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Thor_Enke
April 7th, 2008, 11:59 AM
So, first, hello :)
I'm French, so, I beg your pardon if I do some mistakes when I write in English.
So, I don't really know if the subject was already discussed, but, I'm wondering about the See ?

In this episode, Sheppard says that it's very hot outside, but, if it was that hot, that was not that much hot for the see to evaporate in the atmosphere.

I mean that, for the see to evaporate, it needs more than 50 degrees (in France, I mean).

So, the question is : is it not illogical that Sheppard wanders outside as the temperature is censed to be very hot. A much hot for the see to evaporate. But, if it's very hot outside, why does Sheppard wanders outside for a long time ? If it's that hot outside the city, Sheppard would die ?

What do you think about it ?

And, I repeat, as I'm french, there are certainly mistakes in my words, so, don't hesitate to correct 'em or to tell me if there's something you don't get. Thank you for understanding :cameron:

PG15
April 7th, 2008, 02:22 PM
I suppose if the world was exposed to that much heat for tens of thousands of years, the ocean would evaporate.

Or maybe Atlantis was just sitting on shallow waters.

Thor_Enke
April 8th, 2008, 07:38 AM
Yes, but, the question is...
The ocean needs enough heat to evaporate, but 50 degrees is simply not enough for the ocean to do that. So, it has to be more than 50 degrees. But, if there's more than 50 degrees, Sheppard could not wander outside, indeed, he will simply die ... So, it's kinda illogical :tealcanime49:

talyn2k1
April 8th, 2008, 07:56 AM
Yes, but, the question is...
The ocean needs enough heat to evaporate, but 50 degrees is simply not enough for the ocean to do that. So, it has to be more than 50 degrees. But, if there's more than 50 degrees, Sheppard could not wander outside, indeed, he will simply die ... So, it's kinda illogical :tealcanime49:

Maybe there was some sort of solar event, a flare or something, which caused a relatively brief (by relative, I mean a few hundred/thousand years) heating up of the planet but by the time Sheppard got there the planet had cooled from this effect and was just suffering the effects of daily bombardment of heat which would be less than the short time spike in temperature.

Not sure if that really makes any sense, but hopefully someone got what I mean! :D

PG15
April 8th, 2008, 12:54 PM
Water evaporates at any temperature, but it only does it fast at the phase transitions. You need a certain amount of water vapor in the air (along with other gases) to apply the vapor pressure to keep water from boiling off. That's why water boils at a lower temperature at the top of Mt. Everest; the air pressure is less there.

Now, when a star goes red giant, it also start blowing off solar material, and that means strong solar winds, I believe. This reduces the thickness of the atmosphere, despite our magnetic field, and may cause the oceans to boil off faster as air pressure decreases (water evaporates to increase the pressure back up to where it was; it's called equilibrium).

But yeah, the oceans don't need 50 degrees to evaporate. They're evaporating all the time. However, rain and ranoff keeps the ocean from drying up. If you increase the temperature and/or decrease the pressure though, the equilibrium will shift to a state where the ocean may just have to dry up to keep the air pressure constant.

Mitchell82
April 13th, 2008, 09:11 PM
^someone paid attention in science class.;) But you are right and wasn't the star going "red giant"?