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It’s right on the tip of my tongue, the edge of my mind, about how we will drive to the stars. This is because I’m a science fiction reader and writer and have bathed in notions of faster-than-light travel, generation ships, warp drives, and worm holes since I was a teenager. It’s part of the mythos that human beings will one day have the energy, derived from our understanding of physics, that will let us cross the vast gulfs between the stars. Our stories abound, too, with other beings, other cultures, aliens who supposedly have cracked the secret. And while they are obviously more technically advanced than us, they are not magicians.1
We human beings are aware of and have the potential to use three forms of energy. One is chemical, the making and breaking of atomic bonds, representing electrons donated to or shared between the energy shells of different atoms. This is every form of energy known and used up to the twentieth century. It is the energy of fire, of the chemical processes that drive reactions inside our cells, of burning hydrocarbons to make heat, and of releasing nitrogen atoms from complex molecules that then join together in ravenous diatomic bonds that drive most chemical explosions. It will also drive chemical rockets into orbit around the Earth, as far as the Moon and outer planets, and eventually, by inertia, over vast amounts of time, beyond our solar system.2
Within the last hundred years, we have learned about newer forms of energy. We discovered that heavy atoms—those with lots of protons but that have added or are missing their complementary neutrons—can be induced to break apart at a nuclear level to make smaller atoms and so create heat. This reaction is not normally found in nature in any great quantity—not enough so you would notice—although it is a suspected contributor to the heat at the cores of the rocky planets. Nuclear fission is the energy of the first atomic bombs and of reactor “piles,” and it has since been promoted—although not without opposition—to supply our electrical grid.
And then we learned, almost immediately after discovering the fission process, that the lightest atoms—those with just one or two protons and almost no neutrons—can be induced to come together to make slightly heavier atoms and also to make heat. This is the reaction that drives all the stars—at least until they burn out to become cinders, masses of pure neutronium, or black holes. We’ve been trying ever since to harness this reaction on Earth and put it into our grid, but the fusing process is trickier and more unstable than fission. And so far, although we’ve tried collapsing plasmas with powerful magnetic fields and laser pulses, the only thing that seems to work reliably is a massive gravity source—the weight that brings a star together in the first place. So, although there are a gazillion times more light atoms than heavy ones on this planet, and the newly fused atoms don’t create a waste problem, we still haven’t found a way to use the reaction to make steam and drive generators—we just use it to make bombs.
Finally, in a form of energy that we don’t actually use yet, we know that two particles of the same kind but of a different sort—divided into “matter” and its “antimatter” counterpart—will come together under the right conditions to annihilate each other in a cascade of pure energy without any waste products at all. This sort of reaction is presumed to be the ultimate release of energy, and it’s favored in the Star Trek television series to drive their “warp engines.” The only problem—Hoo-whee! “Only”!—is that while matter exists all around us in a great variety of forms, antimatter is extremely rare, actually nonexistent in our everyday life, and can only be created at great expense in particle accelerators.3 So, driving your ship or powering your grid with a matter-antimatter explosion is going to cost you an arm and a leg, repeatedly, thousands of times a second, over the course of your journey.
So, those are the kinds of energy we know: manipulating electron bonds, creating fission inside big nuclei, and creating fusion of small nuclei, as well as the potential for matter-antimatter annihilation. All the rest is just fantasy and … magic.
But there, on the tip of my tongue, the edge of my mind, are energies as yet undiscovered, that won’t be discovered until we have a different appreciation of physics.
In the short story “Waldo” by Robert A. Heinlein, a young man with myasthenia gravis—or muscle weakness due to an autoimmune disease—is taught by an Amish farmer to tap into the latent energy of the universe by drawing strange glyphs on his machines. And since that story came out in the 1950s, cosmologists have discovered that the expansion rate of the universe is mysteriously increasing—a fact they attribute to what’s called “dark energy.” Some theorists believe this is some kind of “vacuum energy” that exists in the depths of space without any interfering particulate matter around.
Dark energy poses problems, as does the actual expansion rate of the universe. By sighting known stars in distant galaxies—Cepheid variables and certain types of supernovas, whose light provides astronomers with “standard candles”—and measuring their red shift as an estimate of their distance, we can figure that the universe itself is expanding, and that the galaxies are pulling away from each other, at a rate of 73 kilometers per second per megaparsec (km/s/Mpc, an expansion rate measured over 3.26 million lightyears) with an error of plus or minus 1.0 km/s/Mps. This has been confirmed with measurements taken by both the Hubble and the James Webb space telescopes.
But this is a different expansion rate from the one derived by measuring the cosmic microwave background (CMB) radiation. This is the “hum” of energies left over from the Big Bang—after light waves were first freed from all the precipitating particulate matter in the mix—that have been attenuated—or red shifted—from their originally high energy down to about three degrees Kelvin—almost stone cold—by the subsequent expansion of the universe. This measurement yields an expansion rate of 67.4 km/s/Mpc, with an error of plus or minus 0.5 km/s/Mpc. The expansion rate by the microwave measurement has been the standard of cosmology for decades—and it doesn’t jibe with standard-candle observations. The difference is not insignificant. So, what gives?
And now there is a breakthrough discovery that gravity—which has long been conspicuously absent from the calculations of quantum mechanics, the science that deals with the invisible world of subatomic particles—may actually exist at and be measurable at the microscopic level. Einstein’s theories of relativity, dealing with the macro world of planets and stars, and quantum mechanics, governing the realm of the unbelievably small, were long thought to be mutually exclusive and irreconcilable. But if gravity is exerted by grains of sand and maybe by subatomic particles, then we may be in line to create a “Theory of Everything,” combining relativity and quantum physics—the goal of physicists since early in the twentieth century. It may eventually explain mysteries like dark matter, which appears to drive the internal motions of stars in a galaxy, and dark energy, which appears to drive the motion of galaxies themselves and the expansion of the universe. These are exciting times.
And still, the idea haunts me: that somewhere, out between the stars, exactly where we want to go, there’s an abundance of energy that’s just waiting to be tapped—understood, captured, and used—if we only knew how. Maybe by drawing strange glyphs on our equipment?
But this is all just theoretical. And feeding my haunts is the fact that there is so much more we don’t understand about the universe. In fact, as I have suggested in the past,4 we really don’t understand three basic concepts in physics: the real nature of space, of time, and of gravity. But maybe, just maybe, we are beginning to …
1. Of course, as Arthur C. Clarke wrote: “Any sufficiently advanced technology is indistinguishable from magic.” But magic is by its nature impenetrable and practiced on an arcane level of the mind, while technology is—with the right mental and philosophical tools—comprehensible.
2. An offshoot of this chemical energy—or maybe an entirely new form of energy, making four usable forms—is the photoelectric effect. There, a photon—a high-energy particle, as from sunlight—impacts the right kind of material and knocks loose an electron from its orbit around an atomic nucleus. With the right setup—say a semiconductor sandwich connected to a circuit—the freed electron goes one way, and the “electron hole”—the material’s atomic need to complete that electron shell—goes the other. This creates a flow of electricity. Something similar happens in a fuel cell. But it’s still energy based on movement and exchange of electrons, which is in the realm of chemistry.
3. How much would a source of antimatter cost? At CERN’s Antiproton Decelerator, they can potentially make about a billionth of a gram of antimatter per year—or, over about ten years, enough antimatter to power a sixty-watt lightbulb for an estimated four hours—but that is not the CERN equipment’s intended purpose. To make a single gram—1/28th of an ounce—of the stuff would reportedly cost a million billion euros. Yeah, whether you think in terms of euros or dollars, that’s an unreasonable amount to pay to drive your starship over, what, about ten inches?
4. See my blogs Fun With Numbers (I) and (II) from September 2010.