“It’s crazy… but it’s sure as heck not microwaves”.
That was Kenneth R. Foster’s dismissive statement in The Washington Post in September 2018 when he was asked to opine on the connection between Havana Syndrome and Microwaves. Foster was not just anybody. He was a Professor at UPenn, an expert on EM emissions, a bioengineer whose 1974 Science paper on Microwave Hearing/Frey Effect was widely cited. Yet, his statements were nothing less than condescending. He publicly likened the idea to science fiction, quipping that “It is just a totally incredible explanation for what happened to these diplomats. … It’s just not possible. The idea that someone could beam huge amounts of microwave energy at people and not have it be obvious defies credibility. There’s nothing behind it. You might as well say little green men from Mars were throwing darts of energy.” (Skeptical Inquirer, 2019).
…Fast Forward to today: I just got a hold of 2025 pre-publication by Foster in which he is discussing whether pulsed microwave energy could indeed explain those very illnesses. His journey from patronizing skeptic to reluctant convert is a story about the real-life consequences of misguided arrogant skepticism.
When reports of strange ailments among U.S. embassy staff in Havana first emerged in late 2016 and 2017, speculation ran wild. In December 2017, an influential IEEE Microwave Magazine article by Professor James C. Lin suggested an explanation that a a pulsed microwave device could silently beam painful sounds into people’s heads. But to Professor Foster, the microwave theory sounded far-fetched. In his expert opinion, using microwaves as a weapon against humans simply didn’t add up. “That theory is a real stretch,” he told New Scientist in December 2017.
So how did two seasoned academics - Foster and Lin - arrived to such different conclusions? The answer lies in what Foster ignored.
It appears that Foster completely disregarded a body of research that has existed for decades - on non-thermal effects of pulsed microwaves - research that Foster knew well, but chose to brush aside.
Then, in December 2020 the U.S. National Academies of Sciences, Engineering, and Medicine (NASEM) released a comprehensive report on the embassy personnel illnesses. The report gave serious consideration to the non-thermal effects of pulsed microwaves. After reviewing all available evidence, a panel of experts concluded that “directed, pulsed radio frequency (RF) energy …in the microwave range… appears to be the most plausible mechanism” to explain the cluster of symptoms. In particular, the panel found the peculiar combination of acute onset, strange sounds, and neurological signs “difficult to ascribe to psychological and social factors,” and noted that the well-documented Frey effect provided a credible basis for how microwaves could produce such effects without visible trauma. In short, the country’s top scientific advisors had just legitimized the microwave theory.
For Professor Lin, the NASEM report was a vindication. But for Foster, it was a direct challenge. How did he respond? Publicly, with a noticeable lack of enthusiasm. He did not pen any op-eds praising the committee’s thoroughness or expressing a change of heart. On the contrary, he doubled down on his skepticism in his comments to journalists.
But then something happened. Professor Foster started gradually shifting his opinion. Having publicly drawn a line in the sand, he wrote a technical paper published in late 2021 (in Frontiers in Public Health, appearing January 2022) with a title that itself hinted at his lingering doubt: “Can the Microwave Auditory Effect Be ‘Weaponized’?” This paper marked the first time Foster had formally published on the Havana Syndrome controversy.
What was his conclusion on the microwaves? Essentially, “unlikely” – but with some important caveats. He wrote, referring to the idea of using microwave hearing to harm people, “the lack of publicly available information about existing high power RF technology and uncertainties about thresholds for adverse effects does not allow full resolution of the matter.” In measured academic language, this was a step back from absolute dismissal. Still, Foster kept ignoring any non-thermal injury pathways, implying that beyond the audible “click” (a thermoacoustic effect), RF exposure’s only potential for harm would come from thermal or mechanical (acoustic) effects at very high intensities.
Then came the 2022 “A Letter to the Editor regarding a ‘Health Matters’ article” (IEEE Microwave Magazine). This was a rebuttal to a column by J.C. Lin that had raised concerns about RF exposure limits and the results of recent animal studies. Foster’s letter explicitly defends the IEEE/ICNIRP guidelines and attributes observed biological effects to heating. Again, references to non-thermal effect research were nowhere to be found . Notably, James C. Lin’s published Response to Foster’s letter points out that “the letter is understandable, given its authors’ strong convictions that there is nothing but heat to worry about with RF exposure.” This telling remark by Lin underscores that Foster fundamentally interprets RF bioeffects only in terms of thermal mechanisms as if it were the only scientifically substantiated pathway, effectively ignoring and dismissing non-thermal possibilities.
Then, in May 2024, a symbolic shift in opinion took place . Dr. Foster co-authored a Scientific American article with neurologist Dr. Jon Stone titled “We Don’t Need to Choose between Brain Injury and ‘Mass Hysteria’ to Explain Havana Syndrome”. The essay presented a synthesis: a way to reconcile the physical and psychological elements of the mystery. Foster argued that the initial incidents could have been triggered by an external energy source – say, pulsed microwaves or something similar – which caused an acute but transient disturbance (like a sudden bout of dizziness or ringing in the ears). This, in turn, could lead to a longer-lasting PPPD (Persistent Postural-Perceptual Dizziness). The authors noted that “one of us” (certainly Foster) had “said that the [microwave auditory] effect is too weak under foreseeable exposure conditions to cause brain damage.” That was the old Foster talking. But, they continue, “calculations show that it should be possible to beam strong enough pulses of microwaves, millimeter waves or laser energy to disturb the vestibular system at levels anticipated to produce symptoms similar to those initially reported from AHIs.”
This Scientific American piece stunned many. Here was Professor Foster, effectively lending credence to the idea that pulsed energy attacks might have happened. The piece even raises the question of ongoing directed-energy weapon programs: “High-powered microwave (HPM) or millimeter wave transmitters presently exist that, in principle, should be able to produce such effects.” Foster and Stone concluded with a call to move beyond the simplistic framing: “We need to move away from simplistic arguments of ‘brain injury’ versus ‘mass hysteria’… Patho-physiological events, including pulsed energy attacks, could trigger genuine illnesses.” It was, in essence, a plea for open-mindedness, - something that Foster himself clearly lacked in the beginning!
And finally, in August 2025, Dr. Foster put his name on a pre-print (a not-yet-peer-reviewed study) that directly asked the question he once deemed unaskable: “Acoustic Pressures in the Head from Pulsed Microwaves: Can They Explain the Havana Syndrome?”
“The technology for producing high powered microwave pulses is rapidly advancing, and it seems inevitable that some individuals will be exposed to very intense microwave pulses, if only inadvertently in workplace accidents, and the safety of such exposures needs to be examined.”
He goes on to recommend exactly the kind of research one would undertake if one took the Havana/microwave hypothesis seriously: animal studies, computational modeling at various frequencies, and urging the government to share its investigation data with outside experts. But not human volunteer studies (indirect admission that these exposures would be dangerous…hmm)! Has Foster finally engaged with the “non-thermal injury” literature? Not really, with one narrow exception, - he cited one recent computational model study (Dagro, 2021) that reconciles the possibility of the neurological injury with existing microwave emitters.
To be clear, even the 2025 version of Foster did not pronounce “Yes, Havana Syndrome is likely a result of a microwave emissions.” But importantly, he no longer frames the entire discussion as “implausible nonsense.” It is undeniable that the evolution happened: Foster’s tone and assumptions did evolve, albeit reluctantly, from outright dismissal to measured consideration.
Scientific debates of this sort often seem esoteric and academic, but in this case they had direct human consequences. For nearly a decade, Foster’s dismissals shaped how the press, policymakers, and physicians viewed Havana Syndrome. When one of the most cited experts in microwave bioeffects says the theory is “crazy,” it provides cover for those who want to downplay the problem.
For diplomats, intelligence officers, their families who fell ill, and non-government civilians medically diagnosed with Havana Syndrome, Foster’s words added insult to injury. The impact was especially devastating for civilians who lack protections of federal employment or healthcare, whose diagnosed cases could still be brushed aside as hysteria, psychogenic illness, or worse (delusions).
If you, like myself, “live” on X, perhaps you yourself engaged with @KFosterUPenn, and observed his demeaning remarks over the years. It is telling that in his 2025 pre-print he found it important enough to mention that “Expert groups (NASEM 2020) and some scientists – together with many nonscientists on social media” consider microwave emissions to be the underlying cause of Havana Syndrome.
At no point has Foster offered a public acknowledgment of the damage caused by his earlier comments, nor an apology for dismissing entire communities of victims. Nor has he admitted that his failure to engage with the broader non-thermal literature left many with a distorted view of the scientific truth.
This is why the evolution of experts like Foster matters: because when the needle of scientific opinion moves, it influences policy, funding, and public perception. If back in 2017 a figure of Foster’s prominence had said, “This is unusual and serious – we should investigate all possibilities, including microwave origin,” perhaps the government response would have been more unified and swift. Perhaps, the victims would have had an easier time getting diagnosed, recognized, having their cases investigated, and attacks mitigated instead of being ridiculed.
And finally, there is also a matter of Foster’s Scientific Legacy. He will always be known as the man who reflectively and condescendingly barked at a legitimate scientific theory around the role of microwave energy in Havana Syndrome, and then slowly and reluctantly changed his position without an apology after damage was done.