Ok it might sound like a stupid question but i'm curious.
Obviously mankind didn't reach for the sky till the last century but before that(say 1000 years ago), could it be possible for a person to know that breathing becomes difficult the higher you ascend through the astmosphere/sky?

Absolutely. The first person to climb any major mountain would have figured that out.

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Yeah thats what i thought. But whats the height that you need to differentiate? I mean as in be able to tell that it gets more difficult.

I´d say it depends on the rhythm of the climb. I´ve been a couple of times to the Bermejo pass between Argentina and Chile, travelling by car at an altitude of nearly 13,000 ft. As the road climbs to the pass coming from Santiago you don´t have time to adjust to the less dense air, so you don´t feel any difference; you breathe normally.

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I have never slowly walked from sea level to a high elevation, so I couldn't give you an exact number. I have visited Denver, at about 5000 feet, several times, and I notice the difference from sea level. When I have gone from there to 8000 or 9000 feet (such as Vail), I notice a further difference. And going up to submits, like 12,000 feet, I really notice it, even after having gotten acclimated to 9000 feet.

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Maybe if you aren't exerting yourself, but if you're hiking up at high altitude, you definitely notice (acclimatized or not) once you're in the 13-14k range. I haven't been any higher than about 14,500, but at that altitude, it was quite significant.

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Yeah, I was giving an example of how you don´t feel it sometimes, depending on circumstances. Walking up Villa Rica volcano in Chile, or on the streets of La Paz, I´ve felt the difference.

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You know, I grew up in Roanoke, VA, which is about 1000 feet above sea level, but have lived 4 years in New York, which is at sea level. Last year I spent a week in Mexico City, which at 7200 feet above sea level is significantly higher than Denver and its Mile High Stadium that the Broncos' opponents complain about.

I couldn't feel any difference in terms of breathing or energy levels or anything when I was in Mexico City.

I moved to Colorado Springs in late 1985 after graduating Officer Training School (Air Force). At OTS, I was running 5 miles a day. The first time I tried to run here, I thought I was going to have a heart attack. It took a long time before I could run comfortably at this altitude (GPS reports my house is at 6800 feet MSL).

There's both a highway and a cog railroad that goes to the top of Pikes Peak just west of town (elevation 14,110 feet). At the top of the railroad, they have trained observers who watch the people getting off for signs of altitude sickness. That can be serious, even fatal. Just about every year when the Air Force Academy graduation takes place, some out-of-town relatives end up in the hospital. There was even a 2nd year cadet who died of it several years ago.

I no longer run (I'm convinced that it causes brain damage ;}). Today, I'm content to walk amuck.

Hmmm. "Walking Amok" sounds like a good name for a geriatric rock band.

Marco Polo noticed that it took longer to heat water when he was in the Himalayas than when he was at sea level.

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That's weird - I definitely feel it when I go the other way (I live at about 6000 feet). Admittedly, after a few days of acclimatizing, I don't notice it anymore, but initially (assuming a quick trip, such as by plane), there's a definite noticeable difference in energy and stamina at sea level compared to 6000 feet.

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Running doesn't cause brain damage; brain damage cuases running.

With every running step, you slightly "rattle your cage". The more steps you make, the more rattling. That can't be good in the long term. Then there's the oxygen depletion and endorphins. Nope, not going to do it. Wouldn't be prudent.

Running causes brain damage.
Brain damage causes more running.

I've never been on any very high mountains. I've lived most of my life at
around 900 feet above mean sea level. On a car trip to Denver in 1988 I
didn't notice any change, although it may not have occurred to me to look
for signs, and I never exerted myself while I was there. The highest I got
was the roof of the hotel (maybe 12 stories? It was right next to Stapleton
airport) to look at the night sky. On a trip through Glacier Park in 1962 I
walked several hundred feet up to the top of what I assumed then was a
not-especially-high mountain, on a well-worn path from the road. Didn't
notice any effects there, either. I didn't see any effects on my dad, who
a few years later would need to slow down just walking on the level in
Minneapolis, the result of smoking. (He quit in 1968.) Likewise I didn't
notice any effects while driving through the Rockies in 1962, 1971, and
1986. (Montana/Idaho, the pass near Mt. Robson in Jasper National Park
in BC/Alberta, whatever highway goes toward Vancouver from Banff.)
But again, I didn't exert myself at those times.

-- Jeff, in Minneapolis

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Most people don't have much trouble just walking at Denver's altitude although they often notice shortness of breath while running or climbing stairs. There is an Olympic Training Center here in Colorado Springs where athletes train at high altitude. It's supposed to be very helpful when the athletes compete at sea level. I've noticed that when I travel to sea level, I breath much slower than at this altitude.

Pilots have to use an oxygen supply above 10,000ft.

More info about mountain climbing with oxygen here:
http://www.pbs.org/wgbh/nova/everest...firstwoo2.html
Interesting story about the first guys to climb Mt. Everest WITHOUT oxygen (They were labeled "lunatics," who were placing themselves at risk for severe brain damage by the mountain climbing and medical communities) in 1978.

That's an odd observation. The water should heat at the same rate. Perhaps it was related to the water starting off colder at altitude; or maybe he observed that it takes longer to cook things in boiling water at altitude, because the boiling temperature is lower.
(Polo was in the Tien Shan, BTW, north of the Himalayas.)

On the topic of breathing difficulty at altitude, Ötzi, the mummified corpse of a man who lived around 3300 BCE, was found at more than 3100m above sea-level, but evidence from his clothes and equipment showed he lived considerably lower. So it seems he might have been able to notice a change in the amount of breathing required for a given level of exertion.

Grant Hutchison

Pilots have to use an oxygen supply above 10,000ft.

In the US, pilots have to use supplemental O2 if they're flying above 12,500 feet for more than 30 minutes or any time when flying above 14,000 feet.

Sec. 91.211 - Supplemental oxygen.

(a) General. No person may operate a civil aircraft of U.S. registry --

(1) At cabin pressure altitudes above 12,500 feet (MSL) up to and including 14,000 feet (MSL) unless the required minimum flight crew is provided with and uses supplemental oxygen for that part of the flight at those altitudes that is of more than 30 minutes duration;

(2) At cabin pressure altitudes above 14,000 feet (MSL) unless the required minimum flight crew is provided with and uses supplemental oxygen during the entire flight time at those altitudes; and

(3) At cabin pressure altitudes above 15,000 feet (MSL) unless each occupant of the aircraft is provided with supplemental oxygen.

That's an odd observation. The water should heat at the same rate. Perhaps it was related to the water starting off colder at altitude; or maybe he observed that it takes longer to cook things in boiling water at altitude, because the boiling temperature is lower.
(Polo was in the Tien Shan, BTW, north of the Himalayas.)

Is it possible that the fire burns at a lower temperature where the oxygen level is lower? You're right that the lower boiling temperature of water increases cooking times. I used to work with a guy who lived in Divide, Colorado (approximately 9,000 feet MSL). He told me that it took 30 minutes to cook spagetti noodles unless he used a pressure cooker. Living in Colorado Springs (approximately 6800 feet MSL at my house), we have to adjust cooking times and even modify how we do things like baking a cake.

I guess there's an agreement that it becomes difficult above 10,000 but i wonder what the actual figure is below that.
I've climbed a few mountains(like in Kazakhstan), can't remember how big they were but i didn't notice any different. Same with staying at a town on a mountain.
But yeah it definitely depends on how high you go.

Actually, from my observation at least, 9700 feet is not bad at all. Walking and normal activities are perfectly doable. I don't really start to fully notice until more like 12k or so. I have lived my entire life at around 6000 though, so it might be more noticeable earlier to someone from sea level.

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