What causes us to experiance 14lb of pressure at sea level?

Question

What causes us to experiance 14lb of pressure at sea level?

Answer 1

I am sorry but something is missing in your question and the answer you got so far: the surface. Because pressure is weight by unit of surface. I suppose that 'your' surface is a square inch.

Mine (because I am Norwegian) is a square centimeter and the pressure then is about one kilo. If we stay in the metric system, it would mean that the average pressure is then 1,000 hectoPascal. In fact, it is 1,013.25 hPa as defined by the Standard Atmosphere (SA) used to calibrate all instruments.

If you wanted to actually measure that 'weight' say, on your finger tip, you would have to remove the pressure on the other side. That is very difficult but if you rather take a tube full of water and closed at one end, you will notice that the column of water would be no more than ten meters hight. That is because the pressure (weight per unit of surface) would equal one atmosphere or about 1,000 hPa.

This is the reason a suction pump can never lift water higher than ten meters. But that is not a very practical way to measure pressure. A liquid with a much higher specific weight like mercury is much more handy. The column then has to be only 760 mm high. That, converted to inches, is 29.9 and the atmospheric pressure you are more used to read on your type of barometer.

As you go up in altitude, the pressure decreases with about one hPa per 8 meter of altitude. But that is not linear because as pressure decreases, you have to move more to see another fall of one hPa. At about 6 km of altitude (half way to the tropopose - the top of our meteorologic sphere) the fall of pressure of one hPa needs 16 meters of altitude.

Incidentally, I can confirm what Alb 4 says about pressure 'under the water.' I am back from a nice car trip in Norway and drove in several tunnels under some fjords with a bad cold. As you know, when you have a cold, you are very sensitive to pressure difference in your ears. Well, I certainly noticed that at the bottom of the tunnels, the pressure was higher than at sea level. That wasn't too bad but when we drove across the top of the mountains, at 1,500 meter altitude, then back in the deep fjords, it felt extremely unpleasant!

Answer 2

It is the weight of all the air on top of us, to the top of the atmosphere that gives us the 14lbs of pressure at sea level.  The higher one goes in altitude, the lower the air pressure gets until one reaches the atmosphere/space boundary and therefore no air pressure.  Conversely, as one goes below sea level the air pressure will start to increase slightly.

Answer 3

its the total weight of our atmosphere being pulled down by gravity