correlation, critical temperature

[Bill Adlam <wa105@mead.anglia.ac.uk>]

Dave wrote:

>I reiterate that every correlation implies a causal link...These 
>hypothetical variables that correlate yet have nothing to do with each 
>other simply do not exist in reality.  If anyone can cite me just one 
>example I will be only too happy to eat my words.

There is almost certainly a correlation between the number of land snails in 
the world's countries and the number of Olympic medals they have won.  (The 
nations, not the gastropods.)  The correlation coefficient is probably very 
small.  I have no idea whether it is positive or negative, and don't intend 
to spend any effort on finding out.

Correlations are evidence of (but do not logically imply) causation if they 
are statistically significant.  The more significant, the stronger the 
evidence.

>The presence of growth rings in some dinosaur bone suggests that some 
>species may have had winter torpor states or even an ectothermic type of 
>metabolic response below certain temperatures.

Any endotherm's metabolic rate will decrease with temperature below certain 
temperatures.  Once the core falls below the lower critical temperature, the 
metabolic rate falls catastrophically.  I don't know of any extant 
endotherms which naturally fall below their lower critical temperature and 
recover, but maybe some dinosaurs did.

                                                        All the best,

                                                                        Bill