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Viewing Single Post From: The giant space ship example
gbaikie

Quote:
 
So if cooled at 1 K per hour, it would require 30 times more energy
than you said.
So what you are actually saying is it will take about 30 hrs to lower 1 K- if 6,580,000 GigaWatts is correct.
So kinda proves you right, and here I thought you were wrong :)


Come think of it. It may far more than optimistic- I can't believe it would only lower by 1 K in 30 hours. And 1/10 [5.4e16 instead of 5.4e17] of the atmosphere takes about 3 hours instead of 30.
So instead it would have to be at least 10 times this amount of energy.

So if atmosphere required 65,800,000 GigaWatts and it took 3 hrs to cool 1 K, that still be longer than I would expect, though much closer. It would be about the same as earth, and earth has other factors to keep it warmer.

And if you think it would take 1/10th of 3 hours or 1/100th of 3 hours, 1/1000th 3 hours, then requires 10,100, or 1000 times more energy.

So comparing to Earth. Dwarf at 65,800,000 GigaWatts [5.4e21 watts/joules 5.4e16 watts]
"The Earth receives 174 petawatts (PW) of incoming solar radiation (insolation) at the upper atmosphere.[petawatts 10^15 watts] en.wikipedia.org/wiki/Solar_energy
Earth gets 1.74e17 watts sunlight and much this isn't converted heat.
Dwarf needs 5.4e21 watts or 30,000 times more energy.
The dwarf is on average 10 C and earth is 15 C
And dwarf has far less total surface area.
Something seems very wrong about this.

Revising:
How I made mistake by adding 5 orders, probably has something to do mornings and haste.
Unfortunately it's morning and I don't have much time, but I wanted go over some numbers again.
So we settled on Dwarf heat as getting 5.4e15 watts and Earth heat is disputable but receives 1.74e17 watts of sunlight. Roughly Dwarf is getting 20-30 times less heat then earth.

Earth surface area is 510 million sq km
Dwarf surface area is 4 pi r 2 or 18 million sq km or 1/28th the area of earth. About twice land area of US, btw.
Roughly Dwarf is getting same heat as earth does. And dwarf surface air temperature is on average 5 K cooler.

One thing we could have done is start the dwarf at a temperature comparable to earth without greenhouse effect. One way would be the commonly stated -33 C [so a -18 C average temperature].
Or instead could start with Earth as blackbody without the "Visual geometric albedo: 0.367" included. Or as Wiki says:
"If an ideal thermally conductive blackbody was the same distance from the Sun as the Earth is, it would have a temperature of about 5.3 °C. However, since the Earth reflects about 30% (or 28%) of the incoming sunlight the planet's effective temperature...is about −18 or −19 °C".

So starting temperatures could have had the dwarf start at 5.3 C or -18 to -19 C.
If add greenhouse affect to a 10 C dwarf, the dwarf should be warmer than Earth.

Edited by gbaikie, Dec 8 2011, 06:11 PM.
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The giant space ship example · Physical theory for climate