Energy and the Human Far Future

Robert P. Burruss


The sun created life on earth and made the earth green. It drives the seasons and keeps the earth warm. It created human beings, actually shaped us from the matter of the earth. It radiates enough energy each second to supply all present human energy needs for a million years. No god conceived by the solar-powered human imagination, nor inspired by holy books or Steven Spielberg movies, compares in physical size and power to the object that daily traverses the sky and drives the world, and from whose divine gaze we avert our eyes in practical reverence. The sun has the thermonuclear wherewithal to keep things going for at least another billion years.—Robert P. Burruss

The trouble began in 1776. That was the year when James Watt’s improved steam engine went into service in England. Those early engines were large and inefficient, but during the nineteenth century they were made small enough and powerful enough to power boats and then trains and eventually personal vehicles.

Most people today think that steam engines stopped being used about a hundred years ago, when gasoline engines came into use. In fact, one-third of America’s energy goes to boiling water for giant steam engines that turn the generators that sustain the modern electrical world.

Steam engines are heat engines. Heat engine is the generic term for any engine (not just steam engines) that converts the chaotic molecular motions of hot gases into useful work. The descendants of Watt’s ancestral heat engine include modern car engines and aircraft gas turbines, the engines of lawn mowers and the leaf- and snow-blowers that rattle otherwise quiet days, and the steam turbines that drive electrical generators. About 80 percent of humanity’s energy consumption goes to making hot gases from which heat engines extract useful work.

Heat engines multiply the strength of individual humans. The average power of one human body—its average basal metabolic power—is about 100 watts (see sidebar “Bananas and Hand Grenades”). The driver of an SUV that gets 15 mpg at 60 mph uses energy at a rate equivalent to the average metabolic rates of 1,500 people; a passenger on a commercial jet flight uses energy at a rate equivalent to 3,000 people. A typical 2,500-square-foot detached American house uses a year-round average continuous power equal to the average metabolic power of 100 people for heating, cooling, lighting, cooking, and television and computer use. As I write this, snow is coming down, and I am using a computer that uses energy at about four times my average metabolic rate. In addition, a little heater representing about forty human metabolic equivalents is warming my tootsies. The washing machine also happens to be running, at about ten human metabolic equivalents, and the refrigerator is using another six to eight as I sit here. In effect, several dozen Virtual People (VPs) are with me as I write this—unless the furnace is running, in which event some 500 VPs are in my immediate service (see sidebar “Virtual People”). The total energy used by an average American during a seventy-eight-year average lifespan equals half of the energy yield of one Hiroshima-sized bomb.

The combined average energy use rate of all human beings is, according to the Statistical Abstract of the United States, about 13 trillion watts—i.e., 13 trillion joules of energy per second, which equals the nominal power of 20 billion horses, or one Hiroshima bomb every four seconds. That energy can be called “cultural energy” because it drives technological culture.


Bananas and Hand Grenades

The terms energy and power are often erroneously used as synonyms. Power is the rate at which energy is used, as in calories of food energy per day. Two common units of power are the watt and the horsepower. A watt of power is defined as one joule of energy per second. One calorie of energy equals about 4,200 joules. One horsepower equals about 750 watts.

Yes, it is confusing, but consider this example of the relationship of energy and power: One Krispy Kreme custard-filled glazed donut contains about 170 calories of food energy. So does a banana—and so, too, does a hand grenade. Said hand grenade can release its 170 calories of energy in a thousandth of a second, which is a high rate of energy expenditure—about a million horsepower—while the 170 calories of energy in a banana or donut get metabolized over periods of hours and yield only fractions of horsepower.

It is possible (though not recommended) to treat a banana or donut with nitric acid to make a nitro-banana or nitro-donut that could be detonated like a hand grenade. In normal use, though, one banana or donut can supply enough energy to power a healthy human body for two hours of television watching while reclining on a sofa (100 watts, or 0.13 horsepower) or for twenty minutes of a fast walk (~600 watts, or 0.8 horsepower).

The nominal daily food-energy requirement of a human body is 2,000 calories/day, which is about the same as the 100 watts of power used by a typical incandescent living-room lamp bulb. Or we can say that the radiated power of a typical living-room lamp bulb is equivalent to one human body. (Actually, since electric energy delivered at the outlet represents only about 30 percent of the energy in the fuel that was burned to make electricity, each 100-watt electric lamp is equivalent to 3.3 human bodies.) Thus to sit by a lamp at night while reading represents a gross energy expenditure equivalent to about four people—oneself and the fuel burned to make the electricity to light the lamp. If one is watching television, the total energy use rate by the television and the viewer is equivalent to six to ten human beings.

Virtual People

A simple way to think about fossil energy use is in terms of “Virtual Persons” (VPs). One VP represents 100 watts of average annual fossil energy usage, which as we have seen corresponds to the nominal dietary energy of one healthy person (2,000 calories per day equals 96.9 watts). For example, a 100-watt incandescent living room lamp, radiating about 30 percent of the energy in the fuel that was burned to make the electricity it consumes, is equivalent to 3.3 VPs.

All of humanity currently uses energy at an average continuous rate of ~13 trillion watts, which is about twenty times the metabolic or food energy rate of all humanity. Thus, each living person is, from an energy point of view, equivalent to twenty people or twenty VPs.

Of course, energy use is not distributed evenly. In the United States, the ratio of energy use to population works out to ~120 VPs per person. It is as if each American has the physical power of 120 people. Each European or Japanese uses about half the VPs of each American. If you subtract Americans, Europeans, and Japanese and their energy use from the world total, each of the remaining ~4 billion human beings on Earth has access to only ~13 VPs, on average.

The 120 VPs of each American are used for heating and cooling, cooking, personal transport, food production and delivery, lighting, and computers. Averaged over a year, one round-trip flight from Washington, D.C., to London works out to ~4 VPs (assuming seventy passenger-miles per gallon). Domestic utility usage in a 2,000-square-foot house (without air conditioning) comes to 60 VPs; with the AC on it’s about 100 VPs. A 100-watt computer that operates year-round is about 3.3 VPs, again allowing for energy losses in electric generation and transmission. A 20-mpg SUV that travels 10,000 miles in a year is ~20 VPs.

Energy and the Reverend Mr. Malthus

Two centuries ago, the Reverend Thomas Malthus address
ed the dietary energy issue in his “Essay on the Principle of Population.” He could not have anticipated that food production would be supercharged with fossil fuels or that the descendants of James Watt’s steam engine could be brought to bear so as to summon far more bounty from agricultural land than could sunlight alone.

But consider the energy cost: each calorie of dietary energy that arrives on the contemporary American dinner table represents the expenditure of about five calories of fossil-fuel energy required to plant seeds; make and distribute fertilizer; cultivate the crop; harvest it; feed part of it to cattle, pigs, and chickens; cook the product; freeze it; package it; refrigerate it; ship it; heat it up at home; and, after dinner, throw the excess away. Air-freighted food, of course, is the most energy-intensive.

Malthus seems to have been wrong about the limits of food supply—or maybe he wasn’t; the Malthusian principle still applies to cultural energy, the hydrocarbon “food” needs of technological society, which is to say humanity in the collective. If that fuel runs low, “food”-starved nations will fight over the last crumbs.

Freeman Dyson on Dyson Spheres

The British physicist Freeman Dyson gets the credit for the idea of building an energy-collecting sphere around the Sun in his essay “Search for Artificial Stellar Sources of Infrared Radiation,” published in Science on June 3, 1960. The abstract of that essay reads: “If extraterrestrial intelligent beings exist and have reached a high level of technical development, one by-product of their energy metabolism is likely to be the large-scale conversion of starlight into far-infrared radiation. It is proposed that a search for sources of infrared radiation should accompany the recently initiated search for interstellar radio communications.”

Dyson attributed the idea to the science-fiction writer Olaf Stapledon and his 1937 novel Star Maker. The science-fact and science-fiction writer Isaac Asimov also implied the idea in at least one of his essays describing ways to arrange the matter of the solar system so as to maximize the number of human beings that can be alive at one time.

Professor Dyson’s one-page essay in Science states in part (paraphrasing): The time required for an expansion of population and industry by a factor of a trillion is quite short, say 3,000 years if an average growth rate of 1 percent per year is maintained. The energy required to disassemble and rearrange a planet of the size of Jupiter is about equal to the energy radiated by the Sun in 800 years. The mass of Jupiter, if distributed in a spherical shell revolving around the Sun at twice the Earth’s distance from it, would have a thickness of two to three meters. A shell of this thickness could be made comfortably habitable, and could contain all the machinery required for exploiting the solar radiation falling onto it from the inside.

Dyson was clearly describing a rigid spherical structure. More plausibly, a Sun-encompassing sphere would be comprised of a swarm of independent Sun-orbiting objects.

Dyson continued: “It seems, then, a reasonable expectation that, barring accidents, Malthusian pressures will ultimately drive an intelligent species to adopt some such efficient exploitation of its available resources. One should expect that, within a few thousand years of its entering the stage of industrial development, any intelligent species should be found occupying an artificial biosphere which completely surrounds its parent star.”

$200 Billion in Gold under the House

Ownership of land in most parts of the United States theoretically extends all the way down to the center of Earth. A 5,000-square-foot lot is thus the Earth-surface portion of a cubic kilometer of rock and metal, about 35 percent of which is iron (worth nearly $1 trillion at current scrap prices) and 30 percent oxygen (worth about $10 trillion, at the retail cost of oxygen from gas suppliers). The gold portion alone is worth about $200 billion. The energy content of the uranium portion, presuming a plutonium economy, comes to at least $10 trillion at the wholesale cost of delivered electrical energy. And so on.

There is enough metal and oxygen—and energy, too—under an ordinary suburban house to make about 500 artificial planets with a mass of one million tons each. Such an assemblage of small worlds could theoretically—if just barely—house and support the entire current human population of Earth. (Add the artificial planets made from Earth beneath your neighbor’s house, and the current human population could be supported handily.)

If you divide the volume of Earth (1 trillion cubic kilometers) by the number of human beings (6.5 billion), the per-capita share comes to 167 cubic kilometers. Humanity is living on an unimaginable wealth of material but, at present, can’t get at it—but thanks to our Sun, the energy is available to do it.

Japanese Cars from the Moon

In the 1990s, the Japanese developed a high-performance hydrogen-oxygen rocket engine called the “H-1.” Some people thought that real-estate- and resource-deficient Japan was planning to set up manufacturing facilities on the Moon, where solar energy and lunar metals could be used to produce cars, televisions, and cameras. The low-gravity lunar setting would benefit mining and construction; cost of shipping manufactured goods from the Moon to Earth would be lower than pushing them across the Pacific Ocean. GPS-guided gliders could deliver cars right to dealers; cameras could be delivered to consumers’ doorsteps.

However, were Japan, or some other technically adept nation such as Israel, to establish a self-sustaining manufacturing presence on the Moon, said presence would not be seen by people here on Earth as perfectly benign. If cars made of lunar rocks could be delivered with pinpoint accuracy, so could nuclear weapons.

Earth would be perceived as hostage to any nation having permanent facilities on the Moon. One of two things would happen: suspicious nation-states on Earth would want to launch preemptive strikes on the lunar bases. Or, alternatively, they would work to catch up with the supposed Threat From Above, and they would establish their own competing lunar bases.

The precedent for a competitive race to the Moon is the European colonizing of the Americas. So, too, the Apollo program. Some people might lament that, but the biology of us mutant apes might include a need for competition to get things done. Without competition, we might work to satisfy only our current needs rather than future ones.

Mining the Earth to Its Core

If God had had to write environmental impact statements, Earth would not have an oxygen atmosphere. For that matter, Earth would not be green with life—nor would it have come into being at all. The Sun radiates the energy equivalent of 100 billion megatons of TNT each second; imagine trying to propose the construction of a thermonuclear reactor of that scale!

Among the enduring misconceptions held by us beings of the humus is our assumption that we are separate from the rest of nature, operating outside of the rules that govern all other processes. It is a fallacy. We are Sun-powered creatures who think that our creations—computers, highways, airplanes, spaceships—exist outside the natural frame of reference that includes the stars, planets, oak trees, mountain ranges, oceans, dandelions, and summer storms. Our hubris is itself solar-powered and Sun-dependent.

We can think of ourselves as agents of the Sun. Someday our descendants—or those of squirrels or raccoons—might disassemble Earth. If, or when, that happens th
e enterprise need not be judged, nor blame assigned; there is no value in assigning “evil” to the actions of a hurricane or an asteroidal impact. We beings of the humus are part of nature; we can think of ourselves as the eyes of Earth, or the hands or mind of Earth, and the means by which the matter of Earth rises up to look upon itself and reflect.

Scientists say that in a few billion years the Sun will expand and consume Earth. Before then, it is possible that life from Earth will rearrange the material of it and other planets into “artificial” planets and then, eventually, carry at least a portion of Earth to another star. Sun-made life from Earth will have eaten it and carried its substance outward on an indefinitely long voyage.


Human beings use cultural energy at about twenty times the rate that they metabolize energy from food, which means that, from an energy-use point of view, each living human being is equivalent to 20 VPs. From this perspective, the world population is effectively closer to 130 billion rather than to 6.5 billion; if 130 billion human beings were actually living, then the carbon dioxide from exhaled breaths alone, without any fossil-fuel-burning technology, could cause the present rate of increase in atmospheric carbon dioxide. Actually, the exhaled breaths of about 70 billion humans would have that effect because our bodies emit nearly twice as much carbon dioxide per calorie used by our bodies as comes from fossil-fuel-using heat engines. Therefore, somewhat fewer than 70 billion human beings could exist on Earth in chemical equilibrium with the atmosphere—if, that is, no carbon-dioxide-emitting fossil fuels were burned to drive human activities (see sidebar “Energy and the Reverend Mr. Malthus”).

Humanity’s use of energy seems extravagant, especially American use of energy—until you realize that the Sun’s net energy input to Earth is some 8,000 times what human beings use, and the portion of the Sun’s total energy output that shines on Earth is only 1 part in 2 billion of its power. Nature is extravagant, too.

The last hundred years have been the greatest Golden Age in human experience in terms of comfort and long life for the largest number of human beings. But as the reserves of buried fossil sunlight dwindle, technological humanity finds itself increasingly in an energy desert. Ethanol from corn is not sufficient to sustain fleets of cars or maintain access to European, Caribbean, and Asian vacations while keeping the house and office cool in July. Nuclear war is possible. A major dieback this century seems a certainty.

But beyond this twenty-first century of humanity’s main provincial calendar, the future could be bright: human beings might someday gather and use a large portion of the Sun’s effectively limitless flow of energy. If human beings could collect 1 percent of the Sun’s radiant energy, we would have a trillion times more energy than at present.

The strategy for gathering the Sun’s energy would have to unfold in space; it would involve a continuous construction of what is called a “Dyson sphere” to encircle the Sun and collect its energy. The Dyson sphere is an idea that occurs to most people who think about energy and the distant future.

The Sun

The Sun radiates ~4 x 1026 watts—~25 trillion times humanity’s current energy use rate—enough to vaporize Earth in about a week if all of the Sun’s energy were directed to that end. It is an effectively infinite source of energy, one that will keep giving for at least another billion years.

The size of the Sun can be grasped, at least a little, by contemplating the Moon and imagining its distance from Earth (240,000 miles) and realizing that the Earth-Moon separation is less one-third of the diameter of the Sun. Try to imagine what the Sun would look like if its surface were only as far away as the Moon is.

Building a Dyson Sphere

An energy-collecting shell around the Sun would be made of materials from the moons and planets of the solar system. It’s an idea that’s been around at least half a century, long enough to have acquired a name: “Dyson sphere,” after the British physicist Freeman Dyson.

A Sun-encircling Dyson sphere would not be a rigid spherical structure, as Dyson himself initially described it (see sidebar “Freeman Dyson on Dyson Spheres”). Instead, it would consist of a swarm of energy-collecting “artificial planets” that would gather sunlight and convert it into forms of energy that can be beamed as, say, laser light to any location within half a light-year of the Sun. Trillions of such artificial planets could gather sunlight and convey it in concentrated form to large, inhabited artificial planets, some of them farther from the Sun than Neptune and Pluto; antimatter fuel might also be shipped or beamed to distant outposts for use in high-energy rocket propulsion and, naturally, in weapons.

No intentional decision would be needed to build a Dyson sphere: its construction would be a necessary product of a “space civilization” in which people would live on artificial planets that take their energy from the Sun. A Dyson sphere would grow continuously and thereby gather increasing amounts of energy.

Artificial Planets from the Moon

The popular notion that humans will someday live in large numbers on Mars and the larger moons of Saturn and Jupiter is simply not plausible. Poisonous atmospheres, too much gravity, and excessive heat or cold are impediments to colonization of the natural planets. Also, the materials in the cores of planets are just too valuable to justify leaving the planets intact (see sidebar “$200 Billion in Gold under the House”).

With access to stellar amounts of energy, it would be practical to break up the planets and get at their core wealth rather then try to make them habitable. The future is more likely to involve Sun-orbiting artificial planets than colonization of the natural planets.

The Moon is Earth’s stepping stone into the solar system. Construction of self-sustaining permanent bases on the Moon would be a logical first step in the construction of a Dyson sphere. The construction process could be continuous, lasting possibly millions of years, or billions—or until the Sun runs out of fuel.

The building of permanent bases on the Moon might plausibly focus initially on lunar mining for the manufacture of goods to be shipped to Earth. Lunar manufacturing could also lead to the construction of large artificial planets that would be commissioned by wealthy people and potentates and for use as “planet-states” and corporate planets that might form alliances of planet-states.

The components for massive artificial planets—ones weighing thousands of tons and eventually millions and even billions of tons—would initially be fabricated on the Moon and then launched into space for assembly in Earth orbit or solar orbit.

Raw materials would come initially from Earth’s Moon and then later from the moons of Mars and then Jupiter and Saturn. Eventually, the planets themselves, including Earth, would be cut up for use in an endless sunlight-gathering enterprise (see sidebar “Mining the Earth to Its Core”).

Manufactured goods and food would be produced on artificial planets in Sun-powered operations. Interplanetary trade would be the backbone of what could become a “space civilization.”

Energy gathered by artificial planets orbiting close to the Sun—some manned, some automated—could plausibly be beamed to distant human outposts. The beamed energy might be at wavelengths easily and efficiently convertible to electricity. Antimatter might also be produced on the energy-gathering artificial planets; it could be shipped on rockets, or transmitted as speed-of-light particle beams. Antimatter could be the basis and driver of rocket-mediated interplanetary trade in raw materials and manufactured goods.

Within the next thousand years, barring some show-stopping calamity, human beings could use nuclear and thermonuclear energy and sunlight to drive the mining of aluminum, titanium and silicon on the Moon. Huge artificial planets (~100,000-ton, aircraft-carrier size) would be built on the Moon and pushed into solar orbit, each providing a home for a million people or more.

Within the next ten thousand years, the solar system could be swarming with billions of artificial planets—each essentially a Sun-powered life-form that would stand in relation to us metazoan human individuals as we stand in relation to lichens on a rock—or pond scum.

When James Watt began peddling his improved steam engine two hundred years ago, the idea of building a shell around the Sun to collect energy would have seemed as absurd as the idea of personal immortality. In fact, the Dyson sphere idea still seems outlandish—but a little less so. Attitudes change. The matter that comprises your body and mine was once the matter that carried the shapes of dinosaurs and redwoods, whales and clouds, and sandy beaches and volcanoes. Matter endures, though its shapes and arrangements do not. The matter we are made of right now might yet participate in an endless biological process that began when the Sun and Earth were young.

Robert P. Burruss

Robert P. Burruss is a mechanical engineer specializing in energy conversion and heat transfer.

  The sun created life on earth and made the earth green. It drives the seasons and keeps the earth warm. It created human beings, actually shaped us from the matter of the earth. It radiates enough energy each second to supply all present human energy needs for a million years. No god conceived by …

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