Re: If the sun went out how long would life on earth continue?

Hi John, I apologize for taking so long on this one.  The short answer 
to your question is that no one knows the answer.  I have come across some 
interesting information, though, and I will try to give you my thoughts on the 
matter from a physicist's point of view, but you might also want to resubmit 
the question with my answer attached and see if you can get further input from 
a biologist.

First, let's consider how long the planet could support large land animals
like ourselves.  Just think about the temperature difference between night and
day and it should be pretty clear that the atmosphere (at least the troposphere,
where we live) cools quite rapidly by radiation.  It should only be a matter
of days before the surface temperature drops below freezing everywhere on the
planet.  In, fact in six months to a year, the temperature should drop to
less than 150 Kelvin, half its current value.  I would not expect any biological
activity to remain at this temperature.  However, there may be organisms which
could survive in a suspended state if they were to freeze before they starved.
That's something a biologist would have to comment on.  So I would say that 
an upper bound for the survival of large land animals would be less than
six months, just based on temperature.  However, it should be much less than 
this since the food chain, which starts with sunlight (which plants use),
would break down almost immediately.

What would happen with the oceans?  Well, there's a tremendous amount of latent
heat in the oceans, which would help to warm the atmosphere.  However, once
the surface of the ocean began to freeze, it would become more and more
insulated by the cover of ice.  Thus, it appears that the transfer of heat
from the ocean to the atmosphere could be significant only in the early stages
of the cooling.  However, the insulating effect of the ice would allow the
oceans to stay above freezing for quite a while, though once again, the food
chain would break down radidly, and the supply of oxygen would be cut off. 

Now, there is another energy source which is significant - geothermal heat.
There are organisms which live on the seafloor near geothermal vents - fissures
from which superheated water laden with various gases and nutrients are 
expelled.  The question is - are these organisms dependent only on the nutrients 
and heat that they recieve from the vents, or are they connected to the rest of 
the food chain?  There are many more qualified to answer this than I.  I wouldn't
be surprised if they were dependent on the oxygen generated by photosynthesis,
and thus vulnerable.

I have also seen mention of organisms found in core samples from quite deep
in the Earth's crust which may depend only on geothermal heat, but I don't
know how credible this is.

Of course, it's possible that technology would allow a very small population
of humans to survive, just as they might on a lunar base.  However, if such
a facility does not already exist, it is doubtful whether one could be 
constructed before the atmosphere froze out onto the ground, especially
since it would probably take more people to construct it than it would be 
able to support.  It might be possible to modify a bomb shelter to serve such a 
purpose, but it would need to be able to generate breathable air, and there
would need to be a way of obtaining fuel.  With no solar energy, you would
need to use nuclear energy, fossil fuel, or geothernal energy.

In short, we wouldn't last long, but there may be organisms which could survive
indefinitely, either by freezing before they starve, or because they don't
depend on solar energy at all.  I would definitely recommend submitting this
to a biologist for further comment.