To Infinity and Beyond: A Journey of Cosmic Discovery

Centrifugal force states that the faster something spins, the more forcefully something is ejected from it. The Earth's rotation creates centrifugal force, which helps rockets leave the planet's atmosphere.

Coriolis force acts on rotating objects. The Coriolis effect describes how the Earth’s rotation affects things that are not attached to the planet, especially since the Earth spins faster at the Equator than at its poles. A clear example is weather patterns like cyclones, and pilots take the Coriolis effect into account when charting flight paths.

The sun occasionally ejects plasma and magnetic fields from its corona, which are powerful enough to affect the Earth. If they collide with the Earth's magnetosphere, they can disrupt power grids.

Cosmic Microwave Background is trace radiation from the early universe. It was discovered in 1965 and is evidence of the Big Bang theory. It measures the ambient temperature of the universe and remains constant while the temperatures of stars and other matter change.

Developed and abandoned by Albert Einstein, the cosmological constant (represented by lambda (Λ) in physics) was developed to balance calculations. This was necessary because scientists believed the universe was static, but Einstein believed that gravity made this impossible and that the universe was in motion. The cosmological constant helps physicists make calculations.

An exoplanet is a planet that orbits a star outside of this solar system. Since the discovery of exoplanets in 1992, “nearly 4,000 star systems have been observed, containing more than 5,000 confirmed exoplanets” (212). These discoveries are made possible by advanced space telescopes that peer into the deepest recesses of interstellar space.

The implications of the existence of exoplanets are significant. First, scientists gradually realized that the behavior of other solar systems does not necessarily emulate the one in which Earth is located; in one early observation, a gas planet similar to but smaller than Jupiter orbited its host sun in just four days. The universe follows many diverse paths, not just the ones familiar to Earth. Second, the discovery of so many exoplanets in so many heterogenous solar systems once again displaced this solar system from the center of the cosmos. Exoplanets represent the best prospect for an encounter with extraterrestrial life.

The giant-impact hypothesis proposes that the moon was formed when Earth collided with another early planet and the resulting debris coalesced into its own astral body. This hypothesis was proposed in 1946, and the authors discuss it in Part 2 of this book.

Gravity is one of the fundamental forces in the universe. Gravity created the planets and the moons as space debris coalesced under its influence, and it keeps planets in their orbits rather than flying off into interstellar space. It makes space exploration both possible and difficult since gravity can help slingshot spacecraft further on their travels but also pulls objects into its field. As the authors acknowledge in the introduction to the book, “We cannot easily escape Earth’s gravity” (10). This is why the rocket equation is so important: The amount of fuel necessary to break free of Earth’s gravity field with any significant amount of payload is nearly prohibitively expensive.

Instead of emptiness, space is full of stuff: “Even between particles, therefore, we find particles. And permeating all of space and time, between the particles and the virtual particles, is the inescapable influence of gravity” (173). Gravity shapes the universe—the galaxies, stars, and planets—and as the authors put it, “All objects exert a force of gravity that extends to infinity, forming the very shape of the spacetime continuum” (186). Gravity forms the hillocks and valleys that ripple throughout spacetime, curving and warping the intersection between space and time. Gravity is also responsible for such spectacular interstellar phenomena as supernovae, the collapse of stars, and black holes. Its force is both creative and destructive.

The Kármán line is the theoretical point in Earth’s atmosphere where space begins. The Fédération aéronautique internationale (FAI) marks the Kármán line at 100 kilometers above sea level, which is in the thermosphere.

The Kuiper belt is considered the boundary between our solar system and interstellar space and consists of asteroids, frozen gases, and other debris. Pluto and other dwarf planets are also in the Kuiper belt.

Light photons are unique in that they behave both as particles and as waves. Like sound, light behaves as a wave, reverberating through space; however, unlike sound, light does not need air, or atmosphere, through which to travel. Sound is only a wave, meaning it can “bend around walls,” but light “travels in a straight line” (178-79). Because particles can propagate without the need for atmosphere, and because light does not bend, light is also a particle. For many years, scientists postulated the existence of an aether—a miasmic quasi-atmosphere in space—that helped light travel from the sun to the Earth. Einstein’s theory of relativity quashed this theory; the speed of light is constant, which it could not be if it traveled through another medium.

The discovery of the behavior of light, in accordance with the theory of relativity, assisted scientists in determining such phenomena as the expanding universe and the Big Bang theory. For example, if two objects in the night sky appear equally bright, it does not necessarily follow that they are equally distant from Earth or equal in size. Instead, a star’s brightness “decreases exponentially” the farther away it is. In addition, light waves are either blueshifting (approaching) or redshifting (receding). When Edwin Hubble, for whom the powerful space telescope is named, discovered that “distant galaxies are retreating faster than the nearer ones” (209), scientists were able to determine that the universe was expanding. From that, they extrapolated that the universe had a clear beginning in the Big Bang.

Payload is everything carried by an aircraft or spacecraft that's necessary to complete the flight. This includes people, instruments, and fuel. Payload calculations must be precise for the craft to become airborne and have enough fuel to reach its destination. An issue with distant space travel is that ships need exponentially more fuel to traverse these longer distances, dramatically increasing the ship's payload.

Space is that which exists beyond Earth’s atmosphere. There is outer space, which typically refers to the area beyond Earth’s atmosphere within the solar system, and interstellar space, which typically refers to everything beyond the influence of this particular sun. As with most boundaries, the parameters are questioned: “The boundary, what it is, remains fuzzy,” the authors admit; “there’s just no good distinction between ‘space’ and ‘not space’” (40). Authorities question whether the brief space flights of billionaires are actually space travel since they barely pass the Kármán line. Whether interstellar space begins directly beyond Pluto or beyond the Kuiper belt has also been debated.

Space also refers not just to location but also to composition. Space contains less matter than Earth’s atmosphere; it exhibits an absence of light and heat. Still, “[s]pace is not nothing, and it’s far from empty” (170). What one can observe with the five senses does not represent all that is present. For example, quantum physics has broadened the understanding that subatomic particles exist throughout the universe (behaving in ways often contrary to classical physics). In addition, the discovery of an expanding universe has led to theories about dark energy or dark matter within the universe, an anti-gravitational material filling what once was thought to be empty space.

Inseparable from space is the concept of time, as proved by Einstein’s theory of relativity. Unlike the speed of light, time does not represent a constant: “From relativity emerged a cosmos that twists, bends, and ripples like a fabric, where gravity and speed alter the flow of time” (235). Thus, though humans experience time linearly—there is no turning back time or skipping ahead—time itself does not behave in that way. Relativity “also suggest[s] a cosmos in constant motion—with a clear beginning but no clear end” (235). There is evidence to support the theory of a Big Bang which set the universe in motion; however, the limits of human knowledge prevent any such understanding of the universe’s edge or end.