Have you ever looked at the wikipedia page
for terrestrial planets and thought: Man I wish I knew this much about my fictional
terrestrial planet. Why am I even asking. Of course you have. Let's do this. Youtube! Edgar here and welcome to Artifexian hear
you will learn everything You ever wanted to know about worldbuilding...and
then some. Ok so let's build some habitable earth-like
terrestrial planets As always we're gonna need the planet maker
equation and this graph. Oh and we're gonna need s
ome ranges for gravity,
mass and radius That will ensure our planet is in fact habitable. To be clear I mean habitable in relation to
physcial characteristics That is we are going to need to ensure that
our planet features Active plate tectonics has the ability to
hold onto a suitable atmosphere And possess a magnetic field. The ranges for gravity mass and radius We use must ensure the presence of these various
components. With this in mind Stephen Dole in his 1964
work “Habitable Planets for Ma
n” Sets the ranges for habitable earth-like planets
at 0.4 – 2.35 earth masses. 0.78 – 1.25 earth radii and surface gravity
at 0.68 – 1.5 times the gravity at earth. These values are fine but in light of our
current scientific understanding They're a bit conservative. Current research gives us something More like 0.1 – 3.5 earth masses. 0.5 – 1.5 earth radii And a gravity range of about 0.4 – 1.6 So on our graph here, we can disregard everything
above 3.5 earth masses And 1.5 earth radii...leavi
ng us with this
window of creative opportunity. Got it cool. Let's build! Let's go with a mass of 2 earth masses and
a radius of 1.25. Before we solve for gravity and density lets's
graph those mass and radius values. Alrighty then we are in the red band which
indicates our planet will be composed of iron and silicates which
is exactly what we want. One almighty number crunch later and out pops
a high g planet 25% bigger than earth with twice the mass
but with a density comparable to earth. Here
's mercury venus earth and mars and here,
to scale is our planet. Our friendly neighbourhood super earth eh? Now for something a little smaller. How about 1/3 the mass of earth And just over half the radius of earth. Again check the graph to see If we are in the red zone and we are run the
numbers through The planet maker equation and we get these
values What should immediately stick out is that
the density Of our little rock here is relatively speaking
quite high. Such high densities indicate t
hat we are dealing
with is a super mercury A world whose volume is dominated by an large
iron core. Again here's Mercury Venus earth and mars
and here's our little super mercury. But hey, what if you don't want to have a
rocky terrestrial planet Maybe you want an ocean planet. All water no land let's do it. Just like with our standard rocky planet we
have to stick to our ranges For gravity, mass and radius but in the case
of a waterworld We want to be in the blue band here. Here lie the planets
Whose overall mass contains a large fraction
of water. So let's place our world here which gives
us a mass of 0.4 and a radius of 0.85 ish. Plug the values into the equation and we get
a low density low g world. Those characteristics in and of themselves
scream ocean planet Furthermore that dotted line on the graph
indicates a world with 25% water a 52.5% silicates shell and a 22.5%
iron core. Links in the dooblydoo As always flesh out the details of your worlds
even further by calculating escap
e velocity Circumference surface area and volume using
the same equations from the previous two videos. So there you have it! How to build rocky, watery, super mercury
kinda terrestrial planets. Physcial characteristics of the various planetary
types done next up? Orbital characteristics. Stay tuned Guys, if you like what you see here on Artifexian Click the links in the description to find
me on fb and twitter And if you interested hit like and subscribe
for more Awesome science based worldbuil
ding. Thank you all so much for watching. Edgar out!
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