# South Pole FAQ

1. What is physio-altitude?

The atmosphere is less thick at the North and South Poles
than at the Equator. Because of this, the air pressure is less in the
polar regions than at similar altitudes in the rest of the world.

The main reason for this is the spin of the earth. As the earth
spins, it forces the atmosphere to “bunch up” at the equator and
become thinner at the poles. This is due to the centrifigual force
of the earth.

Since we are at the pole, the speed of the earth rotating is 0 mph,
but at the equator the speed is 1040 mph. The centrifigual force
draws the atmosphere toward the equator, because that is where the
speed of the earth is the greatest.

Because of the effect of the atmosphere “bunching up” at the
equator, the air pressure at 9300 feet in the midlatitudes and at
the equator is more than it is at the poles. As an example,
you’re climbing Pike’s Peak, CO, and get to 9300 feet. You measure
the air pressure at 716 millibars. While at the South Pole, elev.
9300 ft., the air pressure is 686 millibars (physio-altitude
10400 feet). If you continued to climb Pike’s Peak, and measure
the air pressure at 10400 feet, it would be about 686 millibars.

2. What is Grid North, South, East and West?

We have a grid system down here to determine our directions.
This is because everywhere you go is north from the South Pole.
What we use is a grid system based on 0 degrees longitude as
north and all of the lines of longitude then act as a compass
direction.

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