View source for Elephants with spiderlegs


== In fiction and art ==

In "star wars", "war of the worlds", and Salvador Dali's pictures <br>
it's likely just an artistic choice to make it look alien/surreal by making it look like something <br>
that cannot be found by a long stretch (pun intended) in our world. <br>
The artists probably have not thought deeply about the physics involved.

== Making it work by by reducing gravity ==

Despite clearly not working here down on Earth with our crushing gravity <br>
interestingly this "gargantuan spiderelephant anatomy" might actually practically work <br>
on low but not too low gravity celestial bodies like e.g. big asteroids where the k in <br>
» F_grav ∝ k * L^3 « <br>
is sufficiently small. <br>

Pros:
* no continuously depleting propellant needed
* more control than jumping

=== Math in more detail & making it work even better by "making the elephants hollow" ===

 F_inertial = m ω^2 r = m v^2 / r
 with
 m ∝ L^3
 and assuming 
 ★ v ∝ L^0
 ★ r ∝ L^1
 we get
 F_inertial ∝ L^2
 with
 A ∝ L^2
 we get
 𝜎 = F/A ∝ L^0

 Good! works for all scales :)
 But speeds stay constants so frequencies drop.
 Not so good. Can we do something about it? Yes ...

 hollowing stuff out
 (as is possible in low gravity)
 changes
 m ∝ L^2
 changes
 𝜎 = ∝ L^-1
 so we can do what we wanted (increase speeds along with size)
 v ∝ L^1 
 and be back at
 𝜎 ∝ L^0
 again

In words: <br>
When scaling to larger sizes forces from accelerations do NOT scale faster than the strength of the material. Given speeds are kept constant! <br>
But if structures are hollowed out, as it is possible under low enough gravity, speeds can be scaled up along with the size.

{{todo|How does this go together with the scale invariant [[unsupported rotating ring speed limit]]? Infinitesimally thin surfaces in the limit maybe?? To investigate.}}

== Conclusion ==

Machines shaped like Salvador Dalì's Elephants might actually work and exist in the future on asteroids. <br>
Heck, space-probes could probably do this in the foreseeable future (written 2021).

== Related ==

* [[Scaling law]]

== External links ==

* [https://en.wikipedia.org/wiki/File:Dali_Elephants.jpg "The Elephants" by Salvador Dali]
* Originally posted here on twitter: [https://twitter.com/mechadense/status/1424965538330128388]