Moving Milk Bottle Cap Mysteries: Ghosts, Poltergeists, or the…

Moving Milk Bottle Cap Mysteries: Ghosts, Poltergeists, or the Ideal Gas Law?

Videos of moving bottle caps on milk containers appearing across social media have captured degrees of media interest

In some news publications, the phenomena had been sourced as having a paranormal origin, albeit a bit tongue in cheek. Other posts have also attributed the mystery movements to ghosts, poltergeists or haunted phenomena 

However most posts, like the one featured, involve persons who are fascinated by the inexplicable movements in themselves. The milk containers in the videos are often nearly empty.  This observation helps in pointing toward a normal versus paranormal explanation for the events at hand

The Ideal Gas Law conveys that the state of an amount of gas is determined by its pressure (P), volume (V), and temperature (T).  The law is usually expressed in the equation:

                                                      PV = nRT

Where n is the number of moles (molecular mass), R is a the gas constant

When the milk container is removed from the refrigerator, the temperature (T) rises as the bottle warms up. The volume (V) of the container is unchanged but there is greater kinetic energy among the (n) gas molecules within it.  The result is higher pressure (P) within the container

The Ideal gas Law equation requires adjustments for high pressures and temperatures, and there should be no other attractive forces among the molecules. But it is a good approximation for the conditions seen in the videos 

Another example of the Ideal Gas Law in action can be seen in the jumping coin experiment


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Delaney76. (2008, April 20). Moving Milk Bottle Cap. YouTube

Elearnin. (2013, May 7). Coin jump up trick revealed | Science experiment. YouTube

Keegan, N. (2015, Dec 24). Spooky moment ‘ghost’ lifts lid off bottle of semi-skimmed milk. The Sun (2015, Dec 22). Watch terrifying moment ‘ghost’ lifts lid off bottle of semi-skimmed milk. The Mirror

Nave, C.R. (2017). Hyperphysics: Ideal Gas Law. Department of Physics and Astronomy. Georgia State University

Wikipedia. (2018, May 11). Ideal gas law