Deep beneath the equatorial oceans, two gargantuan worms made of stone and metal glide in darkness and eerie silence through a mile-wide steel tunnel. Thousands of miles long, weighing trillions of tons, they hurtle ever westward at a thousand miles an hour, circling the earth every day. One of them chases the moon but never catches up to it, and the other flees ahead of the moon but never gains ground.
They sound like nightmare creatures from ancient mythology, but if the future envisioned by Professor Anton Myriad of the Developmental Origination Research Center (DORC) comes to pass, these gargantuan high-tech machines dubbed "Midgard Serpents" will not only become reality, they will provide all the energy needed for all human uses for thousands of years into the future. Dr. Myriad has published the details in a paper titled "Practical Planetary-Scale Power Generation via Artificial Tidal Locking," scheduled to appear in next month's issue of The Journal of Desperately Needed Results.
While the physics behind the Midgard Serpent design is not easy to visualize, the basic concept is simple enough. "Imagine if you could build a railroad track around the equator of the earth," Myriad explains. "On this track is a long train. Instead of a locomotive, the front of the train is tethered to the moon with a long rope. The moon, moving through the sky as the earth rotates, pulls the train around the equator. Electric generators on the wheels of each car generate power as the train rolls along."
Strange as it might seem, this whimsical device would work, in principle. The energy that the train generated would be extracted from the rotational kinetic energy of the earth and the orbital kinetic energy of the moon. So massive are those bodies that even powering all human needs this way for centuries would have little noticeable effect on their momentum. "No, the moon couldn't run out of energy and come crashing down to earth," says Myriad reassuringly. "Instead, the moon would gradually get farther away, by a few meters a year. And it already does that. We might also have to adjust our clocks a little more often, but most people won't notice the difference."
But the rope-to-the-moon scheme could never work in practice. No surface-running track or train could stand up to the titanic forces that a quarter-million-mile-long tether to the moon would generate. Even more important, there is no material known to science that's strong enough to make a lunar tether out of. And if there were, the tether would whip through earth's atmosphere at high speeds with unknown effects, and if it were to break (perhaps due to a meteor or satellite collision) it could devastate the planet.
The Midgard Serpent gets around those problems in an ingenious way. The breakthrough came when Dr. Myriad realized that there is already a tether of sorts connecting the earth and the moon: the force of gravity. The same gravitational phenomenon that powers the ocean tides (which is also what causes the moon to move slowly farther away from the earth at a few meters per year) could pull the "train," if the train is made the right way and runs on the right timetable.
To be moved by tidal forces, the train must be very large and heavy, because the more massive an object is, the more it is affected by gravity, and the larger it is, the more it is affected by the minute variations in the gravitational fields occurring at the earth's surface that we know as the tides. Myriad has calculated forty trillion tons as the ideal healthy weight for a Midgard Serpent. By weighing as much as seven Mount Everests, each 5,000-mile-long Serpent will make a strong enough gravitational connection with the moon to generate vast amounts of power on earth.
Even with that mass distributed along so many thousands of miles, that's way too heavy for any ordinary railroad track, and it also has to move at supersonic speeds, far faster than any conventional train. Not to mention, most of the earth's equator is located over ocean, a difficult place to lay track. So, in Myriad's design, the "track" becomes a sealed tube a mile in diameter, that runs for 25,000 miles all the way around the earth's equator. The tube runs deep beneath the ocean surface, and deep underground where it crosses land. (Fortunately, the ground and the oceans are no barrier to gravitational forces.) The cars of the "train" are steel cylinders filled with dense basalt rock, big enough around to nearly fill the inside of the tube. The air inside the tube is pumped out to create a near total vacuum, and superconducting magnets lining the inside of the tube levitate the massive segments, allowing the Serpent to move with almost no friction at very high speeds.
Midgard Serpent tunnel construction (artist's conception)
Once the Serpent is brought up to it's thousand mile an hour operating speed, it takes up a position that's fixed in a certain way relative to where the moon is in the sky. To maintain that position it must careen nearly all the way around the earth each day as the earth rotates. The ideal position is centered about three thousand miles (forty-five degrees) east of the moon's position over the earth, where the gravitational power transfer from moon to machine is maximized. The DORC calls this "artificial tidal locking," due to its resemblance to a natural astronomical phenomenon in which the same side of a moon or planet always faces its orbital partner. The earth's moon, which always has the same side turned toward the earth, is the most familiar example.
A second Midgard Serpent, using the same tube, is similarly positioned on the opposite side of the world, where the same tidal forces drive it westward in the same manner. Besides doubling the power output, the second Serpent also helps keep the planet in balance, a genuine concern when engineering at this scale. "Making the earth wobble too much could significantly degrade the system's performance," Myriad points out.
The speed of the Serpents, while it presents technical challenges for its construction, is what makes the gravitational tether effective. "When the tide acts on the oceans, it generates a lot of power because the oceans are so massive," explains Myriad. "But the tidal pull changes direction four times a day, and the water doesn't get pushed very fast or very far. So the power of the ocean tides, even though it dwarfs the Midgard Serpent in absolute terms, is very diffuse and difficult to harness. With the Midgard Serpent, the tidal force acts upon the moving mass through a distance of over a quarter mile each second, always in the same direction, pumping power into it. Energy is force times distance, and power is force times speed. It acts like a focusing lens for collecting tidal energy."
This is why the machines have to be so large and heavy. "There's a ratio of about one in ten million," explains Myriad. "For every ton of mass in the Serpent, there's a net lunar tidal pull of about a tenth of a millionth of a ton, or about the weight of a grain of salt. That doesn't seem like much, but for the whole Serpent, it adds up to four million tons of force, or thirty-nine billion Newtons, acting constantly to pull the machine ahead."
Another way of looking at it is that the tidal force makes it seem, to the Serpent, as though the part of the tube it's in is tilted slightly downhill, even though it's actually level. By circling the globe to keep up with the moon, the Serpent stays perpetually in that "downhill" position, like a surfer riding a never-ending wave.
Even though the Serpent is already moving at over 440 meters per second, the apparent "downhill tilt," or tidal force, would cause it to speed up. To prevent that, the system adjusts the magnetic fields of the tunnel's levitating magnets in a way that causes them to act as brakes to keep the Serpent's speed constant. That constant braking generates enormous amounts of electrical power, averaging about seventeen terawatts per Serpent. (That calculation is surprisingly simple: multiplying the 39 billion Newtons of tidal force on the Serpent by the 440 meters per second speed of the Serpent gives you the power in Watts.) The two Serpents together would generate more than enough power to maintain the system and still supply more than the world's present-day power needs of about fifteen terawatts, all without burning a drop of fossil fuels or splitting a single atom.
Day to day changes in energy demand are no problem either, because each Serpent also stores massive amounts of kinetic energy. "When energy demand increases, or the smaller solar tides are out of phase with the lunar tides [thus reducing the tidal force and reducing the Serpents' tidal power output], we can allow the Serpent to slow down just a little and still provide full power," Myriad claims. "At times of low demand or during spring [maximum strength] tides, we can let it catch up, or run a little ahead. Even the largest variations would only make a difference of a fraction of a mile per hour, and it would even out in the long run."
And should future global demand for energy increase beyond what the system can provide, additional parallel Midgard Serpent tubes can be built. Perfection of the construction methods during the building of the first one should reduce the cost of additional ones to a mere pittance. "The bottom line is, there is no practical power limit for the foreseeable future," Myriad concludes.
The DORC is currently seeking funding for a thorough study of the concept, including detailed computer modeling, interactive educational exhibits, and a possible movie tie-in featuring the popular Marvel character Thor.