Megascale engineering

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Megascale engineering is the construction, operation, and maintenance of works large enough to be best measured in megameters (abbreviated Mm). This may generically include any project larger than this size, or other prefixes can be used to distinguish between scales, such as gigascale engineering for gigameters (Gm). Large geoengineering and terraforming projects, orbital infrastructure, and stellar husbandry are generally considered part of these categories.


One megameter is 1,000,000 meters (621.371 miles), approximately equal to:

  • 3⅓ light-milliseconds
  • 4 times the length of Lake Kariba[1], the world's largest man-made lake (223 kilometers).
  • 12.2 times the length of the Panama Canal (82km)
  • 37 times the circumference of the Large Hadron Collider (27km)
  • 1/40th the circumference of the Earth (40.07 megameters at the equator, 39.93 megameters pole-to-pole)
  • 1/13th the diameter of the Earth (12.74 megameters)

Structures and systems

Social barriers

The Great Wall of China is a series of fortifications built over centuries to protect ancient and imperial Chinese states against Eurasian threats. Its modern form spans a length of more than 21 megameters.[2]

The Inland Customs Line was a series of customs checkpoints and connecting hedge barriers in British Colonial India to prevent smuggling and levy taxes on salt. Starting in 1803, it eventually grew to exceed 4 megameters in length before being abandoned in 1879 with the seizure of Sambhar Salt Lake.[3]



Starting in 1934 in response to the Dust Bowl, the Great Plains Shelterbelt project is a ~1.93Mm-long line of tree plantings extending from the Brazos River in Texas to the US-Canadian border to act as a windbreak and evaporation trap and prevent soil erosion.[4][5]

The Great Green Wall project aims to combat climate change and desertification in Northern Africa with a 7.7 megameters long artificial treeline.[6] As of 2019 the project reports approximately 15% completion, with a goal of contributing to the 2030 global agenda of the UN Sustainable Development Goals.[7]

Scientific instruments

Particle physics

The Deep Underground Neutrino Experiment (DUNE) is a particle physics experiment under construction at Fermilab near Batavia, Illinois and the Sanford Underground Research Facility in Lead, South Dakota. The Long Baseline Neutrino Facility at Fermilab will produce a neutrino beamline directed at a liquid argon detection chamber in the Sanford Lab, 1.3 megameters away.[8]

Proposals for the Future Circular Collider, a successor to the Large Hadron Collider at CERN, describe circumferences up to 100km (0.1Mm).[9] The US-based Superconducting Super Collider, abandoned in 1993, would have been 0.87Mm in circumference when completed.[10]


Gravitational waves of interest to astronomical research can be very low or extremely low frequency and therefore of very long wavelength, with 1 megameter corresponding to a frequency just under 300Hz.

The Laser Interferometer Gravitational-Wave Observatory currently consists of two facilities 3.002 megameters apart: one located near Richland, Washington, and another in Livingston, Louisiana.[11]

The Laser Interferometer Space Antenna (LISA), a mission planned by the European Space Agency to launch in the 2030s, consists of a constellation of three satellites forming an equilateral triangle 2,500 megameters (2.5 gigameters) to a side.[12] Earlier proposals for the project covered distances of 1 to 5 gigameters.

The Deci-hertz Interferometer Gravitational wave Observatory (DECIGO) is another planned space-based gravitational observatory by the Institute of Space and Astronautical Science (ISAS) and Japanese Aerospace Exploration Agency (JAXA) with planned distances of 1 megameter between its component spacecraft.[13]

Orbital infrastructure

A space elevator would require an anchor mass in geosynchronous orbit, about 35.79 megameters from the Earth's surface. Several other methods of tether propulsion for surface-to-orbit launch systems have been proposed, including skyhooks and rotovators.

Alternative launch systems that depend on a dynamically stabilized system to transfer mass to orbit include the space fountain and Lofstrom loop.

An orbital ring is a ring-shaped stable station centered around a planet or other celestial body, usable as a habitat, shipyard, solar power collection facility, and/or tether support for surface-to-orbit propulsion. Such a structure around Earth's equator would, at minimum, exceed 81 megameters in circumference.

Stellar engines

A stellar engine may be a Shkadov thruster, which directs a star's output for propulsion, or a Dyson sphere which converts it to usable energy, or a combination of both such as a Dyson swarm.

Construction and use of a stellar engine marks the transition to a Type II civilization on the Kardashev scale.

External links