The invisible heavy hand of the atmosphere
The great force of atmospheric pressure is used to violently crush a soda can.
Ingredients: Empty aluminum soda can, ice water, hotplate, tongs, gloves
Procedure: A complete recipe follows.
1. Place the soda can containing a bit of water on the hotplate.
2. When water comes to a boil, take can in tongs.
3. Rapidly invert the can into the bowl of ice water and observe results.
Understanding: Heating causes the water within the can to boil, filling the can with water vapor. Rapidly inverting the can into the bowl of ice and water rapidly cools the can and the water vapor inside, causing the water vapor to condense. The rapid condensation creates a vacuum within the can. The enormous force of the atmosphere outside the can, and the lack of pressure within the can, causes the can to rapidly collapse.
The violence of the collapse is startling. It is easy to live under the great force of the atmosphere that holds us tougher, and difficult to feel that great force. It is little wonder that our ancestors once believed that there was an invisible thread, a funiculus, tying the top of an evacuated jar to its bottom. The sense of a vacuum is definitely one of pulling inwards rather than pushing inwards. If you suck on a straw, it feels as if your tongue is being pulled into the straw. But the reduced pressure of air in the straw isn't pushing back. A better explanation is that the pressure in your body and tongue is pushing your tongue into the straw!
In side out
Question: An even more dramatic demonstration of the great force of the atmosphere has been witnessed in a poorly designed decompression chamber. Deep sea divers exercising under great pressure dissolve nitrogen under pressure in their blood. If they "decompress" too soon, the nitrogen expands to form large bubbles, leading to nitrogen narcosis, which can be deadly.A man was placed in a high pressure chamber to allow him to gradually recover from a deep dive. Unfortunately, the toilet plumbing was connected to the immediate outside, which was at atmospheric pressure. The man sat on the toilet to "do his business," flushing it from the sitting position. Apparently, his bum created an effective seal, connecting his high pressure innards with the relatively low pressure outside.
What happened next?