Ghosts Are Impossible In Physics

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A-level Physics By: Please log in to see tutor details
Subject: Physics » A-level Physics
Last updated: 23/06/2014
Tags: energy, entropy, ghosts, thermodynamics

“Ghosts are impossible since they break the laws of thermodynamics.”  

A student recently asked me about this quote by Prof. Brain Cox, asking why it is true, so here it goes:  Nothing is ever proven in science, but some things have so much evidence supporting them that they are considered laws; thermodynamics is one such set of laws.  There are four laws of thermodynamics and they can be described as such:

Zeroth Law – If two systems are in thermal equilibrium with a third, they are in thermal equilibrium with each other.  It’s called the zeroth law because it was thought of after the other three and is more fundamental, so instead of renumbering the other three it was called the Zeroth Law.
First Law – Energy can be neither created nor destroyed; it can only change forms.  This also means for an isolated system the total energy remains.
Second Law – No engine or refrigerator, working a cycle, is 100% efficient.  This usually means that energy is lost to heat in any system and you can never get back all the energy you put in.
Third Law – You cannot reach absolute zero.  As temperature approaches absolute zero, the entropy (or disorder) of a system approaches a minimum.  This also means that you can't create order (reduce entropy) by adding energy to a system, the system must spend energy to reduce local entropy and become more organised. 

The British Scientist and author C.P. Snow coined the following ways of remembering the laws:
1) You cannot win (that is, you cannot get something for nothing, because matter and energy are conserved).
2) You cannot break even (you cannot return to the same energy state, because there is always an increase in disorder; entropy always increases).
3) You cannot get out of the game (because absolute zero is unattainable, you must always obey the laws of thermodynamics).

If ghosts were formed of energy and not matter they would lose energy because of the second law of thermodynamics. It would, therefore, be impossible for them to maintain their structure and order for any significant period of time.  If they were interacting with the world they would be moving themselves, or other objects, and perhaps emitting light or sound. Hence due to the First and second law they would fade out of existence.  Haunted Houses are popularly conceived with, so-called, regular hauntings, but this is impossible since the ghost would lose energy and disappear from existence.  The only way to make haunting possible would be for ghosts to draw energy from the environment in order to sustain their existence. 

Entropy is also against ghosts; a system will not become more ordered unless energy is put into it, otherwise it will naturally follow to disorder.  For example a room will become messier unless someone spends energy by putting effort into tidying it.  Hence spontaneous organisation of matter or energy to form an otherwise formless ghost would require spending energy.  Ghosts, if they existed, must be made of energy then they must then spend energy in order to appear, so again they wouldn’t last for long.  But where does energy comes from in the first place? The First Law of thermodynamics states that energy cannot be created, it can only change its form. Again Ghosts would need a source of energy, which means taking it from somewhere else, this would be detectable, but has never been observed in any situation.

The principle of the conservation of energy and the fact that entropy always increases are so fundamental that it would requires very solid evidence before you could throw it away. If you saw a ghost you'd have to rip the book up, I suggest that it would be far more surprising that thermodynamics were nonsense than the fact that ghosts actually exist.  Ghosts are not consistent with scientific understanding of the physical world, this makes them highly implausible.   

These scientific facts will never convince the ghost believers, as they are certain that ghosts are an exception to the laws of thermodynamics. This is the very definition of pseudo science, as it is not just disconnected from reality, it directly opposes it.  It is far more likely that these believers or people that see ghosts are either deluded or mistaken than ghosts actually existing.  Aside from the fact that ghosts are against the laws of nature there is also the massive problem that there is no compelling evidence for the existence of ghosts. Hence we can say with certainty that they do not and cannot exist.

Andrew Gibson A-level Physics Tutor (Nottingham)

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