Hunting the tachyon

How faster-than-light particles stayed hidden for over a century

© Robert Ehrlich


I am a retired former physics department chairperson of George Mason University and my brief bio can be found here. This book (my 23rd) is in part a memoir and in part a review of the scientific evidence for faster-than-light (FTL) particles, which violate a basic principle of Einstein’s relativity.  If confirmed the existence of these particles will turn the world of physics upside down, and raise science fiction-sounding possibilities, including communicating with the past! Until now, FTL particles, known as tachyons, have been considered by most physicists to be nonexistent.  Although there have been many sightings of them in the past they all turned out to be mistakes.  The book traces the story of how I gradually uncovered the “well-hidden” evidence for tachyons over the last three decades, and why this evidence is much more solid than anything previously claimed. 

I wrote the book for the general reader, as the book has no equations, other than the ever-present E = mc2, and I have tried to inject humor and eliminate jargon whenever possible.  A number of my earlier books including the two published by Princeton University Press have also been written for this audience, and sold reasonably well. The book has numerous illustrations, many of them original and it definitely does not talk down to the reader.  Its length will be no more than 160 pages, with an introduction to be written by a very high profile physicist or science communicator who has not yet been selected.  Here are the chapter titles:

  1. Three weird entities: tachyons, neutrinos and me
  2. Faster-than-light means backwards in time
  3. Supernova SN 1987A and its neutrinos
  4. Direct neutrino mass experiments and KATRIN
  5. Theories of everything and anything
  6. Lessons learned

There are a number of existing popular-level books on faster-than-light speeds, including those listed here, however, unlike my book, none of the books listed was written by someone who has found evidence for FTL tachyons.  A draft version of my book suitable for review by outside reviewers is now complete, in case you happen to be either a publisher or a literary agent who might wish to represent me.  Below I have enclosed the first part of chapter one.


Chapter 1: Three weird entities: neutrinos, tachyons and me.

 “Physics advances by accepting absurdities. Its history is one of unbelievable ideas proving to be true.” ― Rivka Galchen

Hidden unicorns

Suppose you got a message from someone claiming to be from the future – maybe even your future self – what would it take for you to believe it was not a hoax?  This question may not just be science fiction if faster-than-light (FTL) particles known as tachyons exist, since they might allow messages to be sent back in time.  It is true, of course, that earlier reports of FTL particles have proved to be mistaken, and many theorists think they are impossible.  There is also much craziness on the internet about topics like “tachyon healing,” which tarnishes the very word.  Nevertheless, despite all of that, this book describes the steadily accumulating, yet apparently little-known evidence for the reality of FTL particles. 

Tachyons have long been the “hidden unicorns” of particle physics – too bizarre in their properties to be anything but mythical creatures, and if real, then too well hidden for any convincing evidence of their existence to have emerged.  This book will show that they have, in fact, been very well hidden, because of some exceptionally good camouflage, but that much of the evidence for tachyons can be found in data that was publicly available for over three decades.  This is an account of my 20-year long meandering quest to see through the camouflage and gradually uncover that evidence. 

Tachyons violate the principle of Einstein’s theory of relativity barring superluminal or FTL speed, and even worse, they erase any absolute distinction between cause and effect, which in physicist-speak is a “violation of causality.”  Tachyons have been declared dead on multiple occasions, most recently in 2011, but now a new experiment based in Karlsruhe Germany known as KATRIN has shown earlier reports of the death of faster-then-light neutrinos to be greatly exaggerated.  This experiment was designed to measure not the speed of neutrinos, but rather their mass, and it expected the neutrino mass to come out less than four millionths that of the electron based on prior work.  Instead, however, the results are weirdly consistent with the neutrino having three different masses.  Most surprisingly, one of the masses is imaginary, this being the other defining characteristic of tachyons besides their FTL speed.  An imaginary mass means that its square is negative, and as a result, the particle strangely speeds up as it loses energy.  Most remarkably, the three masses found by KATRIN were predicted in a paper I published six years ago.  Essentially, the KATRIN results “put the icing on the cake” atop all the previously accumulated evidence that some neutrinos are tachyons.


A confession.  This book has been mostly written prior to KATRIN’s results coming out.  Writing about a discovery before it is made may seem idiotic, but as an 81-yr old with a limited time horizon I thought it might be wise to write this book while I still could.  Part of me even imagined that by putting these words on paper I could somehow bring about the desired outcome of the experiment, which logically I knew was impossible.  Finally, I wrote much of this book prematurely, because I concluded that if I should “hit the jackpot,” I will have much less free time than I have right now.  Don’t worry — if the experiment does not give the predicted results you will not be reading this book because it will not exist.


While this book is primarily about my role in the hunt for the tachyon, it also touches on the work of many others whose work aided in this effort.  In addition, the book suggests a model of a new way of making scientific discoveries.  Some important discoveries arise from accidental observations, as was the case with penicillin, superconductivity, and radioactivity.  More commonly, they are the result of a theory such as relativity, or the Higgs mechanism, which then is confirmed by a single dramatic observation.  The tachyon hunt suggests a third method called data prospecting in which we let data “speak for itself” rather than using it to test some theory.  In data prospecting we find a pattern or anomaly in previously published data, and then try to make an unconventional model to explain that pattern.  We then seek confirmation for the model in a wide variety of other data sets, while always being on the lookout for negative evidence that could doom our model. 

One way to achieve FTL speed that wouldn’t work

The very idea of the speed of light being a cosmic speed limit as claimed by Einstein in his first of two 1905 relativity papers does seem to violate common sense.  For example, imagine that you are in an interstellar spaceship whose engines had a constant thrust that accelerated it at one g.  With that acceleration if you started at rest then after 1, 2 , 3, 4… seconds people on Earth would judge your speed to be 10, 20, 30, 40… meters per second, and as an added benefit you would feel like you are back on Earth with your normal weight.  With a constant rate of increase in speed of 10 meters per second each second, you’d reach the speed of light (300 million meters per second) in 30 million seconds or just under a year.  Einstein, however, proved that as the ship speed increases the constant engine thrust would cause less and less gain in speed each second, because the ship’s mass increases with its speed.   Of course, the effect of a mass increase wouldn’t be sizable until very high speeds are reached.  On the other hand, this mass increase makes the speed of light unattainable, since the ship’s mass increases without limit as the speed of light is approached.  However, in 1962 three clever physicists figured out a possible loophole that might allow FTL speeds, which Einstein said had “no possibility of existence.”

“Meta” relativity

The FTL tachyon was proposed as a hypothetical particle by Bilaniuk, Deshpande, and Sudarshan in their 1962 paper called “Meta” relativity.  Regrettably, none of the authors of that original paper are still alive, but its primary author, Indian physicist George Sudarshan, is one of the giants of 20th century physics.  Sudarshan and his colleagues realized that Einstein’s ban on FTL speed applied only to objects such as electrons that were accelerated over some time interval up to the speed of light, c, which Einstein proved would require an infinite amount of energy.  However, he had ignored new particles being instantaneously created in subatomic collisions, without any gradual acceleration needed.  In this case the new particles might have FTL speeds at the very instant of their creation, without any infinite energy being required to bring them up to light speed. 

ECG Sudarshan.jpg
E. C. G. Sudarshan at TIFR Mumbai in 2009

The mathematical trick used by Sudarshan and colleagues was to allow the hypothetical tachyon to have a mass that was imaginary. In this case the particle would have a real measurable energy only if its speed was FTL.  If the idea of an imaginary mass is not weird enough, consider that since tachyons speed up as they lose energy, they approach infinite speed when their energy approaches zero.  Despite these weird properties, the “Meta” relativity paper noted that “imaginary mass particles offend only the traditional way of thinking.”  You should be aware that throughout this book the word mass refers to the so-called rest mass of a particle, even though FTL tachyons could never be at rest, any more than a photon or a particle of light, whose mass is zero.  When we previously took an imagined spaceship ride, however, it was not the rest mass that increased with speed, but what is usually referred to as the relativistic mass, which is proportional to an object’s total energy.

Image result for einstein in swiss patent office

Fig. 1. Einstein in 1905, while working as a clerk at the Swiss Patent Office.  


What is so special about the speed of light?  The quantity c is a universal constant approximately equal to 3×108 m/sec.  Strangely, the speed of light is even found to be unchanged when the source of light is moving towards you or you towards it.  This idea was key to Einstein discovering relativity.  Equally surprising, the speed of light no longer needs to be measured more accurately, because it is now an exact number:  299,792,458 meters per second. It is exact because by international agreement a meter is now defined as the distance travelled by light in vacuum during a time interval of 1/299,792,458 second. 


When we assume that mass can be imaginary the speed c becomes no longer an upper limit to speed, but rather a “special” speed.  This special speed neatly divides the matter of the universe into three classes: ordinary particles known as bradyons or objects like electrons (and you) that always have sub-light speed, tachyons having FTL speed, and luxons, like the photon that in vacuum always has a speed exactly equal to c.  In this meta-relativity scheme, infinite energy would be required for a particle in one of the three classes to move into another.  Thus, you, being a bradyon, could never exceed the speed of light and catch up to a tachyon.  Likewise, since tachyons gain energy as they slow down, and they would require an infinite amount of energy to slow down to the speed of light.  The phrase “speed of light” refers here to the speed of light in vacuum, and not in a transparent medium such as glass, air or water, in which light travels at a reduced speed.  When charged particles travel through a transparent medium it is possible for them to outrace light in that medium, with the result being a kind of shock wave known as Cherenkov radiation – a phenomenon that gives rise to the eerie bluish glow you would see in a pool of nuclear reactor wastes.  Ever since tachyons were proposed in 1962, researchers have made searches for these hypothetical entities.  While some of these searches initially yielded positive results, they either were one-time observations or irreproducible experiments.  In fact, the Particle Data Group, which annually compiles results of all subatomic particle properties, got so tired of seeing false reports of tachyons that since 1994 they stopped compiling results of tachyon searches. 

Among all the known particles, it is only one or more of the neutrinos that have a chance of being tachyons.  The privileged role of neutrinos stems from their having the smallest nonzero masses of any known particle.  Thus, prior to the KATRIN experiment’s results, conventional wisdom held that only an upper limit was known for their mass, making it impossible to be certain whether it is real or imaginary.  The most recent of the false claims of FTL neutrinos occurred in 2011 when a beam of neutrinos from the CERN accelerator in Switzerland initially were thought to have a speed slightly in excess of c.  Although the excess was only 0.0000237% of c, it was well outside the uncertainties of the experiment.  When this experiment known as OPERA was repeated the corrected neutrino speed was found to be indistinguishable from that of light.  Their initial error in the computed neutrino speed was in part due to a loose cable which led to the measured travel time being too short, thus leading to many references

Image result for opera neutrino anomaly

Fig. 2.  OPERA tracked how long neutrinos took when they traveled through the Earth to reach a detector 730km away in Gran Sasso Italy, and initially found they outraced light.  ITFN: National Institute of Nuclear Physics  

to the “phantom of the OPERA.”  Nevertheless, despite this and other mistaken claims of FTL particles, a small minority of physicists including the author have never given up hope that definitive evidence for tachyons might be found.  With the results of the KATRIN experiment, it now seems that hope has been justified.  However, even for us tachyon aficionados, it is misleading to say we now “believe” in tachyons, because science is all about evidence not belief, and much of this book is a description of that evidence.  Some of this evidence relates to a property of tachyons that has made them a source of fascination to the general public, namely the connection between FTL speed and time travel, or alternatively sending messages if not people back to the past.  In the words of A. H. Reginald Butler’s limerick:

“There was a young lady named Bright,
Whose speed was far faster than light;
She set out one day
In a relative way,
And returned on the previous night.”

A digression: The author’s journey through time

All of us are time travelers in our own minds as we access our memories of past events or imagine the future.  We are also actual time travelers as we “row, row, row our boat” down the stream of time.  I am now near the end of my journey through time, having reached my ninth decade of life, though I remember well that young lad I once was, who mentally still lives within.  That boy developed an interest in science primarily as a result of reading popular science books, and especially by watching that amazing TV program featuring Don Herbert or “Mr. Wizard” who involved kids (both boys and girls) in simple experiments, some of which had truly astonishing results.  Best of all most of these experiments could be recreated by viewers.  The Mr. Wizard shows, which can still be found on YouTube, originally ran from 1951 to 1990, and it has been said by Bill Nye that no other fictional hero has rivalled Mr. Wizard’s popularity and longevity.   Don Herbert has been credited through his inspiration of helping to create a first generation of rocket

Don Herbert 1971.JPG
Fig.4 Don Herbert, better known as Mr. Wizard in 1971

scientists in the U.S. – a group that were responsible for the successful quest to reach the moon.

I have always tried to emulate Don Herbert in my own physics teaching by bringing in many simple demonstrations to illustrate difficult concepts.  Now that I am retired and no longer teaching, I still enjoy speaking to groups (especially young kids), and occasionally putting on a “science magic show,” where I can sneak in some actual physics as well as entertain. Among the sciences, I was initially drawn to chemistry, given my fascination with explosives.  A special note to the authorities: this was done without any terroristic intent, and no humans, or animals were harmed during these “investigations” usually carried out in a nearby vacant lot.  The closest I came to disaster was when I obtained some metallic sodium, which reacts violently with water.  While I was fooling with it in the bathroom, I did get a small piece wet and caused a fire.  My mother came in with a bucket of water to put out the fire, which unfortunately caused a much larger fire.  Somehow, we did get the fire under control before the house burned down.  My mother then marched me and the sodium out to a vacant lot to bury it in damp ground – another error – and following the explosion there was an interesting encounter with a fire marshal.

Remarkably, in those days, before concerns of terrorism and liability arose, kids were able to get their hands on all sorts of dangerous chemicals – either in chemistry sets or directly from chemical companies, as I had done with the sodium.  It was even possible to buy radioactive ores, such as in the “Gilbert U-238 Atomic Energy Laboratory.”   Many decades later, the Gilbert lab set was criticized as “the world’s most dangerous toy” because of the radioactive material it included.  It was quickly pulled from the market after only one year, but the manufacturer continued to assure parents that the tiny bit of radioactive material included with each set was essentially harmless. Gilbert did, however, acknowledge that if the ores were removed from their jars their crumbly nature could result in a powder, which if ingested could be quite harmful. 

I never owned an Atomic Energy lab set, but one of my first jobs while still in college was at the former Atomic Energy Commission (AEC), now the Department of Energy. I remember holding the warm-to-the touch plutonium core of a nuclear bomb, whose intense radioactivity could not penetrate the outer layer of my skin.  I also recall being greatly disappointed when an AEC-sponsored trip I was scheduled to take to see a nuclear bomb test was cancelled due to the signing of the nuclear test ban treaty – so much for my priorities as a young adult. 

After my initial flirtation with chemistry, I was drawn to the kind of science that explains how things work at some fundamental level, which pretty much meant physics.  Ernest Rutherford, who discovered the atomic nucleus in 1911, has been quoted as claiming that “all science is either physics or stamp collecting.”  By this remark, he meant that most fields of science like geology, entomology, and botany are essentially concerned with giving names to things and classifying them into groups, not unlike what stamp collectors do.  Of course, Rutherford whose main work was during the early years of the twentieth century came before many revolutionary developments in many of the sciences that have transformed them into anything but mere classification schemes. 

Rutherford has also been credited with noting that “If you can’t explain your physics to a barmaid it is probably not very good physics.”   Apart from the sexism of this remark, I find myself more in synch with it than his barb about other sciences being merely stamp collecting.  While the mathematics of “good physics” may be abstruse, it is at its essence inherently simple.  During my boyhood early ventures into science, I also enjoyed taking things apart (non-explosively) to see how they work.  However, my efforts to reassemble the watch or other device I had taken apart usually were stymied, and I wisely concluded that I had better avoid the more practical field of engineering (my first major in college) in favor of physics.  Anyway, physics was a much better fit for me given my interest in understanding the “why” behind things, a matter of little concern to most engineers.  Physics is divided into subfields such as optics, atomic physics, and nuclear physics, with most physicists working entirely within one such area.  In my case that was particle physics, with my first foray into this field being the “two neutrino experiment,” when I was a second-year Ph D student at Columbia University.  This famous experiment established the existence of a second type of neutrino, and it resulted in Columbia Professors Leon Lederman, Melvin Schwartz, and Jack Steinberger later sharing the Nobel Prize.   Jack, who was my thesis adviser, had been at Columbia since 1950 after leaving the University of California at Berkeley, where despite his many achievements, he was told to leave for his refusal to sign a Non-Communist Oath.  Jack, never a Communist, always disliked conformity and being told what to do, whether in the political or religious realms. 


Loyalty Oath.  The “Red scare” era was one when many conservative politicians in the United States feared Soviet infiltration that might influence public opinion.  In 1950 the state of California passed a law that required all state employees to sign a loyalty oath that disavowed radical beliefs, specifically membership in the Communist Party or “any party or organization that believes in, advocates, or teaches the overthrow of the United States Government, by force or by any illegal or unconstitutional means.”   Several professors at the University of California resigned in protest or lost their positions when they refused to sign the oath.  Those who left in protest included three German Jewish refugees from Nazi Germany.  In total, the University Regents fired 31 faculty members who refused to sign the oath.  One of the fired faculty members, physicist David Saxon was later appointed President of the entire University of California system in 1975.


Raised in a Jewish family in Germany, Jack had emigrated to the U.S. in 1933 at age 13, one year after Hitler came to power.  Although identifying as Jewish, he once confessed to an interviewer “I’m now a bit anti-Jewish since my last visit to the synagogue, but my atheism does not necessarily reject religion.”  After getting a bachelor’s degree in chemistry and serving in the United States Army Signal Corps Jack did his graduate work under the great Enrico Fermi.  Ironically, Fermi like Steinberger also migrated to the United States after fleeing fascism in Europe, but in his case, the year was 1938, the same year he won the Nobel Prize, and the fascist dictator was Mussolini not Hitler.  At the time of this writing, Jack is still active in physics at the age of 98. 

The two-neutrino experiment was my first real research experience.  In contrast, many of today’s physics students engage in research while they are still undergraduates.  At the time, I had little appreciation for the importance of this experiment, and my role in it was relatively minor, as compared to that of the other three graduate students who worked on it.  Although my work on the experiment was insufficient to merit co-authorship of the paper reporting its results, I did get an honorable mention in it for my “computation of neutrino cross sections.”  Looking back now some 60 years later, I still fondly remember the many night shifts I took at Brookhaven Lab during experimental runs, in which I essentially served the role of a glorified baby-sitter.   I recall one night when Steinberger stopped by to inquire what I was doing, and I responded that I was watching the gauges on an instrument panel.  However, when confronted with his natural follow-up question of why I was doing that, I responded inanely that I would call someone if the readings changed significantly indicating a possible problem.

Despite the smallness of my role in the two-neutrino experiment, my involvement in it planted the seed that perhaps I too might someday follow my adviser Steinberger (and his adviser Enrico Fermi) to make an important discovery.   Physicists are usually divided into either experimentalists or theorists, with very few people able to make significant contributions in both areas – Fermi perhaps being one of the few notable exceptions.  It is interesting that Fermi essentially migrated from theory to experiment, because the seminal theoretical paper on his proposed new “weak interaction” was rejected by the prestigious journal Nature because “It contained speculations too remote from reality to be of interest to the reader.”  Fermi is also noteworthy because he was one of eight scientists whose rejected papers laid the basis for their later winning a Nobel Prize.   Fermi’s experience makes it easier for the rest of us to imagine that our rejected papers really were brilliant, and they were rejected merely because of the idiocy of a reviewer.  Alas, I must confess that in retrospect the rejections of my own papers were justified more often than I thought at the time.  Nevertheless, learning to cope with rejection, and knowing whether to modify or abandon a severely criticized approach are probably two of the most useful skills I have learned in a long career.

Looking back at the two-neutrino experiment it is remarkable that the 1962 paper reporting its results listed only seven physicists as authors.  In contrast, a major experiment in particle physics today might number a hundred or even a thousand times as many.  For example, the two teams that discovered the Higgs particle in 2013 included 3000 scientists on one team and even more on the other. If the Higgs boson has been called the God Particle, perhaps I may be forgiven for referring to tachyons as coming in “good” or “evil” varieties.  In their good variety, as occurs in the case of the omnipresent field associated with the Higgs particle, the imaginary mass tachyon creates an instability in the field after which the excitations so created spontaneously subside, resulting in no observed particles with FTL speed.  Such superluminal tachyons would be the “evil” variety, because they would violate some core physical principles and they would throw much of our current understanding of particle physics into chaos.  Some theorists have even claimed that the existence of such tachyons would spell doom for the whole universe because they could be created from the vacuum of space in pairs having equal magnitude positive and negative energy making the universe unstable.  Not surprisingly, most theoretical physicists have had little use for the FTL “evil” tachyon.  In the remainder of this book, the word tachyon refers to this FTL variety.


The Higgs boson aka the “God Particle” was suggested in 1964 by a group of particle theorists including Peter Higgs.  It has been colloquially called the God particle by Leon Lederman in a popular level book because it supposedly accounts for the nonzero masses of all other particles as they move through the Higgs field “molasses” that fills all space. The Higgs particle associated with the field lives for about 10-22 seconds, and it has a mass about 130 times that of a proton.  It was empirically found in a monumental effort at CERN in 2013.  Higgs and Francois Englert were awarded the Nobel prize for their prediction.

Pattern recognition and “black swans”

I do not consider myself a theorist, since I lack the needed deep mathematical knowledge, nor do I consider myself an experimentalist, since I was never that adept with hardware.  Rather my main contributions in physics have been in the realm of data analysis, and particularly in finding patterns in data that have been previously overlooked, sometimes even long after their publication.  Looking for patterns in data that others have overlooked can be very risky, since often patterns can be only in the eye of the beholder, which is what is normally meant by the colloquial phrase “seeing things.”  Two such examples from astronomy would include the infamous “canals” on Mars, and more recently the “face” on that planet’s surface, with both claimed by some Earthlings to be evidence for a Martian civilization.

Interestingly, the myth of Martian canals was, in part, the result of a linguistic fluke since the Italian astronomer Giovanni Schiaparelli used the Italian word canali meaning “channels” to describe the features he observed in 1877, but it was translated wrongly into canals.  These features were claimed to be very long and straight, and they were taken as evidence by some scientists for a Martian civilization, but they were essentially an optical illusion in an era before telescopic images were photographed.  There are, however, features on the planet’s surface that, while not created by Martians, were likely made by flowing water.  Until recently it was thought there is no longer water on Mars, but NASA announced in 2018 it had discovered evidence for a liquid lake under the south polar Martian ice cap.  In fact, once considered to be rare except on Earth, water is now believed to be prevalent on many bodies in the solar system, with Earth having only 2 to 4% of the total amount making the possibility of life in the solar system much more likely.

The much more farfetched “face” on Mars has been championed by far fewer legitimate scientists than Schiaparelli’s canals ever were.  According to the main proponent of the face being of artificial origin, Tom Van Flandern, it has only a 1% chance of being of natural origin.  Of course, humans are virtually programmed to see faces wherever they look, so this estimate cannot be taken seriously.  Calculating the probability that a random pattern resembling a face will be seen somewhere in all the areas of the Martian surface, or in all the clouds, or all the pizzas, or all the spilled milk one sees on the pavement can be a very tricky business.  Not surprisingly, higher resolution images of Mars later showed the area where the face was claimed to have no resemblance to a face.