Editing Megastructure (section)

===Planetary scale===
* A [[Bishop Ring (habitat)|Bishop Ring]], [[Halo (megastructure)|Halo]] or [[Orbital (The Culture)|Orbital]] is a space habitat similar to but much smaller than a Niven Ring. Instead of being centered on a star, it is in orbit around the star and its diameter is typically on the [[order of magnitude]] of a planet. By tilting the ring relative to its orbit, the inner surface would experience a nearly conventional day and night cycle. Due to its enormous scale, the habitat would not need to be fully enclosed like the [[Stanford torus]], instead its atmosphere would be retained solely by centripetal gravity and side walls, allowing an open sky.
* [[Globus Cassus]] is a hypothetical proposed project for the transformation of Planet Earth into a much bigger, hollow, artificial world with the ecosphere on its inner surface. This model serves as a tool to understand the World's real functioning processes.
* [[Shellworld]]s or paraterraforming are inflated shells holding high pressure air around an otherwise airless world to create a breathable atmosphere.<ref>[http://www.jbis.org.uk/paper.php?p=2009.62.32 "Shell Worlds – An Approach To Terraforming Moons, Small Planets and Plutoids"], K. L. Roy; R. G. Kennedy III; D. E. Fields, 2009, JBIS, 62, 32-38</ref> The pressure of the contained air supports the weight of the shell.
* Completely hollow shell worlds can also be created on a planetary or larger scale by contained gas alone, also called gravitational balloons, as long as the outward pressure from the contained gas balances the gravitational contraction of the entire structure, resulting in no net force on the shell. The scale is limited only by the mass of gas enclosed, the shell can be made of any mundane material. The shell can have an additional atmosphere on the outside.<ref>[http://yarchive.net/space/exotic/bubbleworld.html Dani Eder]</ref><ref>{{cite web | url=http://gravitationalballoon.blogspot.com.au/2013/12/ederworld-analyzed-concentric-gravity.html | title=Ederworld Analyzed (Concentric Gravity Balloons to Maximize Volume) | date=11 December 2013 | publisher=Gravitational Space Balloons | via=blogspot.com.au | access-date=30 June 2020 }}</ref>
*It can also refer to [[Terraforming|terraform]]ed or artificial planets with multiple concentric layers.