To Infinity and Beyond, published in 2023, was written by famed astrophysicist Neil deGrasse Tyson and his senior producer on the StarTalk radio show, Lindsey Nyx Walker. The authors explain complex scientific concepts in straightforward language, using examples from everyday life and popular culture to illuminate complex ideas about space. Alongside research publications, Neil deGrasse Tyson has authored more than a dozen science books for general audiences and has appeared on radio and television shows.

This guide refers to the hardcover edition published by National Geographic in 2023.

Summary

For most of human history, the understanding of what exists beyond the confines of Earth was limited to mythology. With the advent of the scientific revolution and the development of technologies like the telescope, humanity began to gain a more accurate understanding of the solar system and what lies beyond it. The Voyager space probes, launched in the 1970s, still roam the galaxy as ambassadors of the hopes and dreams of Earthlings. Today, telescopes like the James Webb Space Telescope transmit images back to Earth, confirming that this planet is only one among trillions.

In Part 1, the authors trace the history of flight and humanity’s quest to know more about the heavens. They discuss the layers of Earth’s atmosphere and that temperature changes are caused by the movement of molecules. Air behaves as a fluid, contrary to appearances (this is measured by air pressure), and the discovery of buoyant force, where an object floats if it weighs less than the displaced liquid around it, transformed the seagoing industry.

The first travelers to leave the Earth’s surface were “balloonatics” who used hot air balloons—though these vessels did not rise above the Earth’s atmosphere. Likewise, airplanes rely on air to work, so they cannot travel into outer space. It takes a rocket with its own fuel supply to break free of Earth’s gravity. Rockets also get some help from the Earth’s rotation as the centrifugal force flings them outward.

The authors question whether recent attempts to reach outer space by billionaires such as Jeff Bezos and Richard Branson are technically “space flights.” They also discuss the post-World War II “space race,” which was fueled by political tensions between the USSR and Western nations. Finally, the authors tackle the most significant obstacles in manned space missions. They end on a hopeful note, saying that as technology becomes more sophisticated, the possibilities for interstellar flight become more plausible.

In Part 2, discuss the solar system, starting with the sun. The sun contains its own atmosphere—the solar wind—and delineates where the solar system begins and ends. Beyond its sphere of influence resides interstellar space. The innermost planets that orbit the sun, called the rocky inner planets, include Mercury, Venus, Earth, and Mars. Mercury is the least explored of these, in part because its orbit is so swift and it is difficult to land a probe there. Venus is a boiling hot planet with a toxic atmosphere, and its transit helped confirm the hypotheses of Copernicus and Galileo: The planets revolve around the sun, not the Earth.

Earth is discussed in terms of its relationship to the moon. Without the moon, the tilt to Earth’s axis—which is key to maintaining seasons and, thus, life—would be unstable. The moon likely developed because of a large planetoid sideswiped the Earth, and the resulting debris coalesced into this natural satellite. Mars, the planet that most resembles the Earth, has held human fascination (particularly science fiction writers) for generations. Terraforming Mars is often discussed as a solution to climate change and overpopulation on Earth, but the authors suggest that it would be better to solve these problems rather than to look toward Mars.

An asteroid belt separates the inner planets from the gas giants Jupiter and Saturn. Jupiter protects the inner planets as its massive gravitational force pulls in many of the largest objects that hurtle in from outer space. Saturn’s atmosphere is made almost solely of hydrogen, and it is so lightweight that it could theoretically float in water. Some of Jupiter and Saturn’s moons intrigue scientists because they contain deposits of underground water, one of the necessary components to support life—at least as humankind understands it.

Scientists believe that the solar system’s ice giants, Uranus and Neptune, are too far from the sun to support life. Most exoplanets beyond the solar system are likely similar to these two barren worlds. Pluto is no longer considered a planet but rather a dwarf planet. Just beyond Pluto resides the Kuiper belt, filled with small planetoids and space debris. It separates the solar system from interstellar space.

In Part 3, the authors tackle the definition of space: where it begins and what it contains. Contrary to conventional wisdom, space is not empty; it is filled with particles, some of which are only barely understood, like dark matter. They also discuss how light functions as both a particle and a wave. Light assists in measuring distances and calculating spacetime. The other significant force in the universe is gravity. While human bombs don’t work in space, the deaths of stars cause enormous supernovae, which send shock waves throughout the universe. These explosions indicate that the universe had a clear beginning—the Big Bang—and it might have an ending. However, humanity can never know this for sure. The universe appears to be infinite; if there are limits, they are far beyond the observational capacities of humankind. However, this does not deter scientists from looking beyond the solar system for exoplanets, of which there are probably trillions. The idea that life exists only on Earth may someday be seen as misguided.

In Part 4, the authors tackle the concept of time and how it is inextricably linked to space. The universe is 13.8 billion years old and is expanding. The authors discuss the possibility of time travel. Traveling into the future would be risky because one would have to plot not only a date and time but also a location, and there is no guarantee that the location would be accurate. There is evidence that time dilation—slight differentiations in time based on speed and location—occurs. While the speed of light is a constant in Einstein’s theory of relativity, time itself is not. Thus, astronauts age slightly more slowly than their counterparts on Earth.

Travel to the past is hampered by more obstacles. While equations allow for the possibility, technology proves more challenging. Wormholes are inherently unstable, warp drives require impossible amounts of energy, and tachyons would break several laws of physics. They authors also discuss causality and the issue of paradoxes: Traveling back in time to change an event implies that it never happened in the first place, and according to physics, this cannot happen. The only exception might be entering a causal loop, wherein one cannot actually change the past, or traveling via a “jinnee particle” where one is stuck in a closed loop.

These conjectures lead to one of the most prevalent speculations in both popular culture and physics today: the many-worlds theory. Following the strange rules of quantum physics, this suggests that all possibilities are open until one path is chosen. In that instance, all other possibilities spawn different universes wherein those different paths are instead taken. This is different from the multiverse theory, in which one can travel among different universes. In the many-worlds theory, no separate spacetime can be accessed from this one.

In the Conclusion, the authors note that, for all the discoveries made and knowledge gained about the universe, this is merely the beginning of a much longer journey. The human desire to seek understanding of and access to the universe will continue to propel this odyssey forward.