Poltergeist - The Night Side of Physics, by Keith Linder

Reviewed by James Houran


First and foremost, mine is hardly an impartial book review. It instead reflects my skeptical leanings as a long-standing researcher in this realm of anomalistics. That does not mean a debunker of the psi or survival hypotheses, but rather someone who gets irritated by authors or academics who strive to prematurely interpret observations (i.e., theory-formation) rather than focus on identifying reliable and valid observations in the first place (i.e., model-building) (for discussions, see Houran, 2017; Houran et al., 2018, 2019. Furthermore, the commentary often references my own studies as a point of contrast to the points or issues raised in this book. This is because my research team, for better or worse, seems to be among the select few that is actively publishing and theorizing in this area.

In my experience, “sciencey” authors tend to write one of four types of books in this domain: (a) purely descriptive witness narratives geared towards entertainment, (b) sensationalized accounts of casual field investigations that could be pro or con about parapsychological claims, (c) summaries or syntheses of current academic research and theory, or (d) essentially “how to” guides for amateur ghost-hunting excursions. Each approach has its own purpose, strengths, weaknesses, and of course, intended audience. Whether deliberately or unwittingly, this book ambitiously touches on each of these four types. This makes it relevant to researchers and intelligent lay-people alike who are interested in model-building and theory-formation on poltergeist-like phenomena. 

Content Overview

The catchy title comes from Catherine Crowe (1848), who “…wrote about the ‘night-side of nature,’ by which she meant a spiritual world revealed to us through premonitions, clairvoyance, apparitions of the living and of the dead, poltergeists, and other phenomena” (Alvarado, 2003, p. 66). The book is the third installment in a series of books by Keith Linder, an IT specialist and amateur paranormal investigator, or in this case, someone perhaps better described as a “citizen scientist.” Citizen science (or “community, civic, or crowd-sourced science”) involves the active participation of amateur (non-professional) scientists within academic studies helping to generate new knowledge and information (Gura, 2013).

This book, like Linder’s previous ones, addresses the anomalous and disturbing events that happened to him and his girlfriend after moving into their suburban residence, for example, spontaneous fires, stone-throwings, ostensible teleportations, water puddles appearing, objects levitating, and strange sounds. These earlier books are important background reading before anyone dives into the latest tome, although nice summaries and reviews are available (see Knibb, 2019; Romer, 2019; Ruffles, 2019, 2020).

The material is presented as part an “experience sampling study” and part “theoretical analysis” of their experiences at the “Bothell Hell House.” This moniker reeks of context effects that do not help to reduce the sensationalism that plagues this domain (Hill et al., 2018, 2019), but the contents are thankfully more grounded in hardcore scientific concepts. Specifically, and consistent with the idea of cumulative theory-building (Lange, 2017), Linder nicely strives to relate their anomalous events to past poltergeist cases and current scientific theory, all in an attempt to explain the nature of poltergeist outbreaks. 

And what is the book’s conclusion? Linder argues that poltergeist phenomena are not manifestations of macro-psychokinesis (or what parapsychologists often refer to as “recurrent spontaneous psychokinesis” – RSPK, e.g., Roll, 1977; Roll & Persinger, 2001). Rather, the book implicitly and boldly claims to be the first to frame these anomalies within quantum mechanics, which describes “spooky science” or a diverse array of seemingly bizarre behaviors that only emerge on the very smallest of scales. Accordingly, readers take a roller coaster ride of paranormal lingo, physics jargon, and fun (but not necessarily fresh) speculations that try to finally piece together the puzzle that these anomalies present. It is ironic that Linder — despite correctly calling for systematic research to collect hard data that builds on existing scientific knowledge —often fails to acquaint himself with findings on this topic that have come from different perspectives. Physics is certainly one relevant area, but it is not the only one. Poltergeists are not just a physics problem (Laythe et al., 2018; Ventola et al., 2019), but also involve mechanisms rooted in psychology, anthropology, and sociology (Drinkwater et al., 2019; Hill et al., 2018, 2019).

Pros, Cons, and its Contribution to the Literature

On a positive note, this book is (a) clearly written, (b) a reasonably easy and quick read, and (c) aims to educate readers on the phenomenology of poltergeist phenomena, often by delving into complexities or nuances in the events that Linder claims skeptics and amateur investigators often miss or ignore but which reveal important insights into the nature of these occurrences. This last point echoes sentiments previously voiced by parapsychologists (e.g., Schmeidler, 2001; Solfvin, 2017; Stokes, 2018), so his stance is neither new nor controversial. But the book is certainly filled with details and descriptions that could make a nice academic case study if systematically analyzed and interpreted against the empirical literature. As it stands, the book is akin to an extended term paper that was written by a smart and sincerely interested student intent on sharing his speculations and beliefs.

The elements above are not negatives per se, but the book’s ideas arguably follow from several limitations and misconceptions that undermine its accuracy and impact. First, the book is primarily based on a slew of online references and anecdotal reports from all sorts of sources of varying quality. This misstep is repeated in his “Required Reading” section, which only lists one physics-type book among 11 listings — not even one journal article from the parapsychological, social scientific, or physics literature! At the very least, Linder should know about and recommend Stapp’s (2011) fascinating book on quantum mechanics and observer effects. Readers are therefore left to wonder to what extent is Linder informed by his expertise of the various subjects or his reading of others’ expertise (or lack thereof). This is particularly true for his presentation of quantum mechanics, which this reviewer was personally told by Dr. Dan Hooper (American cosmologist and particle physicist specializing in the areas of dark matter, cosmic rays, and neutrino astrophysics) is an extremely difficult topic even for professional physicists in this area.

Second, and contrary to the impression that Linder gives, this book is not the first attempt to contextualize poltergeist (psi) phenomena relative to existing scientific principles (e.g., Marwaha & May, 2019; Roll, 2003; Sheehan & Cyrus, 2018; von Lucadou, 2011) and specifically quantum theory (e.g., Bierman, 2010; Maher, 1999; Radin, 1997, 2006). Linder’s apparent lack of expertise in quantum mechanics seriously weakens his main thesis without him knowing it, namely the idea that poltergeist phenomena are actually quantum phenomena personally witnessed by (or that happen to) we human observers. True enough, some haunt and poltergeist anomalies can prima facie resemble quantum effects — such as object “teleportations” that mirror the mechanical phenomenon of “quantum tunneling” whereby a wavefunction propagates through a potential barrier. 

But returning to the idea of cumulative model-building and theory-formation, a subject expert like Dr. Hooper would ask Linder to explain how this happens given that studies strongly suggest that quantum effects like entanglement or tunneling do not manifest in the macro-world. To clarify, quantum properties such as the superposition of states or quantization (i.e., the procedure for constructing a quantum field theory starting from a classical field theory) do not seem to apply in the living world on a human scale. 2012 Nobel Prize–winner (shared with David Wineland) Serge Haroche proved this with his experiments (for a listing, see: https://www.college-de-france.fr/site/en-serge-haroche/bibliography.htm). In other words, “when an object interacts too much with its environment and becomes too large, it is no longer a quantum object” (Bobroff, 2019, para. 15).

But wait…poltergeists might not simply be impersonal, quantum phenomena at all! Linder later states that be believes the most inclusive theory of poltergeists is not RSPK or pure physics but “entities” (i.e., intelligent presences) that apparently leverage physics. More precisely, the final analysis comes down to “sound waves undetectable to the human ear are what the poltergeist uses to carry out its machinations” (p. 361). Here he means infrasound and related effects, which several years ago were explored in the context of ghostly experiences but seem to produce mixed results in real-world conditions (Dagnall et al., 2020).

Linder is a layman, not a professional researcher or writer, and naturally that shows. One can sympathize with his struggle to understand why the anomalous phenomena occurred and how. He should be applauded for his aspiring scholarship and enthusiastic speculations, but Poltergeist - The Night Side of Physics does not advance theory-formation on its intended topic. Instead, it does have value to promote widespread and systematic model-building on poltergeist phenomena via the ideological approach professed or implied throughout its pages. Namely, this book documents various types of qualitative and sometimes quantitative information that professional parapsychologists, physicists, and other scientists can use to test existing and new ideas. Linder himself uses an entire chapter to push the “paranormal field or community” to adopt project management approaches for collecting reliable data using scientific equipment. He is not talking to parapsychologists here so much as the amateur paranormal investigator community (cf. Hill et al. 2019). Serious academics cannot criticize this basic idea; certainly not this reviewer who has collaborated with both skeptics and advocates to promote more citizen science in this domain but working in tandem with professional scientists (Houran, 2017; Laythe et al., 2021).


Although this book is on the right track about research methodologies and the role of citizen scientists, it still irks me that Linder falls prey to the same temptation that arguably stunts aspects of parapsychology and general anomalistics, that is, premature theory-formation. “Yes, poltergeists are quantum effects…yes, they use infrasound… and yes, they are the actions of entities!” Before science can say “yes” to some or all of these assumptions, a wealth of high-quality data must first be collected using competitive hypothesis testing, stringent research designs, and rigorous measurements.  It is not enough to say that the “jury is out,” it is better to say that we are still learning about how even to collect and analyze certain types of evidence in these cases.

Overall, lay people with a casual interest in the paranormal will enjoy this entertaining, though somewhat disjointed and convoluted, presentation. But readers with an eye to empirical research might well find that they get more ideas and inspiration from the empirical observations and philosophical questions that Linder presents in this book versus his rhetorical and theoretical conclusions. Ideally, this book will help to promote the use of trained and supervised citizen scientists in parapsychology, as well as to recruit people with an adventurous and curious spirit to fill those roles in earnest.


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