This week, I’ve asked my favorite Professor of Chemical Engineering to answer some questions about the science of ghosts, specifically about their thermodynamics. If you’re a science nerd, you’re in luck! He’s in full professorial mode here. But if you still get hives when thinking about middle school science, don’t panic! I’ll translate as we go along.

ICY ELECTRIC SPIRITS

Question: Ghosts produce cold spots and electromagnetic energy fields (which I’ll be calling “EME fields” because it’s shorter to type). Does that make sense from a science standpoint? Can they do both? My experience is that anything with an EME field, like toasters and light bulbs, creates heat.

Professor: Ah. Like much of science, the answer is: it depends. An EME field is generated by an electrical charge that then moves. In classical electrodynamics, you could think of the field as a wave and our ability to sense the energy from that wave depends on the amplitude (height of the wave) and frequency (how often the waves come by). The frequency of a lightbulb is fine-tuned to the visible spectrum so we can see it; the brightness is a function of the amplitude. Microwaves are fine-tuned to generate an amplitude and frequency that water can absorb and heat up. The air inside the appliance stays cool because the EME waves themselves are not tuned to heat air molecules. So, an EME source, depending on its amplitude and frequency, might well not FEEL hot or cold in and of itself. 

Question/Translation: So, like a microwave, ghosts might emit heat energy, but at a frequency that doesn’t heat air? Still, the air inside a microwave oven is at room temperature. It doesn’t feel cold. Why would the area around a ghost be frigid?

Professor: Let’s start with some basic assumptions about the physical nature of ghosts. Fundamentally: they are visible, have a cohesive shape, and are typically white or close to white. Second, they can appear to move. Third, they can disappear. These are clues about whether they’re solid, liquid, or gas.

Question/Translation: Those assumptions about ghosts seem reasonable. When they appear, they have a shape, their color is pale, they move, and they can disappear. But before you discuss whether they’re solid, liquid, or gas, there are really four states of matter, aren’t there? What about plasmas?

Professor: Let’s discuss plasmas later. Right now, I want to start with gas.

Question: I hate delayed gratification, but go ahead.

WHAT STATE OF MATTER IS A GHOST?

Gas?

Professor: Most (but not ALL) gases are clear and colorless—so, not visible. Forgetting really weird chemicals, the only reasonable GAS could be ozone, which is a very light, pale blue and ozone is generated from EME fields, so a ghost could be ozone (and the ghost would then smell really…. Clean). Ozone is slightly corrosive and the impact on the skin would feel cold.

Question/Translation: So ghosts could manifest as ozone gas? Here’s an article that claims that ectoplasm, which forms the “body” of ghosts, smells like ozone. Points on that hypothesis, Professor!

Solid?

Professor: Ghosts likely aren’t solids (say, dust clouds). They’d be visible, and a dust cloud could move, but there’d be a solid residue when it fell to the earth by gravity, which is not reported.

Question/Translation: So ghosts probably aren’t solid because they’re transparent and a cloud of particles (which would be see-through) would leave dust behind. True, ghosts aren’t dusty, although sometimes they leave slime behind. Neither would endear them to the homeowner.

Liquid?

Professor: That brings me to liquids. Ghosts could be condensed vapor (such as water mist), which would be visible, cool to the touch, and, if fine enough, would just evaporate, leaving no residue (and potentially not even any wet areas).

Question/Translation: So maybe spirits appear by making themselves into clouds!

DO GHOSTS OBEY THE LAWS OF THERMODYNAMICS?

Professor: And now let’s talk about whether ghosts obey the laws of thermodynamics.

Question: Must we?

Professor: Isn’t that what you asked me to do?

Question: Good point. For non-science types, meet me at the next non-bold paragraph, where I’ll translate.

Professor: The basic relationship between mass, temperature, and energy is given by:

Q = (m*Cp*T_final) – (m*Cp*T_initial)

In this equation, Q is thermal energy (say, in Joules;  1 W = 1 J/s); m is mass (say, in kg); T initial and final are the initial and final temperatures (say, in ⁰C, before and after the apparition of the ghost); and Cp is the “heat capacity” of the air/surroundings that we are sensing—let’s assume it’s the air that we are feeling (in, say, J/kg-⁰C). Cp is a thermodynamic property of the material (for air, it is 1,005 J/kg-⁰C).

Note—this is a bit simplified and has a few assumptions built in, but is a very good and reasonable approximation if we are looking at a specific relatively small area around the ghost and limited to looking at what happens from right before the ghost appears through the apparition and ignore, for instance, the impact of other external energy sources that might be affecting the area. 

So, to create a cold spot, T_final must be less than T_initial. Cp is a property of the air and will not change. So, either:

1. 1. 1. 1. Thermal energy is being consumed (Q is negative) and the mass is either unchanged, or increases; or
         2. Thermal energy is neutral or is being generated (Q is zero or positive) and mass is being consumed.

Question: Let me make sure I understand what this equation says about ghosts. A cold spot would form when the final temperature is lower than the temperature at the start. For that to happen, the spirit must either suck matter (like air molecules) out of its surroundings or use energy. That matter needs to go somewhere, or the energy needs to change something. Where and what?

POSSIBLE SCIENTIFIC EXPLANATIONS OF GHOSTLY APPEARANCES

Professor: Some options include (but are not necessarily limited to):

The Cloud Hypothesis

1. 1. 1. 1. Something (like water) condensing (so a change in the state of matter). This consumes energy, would feel cold, would result in something visible, etc. It has no relationship with an EME field, so an EME generation would be completely separate and unrelated.

Question/Translation: In this hypothesis, the ghost uses energy to change moisture in the air into a cloud. This would feel cold and look white, just like a ghost’s apparition, but it wouldn’t create an electromagnetic field. So there’s one missing piece to this hypothesis.

The Chemical Reaction Hypothesis

1. 1. 1. 2. An endothermic reaction that generates something visible. The reaction of oxygen converting to ozone IS endothermic and is formed by an EME field and the ozone would be visible. Faint, but visible. It could also dissipate really quickly, almost immediately upon the EME field turning off.

Question/Translation: In this hypothesis, the ghost uses energy to create an electromagnetic field, which changes oxygen in the air (O₂) to ozone (O₃)_. The ozone would look like a pale blue ghost and would disappear soon after the spirit shut off the EME field. All pieces—EME field, cold spot, apparition—accounted for!

The Probably-Impossible Hypothesis

1. 1. 1. 3. Conversion of energy to matter is theoretically possible. There are few practical cases (aside from the Big Bang) or small lab-scale (converting photons to electrons). But, it is possible there are things we just don’t understand, and it IS possible!

Question/Translation: Living things change food (which is a type of matter) into energy. Could nonliving ghosts do the opposite, turning energy into ectoplasm? Energy has changed into matter VERY rarely in outer space and at the atomic level, but it’s never been documented under what humans consider normal conditions. Still—science is constantly discovering new things!

The Fusion Hypothesis

1. 1. 1. 4. Consumption of mass is theoretically possible—essentially this would be a fusion reaction. In a normal reaction, total mass is conserved (though the mass of any one species changes). To consume the total mass of the system, you’d need a fusion reaction, which is theoretically feasible.

Question/Translation: The ghost changes matter into energy through the same reaction the sun uses. Cold spots are accounted for; apparition and EME field are not.

1. 1. 1. 5. Plasmas – see below

WHAT ABOUT PLASMAS?

Question/Translation: Yay! This is where we discuss plasma. For those of you who have never heard of it, it’s a state of matter we don’t often see, sort of between a gas and a liquid, right? Could an apparition actually be a ghost changing from a gas to a plasma?

Professor: This is indeed interesting. Unlikely, but interesting. 

Question/Translation: This sounds suspiciously like, “No.”

Professor: Plasmas are another state of matter and are sort of like a gas, but not really a gas. (Critical Fluids are the state of matter that is between a liquid and a gas and occur at really, really high pressures, so not applicable here).

Question/Translation: Obviously, you’ve never seen a ghost. I, personally, would call that a high-pressure situation.

Professor: Essentially, the sun is a plasma. It consists of gas molecules that essentially have been blown apart so there are “free” electrons. They are typically formed by subjecting a gas to very high EME fields, often under vacuum and often they have to be heated to initiate the plasma and then they generate more heat (as opposed to cold). They are highly unstable and the plasma typically converts back to a gas as soon as any of those things (EME, vacuum, temperature). So, it is unlikely. But, like some of the discussion above, we don’t really have a great understanding of them (because they’re hard to study), so it COULD be. 

Question/Translation: What you’re saying is that EME fields measured near ghosts aren’t high enough to form plasmas; there’s no vacuum, which is essential for forming plasmas; and a plasma wouldn’t generate an EME field, anyway. Scratch plasma as a hypothesis.

CONCLUSIONS

So what hypothesis accounts for ghosts looking white and misty and occurring with cold spots and EME fields nearby? I think the only one is the Chemical Reaction Hypothesis (AKA the ozone suggestion): a ghost materializes by creating an EME field that converts oxygen in the air into ozone.

Professor: Another possibility: The being takes in/absorbs energy from the surroundings in the absence of any chemical reaction, causing the temperature to drop and mist to form (like a cloud). This does NOT explain the EME field, but that could be separate, unrelated phenomena—that this being also generates an EME field in addition to absorbing energy from the surroundings. 

Question/Translation: I stand corrected. Another possibility is The Cloud Hypothesis. The spirit could absorb energy, dropping the air temperature and causing a cloud of water vapor to form. And the EME field? This is a multi-tasking ghoul, and it produces one for the sheer fun of it.

MORE RESEARCH NEEDED?

So, how would we prove which of these two—the Chemical Reaction Hypothesis or The Cloud Hypothesis—is the culprit? (Or show that neither is?)

Professor: One option is to test for the strength of the EME field, the temperature, and take a gas sample. ONE challenge: if it is an unstable compound, such as ozone, then it very quickly dissociates back once the EME field is one—so we might need to test it in the haunted house, which the ghost might not appreciate.

It would be helpful to also to test for a pressure change—not a very sensitive measurement, but could be an indicator of what is happening.

Lastly, we COULD do a complete thermodynamic analysis to estimate to determine the likelihood of some of these things. Knowing the strength of the EME field, the temperature, pressure, and local air composition, we could look at the thermodynamically favorable things that are formed (e.g., ozone, condensed water, etc.) by determining the fugacity (Gibbs Free Energy) of each and determining which set of conditions is most favorable.

Question/Translation: You had to get fugacity in here, didn’t you? Your students say that fugacity is the hardest thing they learn.  Okay, let me make sure I understood your response. To answer my question, we’d need to measure the  EME field’s strength, the temperature, and the atmospheric pressure. AND take an air sample. (I’m sure the ghost will stand still as we fumble with our instruments.) AND, if we can’t analyze the air sample immediately, then an extremely complicated calculation is needed.

Professor: That is completely accurate.

WHAT YOU CAN DO

Question/Translation: Thank you, Professor, for being such a good sport about my questions. I’m not at all psychic, but I urge those who are to take an EMF meter, thermometer, barometer, and air sampling gear to your eery encounters. Then report to your local chemical engineer for further instructions.

On second thought? Call them first…