Astrophysics for People in a Hurry

Nonfiction | Book | Adult | Published in 2017

A modern alternative to SparkNotes and CliffsNotes, SuperSummary offers high-quality Study Guides with detailed chapter summaries and analysis of major themes, characters, and more.

Download PDF

Summary

Background

Chapter Summaries & Analyses

Preface-Chapter 4

Chapters 5-6

Chapters 7-12

Key Figures

Themes

Index of Terms

Important Quotes

Essay Topics

Tools

Beta

Discussion Questions

Themes

The Laws of Everything

One of the most important lessons offered by astronomy, astrophysics, and cosmology is that the physical laws that govern life on Earth are the same everywhere in the universe. Knowing this helps us better understand how our universe works.

Isaac Newton showed the laws of gravity apply not only to objects in everyday life—apples falling from trees, for example—but also to the heavenly bodies beyond the sky, like the Sun, Moon, and planets: “This universality of physical laws drives scientific discovery like nothing else” (35). In the 20th century, scientists realized the Milky Way, the long streak of stars across the night sky, is part of a galaxy of stars that we live in and that there are billions of such galaxies in an expanding universe. Studies of these distant objects show they obey the same laws of gravity, motion, and energy as the apples in an orchard here on Earth.

Newton’s realization changed humanity’s attitudes about their place in the cosmos: “Again and again across the centuries, cosmic discoveries have demoted our self-image” (204). No longer was Earth the special center of everything; instead, it’s one of many planets orbiting a star that, in turn, is one of many stars. This was a stunning idea that challenged the beliefs of organized religion and everyday common sense.

The universality of physical laws opens doors to new kinds of knowledge. We have learned that the material we’re made of comes from giant stars fusing hydrogen into the heavier elements then exploding and spreading those elements out into space, where they combine with gas clouds and coalesce into new stars and planets. The laws that govern these phenomena work very precisely and consistently; this means that life can thrive, not just on Earth, but on the countless Earth-like planets strewn across our galaxy. Universal physical law suggests that among the billions of galaxies in the universe, life must be very common.

Science’s view of a consistent universe has made possible most of the technical progress of the human species. Jet planes, microwave ovens, satellites, and modern chemistry all take advantage of our understanding of universal physical laws. The realization that we’re tiny things in a vast cosmos humbles us, but it also opens the universe to our understanding and permits us to build a better world—one that perhaps someday will fulfill the dream of an earthly paradise.

The Wonderful Strangeness of the Universe

Science has made great strides in understanding our universe. In the process, it has uncovered remarkable facts, some of which are wondrously strange. Strangest of all are the enormous sizes and distances of our cosmos, facts so far beyond our ken that we can only stare in awe at their enormous scale.

The universe began as an infinitesimal dot that expanded over 14 billion years to become a vast realm, the far reaches of which we can only guess at. There are more stars in the universe than grains of sand on a beach; we study those distant objects mainly through microscopically tiny photons that travel six trillion miles per year, sometimes for billions of years, to reach us. Those photons range enormously in power, so scientists need receptors as small as a shoe box and as large as an assembly spread over 5,000 miles to detect them.

Equally strange is that most of the matter and energy that make up the universe is invisible to us. Dark matter shows itself only through its gravitational effect; dark energy only appears as a force that stretches out the universe and makes it expand at an ever-increasing rate.

Our universe is so vast that its furthest reaches hurtle away from us so quickly that light emitted from those distant quadrants will never reach us. Someday, the universe will be expanding so quickly that everything beyond our Milky Way galaxy will no longer be visible, and future beings here will think there’s nothing to existence but the Milky Way.

Also amazing is the science that makes these discoveries. We can locate planets orbiting distant stars; we can detect particles so small that trillions of them exist inside each of the 100 billion bacteria that live inside a single centimeter of a human gut. Yet the magnificence of those intellectual achievements might easily be dwarfed by the most common mind of some yet-undiscovered alien species in the same way that we’re vastly more intellectually capable than chimpanzees, “whose genetic identity varies in only trifling ways from ours” (200).

These jaw-dropping, stunning scientific discoveries may overwhelm our ability to comprehend them, but they also induce an awe and respect for the magnificent strangeness of our universe.

The Cosmic Perspective

People once thought Earth and a heavenly region above the sky were all that existed. Science, especially astronomy and astrophysics, has proven that our planet is but a tiny blue dot in the immensity of a universe filled with billions of galaxies of stars. Our perspective has changed: We’re no longer so special; instead, our cosmos turns out to be very special indeed.

The sheer size and age of our universe might at first make a person feel glum about being so tiny a part of that universe, but we are similarly gigantic when compared to an atom. This puts us somewhere in the middle of a realm whose dimensions stretch from the infinitesimal to the uncountably immense. We can gaze in both directions; for the author, contemplating the dimensions of our universe reminds him of the remarkable abilities of the human brain to discover and comprehend those immensities. Thinking about our magnificent universe also makes him feel “alive and spirited and connected” (198):

I began to think of people not as the masters of space and time but as participants in a great cosmic chain of being, with a direct genetic link across species both living and extinct, extending back nearly four billion years to the earliest single-celled organisms on Earth (199).

Every breath and every drink of water contains atoms that were in the bodies of every person who ever lived. We interact with our ancestors daily at the atomic level as part of one continuous, uninterrupted process that joins us all together.

Instead of feeling disappointed or humiliated at our small size, we can feel thrilled by the vastness of our universe and excited by the challenge of observing it, understanding it, and perhaps exploring its depths as we venture out into space.

One of the great tasks for humankind is to transcend our petty self-importance, lest we destroy ourselves in a rage of anger at the discovery that we’re not so very important after all. If we lose our curiosity or become complacent, then “arms-bearing, resource-hungry people and nations would be prone to act on their ‘low contracted prejudices’” (208). It’s vital to our survival and beneficial to all humans that we retain our respect for the sciences and the lessons they teach, especially about working together to discover the wonders and possibilities of our expanding universe.

The immensity of our universe suggests a grandeur almost beyond imagining, yet we’re embedded within that grandeur. It’s all around us, all the time. In a sense, it’s a privilege to live in so impressive a place. The hope is that together we use our growing knowledge of the cosmos wisely to uplift us all.