Pressure gives soda its fizz, causes altitude sickness

A few days ago, I saw some spectacular pictures of an underwater volcano, along with other pictures of a volcano on land. It made me realize what a difference the incredible pressure of the deep sea made in the appearances of these two eruptions.

The glowing red magma was identifiable in both. But the surface volcano was spewing ash and gas. These gases were not obvious in the undersea volcano, but they were likely still present. You could see the water boiling underwater, but only at the surface of the lava. Any farther away and the crushing pressure of the water prevented bubbles of steam from existing, even though the temperatures were likely many hundreds of degrees.

Even so, these examples are nowhere near the range of pressures that exist in the universe. At one end of the spectrum is the vacuum of space, where only a few protons, neutrons and electrons would be found in a large volume.

But add enough matter in a smaller area, such as in a star, and compress it with a supernova explosion and the gravitational force can be enough to compress the matter into a neutron star or a black hole.

In a neutron star, the usual space that exists between the nucleus and electrons of atoms in “normal” matter is gone, so that neutrons are crammed together as closely as they can be packed, and atoms as we know them do not exist.

And if you know what is inside a black hole, you can win a Nobel Prize. All I know is that they are even denser than a neutron star.

Closer to home, and on a much more manageable scale, by adding pressure, you can dissolve more gas in a liquid than at normal atmospheric pressure. This is what gives your soda a fizz: Once you open the bottle or can, the extra gas can no longer remain at the lower pressure, and it bubbles out.

So it is with scuba divers, but unfortunately, with painful or even fatal consequences. Divers they must use compressed air to counter the water pressure at depths. Otherwise, they wouldn’t be able to inflate their lungs.

At higher pressures, this means more air can be dissolved in a diver’s blood and body fluids. That is fine, as long as it remains dissolved, and it is no problem if the diver surfaces slowly enough to lower the pressure gradually: The gas just “undissolves” out of the blood through normal breathing.

But if the pressure is released too quickly, as would happen if a diver surfaced too rapidly, bubbles would form in the blood vessels, resulting in a painful condition called the “bends.”

In another hobby, such as climbing mountains, pressure still can influence your body. At high altitudes, where air pressure is lower, there is more space between the air molecules, so a lung full of this low-pressure air actually contains fewer molecules of oxygen. Essentially, the lower pressure means less gas can dissolve in your blood. This can also be dangerous at high altitudes, such as on Mount Everest.

It can also be uncomfortable for people visiting Colorado from lower elevations, creating altitude sickness. Fortunately, if you wait a while, your body actually can compensate for this. It solves the problem by adding more red blood cells, so the oxygen collection becomes more efficient. If you give your body a few days or weeks, it will compensate for the reduced gas transfer, and your body will have “acclimatized” to the new altitude.

Just a few things to be aware of when you are deciding what kind of activities to participate in.


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