Expert: Jayendra Upadhye - 9/24/2004

Question
This is very hypothetical, but I ask this question to my highschool science classes to make them think. If the sun could die out without an earth destroying explosion, would the earth freeze first or run out of Oxygen?  

Answer
Hello Miss Amy,
What strikes me here is the percieved connection of oxygen / sun.
The Arctic Tundra has an enigmatic answer locked away in its ICE. (SEE last part of the answer.)
True that the sun powers oxygen regeneration by driving the photosynthesis process on earth, but even if that were to stop, oxygen still would be the most abundant uncombined element after nitrogen, in the earth's atmosphere.
It took blue green algae 2 billion years to alter the composition of the primordial earth's atmosphere to its present oxygen rich form. (Actually it is a corrosive  oxygen rich atmosphere, but still "life giving" to us!).
The action of freezing due to lack of heat is "instantaneous", in terms of geological time.
In the "Dry" (low humidity inland continental areas this sudden rapid drop is apparent, where people may shiver in the shade, and "roast" in the hot sun. (I have personally experienced this queer thing on hill stations at high altitude).
IF the sun were to wink out, the freezing action would immediately proceed, and dependiing on the specific heat of air (differs wet or dry air), the "loosing of heat" would irrevocably proceed to its logical sub zero destination of 2.73 degrees kelvin which is the temperature of absolute space! (the temperature of the cosmic background radiation).
NOTHING CAN BE COOLER THAN 2.73 DEG KELVIN FOR THIS REASON.
(Actually each night we see the beginning of this process, which luckily is interrupted by the arrival of the sun each morning! It is a dily battle of heat intake and heat loss.
summer and winter are merely indicators of the rise and fall of averages!).

Ofcourse areas of active volcanisms would continue to remain hot, but the cooling and liquifying ATMOSPHERE would be another problem.
1 - Areas far from these volcanoes would soon start
   experiencing heavy rain and then snow, till all the
   water in the atmosphere would be drained out.
2 - then would follow rains of gases one after the other as
   their dew points were "breached".
3 - with each rain, the atmosphereic partial pressure
   of "that" gas would drop to zero. (law of partial
   pressures).
4 - In the end, atmospheric pressure and temperature would
   be maintained at the level made possible by volcanoes.
   In that event only helium and hydrogen would remain
   liquid.
5 - Liquid helium with its superfluid properties would be
   doing strange things in a planetwide ocean of liquid /
   frozen gases! (water ice would be at the bottom).

6 - Humans needless to say would have perished from
   freezing and hunger long before all this came to pass!

try to induce the students to think of these "other" things associated with the problem, to enable to see it in its totality.
Like partial pressure of gases (dalton's law?), superfluidity, superconductivity exhibited by elements at crygenic temperatures, etc.
Right now most probably, it is raining helium rain in the cool atmosphere of saturn!

SIMPLY PUT, THE COLD WOULD KILL YOU FIRST, THE OXYGEN SUPPLY WOULD OUTLAST THAT.
LAST but not the least, introduce an element of the unexplained..to excite their curiosity..the riddle of the woolly mammoths "flash frozen" in the Arctic Tundra, some with food still in their mouths! Did the sun momentarily pass thru a "sleepy phase", freezing them thus in a matter of minutes?
Jayen