Re: Mt.Wilson

On Wed, 14 Dec 2005 09:29:19 -0800, G.T. wrote:

> Mike Simmons wrote:
>> On Tue, 13 Dec 2005 16:27:53 -0800, G.T. wrote:
>>
>>
>>>Can you explain this phenomenon? I've been up to 12,000 ft at night and
>>>never had trouble seeing stars. I don't think I've been higher than
>>>that during the night, nor during the day, actually. What's the
>>>difference between 12,000 ft and 16,000 ft (other than the obvious 4000 ft)?
>>
>>
>> A lot less oxygen. The decrease in atmospheric pressure is approximately
>> exponential so the higher you go the more of a difference each incremental
>> increase makes. Think of going from sea level to 4000 feet. Most people
>> won't notice any change. 4000 to 8000 is noticeable but not huge. 8000 to
>> 12,000 matters a lot and acclimatization really matters (which certainly
>> isn't true for going from sea level to 4000 feet).
>>
>> Even when fairly well acclimatized at base camp at 15,000 feet I ran into a
>> wall at about 16,500 on that climb (the next camp was at about 17,200). I
>> was the strongest in the group when we started that day and was left behind
>> half-way up when I went from an easy stroll to five breaths per step. I
>> went from good to bad in about 500 feet or less. I understand even some
>> professional climbers have ceilings they just can't penetrate.
>>
>> This is what makes it so amazing that people can go to great heights. The
>> higher you go the greater the effect of going even higher. How some
>> climbers can do what they do is beyond me.
>>
>
> Yeah, riding mountain bikes at 12,500 is pretty compared to my native
> 1500 ft.
>
> But is the lack of oxygen the reason for poorer seeing conditions? It
> seems the higher one goes the better the seeing would be?
>
> Greg

Greg,

Bill's explanation that the retina doesn't work that well without a
sufficient amount of oxygen is the problem. You won't notice it during the
day when there's plenty of light. You might not notice it at night,
either, since you'd still see lots of stars but you might see a lot more if
you were able to breathe air with a normal pressure of oxygen. That's what
it was like for me -- I saw what seemed a reasonable number of stars at
about that altitude. That's why it didn't occur what was happening to me
when I went significantly higher. I kept wondering why there were thin
clouds at night but never during the daytime! ;-)

Mike Simmons
.

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