The sky is often overlooked as an empty void, but is a substantial, dynamic environment that begins at Earth’s surface and is filled with gases, dust, spores, and microscopic life. Wind shapes landscapes, powers windmills, sows seeds. Some winds are given local names, such as Japan’s matsukaze and Argentina’s zonda. Clouds are floating lakes. In lightning, the cloud first sends a short electrical “scout” downward; the Earth responds by arcing a long bolt upward, heating the surrounding air to create thunder.

The sky holds symbolic power—home of gods, destination of souls, metaphor for ideals. Trees frame our perception. Watching sunset at Big Sur, Ackerman explains blue skies and red sunsets as arising from the scattering of light as it reaches the atmosphere. At night, the sky is a window on space, and sailors use the stars to navigate, as they have done for thousands of years.

Light influences biology and psychology. It affects moods, regulates hormones, sets circadian rhythms. The lack of sunlight in Northern latitudes correlates with depression. Those experiencing seasonal affective disorder—a form of depression connected to the lack of natural light in winter—often experience relief when exposed to bright artificial light. 

Many organisms produce light via bioluminescence—deep sea angler fish use glowing lures to attract prey, fireflies use the chemicals luciferin and luciferase to produce flashing lights, in a part as a mating signal. Ackerman describes rowing through a bay whose water glowed with bioluminescence emitted by microscopic creatures. Triboluminescence produces light through friction—crushing wintergreen Lifesavers in the dark creates blue-green flashes from broken sugar and oil of wintergreen.

Color isn’t intrinsic to objects but created in the brain that perceives them. We see the wavelength an object reflects rather than those it absorbs; an apple is “everything but red” (252). Edwin Land, inventor of the Polaroid camera, developed color constancy theory: The brain compares objects to their surroundings in order to perceive consistent color regardless of light.

Language shapes color. Ancient Greek had few color words; Welsh’s glas covers blue, gray, and green. English lacks vocabulary for nature’s subtle shifts—such as the changing shades of red in developing fruit.

Color has both psychological and physiological impacts. Ackerman was brought to tears by yellow sulfur. Red light increases hand-grip strength; blue calms tremors. Green waiting rooms create restful effects. Watching sunsets is “visual opium” that, for Ackerman, makes life feel worth living.

Autumn colors signal decay. After the summer solstice, trees withdraw nutrients, forming a corky stem layer that chokes leaves. Chlorophyll breaks down, revealing hidden pigments.

Carotenoids produce yellows and oranges. Anthocyanins, newly produced by trapped sugars, create reds and purples. Cool nights and sunny days maximize display. These colors serve no adaptive purpose—a “haphazard marvel.”

The spectacle moves us, connecting with hopes about death: “Not to vanish, just to sublime from one beautiful state into another” (259). The noun “fall” refers to the falling of leaves, and versions of this word for the autumn season have existed for thousands of years. For Ackerman, the word evokes the biblical fall of Adam and Eve. Children play in fallen leaves that decay to enrich soil. The swooping trajectory of a falling leaf evokes human dreams of flight.

In animals, vision and color aid survival through camouflage, communication, and deception. Color comes from pigments or structure—polar bears’ transparent hairs house tiny air bubbles that scatter white light, making the bears appear white; blue jay feathers have no blue pigment, only a cellular structure that reflects blue light while absorbing other frequencies.

Many aquatic animals have evolved countershading, with darker coloration on their backs and lighter on their bellies. This coloring, seen in both penguins and white sharks, camouflages them from above and below. Insects mimic twigs, leaves, droppings, or dangerous creatures. Bright colors can serve as a warning, as in poison dart frogs, or as a form of mating display, as in peacocks and many other bird species. 

Cats’ eyes glow at night because of the tapetum, a layer of reflective cells found in the eyes of most terrestrial mammals, which sends light back for a second pass over the retina, improving night vision. Predators have vertical pupils for forward vision, while prey animals have horizontal pupils for wide field. Many animals are color-blind; bees see ultraviolet light, revealing flower patterns invisible to humans. Bees process images so fast that a human movie would appear as still photographs.

Is artistic vision genius or biological anomaly? The 20th-century philosopher Maurice Merleau-Ponty described the work of Impressionist painter Paul Cézanne as making “visible how the world touches us” (267), but Cezanne himself feared that his style was merely the result of myopia and possible retinal damage from diabetes.

The famous halos around light sources in paintings by Vincent Van Gogh could stem from damage to his vision arising from glaucoma, exposure to paint thinner, or digitalis poisoning. Prior to the advent of synthetic pigments in the modern era, brilliant pigments contained toxic copper, cadmium, and mercury; painter Pierre-Auguste Renoir’s favored paints had high metal levels that may have contributed to his rheumatoid arthritis.

Patrick Trevor-Roper theorized a “myopic personality,” suggesting that near-sighted artists like Edgar Degas tend to be more introverted and to work at a smaller and more intimate scale. Cataracts changed JMW Turner’s and Claude Monet’s color perception. After surgery, Monet was surprised by blueness and appalled by the strange colors in his recent paintings, anxiously retouching them. In Ackerman’s view, genius requires emotional depth, curiosity, and a “willingness to be fully available to life” (270).

Perceptions of beauty are shaped by evolutionary biology. Dilated pupils subconsciously signal attraction; in Renaissance Italy and later in Victorian England, women used belladonna, a toxin derived from a plant in the nightshade family, to induce dilated pupils for cosmetic purposes. People viewed as attractive get better grades and lighter sentences. Parents show more affection to cuter babies. The pursuit of beauty has driven cosmetics from ancient Egypt to modern plastic surgery.

Non-physical qualities can influence perceptions of beauty. Ackerman found the actor Omar Sharif handsome in films but unattractive after an interview in which he stated that his favorite thing to do is play bridge—a habit Ackerman associates with a lack of personality. Conversely, people who are not conventionally attractive can become beautiful through personality. She quotes Shakespeare’s A Midsummer Night’s Dream: “Love looks not with the eyes, but with the mind” (276).

Ackerman describes a space shuttle launch at night as a total sensory assault. The huge size of the rocket, the bright floodlights, and the visual and auditory intensity of the launch itself contribute to a feeling of awe. Birds and insects panic as the shuttle rises, a “huge steel muscle dripping fire” on a 700-foot “waterfall of flame” (280). Spectators are moved to tears.

For Ackerman, the launch symbolizes humanity’s journey from origins to mastery. Escaping Earth’s gravity is the culmination of millennia of language, cities, and technological development. From orbit, night/day and up/down are relative. The launch expresses our longing to be “jettisoned free from routine” toward the infinite (279).

Visual images condense complex experience, often evoking strong emotions. Picturing an image in the “mind’s eye” evokes a stronger response than hearing it described in words. A photograph symbolizes wars; a gesture represents love.

Studying astronomy, Ackerman learned that there are rings around Jupiter, Uranus, and Neptune—not only around Saturn, as commonly believed. She felt emotionally moved by images of these planets with their unique rings, a response she attributes to the ring’s role as a universal, ancient symbol of infinite love, life’s cycles, sacredness, eternity, and perfection. People are drawn to rings in games, rituals, and relationships, as they answer a human longing for symmetry and wholeness.

Ackerman imagines the experience of viewing Earth from space, noting the interconnectedness of all ecosystems and the illusory nature of borders. 

She relates this imagined experience to her own memory of to learning to fly a small airplane, witnessing both the beauty of American landscapes from the air and the environmental devastation wrought by industrialization. Some things are only understood from another viewpoint—as one must be in the ocean to grasp its depths.

The possibility of seeing Earth from space, Ackerman argues, is the most important development of the 20th century. This perspective redefines “neighborhood,” making us planetary citizens, offering the chance to work together as caretakers.

Synesthesia—stimulation of one sense triggering another—offers a window into unified perception. According to psychologists Daphne and Charles Maurer, in The World of the Newborn, the newborn “hears odors, and sees odors, and feels them too” (289), living in a “mêlée” of blended senses. 

The term synesthesia comes from Greek “to perceive together.” Neurologist Richard Cytowič links it to the limbic system, arguing synesthetes’ cortex doesn’t fully govern this region. He calls them “living cognitive fossils,” suggesting that synesthesia “may be a memory of how early mammals saw, heard, smelled, tasted, and touched” (290).

The composers Aleksandr Scriabin and Nikolai Rimski-Korsakov associated musical keys with colors. 19th-century poet and essayist Charles Baudelaire influenced the later French Symbolist poets by celebrating correspondences between sounds, perfumes, and colors. Poet Arthur Rimbaud assigned colors to vowels. Novelist Vladimir Nabokov, in Speak, Memory, described “colored hearing”—comparing the texture of the letter “a” to weathered wood and “g” to vulcanized rubber. For these artists, sensory “leaking” was essential to creativity.

Writers rely on eccentric sensory rituals for focus. English poet and critic Edith Sitwell lay in an open coffin before writing; German playwright and philosopher Friedrich Schiller inhaled rotten apples that he kept in his desk.

Poet and novelist Stephen Spender theorized that because writing makes one forget the body, sensory “anchors” are needed. This explains American poet Amy Lowell’s cigars, French novelist Victor Hugo writing nude, and the French writer Colette methodically picking fleas from her cat.

Writers listen to single pieces obsessively for emotional consistency. The American experimental fiction writer William Gass photographs urban decay before writing; poets find inspiration walking. English romantic painter JMW Turner had himself lashed to a ship’s mast in a storm—jolting his senses to break routine and access deeper creative consciousness.

The senses define human experience—a “palatial and exquisite rut” from which we cannot escape (301). Even mystical experiences filter through perception. The “real world” is a fiction. The brain constructs reality from limited sensory input edited for survival, not truth. We can’t perceive molecular motion or non-relevant phenomena.

We have more than five senses—gravity, proprioception, possibly a latent magnetic sense. Senses crave novelty. Constant stimuli fade. Life passes in a “comfortable blur” as brains generalize.

The challenge and joy of life are in cultivating curiosity and varied experiences. Knowledge is bounded by mystery, but the journey matters. Life is a “savage and beautiful country” to explore, galloping over “sun-struck hills every day” (309).