On 05Jul2020 1617, Vareck Bostrom wrote:
> If a dense atmosphere goes up to 2.49x pressure (252 kilopascals) with
> an earth-like mix (78% N2), that should be probably treated as Dense
> (tained) then, right? As that would be above the partial pressure for
> N2 at which nitrogen narcosis effects can be noticed.
>
> "Very Thin" goes up to 0.42 (42.6 kPa), if the atmosphere is pure
> oxygen at that pressure it should be breathable without assistance,
> even down to about 53% O2 at 42.6 kPa would give a physiological
> effect similar to sea level air on Earth. It seems strange to refer to
> it as Vacuum (Very Thin) as the pressure range includes that of high
> mountains on Earth, which have been climbed without supplemental
> oxygen. As I noted, pressure inside space suits in the real world
> would qualify as "Vacuum (Very Thin)" on that table. I wonder how the
> level for "Trace" was chosen - to me it makes more sense that the high
> end of Trace should be ~6.3 kPa for the reason I mentioned above,
> that's the level at which human life is not possible regardless of air
> mix as water boils at human body temperature at that pressure. Also I
> don't think that table lines up with the T5 table, or at least the
> inferred T5 table based on atmosphere heights vs altitude for a
> standard atmosphere, also presuming an Earth-like scale height.

Which  is why, IMO, CT's trick of just leaving actual numbers off was
smarter. When summing up an atmosphere in a single hex digit, there's no
room for nuance. In CT the number gives a rough idea of density or
pressure, and says what the effect is. It leaves it to the referee to
decide if you need a compressor because the air is thin and has an
Earth-like composition, or because it's Earth-like in pressure, but has
very little oxygen in it.

If you want more detail, it has to come from more than just that single
digit - you need supplemental notes, and so on. In my experience that
means all sorts of quibbling from people, usually on the grounds that
something is 'impossible', often when it's not physically impossible and
so merely contradicts whatever model of planet formation and evolution
the complainer prefers. I do notice that this has died down somewhat
since the discovery of all those 'super-Earths' in recent years, and hot
gas giants, and so on have shown that our old models were way too
conservative.

I've decided that simply making up what a world's atmosphere, climate,
etc. are like and adding some vague babble that doesn't seem completely
silly (so, make sure a hot world isn't way at the cold edge of the life
zone, etc.) is good enough. Then describe the things that are game
relevant and get on with the game.

--
Rupert Boleyn <xxxxxx@gmail.com>