Re: Oxygen level in Mesozoic

["James R. Cunningham" <jrccea@bellsouth.net>]

Bearing in mind that I think the analysis of atmospheric composition from amber
bubbles is somewhat conjectural, if one accepts it more or less at face value,
all the rest of the atmosphere is included in the bubble too, so we would have
a pretty good idea of the composition of the rest of the atmosphere.  For
example, the amount of nitrogen is thought to have been about the same as now.

jabartle wrote:

> ... even if we knew that O2 pushed past 30% we are ignorant of the
> composition of the rest of the atmosphere!

If we accept the amber results as valid (I'm not quite convinced yet), then we
do have an idea of the composition of the rest of the atmosphere.  Nitrogen and
the other atmospheric components are contained in the bubbles too.  Total
nitrogen is thought to have been about the same as now.

> , so I would not blow up the atmosphere quite yet

Nor would I.

> [nor even be sure that this combustion limit applies to the past].

Are you postulating that the rules of physics and/or chemistry may have been
significantly different?  I have some trouble accepting that.

> would not be surprised to find the dynamics were rather different for our
> dear vertebrated friends.

Re that, I'm only expressing an opinion regarding mechanical flight
capability.  The animals (like airplanes) tend to fly at the same indicated
airspeed as the density altitude changes, so excepting initial launch there
might not be as much difference as one would expect at first glance.