Humanity's home is far from factory-fresh these days. Frankly, the Earth has received its share of scratches and dents, including large asteroid impacts, megavolcanoes, earthquakes, ice ages, and heat waves. It's to be expected. There are over four billion years on the clock, after all.
Though it has long been clear that Earth 1.0 is in need of an upgrade, it was not until a few years ago that someone began to take the notion seriously. In 2004, at a respected international design exhibition called the Venice Architecture Biennale, a young artist and architect named Christian Waldvogel displayed his plans for total global annihilation and the creation of Earth 2.0.
According to Waldvogel, a brave new world could be built from the remains of our current one. The circumference of this construction-- dubbed Globus Cassus, or 'hollow sphere' in Latin-- would be comparable to the giant planet Saturn. During the multi-million year assembly period, massive hoses would worm deep into the Earth's fiery bowels and suck liquid metal and magma into orbit through four space elevators sited at equal distances around the equator. This material would be squirted out and transformed into a lattice framework to support the rest of the edifice. As the Earth gradually shrivels and shrinks under this onslaught, its gravity would weaken. Over generations, the skies would darken with the relentless encroachment of the enormous structure above.
Of course it would be easy to dismiss the idea as ridiculous fantasy, one belonging only on the pages of the very pulpiest science fiction. Yet the Globus Cassus concept is outlined in all seriousness, with the same level of detail as befits any other entry in an eminent international architectural exposition. While there is much that is quibble-worthy about the plan-- both in engineering terms and in its underlying rationale-- Waldvogel makes a good case for the idea as an intellectual and philosophical exercise. He presents his scheme as both an architectural design, and as a thought experiment that could turn the way we think about our current planet-- and human society-- inside out.
Waldwogel's suggestion involves the redistribution of the Earth's material from its present clumpy solid-ball form to that of a 150 km (93 mi) thick hollow shell– one with a diameter of 85,000 km (52,817 mi), around seven times that of our current planet. People, plants and animals would live on the inside surface, with rotation of the giant habitat providing a centrifugal gravity-effect to hold everything in place. The habitable surface area would be approximately ten times that of the Earth's. The geometrical construction would take the form of a rounded twenty-faced icosahedron, with air, sea and lands of plenty located on the equatorial regions, and continent-scale silica glass windows allowing sunlight into the interior.
The design appears commendably thorough. Dimensions are calculated carefully with an architect's attention to detail. The symmetrical construction processes, materials used, and function of the space elevator 'scaffolding' are described exhaustively. Even the issue of temporary accommodation for the future occupants is addressed: it's proposed that while construction takes place, humans, plants and animals wait patiently-- through countless successive generations-- in holding areas or archival nodes in the space elevators. Nor is the provision of basic amenities like air and water overlooked. When the excavated Earth shrivels to a size where gravity can no longer retain its atmosphere and hydrosphere, the envisaged migration of gas and liquid onto the equatorial regions of the newly-built structure is described poetically as the “Great Rains”. Waldvogel uses detailed computer graphics to illustrate his ideas, and has even published a glossy coffee-table book with colourful pictures depicting the construction of his idealized new world, and the irreversible destruction of our current one.
Yet curiously there are numerous objections to the concept. Perhaps the most fundamental relates to the construction material. Our current understanding of physics dictates that no molecular bonds in any conceivable material could ever be sufficiently strong to hold the structure together: certainly Waldvogel's proposed ferrous-nickel framework would be hopelessly inadequate. Globus Cassus would simply come apart from the internal stresses of its rotation and tidal forces from the Moon and the Sun. Carbon nanotubes form one of the strongest currently-known molecular structures, and are frequently proposed as a construction material for futuristic engineering projects-- but even their great tensile strength would be insufficient to keep the hollow habitat in one piece.
Then there's the problem of the prolonged construction time, and a related objection to one of the principal stated reasons for the project: the provision of extra living space for the ever-growing human population. The proposed temporary accommodation in the 'archival nodes' provides insufficient gravity at geostationary altitudes for long-term human occupancy. Yet if humans can be made to live in the nodes long-term, why the need for Globus Cassus in the first place? In fact there are numerous alternative proposals for large-scale habitats which could be built more easily: hollowed-out asteroids, giant rotating space stations such as the proposed Stanford torus or Bernal sphere, or even the terraforming of planets such as Mars or Venus.
Waldvogel is far from the first to propose the construction of giant hollow worlds in space. Visionary physicist Freeman Dyson gave his name to the concept of a 'Dyson Sphere'– a colossal structure totally enclosing a star, capable of capturing all its energy for use by a power-hungry civilization. The dimensions of such a structure would be vastly greater than that of Globus Cassus, and rotating versions would have the same ‘artificial gravity’ acting on the equatorial regions of the inner surface, providing mind-bogglingly huge tracts of habitable land. Of course many of the same objections to Globus Cassus apply to the Dyson Sphere, and the time, energy, and technological difficulties would be correspondingly magnified. Dyson never seriously proposed one of his enormous namesake spheres for our own solar system, but he did see the idea as being theoretically feasible– suggesting a possible way to detect mega-engineering civilizations elsewhere in the galaxy. The 'energy exhaust' from such a construction would be predominantly in the longer wavelengths of infrared, and this tell-tale electromagnetic signature could be detected from Earth. Although a few SETI searches have been carried out with this in mind, no such signature has yet been detected.
Practical objections aside, there are more basic questions to ask of Waldvogel, Dyson, and other would-be mega-engineers. Precisely why a terrestrial or extraterrestrial civilization would want to build such structures may be beyond the grasp of our puny 21st century minds, but it’s hard to accept Waldvogel’s ‘extra living space’ justification. Apart from the aforementioned easier expansion options, it’s not explained why our near-omnipotent descendants– capable of transmogrifying simple Earth rock into impossibly strong wonder-material and fashioning it into an outlandish, outsized, inside-out living space over the course of millions of years– would still not have mastered basic birth control.
Maybe advanced civilizations would build these structures simply to test their technological prowess, or to provide enclosed habitable areas within which they can observe the evolution of life and intelligence on a far grander scale than that which mere lumps of rock can provide.
Perhaps aware of these unanswered questions, Waldvogel provides an intriguing alternative rationale for his hollow global proposal. He asks us to view the Globus Cassus concept as more than just a simple mega-architectural exercise, and suggests that much of its importance lies in its underlying philosophical foundations. With a scheme that explicitly requires the complete destruction of Earth and its rebuilding inside-out, it follows that human society might also end up with a radical re-design. The precise nature of the proposed 'Cassian' society is left vague and open to discussion, but it’s suggested that its values would in some way reflect the shape of the New World. Looking upward, the vision-enhanced citizens of the Globus Cassus would see, instead of blue sky, their neighbours eighty-five thousand kilometres away on the opposite side of the sphere looking back down on them. Waldwogel's hope is that such a situation might change their perspective: with people forced to face each other in this way, maybe they would be, well, nicer. In such a large, well-resourced environment, more open social structures might have the freedom to evolve compared to the rigid hierarchies of the tired old rock-ball we now call home. Waldwogel’s website invites us to consider his proposal in these utopian terms, as a social and metaphorical ‘antipode’-- or opposite-- to our current Earth, as well as a physical one.
The idea's resemblance to science fiction doesn't deprive it of philosophical value. At a time when we are increasingly encouraged to see the Earth as something threatened, fragile and in need of ‘saving’, it’s intriguing to contemplate its complete destruction in a positive light. Perhaps in the future, crowds of conservation-minded conservatives will protest on the streets, waving placards reading “Stop Global Hollowing NOW!” and “Halt Earth Change.” As the ground starts to thrum and quiver with the work of fearsome engines, it's easy to imagine idealistic social reformers cackling manically at their command consoles in the space elevators towering overhead, as they celebrate the dawn of Earth's final metamorphosis.