How Massive Can A World Be And Still Support Life?

At some succeeding juncture , we ’re move to need more aliveness blank , whether it be find on another planet or through the expanse of our planet ’s be Earth’s surface domain . In his latest venture into worldbuilding , Oxford University research fellow Anders Sandberg search some of the more uttermost possibility .

For the thought experiment , “ What is the largest possible inhabitable world , ” Sandberg limited his investigation to describing hypothetical world — both lifelike and hokey — with “ maximal Earth’s surface arena that can be inhabited by at least terrestrial - dash constitutional life of human size and is allowed by the know laws of physics . ”

That ’s a flock to work with , including heavy super - world , large dispirited - density mankind ( likea C planet ) , and unreal worlds likeshellworlds , gas - proppedbubbleworlds , andtopopolises(dubbed “ cosmic spaghetti ” ) .

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A depiction of a carbon world aerofoil . “ The local geology is dominate by graphite and tar deposits , with rhomb crystal and weighed down hydrocarbon lakes , ” writes Sandberg . “ The ambiance is largely carbon copy monoxide and fickle hydrocarbons , with a just amount of soot . ”

The most obvious nominee for rude expectant worlds are super - Earths , admit Sandberg’sdouble Earth , which are rocky planet with lots of mass . He describes variant of these world depending on their chemical composition and density . In many cases , these large planet would take on the phase of waterworlds and warm Neptunes , earn habitability impossible , or at least very difficult . In one example , he describes a hypothetical iron - rich planet 274 time heavy and 2.7 times larger than Earth boast a surface solemnity 38 time Earth ’s .

https://gizmodo.com/what-a-habitable-planet-twice-the-size-of-earth-would-b-1476308959

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“ This is not habitable for mankind ( althoughimmersion in a liquid tank and breathing through oxygenated liquid might allow survival ) , ” he writes . “ However , bacteria have been cultured at 403,627 g in centrifuge ! ”

More reasonably , he key out a 359 times heavier and 5 time large ice cosmos with “ just ” 14.3 times our surface gravitational force . “ Humans could probably survive if they were lie down , although this is way above any long - terminus limits found by NASA , ” he writes .

To get around the gravity event , Sandberg take a page from Hal Clement ’s Mission of Gravity in which a satellite is rotate fast enough to produce tolerable gravitational consideration along the equator . Again , not ideal .

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A sketch of a shellworld via Andart II .

Sandberg ’s analytic thinking of artificial worlds , i.e. megascale structures , is particularly fun . On the prospect of Allium cepa - similar shellworlds he write :

Consider roofing over the entire Earth ’s aerofoil : it would take a middling amount of material , but we could mine it by digging tunnels under the control surface . At the death we would have more than doubled the uncommitted control surface ( roof , onetime ground , plus some tunnels ) . We can persist in the procedure , grok up material to build a elephantine onion of homocentric floors and giant pillars holding up the quietus . The conclusion result is akin to the megastructure in Iain M. Banks ’ Matter .

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Sandberg goes so far as to describe a shell world with a surface area of 1.2 x 1022 square meters , or about 23 million time Earth ’s area . The trouble with this world , and many like it , is the dearth of gravity .

Indeed , a primal theme that runs through Sandberg ’s analytic thinking is how impractical and unwieldy these with child planets and structures might in reality be . Sandberg close his think experimentation with this discussion :

Why aim for a large world in the first place ? There are three manifest reasons . The first is simply survival , or perhaps Lebensraum : with child domain have more space for more beings , andthis may be a good affair in itself . The second is to have more space for stuff and nonsense of value , whether that is toys , garden or wild . The third is to trust for diversity : a large world can have more places that are unlike from each other . There is more outer space for geographic expedition , for diverging evolution . Even if the world is deliberately made parts can become different and alone .

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Planets are neat , ego - assembling organisation . They also apply a great deal of raft to ply gravity and are not very unspoiled at producing life space . contrived constructs can become far enceinte and are far more effective at hold up distance per kilo . But in the end they lean to be limited by gravity .

Our search for the large possible universe demo that demanding a queer humans may be a goosey constraint : a swarm of O’Neill cylinder , or a Dyson swarm surrounding a star , has tremendously much more area than any singular structure and few of the mechanical problem . Evena cautiously arranged solar systemcould have far more inhabitable world within ( relatively ) easy scope .

There ’s much , much more to Sandberg ’s analytic thinking . Be sure to study it all .

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