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Advanced Waves Detected

by John G. Cramer

Alternate View Column AV-219

Keywords: advanced waves, Wheeler-Feynman, back in time, absorption deficit

Published in the July-August-2022 issue of Analog Science Fiction & Fact Magazine;
This column was written and submitted 03/07/2022 and is copyrighted ©2022 by John G. Cramer.
All rights reserved. No part may be reproduced in any form without
the explicit permission of the author.


One of my earliest Alternate View columns, published in the August-1985 Analog, described advanced electromagnetic waves, which are light waves that carry negative energy and travel backwards in time.  Now there is evidence that such time-reversed advanced waves have actually been detected.

Let's begin with the electromagnetic wave equation (EMWE), a simple equation involving space and time second-derivatives that describes light itself.  Being 2nd-order, it has two independent solutions.  One solution (called the retarded solution) describes the behavior of ordinary light.  Retarded light waves travel through space with a speed of exactly c=299,792,458 meters/second, carry positive energy, and traverse a given distance in a positive time.  For example, when an ordinary retarded light wave travels one light-year, it arrives one year after it starts.

However, the EMWE also has a second solution, called the advanced solution, describing a kind of light wave that also travels at c but carries negative energy and traverses a given distance in a negative time.  An advanced-wave flashlight would charge its battery as it produced its beam.  An opaque object absorbing the advanced-wave light would lose energy and become colder.  And an advanced wave traveling one light-year arrives one year before it starts.  Physicists usually discard this advanced solution as "unphysical" or "violating causality".  That choice destroys the intrinsic time-symmetry of electromagnetism, building into it a gratuitous "arrow of time" (but they do it anyway.)

In the 1940s young Richard Feynman and his PhD supervisor John Wheeler decided to take the advanced solution seriously and to use it to formulate a new electromagnetism, now called Wheeler-Feynman absorber theory (WF).  WF assumes that an oscillating electric charge produces advanced and retarded waves with equal strengths.  However, when the retarded wave is subsequently absorbed (in the future), a cancellation occurs that erases all traces of the advanced waves and their time-backwards "advanced effects".  WF gives results and predictions identical to those of conventional electromagnetic theory.  However, if future retarded-wave absorption is somehow incomplete, WF suggests that this absorption deficiency might produce experimentally observable advanced effects.

Experimentalists have looked for WF advanced effects.  In 1973, radio astronomer Bruce Partridge attempted to detect experimentally a cosmic absorption deficit of 3-centimeter-wavelength microwaves as an advanced effect.  He hypothesized that such a deficit should inhibit initial microwave emission.  He precisely measured the input power to a microwave source, looking for changes that depended on whether its output radiation was pointed at a local absorber or into free space perpendicular to the galactic plane (presumably a low-absorption direction.)  A related experiment, also using 3-centimeter microwaves, was performed in 1980 by J. F. Schmidt and his thesis supervisor Riley Newman.  They looked for "early" signals in a downstream dipole antenna intended to detect uncancelled advanced microwave pulses emitted by their transmitting antenna.  Neither experiment detected any indication of advanced waves.  Thus, for 35 years the issue of the existence of advanced electromagnetic waves seemed to be settled: there were none.

That changed when a 2015 Physical Review D paper by Niknejadi, Madey, and Kowalczyk (NMK) addressed the nagging problem that conventional electrodynamics fails to accurately predict observations of the radiation of coherently oscillating electrons in a free-electron laser, particularly when radiating into free space.  The authors found it necessary to revive the WF assumption that an oscillating electron radiates advanced and retarded waves with equal amplitudes.  They found that the WF approach resolved many problems encountered in conventional electrodynamics (which ignores advanced waves).

NMK also proposed a new experiment to detect advanced effects.  They suggested redoing the Schmidt-Newman experiment, but with a much smaller downstream antenna.  Their calculations showed that if the downstream antenna length is comparable to the emitted wavelength, no advanced signal should be observed.  However, if the downstream antenna length is reduced to 1/10 to 1/20 of a wavelength (reducing absorption), an early-arriving advanced-radiation signal should be observable.

Inspired by the NMK predictions, retired Croatian military electronic-surveillance specialist Darko Bajlo mounted a search for advanced radiation using pulsed radio waves with wavelengths of 0.91 to 2.00 meters.  He mounted a 1/20 wavelength monopole antenna at distances D of 3 to 10 meters downstream from the transmitter and elevated so that the two-antenna axis pointed 10° above the horizon.  (Aiming above the horizon shrinks the long tangential path through Earth's atmosphere, thereby reducing absorption by atmospheric dust and water vapor.)

At first, on humid summer days Bajlo found no detectable advanced signals.  Suspecting atmospheric absorption, he did new measurements on cold clear dry days, performing 500 runs between December 3, 2016 and January 5, 2017.  He made the observations as the Earth rotated and the antenna axis swept across the galactic center, where wave-absorption variations might occur.

In a number of these measurements, he observed strong advanced signals (6.94 to 26.5 standard deviations above noise) that arrived at the downstream antenna a time 2D/c before the main transmitted pulse signal.  He explored the effects on the signal strength of lowering the antenna angle, increasing its length to 1/10 and 1/6.7 of a wavelength, or increasing the downstream distance to 18 meters.  These variations all decreased the advanced-signal amplitude.  Variations in the advanced-signal amplitude as the antenna axis swept across the galactic center were also observed.  The amplitude was reduced up to 50% of off-center maximum when pointed directly at the galactic center (where more absorption is expected.)

These results constitute a credible observation of advanced waves.  However, Bajlo's results are presented only in a 7-page 2017 online report and have never been published in a refereed journal.  One US investigator with good equipment has been unable to reproduce these results.  Bajlo's observations have, however, been reproduced by Julius Madey, whose late brother John was co-author of the NMK publication.  Madey reports that with his own apparatus he has observed several advanced-wave detection events that corroborate Bajlo's results.  His results are also unpublished.

Strictly speaking, the rules of the physics community concerning what constitutes the valid observation of a new phenomenon (a 5-standard-deviation effect, adequate account of statistical and systematic errors, publication in a refereed physics journal, reproducibility by independent investigators, compatibility with theory) have not been fully met by Bajlo's observations.  Nevertheless, they constitute a compelling case that advanced electromagnetic waves may actually exist and have been observed.  This has interesting implications.

First, this suggests that "standard" classical and quantum treatments of electrodynamics that reject advanced waves and advanced potentials are leaving out an important aspect of Nature and, at some level, are therefore wrong.  Second, theoretical work like WF electrodynamics and my own transactional interpretation of quantum mechanics, which do include advanced waves, should be taken much more seriously.  Third, the advanced-wave signal depends on an absorption deficit along the antenna axis.  That means that one could map the universe, as Bajlo has made a start at doing, by accurately measuring the microwave-absorption deficit in each sky-pixel, thereby creating a new branch of radio astronomy.  And finally, the observation of advanced waves indicates cracks in the seemingly impenetrable armor of that least-well-understood law of physics, the Principle of Causality.

Bajlo observed an advanced 1.67-meter radio-wave pulse in the 1/20 wavelength antenna 4.30 meters downstream from the emitting antenna.  It appears on his oscilloscope screen with about half the amplitude of and 28.6±0.2 nanoseconds before the main pulse from the transmitter.  The main light-speed pulse takes about 14.3 nanoseconds to reach the downstream antenna.  This means that the advanced signal was detected in the downstream antenna 14.3 nanoseconds before the transmitter actually transmitted the pulse!  The downstream antenna observed a pulse from 14.3 nanoseconds in the future.  Note also that Bajlo's transmitted waves will not reach the galactic center's region of incomplete absorption for another 26,000 years, yet the signal indicating that partial absorption will happen there was observed even before the pulse was transmitted!

Pulses from the future are certainly intriguing, but 14.3 nanoseconds is a very short time.  Could that be increased to milliseconds or even minutes?  What about simply making the transmitter-to-antenna distance much longer?

That probably wouldn't work.  Bajlo increased the downstream antenna distance from D=4.3 to 18 meters and observed advanced pulses arriving 60 nanoseconds before transmission with about 14% (instead of 50%) of the main pulse amplitude.  This reduction in relative amplitude with increased distance suggests that attempting a much larger time-advance by greatly increasing D would make the advanced signal undetectably small.

However, perhaps large time-advances could be achieved by "daisy chaining".  Suppose we made a triggerable Bajlo-type radio-pulse generator, re-triggerable every 500 nanoseconds or less.  It beams pulses to a mirror 7.5 meters downstream, where they are reflected back past a 1/20 antenna (close-to but shielded-from the transmitter), then reflected out into space.  The 1/20 antenna should detect an advanced signal 50 nanoseconds before transmission.  Now construct 20 such identical units, arranged in a circle for minimum interconnect delays, with each unit triggering the next with its advanced signal.  The advanced signal at the 20th unit will precede the initial trigger by 1.0 microseconds.

Now suppose that a trigger-counter in unit #1 permits triggering except when it reads <1 or >1,000,000.  Now route the advanced signal from unit #20 back to trigger unit #1.  The result should be that the earliest advance signal from unit #20 (counter=0) will occur one second before the initial trigger (counter=1,000,000)!

I'm told that with modern high-speed electronic trading, anticipating stock-market fluctuations by even a few milliseconds could be extremely profitable.  Information time-travel paradoxes are also easy to construct.  I will leave it to the reader to consider other applications, implications, and paradoxes.

In summary, it appears that advanced waves do exist and have been detected.  Much more work must be done to ensure that this effect is real and can be extended, but the physics implications are gigantic.

Remember that you saw this advanced information first in this column.

John G. Cramer's 2016 nonfiction book (Amazon gives it 5 stars) describing his transactional interpretation of quantum mechanics, The Quantum Handshake - Entanglement, Nonlocality, and Transactions, (Springer, January-2016) is available online as a hardcover or eBook at: or

SF Novels by John Cramer:  Printed editions of John's hard SF novels Twistor and Einstein's Bridge are available from Amazon at and .  His new novel, Fermi's Question is coming soon from Baen Books.

Alternate View Columns Online: Electronic reprints of 219 or more "The Alternate View" columns by John G. Cramer published in Analog between 1984 and the present are currently available online at: .


Wheeler-Feynman Absorber Theory:

    J. A. Wheeler and R. P. Feynman,  "Interaction with the absorber as the mechanism of radiation," Reviews of Modern Physics 17 157 (1945); and "Classical electrodynamics in terms of direct interparticle action," Reviews of Modern Physics 21 425 (1949).

The Partridge Experiment:

    R. B. Partridge, "Absorber Theory of Radiation and the Future of the Universe", Nature 244 263 (1973).

The Schmidt-Newman Experiment:

    J. D. Schmidt and R. Newman, "A search for advanced fields in electromagnetic radiation," Bull. Am. Phys. Soc. 25 581 (1980); and J. D. Schmidt, PhD Thesis, UC Irvine, (1980).

The NMK Calculation:

    P. Niknejadi, J. M. J. Madey, and J. M. D. Kowalczyk. "Radiated power and radiation reaction forces of coherently oscillating charged particles in classical electrodynamics," Physical Review D 91 096006 (2015); LINK.

The Balilo Experiment:

    D. Bajlo, "Measurement of advanced electromagnetic radiation", (preprint), 16 January 2017;

The Transactional Interpretation of Quantum Mechanics:

    John G. Cramer, The Quantum Handshake - Entanglement, Nonlocality, and Transactions, Springer: Berlin/Heidelberg, Germany (2016); ISBN 978-3-319-24640-6;
"The Transactional Interpretation of Quantum Mechanics", Rev. Mod. Phys. 58, pp. 647-687 (1986) LINK, and
"The Arrow of Electromagnetic Time and the Generalized Absorber Theory", Foundations of Physics 13, 887 (1983) LINK

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