As Halloween approaches our minds may well turn to ideas of ghosts and spirits. Even as a science enthusiast, Halloween has always been my favourite holiday. But when considering ideas of wraiths and ghouls, it’s inescapable for me that science, in general, isn’t exactly positive about such ideas. Despite this, believers in the paranormal are fed constant misinformation via the media that science somehow supports the idea that consciousness survives death.

Let’s begin the ultimate Halloween showdown as physics faces down the supernatural.

Physics vs Phantom

The most common examples of this involve the misuse of certain elements of quantum physics, the conservation of energy and Einstein’s energy/mass equivalence equation. Terms like “energy” and “quantum” are thrown out to support ideas of the paranormal with little regard to their actual uses and applications.

With this in mind, let’s examine what physics actually says about the possibility of ghosts and spirits wandering the Earth.

What is a “ghost” anyway?

It’s pretty tricky to provide some definition of what exactly a ghost is, despite hundreds of years of investigation, no one has actually been able to isolate one. Now, of course for the pedants, I must add that this is very likely because ghosts don’t actually exist. But that isn’t as interesting as speculation.

So let’s use the definition of ghosts that is most commonly held in popular culture, in both fiction and in what believers state that they experience in hauntings.

This definition would include:

Ghosts are the spirits of the dead. Some intrinsic part of who or what we are survives our physical death and is able to walk about disembodied.

Ghosts can be seen by both the naked eye and by recording devices such as cameras.

Ghosts can manipulate physical objects: Playing piano in the dead of night; throwing Lego bricks; scratching ghost hunters. Things like that.

Ghosts have some interaction with the physical world. In addition to manipulation of objects, ghosts can affect temperature and electromagnetic fields and the like.

With that short list of qualities, it’s pretty clear that ghosts should be both measurable and quantifiable by science, just as anything with a physical effect should. Thus they should also obey and conform to well established natural laws.

This gives us some basis to assess what physical laws would say about ghosts.

Does the conservation of energy suggest life after death?

Nick Groff is one of a current crop of para-celebrities that wander around dark buildings scaring themselves silly on paranormal television shows such as Ghost Adventures and Paranormal Lockdown. But as well as excelling at looking scared in black and white, Groff has something to say with regards to the connection between the conservation of energy and the existence of ghosts.

Nick Groff looking concerned on “Paranormal Lockdown”

In 2012, he told the Huffington Post: “Energy can’t be created or destroyed; it can only change forms — that’s a law of physics. Not a theory of physics — a law. It’s called the law of conservation of energy. It means that if you take an isolated system, such as a person, the energy contained in that person can’t be destroyed. It can change forms from chemical energy — like the signals that travel down your nerve pathways — into kinetic energy, the energy required to move your arm, for example, but the energy is always there.

“This law makes sense to me. It means that when we die, our energy must go somewhere. The flesh and bones — the empty vessel — is left behind, but the energy survives.”

It’s a view shared by many ghost believers, but does it have any basis in truth?

To assess this, first, we must consider what scientists tell us about the concept of energy.

Energy is a property of matter that is used to do work on a system. If we want to change the state of a system we put energy into it.

We are aware of the forms energy takes, electrical, nuclear, chemical, heat, kinetic and potential (stored) being the main types of energy we encounter every day.

Groff is correct when he says energy cannot be created or destroyed, only converted, but when we consider that statement we must bear in mind the forms energy takes in our body. Unfortunately, mirroring the adage that even a broken clock is right twice a day, this is where Groff starts to go wrong.

Our bodies aren’t thermodynamically isolated systems. An isolated system cannot exchange either matter or energy with its environment. Clearly, we do both, and in both directions.

We absorb both matter and energy and pass it into the environment, energy via heat and matter via… well… you know. When we die, this process only halts in one direction. We stop taking in matter, but our bodies continue to expel heat until we’re in thermal equilibrium with the environment. As for the rest of the energy that comprises us?

Grim though it may be, why should we suspect that our carcass is any different to the animal matter many of us consume?

It’s not pretty. It’s not romantic. But, that’s you that is.

Our energy does go on: to sustain other organisms in the ecosystem as chemical energy to be consumed.

The complete picture?

With the discovery of the Higgs Boson, CERN completed what is known as the standard model of particle physics. This is relevant to the idea of “vital energy” as energy is a property of matter, it doesn’t sit in isolated clumps.

If there is some new energy, carried by an as-yet-undiscovered particle, then it should exist at everyday energy levels. Yet, in our search for the Higgs Boson, everyday energy levels have been thoroughly-probed and well understood, and this “vital particle” remains undiscovered.

There are lots of questions left to ask in physics, Cosmologist, Tim O’Brien, defines these gaps in our knowledge as “known unknowns”. In that we know the physical definitions of things such as dark matter, we know what it does, we can measure its effect of the universe very precisely. We just don’t know what it is.

There is no evidence of any “vital energy” that differentiates between dead matter and living matter, and perhaps most worryingly for physicists, we don’t see any physical phenomena that require the addition of such factors to the standard model.

We could probably end the discussion here, but let’s go further and delve into the consequences of such a “vital energy”. Even if it did exist would the laws of physics allow it to form a “ghost”?

And if so, how long for?

The Second Law of Thermodynamics

Let’s say we have our free-floating blob of “vital energy” or ghost if you prefer, there’s going to be a pretty immediate restriction placed on that energy.

If it manages to stay in one compressed form the second law of thermodynamics states that the amount of useless energy within that lump, it’s entropy, is going to grow.

Every time our spook startles a photogenic ghost hunter on a syndicated US TV show by throwing something, or slowly shutting a door, it’s going to lose energy. Furthermore, the energy our spook holds on to is going to become gradually more and more useless. To keep its structure, the ghost would have to convert energy from its surroundings. This is something that should be measurable and demonstrable, and yet no-one has done either.

Therefore, ghosts would need a pretty much constant source of energy to remain ordered. Many ghost hunters claim that cold-spots represent just such an attempt by a ghost or spirit to draw energy from its surroundings.

“ Everything that enters an environment, even ghosts, change it in some way. When we move, breath etc. we stir up the air around us, our collective body temperatures raise the temperature. The most common theory for why cold spots occur is when a ghost is in an area they use the heat in order to manifest…” (Seeks Ghosts, 2011)

The problem with this is that according to the zeroth law of thermodynamics, heat is only exchanged between a colder body and a hotter one until a thermal equilibrium is reached, i.e. both bodies are at the same temperature.

Heat exchange between a body and the atmosphere surrounding it, and another body in that atmosphere, would happen via convection. This would result in convection currents as seen above (replace the window with our spook). What we would experience is a cycle of cool air falling and hot air rising through the area, not isolated cold areas.

The principle of thermodynamic equilibrium simply doesn’t allow for heat to be drawn at will in a limited area, the exchange of heat would spread to all areas in thermal contact. A far more likely explanation for cold spots are draughts.

As the feeling of cold is not actually due to temperature as such, but the rate at which heat is drawn from us, a far more likely explanation for a sudden cold sensation is exposure to a column of frigid air. Thermodynamically speaking, heat is often associated with entropy as it’s not a usable form of energy. Heat is generally an end product of various thermodynamic processes, the final energy transformation.

So, when we hear tales of 18th-century spirits tossing pint glasses around struggling UK pubs, the laws of thermodynamics should make us extremely suspicious.

Newton’s Laws of Motion

Perhaps the most common phenomena associated with ghosts is the ability to pass through walls as if they are not there, such as related in the tale of the Grey Lady below:

“Sightings of the Grey Lady walking the Ghost Corridor have been part of local legend from before the Victorian era. Dressed in grey and in Tudor style, the grey lady walks the length of the corridor and turns right before the end to disappear through a wall. In the 1960’s the lath and plaster removed from this wall revealed a Tudor doorway — at the exact spot where the grey lady walks through the wall!” (The Grey Lady of Gainsborough Hall)

Now with that tale in mind, let’s consider Newton’s first law:

“Newton’s First Law states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force.” (hyperphysics)

Therefore, from this, we can gather that for a ghost to begin to move, there must be some force acting on our spook. You and I move by applying a downward force on the floor, which in turn applies an equal and opposite force on us according to Newton’s third law: “For every action, there is an equal and opposite reaction. The statement means that in every interaction, there is a pair of forces acting on the two interacting objects. The size of the forces on the first object equals the size of the force on the second object.” (Physics classroom)

It wouldn’t be unreasonable to assume ghosts move in the same way. In support of this, there are accounts of experiencers seeing spirits walking through hallways or up staircases in addition to hearing ghostly footsteps. Ghost hunting groups often advise amateurs to detect ghost pathways by dusting surfaces with flour or other fine powders to detect footprints. This leads us to conclude that the ghost must be material, as it is the only way they could exert the required force to propel themselves.

This leads to an inevitable question: If ghosts are composed of matter, what happens when they walk into a wall?

“Thou shalt not pass”: The Pauli Exclusion Principle

The Pauli exclusion principle is the facet of matter that forbids particles known as Fermions, including protons, neutrons and electrons, from cramming into the same state defined by four principle quantum numbers.

Just what any kind of “phasing” would require. In addition to this, even though most of an atom’s volume is technically empty space (a popular analogy being a football placed on the center circle of a football stadium representing the nucleus and a fruit fly orbiting the outer wall representing an electron), that “empty space” is filled with electromagnetic force.

It’s the repulsion between these forces that forbids matter from passing through matter. The reason you don’t fall through the floor into the center of the Earth is a result of the electromagnetic repulsion between the electrons in your atoms and those in the ground.

Phasing on a macroscopic scale isn’t possible.

Also, if ghosts are material, they can’t possibly pass through a wall as an immaterial object, otherwise logically they would just pass through the floor, even if this can be controlled at will, a ghost would have to be simultaneously material and immaterial in order to both exert force on the floor and pass through the wall at once. The ability to pick up and interact with objects such as documented above is another aspect of ghost accounts that would require them to be physical material objects consisting of atoms. To move, pick up or interact with an object there must be friction. Friction is generated when two surfaces move against each other, again requiring that our spook is composed of physical matter. Ghost hunters and believers, in general, seem to have no objection to the physical nature of ghosts, but the ability to interact with the physical world comes at a price; restriction to the known and well-established laws of physics.

But wait! Isn’t energy and matter interchangeable according to the most famous equation ever transcribed? Could Einstein’s energy/mass equivalence rescue the ghost hypothesis?

Is E=mc² a ‘life-after-death’ line for believers?

When considering Einstein’s energy/mass equivalence, it’s important to understand that it doesn’t state that MATTER and energy are interchangeable, but that MASS and energy are interchangeable.

Both energy and mass are properties intrinsic to particles. When mass and energy are interchanged, the matter associated with the mass is annihilated. Also, the factor involved, the speed of light squared, c² (9.0 x 1016 m2/s2) ensures that the tiniest amount of matter yields a huge release of energy.

Let’s take this account of a ghostly hitchhiker that disappears, as they are prone to do, and assess the typical amount of energy that would be released as our phantom passenger disappears: “She hopped right in the front seat. She had on this fancy kind of white dress, like she’d just been to a wedding or something, and those new kinds of disco-type shoes, with the straps and that…. I asked her where she was going and she said she had to get home.

“A couple of miles up Archer there, she jumped with a start like a horse and said ‘Here! Here!’ I hit the brakes…. I looked around and didn’t see any kind of house. ‘Where?’ I said. And then she sticks out her arm and points across the road to my left and says ‘There!’ And that’s when it happened…. I looked to my left, like this, at this little shack. And when I turned she was gone. Vanished! And the door never opened. May the good Lord strike me dead, it never opened.” (Cab driver Ralph gives his account of an encounter with Chicago area’s Resurrection Mary. Suburban Tribune, January 31, 1979)

Now, we can assume that as Mary, our spook, opened the car and hopped in without alerting the driver that anything was unusual, she had the typical mass of an average living female. That’s roughly 74.4kg in the US where this encounter took place. If Mary’s dematerialisation represented a switch between mass and energy, just how much energy would be instantly released?

Roughly we’d be talking about 6.7 x 1018 Joules. To put that into perspective, the nuclear weapon that devastated Hiroshima released 6.3 x 1013 Joules, so our ghost converting its mass to energy would release the equivalent of the yield of over one-hundred-thousand nuclear detonations!

Hardly likely Ralph would have survived to relay his encounter to the Chicago Tribune. Hardly likely the Chicago Tribune would have survived, or Chicago for that matter!

Science, especially physics doesn’t seem to allow the traditional idea of a ghost to exist. Despite this, we are all still fascinated by ghost stories, whether they are presented as fictional or as real-life encounters.

Part of our nature seems destined to always be fascinated with the possibility that some part of us continues after death. Perhaps that’s why, no matter how scientifically literate we become as a race, ghost-stories still persevere. As does that tendency to wonder in the dark, when we hear a noise we can’t explain “What if….”