To Infinity and Beyond: A Journey of Cosmic Discovery

How space is defined relies as much on long-standing cultural misperceptions and conventions as any scientific reality. For example, the tendency to compare space to the ocean often dominates the cultural discourse about it. In addition, the idea that space encompasses a vast area of nothingness is mistaken: Space is full of matter, some of it not yet understood. The authors argue that to discover a pocket of actual nothingness within the universe would truly be remarkable. Still, the farther one travels out into the reaches of space, the fewer particles one finds. However, this does not account for the quantum realm, where matter pops into and out of existence, following none of the rules of classical physics—even if invisible to current technology.

In the early days of the scientific revolution, astronomers sought to explain what existed between celestial bodies by identifying a “heavenly aether.” This allowed them to rationalize the fact that light traveled through space and toward the Earth; after all, it must travel through something rather than nothing. Thus, the movement and makeup of light became of great interest to physicists. Some argued that light functioned as a wave, while others argued that light functioned as a particle. Both arguments, it turns out, were right. Sound waves need air to travel, while light does not; scientists once invoked the aether to explain this. Sound waves, however, can “bend around walls” (178-79), while light “travels in a straight line” (179). Thus, light also behaves as a particle. A particle does not need any medium, like the aether, to transmit.

By the 19th century, the idea of the aether was slowly losing credence. With the invention of the interferometer, an instrument that measures the speed of light, scientists realized that the aether did not exist: The speed of light is constant and does not change according to any medium through which it travels. This revelation opened the door for Albert Einstein to propose his special theory of relativity (E=mc²: energy=mass times the speed of light squared), which revolutionized how the universe was viewed.

One cannot talk about space without recognizing the centrality of gravity. Lagrange points, named after an Italian mathematician, illustrate how gravity and matter interact within spacetime. The first Lagrange point lies between the sun and the Earth, while the second lies on the other side of Earth, away from the sun. The third point rests behind the sun. The fourth and fifth points are the most stable; the fourth lies in front of orbiting objects, while the fifth follows the object at an equivalent distance. Putting telescopes at these points requires little energy as they can rest between two counterpoints. The authors use the metaphor of balls on a hill: Points one, two, and three are like balls perched on a hilltop (in danger of rolling off), while points four and five are like balls resting in a valley. This equilibrium, however, is inherently unpredictable; that is, this arrangement and stability “cannot last forever” (188). Minor shifts in the solar system impact their positions.

Shock waves are another misunderstood phenomenon. While Hollywood movies have often portrayed enormous explosions in space, they would not happen this way in reality. Earth bombs are effective not because of their explosive power or the attendant shrapnel but because they produce shock waves with enough force to destroy matter. In space, there is not enough densely packed matter to produce a shock wave with an Earth bomb. However, outside of the solar system, exploding supernovas—the deaths of stars—produce massive shock waves. In addition, gamma-ray bursts (GRBs) are the strongest explosions in the universe thus far detected. Scientists are unsure what produces these bursts, but they may be related to the stellar death of the most massive stars in the cosmos.

A sonic boom a shock wave in audio form—is nearly impossible to produce in space. On Earth, however, the speed of sound can be “broken” and is measured in Mach units (named for an Austrian physicist). Mach 1—the speed of sound—varies according to the medium through which the sound travels. Unlike the speed of light, which is constant, the speed of sound is relative. The authors also note that the most intense shock waves ever produced on Earth derived from the detonation of nuclear bombs in Hiroshima and Nagasaki at the end of World War II. They emphasize that with every advance in technology comes an increasing threat of more sophisticated weapons.

The authors then tackle the perplexing question of darkness: If there are infinite numbers of stars, then why would one see darkness in between the pinpoints of light? Light travels unencumbered through space; thus, the night sky should be white rather than black with the proliferation of stars. Two phenomena prevent this. First, not all stars are equidistant from Earth, and light dilutes with distance. In addition, if the number of stars—and the universe itself—were infinite, then this would still produce a white sky, no matter the distance. This proves that the universe is finite. Second, the universe is expanding, which also gives rise to the understanding that the universe had a beginning (The Big Bang). Therefore, it must also have an end or a limit. The study of light, particularly the effect of splitting light, also contributes to this understanding. The patterns of light reveal the makeup of matter; rainbows are like fingerprints, revealing the unique signature of an element. As it turns out, the Milky Way galaxy is not necessarily representative of other galaxies in the universe.

Another potentially unsettling fact about the universe—only now conceivable with the advent of modern telescopes like the Hubble and the James Webb—is how vast it is. There are not merely billions of galaxies in the universe; there are trillions, a measurement of exponential increase. With this, the interest in exoplanets has blossomed in recent years. As of now, thousands have been discovered. Astrophysicists and others continue to look for exoplanets in the “Goldilocks zone,” wherein the conditions appear to be “just right” for the development of life—there might be millions within the Milky Way alone. Thus, the discovery of another inhabitable planet is possible, but to get there would take generational thinking. That is, any space “pilgrims” would have to travel in a ship for thousands of years to reach such a planet, which presents its own moral and technological dilemmas.

In sidebars, the authors address such topics as vacuums and voids; whale songs; stellar warfare and how it is (erroneously) portrayed in pop culture; the scientific missteps of Marvel’s Incredible Hulk; how aliens might intercept Earth’s radio waves; and what outer space might smell like.