local p = {}

increment = 10 -- in meters  Basis is meters and kilograms throughout.
G = 6.674E-11 -- 6.674×10−11 N⋅m2/kg2
M = 1E24

function localg (r)
	-- black hole has gravity GM / r2
	return M * G / (r*r)
end

function deltapressure (pressure, gravity)
	-- for a given global increment, return the increase in pressure in atm, pressure in gs
    -- density of "air" per pressure in atm is (1.225 kg/m3) / atm
    -- pressure of air is 101325 newton / m2 at 1 atm
    -- newton weight is kg * gravity
    -- so x atm of pressure weigh x * gravity * 1225 kg per kilometer per square meter
    return pressure * gravity * 0.001225 * increment
end

function p.main (frame)
	-- we SHOULD start at the "exobase", which on Earth is roughly 7000 km from the center
	-- I am not finding decent figures for exosphere pressure
	-- for now let's calculate from an arbitrary (too high) 1 pascal and see from there what the dependence is
	-- exobase equivalent is where GM/r = same as on Earth, i.e. r = 7000 km * M / mass of Earth
	local r = 7000000 * M / 5.97237E24 -- kg, mass of Earth
	local p = 1 -- arbitrary 1 pascal
	local it = 0
	output = "radius gravity pressure"
	repeat
		it = it + 1
	    p = p + deltapressure (p, localg(r))
	    r = r - increment
	    output = output .. r .. "," .. localg(r) .. "," .. p .. "<br />"
	until (it > 100 or r<0)
	return output
end
return p