifically knowledgeable and able to apply technology, such as radio broadcasting.
Anthropic principle – This principle asserts the universe is the way it is because if it were different, we would not exist.
Anthropogenic warming – This is global warming caused or influenced by humans.
Antimatter – The mirror image of matter. In matter, the electrons in atoms are negative, and the nucleus is positive. In antimatter, the electrons in atoms are positive, and the nucleus is negative.

Baryogenesis theories – Refers to a class of theories that assert the existence of a process that creates an asymmetry between matter and antimatter in the universe. Baryogenesis theories are postulated to explain the absence of antimatter in the universe. These theories are unproven and considered speculative.
Big Bang duality – This theory postulates that the Big Bang did not originate as a singularity (one highly dense energy particle), but a duality (one highly dense energy particle and one highly dense energy antiparticle). The expansion of energy (commonly referred to as the Big Bang), according to the Big Bang Duality theory, was the result of a matter-antimatter particle collision in the Bulk.
Big Bang theory – The theory that the universe originated from a highly dense energy state that expanded to form all that we observe as reality.
Big Crunch – This theory held that gravity would eventually overcome the expansion of the universe, and force all reality into a highly dense energy point.
Black hole – Refers to a region of space whose gravitation is so intense that not even light can escape, thus the name “black hole.”
Bubble Universes – Refers to entire universes that theoretically exist in the Bulk. The bubble universes may or may not resemble our own.
Bulk – A super-universe capable of holding countless universes. In theory, it contains our own universe, as well as other universes.

Casimir-Polder force – The attractive force between two parallel metal plates placed extremely close together (approximately a molecular distance) in a vacuum. Science believes the “attraction” is due to a reduction in virtual particle formation between the plates. This, in effect, results in more virtual particles outside the plates whose pressure pushes them together.
Celsius – A temperature scale, at which water freezes at zero degrees (0º C) and boils at one hundred degrees (100º C).
Chaotic inflation theory – This theory asserts that the universe does not inflate uniformly, but may accelerate in regions of space devoid of matter and radiation. The non-uniform inflation causes portions of the universe to separate from the existing universe. These portions form mini-universes (“bubble” universes). The word “bubble” is used to describe this concept because when bubbles form, occasionally a smaller bubble will form on a larger bubble, and then separate from it.
Chronology protection conjecture – This is a conjecture by physicist Stephen Hawking, published by him in a 1992 paper, which asserts the laws of physics prevent time travel on all but submicroscopic scales. This conjecture has been an object of debate, and has substantial supporters and adversaries. We have no consensus that it is a scientific fact.
Classical mechanics – Refers to Newton’s three laws of motion, enunciated by Newton in the 17th Century. It is widely used today by almost everyone since it provides excellent agreement with phenomena in our everyday experiences (the macro-world). For example, if you play billiards, Ping-Pong, or even marbles, you are intuitively using Newton’s laws of motion. Newtonian mechanics and Newton’s laws of motion are synonymous to Classical Mechanics.
Closed time-like curves – In mathematical physics, a closed time-like curve is a solution to the equations of general relativity that demonstrates a particle’s world line closes on itself (returns to the starting point). Numerous theoretical physicists interpret this to imply time travel to the past is possible.
Conservation of energy – Arguably the most sacred law in physics, namely that energy cannot be created or destroyed, only transformed from one form to another.
Conservation of mass – This law is similar to the conservation of energy, namely mass cannot be created or destroyed, only transformed from one form to another, including the transformation to energy.
Cosmological constant – An arbitrary constant, originally proposed by Albert Einstein, to force his equations in general relativity to predict a static universe. In 1929, when Edwin Hubble discovered the universe was expanding, Einstein proclaimed the cosmological constant his “greatest blunder.” Today, physicists are using the cosmological constant, along with mathematical manipulation of general relativity, to model the accelerated expansion of the universe.
Cosmological horizon – The observable universe. Its basis is the time light has had to travel to us from the edge of the observable universe, in accordance with the age of the universe (13.7 billion years old).

Dark energy – A theoretical force postulated to be responsible for the accelerated expansion of the universe. Scientists describe it as a “vacuum” force, while others describe it as a “negative” force. In reality, no scientific consensus exists regarding the nature of dark energy, including its existence.
Dark matter – This is mass in galaxies, galaxy clusters, and between galaxy clusters that cannot be observed directly, but is postulated to exist to explain why the farthest-away stars from the center of the galaxy rotate at approximately the same rate as the stars nearer the center of the galaxy. From the laws of physics, the farthest-away stars should be rotating much slower than those nearer the center. Therefore, scientists have postulated that more mass, namely dark matter, is in the galaxy than we observe since it did not emit or reflect light. The existence of dark matter has been confirmed by gravitational lensing (gravity bending light) observations. Scientific calculations indicate that dark matter may account for about 90% of the total matter of the universe. Scientific speculation asserts that a particle is associated with dark matter, namely the WIMP particle (Weakly Interacting Massive Particle). To date, there is no conclusive evidence that the WIMP particle exists.
Del Monte Paradox ¬– An observation made by Louis Del Monte and introduced in this book, namely: Each significant scientific discovery results in at least one profound scientific mystery.
Dilated – Typically used as a verb in this book, and refers to one clock traveling at the speed of light running slower than another clock at rest.
Dirac sea – A theory postulated in 1930 by Paul Dirac (British physicist) that empty space (a vacuum) consists of a sea of virtual electron-positron pairs. This eventually led to the discovery of antimatter.
Doppler shift – The elongation or compression of a wavelength of light or sound, which depends on the motion of the emission source relative to an observer. For example, light’s wavelength elongates as the galaxies farthest from Earth move away from us due to the expansion of space. The Doppler shift is toward the red portion of the spectrum, since red is the color of longer wavelengths of light.

Earth-like – Refers to a planet that is similar to Earth. Typically, the planet would be in the habitable zone of the star it orbits, be large enough for gravity to hold its atmosphere in place, and have liquid water, to name a few of the properties of an Earth-like planet.
Entropy – In nature, all processes produce waste energy (heat) that escapes and becomes unavailable to do mechanical work. The waste energy that escapes is a measure of the entropy, and increases the disorder of a system. Since the universe is continually evolving through cosmic processes, the entropy of the universe is always increasing.
Entropy apocalypse – Refers to a point in time when all energy is heat, and unavailable to do mechanical work. It spells doom for all life.
Euclidean geometry – The geometry developed by the ancient Greek mathematician Euclid. Mathematicians refer to it as a “flat” geometry, where parallel lines remain equidistant (the same distance apart) to infinity, and the sum of angles within a triangle equal 180 degrees. We typically learn this geometry as schoolchildren.
Existence Equation Conjecture – This theoretical equation enables the calculation of a mass’ kinetic energy as it moves in the fourth dimension of Minkowski space. The equation is unusual in that it indicates the kinetic energy of a mass moving in the fourth dimension is negative, and massively large. A speculative interpretation of the Existence Equation Conjecture is that existence requires negative energy, which is being syphoned from the universe, and results in the accelerated expansion of the universe. The Existence Equation Conjecture is discussed more fully in Chapter 12, Appendix I and Appendix II.
Existential risk – Any risk with the potential to destroy humankind or drastically restrict human civilization. In theory, an existential risk could end the existence of Earth, the solar system, the galaxy, or even the universe.
Extraterrestrial life – Life that exists outside of the Earth. For example, if we discover microbial life on Mars, it would be proof of extraterrestrial life.

Fahrenheit – A temperature scale, at which water freezes at thirty-two degrees (32º F), and boils at two hundred twelve degrees (212º F).
Field – A concept in the physical sciences used to imply mediation at any distance, without the use of particles as mediators. For example, gravity exerts an attractive force between two masses via a gravitational field. If, however, science discovers the particle of gravity called the graviton, the mediation (the force-carrying particles) between the two masses will not be a field, but be by graviton particles. The field concept in physics is an old concept, and pre-dates understanding the role that particles play as mediators.
Fossil record – Generally refers to the total number of fossils found, and the information derived from them by paleontologists, which are scientist that study fossil (prehistoric) animals and plants.
Four fundamental forces – Modern physics recognizes four known fundamental forces, namely gravitational, electromagnetic, strong nuclear, and weak nuclear. All physical forces theoretically trace back to one or more of these forces.
Fourth dimension – In a 1912 manuscript on relativity, Einstein equated the fourth dimension to ict (where i =√(-1), c is the speed of light in empty space, and t is time, representing the numerical order of physical events measured with “clocks”). The entire thrust of using four-dimensional space in the special theory of relativity is attributed to Russian mathematician Hermann Minkowski. In 1907, Minkowski demonstrated Einstein’s special theory of relativity (1905), presented algebraically by Einstein, could be presented geometrically as a theory of four-dimensional space-time.

Galaxy – Refers to a system of millions to billions of stars, along with gas and dust, held together by gravity. Most stars, like our sun, have planets and other celestial bodies orbiting them. There are billions of galaxies in our universe. Typically, galaxies are separated from one another by vast regions of space (measured in light years).
Gamma rays – Refers to short wavelength, high-energy, electromagnetic radiation emitted by radioactive substances.
General theory of relativity – A theory developed by Albert Einstein dealing with gravity and non-inertial frames of reference. It is termed the “general theory of relativity” to differentiate it from the “special theory of relativity,” which focused on inertial frames of reference.
Gravitational lensing – Refers to the phenomenon that light’s path can be affected by gravity. For example, light from distant galaxies bends as it passes through the gravitational field of another galaxy. This can result in magnifying, distorting, or producing multiple images of the original light source for a distant observer.
Gravity (or Gravitation) – Refers to the attractive force one mass exerts on another mass.
Ground state – Refers to the lowest energy state of an atom or particle.
Ground-state entropy – Refers to the lowest entropy state of a system.

Heisenberg uncertainty principle – This scientific principle holds it is impossible to accurately determine both the position and velocity of a particle simultaneously. In the context of quantum mechanics, it conceptually conveys the probabilistic nature of physical phenomena at the atomic and subatomic level (quantum level).
Hubble volume – The region of the universe surrounding an observer, beyond which objects recede from the observer at a rate greater than the speed of light, due to the expansion of the universe.

Inertial frame of reference – A frame of reference at rest or moving at a constant velocity.

Kelvin – The International System of Units (SI) absolute thermodynamic temperature scale, using as its null point zero degrees Kelvin (0º K), which refers to a state devoid of all heat and motion. The Kelvin temperature scale equates to the Celsius temperature scale via the following equation: K = [°C] + 273.15.
Kinetic energy – The energy associated with an object due to its motion.

Lamb shift – This refers to the small difference in energy between two states of the hydrogen atom. American physicist Willis Eugene Lamb (1913-2008), first detected it, and received the Nobel Prize in Physics in 1955 for his discoveries related to the Lamb shift.

Macro-level – This is our everyday world. It is the reality that we can typically see and touch.
Mass – In physics, this typically refers to matter, such as a subatomic particle, atom, or an assembly of subatomic particles and atoms.
Mediators – In physics, mediators are the particles that carry force between entities. For example, the photon is the force carrier for the electromagnetic force.
Minkowski space – Refers to the mathematical, four-dimensional concept of space-time developed by Hermann Minkowski in his 1909 paper “Space and Time.” Minkowski space-time found application in Einstein’s special theory of relativity, and in the development of the Existence Equation Conjecture.
Miracle – This refers to an act by a supernatural being, which typically suspends the laws of physics.
Moore’s Law – This is more of a general rule or observation than an actual physical law. Moore’s law states the number of transistors that can be placed inexpensively on an integrated circuit doubles approximately every two years.
Multiverse – Refers to the concept that there are other universes beyond our own. The phrases, “parallel universes,” “alternative universes,” “quantum universes,” “parallel dimensions,” and “parallel worlds” are synonymous to the multiverse.
Muon – A negatively charged particle approximately 200 times more massive than an electron.
Neutrino – An elementary particle with close to zero mass, no electrical charge, and travels close to the speed of light.

Newton’s laws of motion – See Classical Mechanics.
Newtonian mechanics – See Classical Mechanics.
Nomads – Refers to groups of people, typically a clan or tribe, whose civilization survives by moving from one location to another location, more favorable to their survival.

Occam’s razor – A principle of science that holds the simplest explanation is the most plausible one, until new data to the contrary becomes available.

Particle – In physics, this can refer to a massless object or, alternately, a small object with mass. A photon is an example of a massless object. A muon is an example of a small object with mass.
Particle accelerator – Refers to apparatus that uses electromagnetic fields to accelerate subatomic particles to high velocities, even velocities approaching the speed of light.
Photoelectric effect – Refers to the ejection of electrons from any substance due to the incidence of electromagnetic energy (light).
Photon – Refers to a particle (energy packet) of light (electromagnetic radiation). The photon has no mass, and travels at the speed of light in a vacuum.
Planck length – The smallest unit of length theoretically possible, which suggests that space, itself, may be quantized. The Planck length is equal to approximately 1.6 x 10-35 meters, and is defined using three fundamental physical constants: the speed of light in a vacuum, Planck’s constant, and the gravitational constant. At the Planck length, gravity is thought to become as strong as the three other fundamental forces (electromagnetic, strong and weak nuclear), and quantum effects dominate.
Planck time – This is the time it takes light in a vacuum to travel one Planck length. This is the smallest unit of time that science believes change can occur. It is approximately equal to 10-43 seconds. This implies that time itself may be quantized.
Products – Refers to the resulting substances of a chemical reaction. The substances may be compounds, elements, or both.

Quantized – Refers to the discrete nature of a substance, like mass or energy. In this book, it is typically used as a verb when describing the discrete nature of reality (mass, energy, space, and time).
Quanta – A discrete packet of energy, like a photon.
Quantum – Synonymous with quanta.
Quantum entanglement – Refers to a phenomenon in quantum mechanics where a pair of particles or photons interacts with each other, and forms an invisible bond. When a pair of particles becomes entangled, their quantum state, which completely describes their state of being, communicates and correlates with each other, even when the particles are separated by a distance. Thus, changing the quantum state of one entangled particle forces the quantum state of the other entangled particle to change in a way that they remain in a correlated quantum harmony. This phenomenon is a scientific fact, but not completely understood. One mystery is that the communication between entangled particles appears to travel faster than the speed of light in a vacuum.
Quantum fluctuation – An effect observed in quantum physics, where a temporary change in the amount of energy occurs at a point in space, in accordance with the Heisenberg uncertainty principle. This effect gives rise to “virtual particles” or “spontaneous creation.” This is a scientific fact.
Quantum level – Refers to the scale of atoms and subatomic particles.
Quantum mechanics – Refers to the scientific principles that explain the behavior of physical objects and their interactions with energy on the scale of atoms and subatomic particles.
Quantum universe – A theory that the entire universe consists of quantized matter and energy.
Quark – The quark is an elementary particle and a fundamental building block of other particles, like protons and neutrons. There are six types of quarks, known as flavors, including up, down, strange, charm, bottom, and top.
Qubit – In quantum computing, the qubit is the quantum bit of information analogous to the classical computer bit. Whereas the classical computer bit contains information, and can represent a 1 or 0, the qubit can represent a 1, 0, and a superposition of both at the same time. For example, using a classical computer bit, a polarized photon could be expressed by either a 1 for horizontal polarization or a 0 for vertical polarization. A cubit represents both states simultaneously.

Reactants – Refers to the substances (elements and compounds) that react in a chemical reaction to form one or more new substances (products).
Redshift – Refers to the elongation of a light wave, as its wavelength stretches, due to the emission source moving away from an observer. Longer wavelengths of light are in the red portion of the spectrum.
Relativistic mechanics – This refers to any form of mechanics that are derived from and/or compatible with Einstein’s general and special theory of relativity.

Singularity – In the context of the Big Bang, this refers to the point of infinitely dense energy that gave birth to the Big Bang.
Space-time – This refers to the concept that time is dependent on space. In effect, space and time are fused together in a mathematical model to form a continuum known as space-time. This has enabled physicist to simplify numerous physical theories and describe the universe more precisely.
Special theory of relativity – A theory developed by Albert Einstein, based on two postulates:
Physical laws have the same mathematical form in any inertial system (a system at rest or moving at a constant velocity).
The velocity of light is independent of the motion of its source, and will have the same value when measured by observers moving with constant velocity with respect to each other.
From these two fundamental postulates, Einstein was able to develop his famous mass-energy equivalence equation, the time-dilation equation, and the relativistic kinetic-energy equation. The special theory of relativity is one of the most successful theories of modern science.
Speed of light in a vacuum – This is the speed at which light (electromagnetic radiation) travels in a vacuum, which is exactly 299792458 meters/second. Scientists universally view light as the upper-speed limit in the universe. Nothing travels faster in a vacuum than the speed of light.
Spiral galaxy – A galaxy having a spiral form with spiral arms. The oldest starts in a spiral arm near the center of the galaxy. Our Milky Way galaxy is a spiral galaxy.
Spontaneous symmetry breaking – A theory that holds a system in a symmetrical state is able to transform to an asymmetrical state.
Standard Model – This refers to the Standard Model of particle physics, which mathematically models the behavior of elementary particles and their interaction relative to the electromagnetic, strong and weak forces.
Star – This is a self-luminous celestial body, like our sun, consisting of gas held together by gravity. The luminescence is the result of nuclear reactions within the body, whose energy makes its way to the surface, and emits as radiation.
String theory – A mathematical theory that represents all mater, such as subatomic particles, as consisting of strings that vibrate in one dimension, and exist in eleven dimensions. A number of prominent physicists consider string theory to be a contender for the theory of everything.
Supernatural being – A being that exists outside the natural realm. The word deity and god are synonymous with supernatural being. Depending on specific religious beliefs, the supernatural being has specific powers over the natural world.
Super-universe – See Bulk.
Symmetry of physical laws – A concept in physics that argues that a physical law is unchanged by any theoretical transformation. This is a simple example: A geometric sphere maintains all elements that define it as a geometric sphere, regardless of any rotational transformation. Most physicists believe physical laws are symmetrical.

Theory of everything – A self-contained mathematical model that describes all fundamental forces and forms of matter.
Thought experiment – This is a conceptual experiment. It considers a hypothesis, theory, or principle, and thinks through the ramifications, to illustrate a point. A thought experiment may or may not be possible to perform in reality. The objective is to explore the hypothesis, theory, or principle, and its potential consequences. Einstein is historically considered the master of the thought experiment, or “Gedankenexperiment” (in German).
Time – The traditional definition of time is the numerical sequence of events as measured by clocks.

Uncertainty principle – See the “Heisenberg uncertainty principle” above.

Velocity – The distance an object travels divided by the time it takes to travel that distance.
Virtual particle – A particle that exists for a limited time, and obeys some of the laws of real particles, including the Heisenberg uncertainty principle, and the conservation energy. However, their kinetic energy may be negative.

Wavefunction – The wavefunction, in quantum mechanics, describes the probability of a particle’s state (position, momentum, and other attributes).
Wave-particle duality – Refers to the exhibition of both wave and particle properties.
Word line – The unique path that an object takes as it travels through four-dimensional space-time.