Quote Originally Posted by jeffro View Post
The fluid level in the Soda Bottle shouldnt ever get more than 3/4 full but it will get almost completly empty itself at times like magic.
It works with the pull of the moon like the ocean tides.
Barometric pressure doesn't vary with the tide or the pull of the moon. If it did, you would think barometric pressure would get higher at higher altitude where the moon's gravity is higher but barometric pressure gets lower at altitude.

A barometer measures the amount of atmosphere above the measuring point. The amount of atmosphere or air density varies with the weather and not with the moon. Typically, a low pressure front is bad for fishing so that is why the fishing seems to be better when the water goes into the bottle. The higher atmospheric pressure pushes on the water which compresses the air in the coke bottle and the water rises into the bottle. The water is not sucked into the bottle, it is pushed in by the atmosphere.

Low pressure systems can actually expand the air in the coke bottle so that some of the air will escape; but you wouldn't know it, unless you were watching the bottle. So an empty bottle represents the lowest barometric pressure that has occurred, and not necessarily the barometric pressure when you first put the bottle in the water. This means that water going up the bottle in several months can actually be a lower pressure than when you first put the bottle in if you happened to put the bottle in during a high pressure.

You can do an experiment by putting coke bottles into the water at different times and you will see that the water levels will be at slightly different levels for a while; but once you get a super low pressure, the bottles will synchronize as the air escapes from the bottles that were put in during higher pressure. It's a cool experiment.