To Infinity and Beyond: A Journey of Cosmic Discovery

The authors note that humans have been fascinated with space for as long as they have been recording their history, art, and literature. Ancient epics like The Epic of Gilgamesh employ constellations as characters, and the stars have been consistently important in world religions. The invention of the telescope in the 17th century allowed humans to see, for the first time, that the bright dots in the sky were different kinds of celestial bodies. However, to explore those bodies, one first had to understand Earth’s atmosphere.

The Earth’s atmosphere consists of five different layers—the troposphere is the lowest, followed sequentially by the stratosphere, mesosphere, thermosphere, and exosphere. The authors note that the atmosphere becomes colder the higher one travels in the troposphere and stratosphere; getting closer to the sun, in this case, does not ensure warmer temperatures. This is the result of the greenhouse effect: Earth’s atmosphere allows for the penetration of the sun’s light, which becomes heated when trapped within the troposphere. As the authors note, “A July day feels hot not because the sun heated the air from above, but because the ground heated the air from below” (22-23). The stratosphere—where the ozone layer resides—protects Earth’s inhabitants from the harmful ultraviolet energy emitted by the sun.

Beyond the stratosphere, the mesosphere and thermosphere become hot again as they experience the brunt of solar activity (this is where meteors burn up before entering the lower atmosphere). The exosphere barely contains any atmospheric molecules at all; this is the point at which the Earth’s atmosphere begins to resemble outer space.

Air itself is considered a fluid and carries actual weight, creating buoyant force and barometric pressure. Buoyant force is what allows enormous ships made of steel to float above the ocean: “[T]heir total volume—including all the air of its hollowed innards—weighs less than the weight of the water they displace” (30). Barometric pressure measures the weight of air itself. The discovery that air weighs less at higher altitudes led to the development of flight.

Balloons first lifted humans into the sky in the 18th century. The authors also mention the exploits of Felix Baumgartner to discuss the concept of space. In 2012, Baumgartner used a specially developed hot air balloon to reach the stratosphere, then jumped from what he claimed was space, though the authors take exception to this because the Kármán line (an altitude of 62 miles/100 kilometers, twice the height of the stratosphere) typically differentiates Earth’s atmosphere from space. This is the point at which airplanes can no longer fly because they need air to pass over their wings. The authors also discuss whether people like Jeff Bezos, the billionaire founder of Amazon, or Richard Branson, the billionaire founder of Virgin Group, are actually astronauts. They traveled briefly beyond the Kármán line, but their flights were short and their motivations were personal, not scientific.

Airplanes can fly because their wings are designed to allow faster airflow over the top of the wing than the bottom; the lower pressure above the wing helps create lift, and jet engines (or propellers) push the plane forward. Rockets, on the other hand, must go beyond an atmosphere rich in air and oxygen and carry their own self-oxidizing fuel. The most dangerous part of a rocket launch is during the moment called “max q,” or maximum dynamic pressure. This is the point at which the Challenger space shuttle explosion took place. Rockets also utilize the rotation of the Earth to achieve speed and lift. This is the result of centrifugal force; the faster something spins, the farther one is flung away from it.

The reason that people stay anchored to the spinning Earth is because of gravity. Isaac Newton famously “discovered” the force of gravity, though the original story of an apple falling onto his head is apocryphal. Newton studied the way in which the moon seemed tethered to the Earth and eventually came to understand that gravity is what keeps the two celestial bodies in sync—maintaining certain speeds at specific distances is what is called an orbit. Astronauts become weightless in space not because of space itself but because of gravity; their speed keeps them anchored in orbit rather than falling into the planet.

The authors also acknowledge that scientific advances, particularly concerning what was once called the “space race,” are inextricable from politics and war. The first rockets were developed during World War II with the express purpose of annihilating enemies. Werner von Braun, for example, conceived the V2 rocket, the first weapon to travel into space, as a “vengeance weapon” during World War II. The authors note that building the V2 relied heavily on imprisoned workers—mostly Jews—during the Nazi regime. Von Braun later defected to the United States and helped innovate the Saturn V rocket that would take astronauts to the moon.

Other political concerns the authors address are the satellites in orbit: Since Sputnik was launched in 1957, thousands of other satellites have joined it. Many of them stay in orbit rather than falling toward Earth’s atmosphere and burning up; this means that even when they become non-functional, they litter the skies. Space junk, should it continue to grow, could impede humans’ ability to ever reach outer space again.

The most significant problem when it comes to launching rockets—especially rockets that could go farther than the moon or carry more equipment—is “the rocket equation” (72). This equation reveals that as the rocket’s payload (necessary cargo) gets heavier, the rocket needs an exponentially greater amount of fuel to successfully launch and travel. The weight of the fuel itself must then be taken into consideration. The hope is that as technology continues to become smaller and more refined, this conundrum can be overcome.

The authors also note that bringing astronauts back to Earth presents its own set of problems. They illustrate one of these problems through meteorites: When meteorites hit the atmosphere, they encounter friction, which both slows them down and converts to heat, burning them up before they hit the ground. Thus, spacecraft must maintain a sophisticated heat shield—what the authors call “aerobrakes”—to return to Earth safely. This has been done before, but with better heat shields, missions can travel longer and farther.

Throughout each part of the book, the authors include sidebars briefly explaining related topics. Often, these sidebars explore popular culture and its relation to (or mistakes about) science. In Part 1, the sidebars include a discussion of the curveball in baseball; the real impact of Martian dust storms (as opposed to how The Martian portrays it); how gravity works in space (as opposed to how the 2019 film Ad Astra portrays it); and the contributions of human computers (as dramatized in the book Hidden Figures). Several sidebars discuss advancements in science and explain scientific concepts. For example: the Ingenuity helicopter was the first craft to fly on Mars; there is a difference between speed and acceleration; the Coriolis force reveals how anything not tethered to Earth is affected by its rotation (such as cyclones); what it would be like to fall through the center of the Earth; and whether an elevator to space is a feasible endeavor.