* RSR's Light Speed Experiment Proposal: A 2019 article posted here at Real Science Radio (at rsr.org/stretch) proposed an experiment, Einstein, Lisle, and Hartnett notwithstanding, that just might enable the measurement of the one-way speed of light. Let's think through the following.
* Billions of Frames Per Second Cameras: The field of physics almost with one voice has maintained for over a century that the one-way speed of light cannot be measured and therefore that it cannot be shown to be equal to its roundtrip speed. Do high speed cameras require a reassessment of that long-standing claim?
* RSR's One-Way Speed of Light Series:
- Stretch Cosmology Pt. 1
- Veritasium, Lisle, and Light's One-Way Speed Pt. 2
- RSR's One-Way Speed of Light Experiment Proposal Pt. 3 (this show)
* A Fast Camera Proposal for a One-Way Measurement: RSR's asks whether 10-trillion FPS cameras (and Caltech's planned faster versions) might be used in a round-trip configuration to challenge the conventionality thesis and measure the one-way speed of light. Here's the concept for neutralizing that pesky 2-way speed of light problem...
* Light Speed in a Vacuum: To state the problem more fully, it's the one-way speed of light in a vacuum that can't be measured. Scientists at Cambridge and Harvard have slowed light down to 38 mph by shooting a laser through extremely cold sodium atoms, so it's relatively easy to measure that one-way speed. But this RSR experiment, especially its second iteration, through water vapor, will measure a speed so very close to the speed through a vacuum that the difference cannot falsify the primary results, that is, that it is possible to measure light's one-way speed! After all, there is no known perfect vacuum, not at CERN and not even in space. So if anyone wants to quibble they might as well argue that physicists have never measured even the roundtrip speed of light. For interestingly, even interstellar space is estimated to contain anywhere from a million molecules per cubic centimeter down to a thousand atoms per cubic meter.
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* Vacuum Rabbit Trail: The European Organization for Nuclear Research has bragging rights for their massive super-rarified ultra high vacuum that they compare to the vacuum in space as far away from Earth as the moon. One RSR caveat on that though. It just so happens that the Earth's atmosphere extends beyond the Moon. So that environment isn't as void of particles as many may expect. And that atmospher extension is another young-earth argument because it is one of scores of transient conditions and events in the solar system that could not long persist. And while we're on this rabbit trail, the more than 100 annual meteor showers caused by Earth flying through known streams of cosmic debris is evidence, directly observed by millions of people, that Earth orbits in a dusty region of space, whereas evidence only known to those who study the solar system tells us that as the asteroid belt is approached the estimated number of micrometeroites per cubic kilometer decreases significantly. So something, recently, dirtied up Earth's environment.)
* Light Speed in Milk and Stuff: RSR's proposed light speed experiment is performed first with the bottle filled with water and a splash of milk. The milk sufficiently increases the refractivity of the medium so that the laser's progress can be captured on video. The experiment is then repeated with the bottle empty except for some water vapor. The speed of light in a vacuum is:
- 50% faster than in glass
- 25% faster than in water, but only negligibly faster
- three hundredths of 1% than in air.
Of course the introduction of milk in the water, and even the water vapor alone, will reduce the speed of light through these mediums. But that reduction should be quantifiable and sufficiently minimal as to not prevent the one-way measurement of the speed of light (unless, as pointed out above, it is argued that the 2-way speed can never be measured).
* Photons Bouncing Off Photons: A laser pulse in a pure vacuum would only be detectable, it is believed, by a camera situated directly in the path of the beam. A camera aimed at the beam from off to its side would not detect the laser directly because there would be no matter to scatter the laser's photons such that some could be detected by that camera. If photons normally interacted with one another, a second beam of light could be emitted from a camera and bounce off the target beam to be videotaped, with the camera then recording the returning light signal. If that were possible, RSR argues that its light speed experiment configuration could still resolve the one-way speed question because the round trip of that second much shorter beam would be a negligible factor compared to the lengthier main axis of the laser beam's path. However, visible light photons rarely collide. There are known ways to cause them to collide and high energy photon-photon collisions do occur. Regardless of these particulars though, if this proposal gets to the attention of the scientists at CIT or CERN, perhaps they could arrange for this experiment to be conducted in an optimal configuration.
* No Sneakin' Around: The experiment above, first proposed on Sept. 3, 2019, avoids the kind of systematic error that evolutionists make when they "sneak" intelligence into their "natural selection" computer simulations. For example, we would discredit the results if we snuck the round-trip speed of light into the synchronization of the cameras themselves and used that very synchronization in the experiment. To avoid this, the experiment design does not rely on the cameras being synchronized. (And in any configuration, other than perhaps in a photon-to-photon collision mode, the results do not depend upon roundtrip optics to and from any individual camera.) Instead, we position the three cameras close enough to the laser beam so that any roundtrip optics in any configuration is insignificant compared to the lengthier transit of the laser through the bottle. That is, evaluate the results through a range of values for the speed of light to the camera as though it were half c up to infinite. If none of those values changes the overall result of the experiment, we did not sneak in c (as Röemer reportedly did in 1676 when he first measured lightspeed). As a beam transits the bottle, it will produce photographable scatter from the refraction off of the various materials filling the bottle. If the beam's transit to the bottom of the bottle is instantaneous, and it's return trip is at half of today's assumed speed of light, then the cameras' registering of the scatter will show a different number of frames between the outgoing and returning beam as they would if the outgoing and returning beams travel at the same speed on both legs of their round trip. The differences are quantified below. However, if the beam's transit to the bottom of the bottle is not instantaneous (and of course the cameras' frame rates are fast enough to capture this), it seems that the leading edge of the beam (or pulse) would come into view of each camera from the right boundary of its field of vision and, frame-by-frame, pass to left boundary (with perhaps ten frames showing its progress across a single camera's field of view). If this happens, a single camera could accomplish the goal of the experiment, as it alone could demonstrate that the light did not travel instantaneously on its outgoing journey. In this case, we could calculate light's one-way speed based on the width of the single camera's field of vision, the cameras frame rate, and the number of frames it takes to record the beam's journey across that field.
The three-camera configuration enables a different kind of measurement. The two additional cameras (above, numbered 2 and 3) along with a reflector at the bottom of the bottle might enable separate video recordings of both the outgoing and the return trips of the same beam. (If the single camera configuration provided any one-way speed measurement, this could also corroborate that result.) Regardless of whether the beam's one-way speeds are identical, camera #3 will be the first camera to record the beam's return trip. That last camera would then record fewer frames between the beam leaving its field of view and when it again reentered its field of view on its return trip. If sufficient frame rates enable this experiment to work, then the first camera, #1, will register the most frames separating it's initial recording and it's final recording of the laser's scatter. For example, consider if the camera operated at quadrillions of frames per second. Next, consider what could be learned if each camera captured on ten frames the refraction produced by the passing laser. Only to simplify this explanation of the experiment, assume that the cameras were positioned next to each other such that the beams entire journey would be captured on one or another camera. So when Camera 1 first registers the beam, we count 10 frames until the beam disappears. If the one-way speed of light is the same as its roundtrip speed, the camera will then have 40 empty frames until it begins to register the beam on it's return trip, and the data from that camera will end with its frames 51 to 60 showing the end of the laser's journey. In this circumstance, Camera #2 will not show 40 empty frames between its first and last registering of the scatter, but only 20 empty frames. Camera #3 will show no empty frames and the reflector, in this simplified explanation, would be positioned at the edge of that camera's field of view.
If the one-way speed of light is not the same as its roundtrip speed, and its speed on its initial leg is instantaneous, it is presumed that all three cameras would still register the scatter produced, although they would all be registering that refraction at the same time. (This would be an indirect way to synchronize the cameras, after the fact in the analysis of the data they record. A difference this would make as compared to the above discussion is that the light scatter registered by each camera's field of view would not show it moving from right to left, but that scatter would appear instantaneously horizontally across the camera's display and disappear instantaneously, and not from right to left.) Also in this case of an instantaneous outgoing one-way trip, the number of frames results from Camera #3 will be identical to what it would be if the one-way speed of light were the same as its roundtrip speed. Camera 3 will show ten frames of the outgoing leg immediately followed by ten frames of the return leg (although, there very well may be a difference in how the instantaneous leg registers the refraction as compared to the non-instantaneous leg, as just described). So Camera #3 in this experiment would not be able to distinguish, based on numbers of frames, between varying one-way and roundtrip speeds of light. Consider though Camera #2. Camera #2 would have only ten empty frames between its registering the beam on its outgoing and return trips. That is because Camera #2 would register the laser instantaneously with Camera #1, and would only have to "wait" the equivalent of the ten frames it takes for the light reflected to cross Camera #3's field of view. So the data from Camera #2 will end with its frames 21 to 30 showing the end of the laser's journey from its perspective. Consider then Camera #1. In this circumstance, Camera 1 will show 20 empty frames between its first and last registering of the scatter.
So compare the differences in the empty frames between registering the light's outgoing and return trips. If the outgoing trip is instantaneous, Camera #2 will have 10 empty frames and Camera #3 will have 20 empty frames. If the one-way speed of light is the same as its roundtrip speed, Camera #1 will have 40 empty frames and camera #2 will have 20 empty frames. The ratios in this configuration are the same. But by using differing configurations and by determing the actual number of frames it takes for the laser to traverse a single camera's field of view, the results could become definitive.
While a seemingly wild idea, quantum physicists can believe as many as six impossible things before breakfast. So, many would not be shocked if light behaved in the extraordinary way that Dr. Jason Lisle and Dr. John Hartnett propose. Regardless though, RSR makes the following prediction (which is merely what most physicists would expect). If the beam leaves a record of its travels on each of the camers, then considering the time that would pass between the beam leaving and then reentering each camera's field of view. RSR predicts that we could calculate the increasing number of camera frames (time) that pass, as we move from the last, to the middle, to the first camera, between the leading edge of the beam leaving the field of the camera's view (as it heads toward the bottom of the bottle) and reappearing on its return trip. And of course, if the camera frame rates are not fast enough to distinguish between the outgoing and return trips of the beam, then just get a faster camera or a much taller bottle.
Please send any comments to Bob@rsr.org. Thanks!
* On the One-Way Speed of Light Claim from Einstein and Creationist PhDs Jason Lisle & John Hartnett: The world of physics insists that the speed of light is known only from round-trip measurements. The context of this observation speaks generally of light in a theoretical vacuum or in space (which is a near vacuum). Hundreds of laser beam flashes aimed at the Moon demonstrate one example of this kind of measurement. 
These lasers strike the Apollo 15 retro-reflector base plate and then bounce back as researchers measure the time of the round trip, about 2.51 seconds. (These experiments, by the way, indicate that the moon is recessing from the Earth at more than one inch per year.) Long before these actual experiments, in Einstein's 1905 paper on special relativity he presented a thought experiment in space. "Let a ray of light depart from A... let it be reflected at B... and reach A again..." A page earlier he had described not the measurement of light's one-way speed but about, "establishing by definition that the 'time' needed for the light to travel from A to B is equal to the 'time' it needs to travel from B to A." Establishing this by definition instead of by measurement is referred to as doing this by convention. Regarding this Einstein continued, "We assume that this definition of synchrony is free from contradiction..." And we "assume the quantity... c to be a universal constant--the velocity of light in empty space." This Einstein synchronisation is sometimes abbreviated as ESC for the Einstein Synchrony Convention.
* Starlight & Time, the Conventionality Thesis, and Anisotropic Synchrony Convention: Agreeing with Einstein, the consensus view in physics is that no one has ever measured the one-way c but presents that speed as a convention, that is, an assumption, or, as Einstein wrote, even just a definition, also called the conventional unidrectional speed. By this widespread reckoning, it would not violate any actual measurement to propose that the one-way speed of light toward an observer (say, on Earth) can be infinite as long as the light reflected back travels at half c for the other leg of its roundtrip, producing an average speed of 186,000 miles per second. Creationist astrophysicist Dr. Jason Lisle, as supported by RSR friend and cosmologist Dr. John Hartnett, has used this to address the starlight and time challenge by claiming that light instantly arrives at Earth after being emitted from even the most distant galaxies. If so, of course that great distance would thereby be irrelevant to light's travel time to Earth and also to the age of the creation. Photons are both relativistic and elementary quantum particles. Einstein's theory of relativity and quantum mechanics both make so many counterintuitive observations that many who study these fields, we submit, would not be shocked if light behaved in this way. Drs. Lisle and Hartnett, with many others, argue that such anisotropy cannot be experimentally disproved, that is, that light cannot be shown to not have this different property when measured in different directions. Effectively agreeing with this, Grünbaum in his second enlarged edition of Philosophical Problems of Space and Time points out that "a choice... which renders the transit times (velocities) of light in opposite directions unequal cannot possibly conflict with... our descriptive conventions" (p. 366, emphasis in the original). With this Karlov agrees, regarding "the constancy of the speed of light... but other choices... are physically just as permissible" (Australian Journal of Physics, 1970 Vol. 23, p. 244, emphasis added). Various philosophers of physics though, and others, have proposed theoretical ways to test the one-way speed of light. Routinely then, the physics community responds by claiming these proposals include faulty assumptions that "sneak in" the roundtrip speed of light (in much the same way that computational evolution simulators "sneak" intelligence into their algorithms). For example, reasoning can be shown to be circular if an experiment assumes the constancy of the speed of light which is the very thing that it is designed to demonstrate. So this conventional unidirectional speed means that the 300,000 kilometers per second claimed universal speed limit has never actually been experimentally verified and is only an industry-wide assumption made to simplify the math (and to please our sensibilities). Some creation physicists have begun to argue therefore that, as believed by mankind's early scientists (from Aristotle to Descartes and beyond), and compatible with Einstein's theory of special relativity, and arguably, with all measurements made to date, the one-way speed of light from even the furthest galaxies to the Earth could be infinite.
If so, human beings would be seeing astronomical events unfold as they happen in a "real-time" universe and Adam would have seen the light from the stars made only two days before He was created, without any other supernatural or natural explanation needed. In 2010 Dr. Lisle proposed this Anisotropic Synchrony Convention (ASC) to answer the young-earth creationist's starlight and time question. This argument includes the claim, as boldly stated by Dr. Hartnett in 2019, that "there can be no experiment that can refute the conventionality thesis", such that no one can even theoretically devise a way to demonstrate that the one-way speed of light equals the roundtrip speed. What follows are four proposed methods to demonstrate that the one-way speed of light approximately equals the roundtrip speed, the first three having already been performed, which we use to address the Einstein's Synchrony Convention. And the fourth experiment, not yet performed but here proposed, which addresses Lisle's ASC.
* Did this 2019 Laboratory Video Measure the One-Way Speed of Light? Through water, light travels 25% slower than through a vacuum, at 225,000 kilometers per second rather than 300,000. At rsr.org/asc#camera (and just below) see a 2019 video made at CIT using a 100 billion frames per second (FPS) camera. At 4:33 (see the screenshots, just above) a laser beam is shot through a bottle of water with a bit of milk in it. The milk increases the amount of photon scatter produced by refraction to make the beam's progress easier to capture on video. (The milk of course would also further slow down the light.) Amazingly Caltech's two cameras, the fastest in the world, one with a maximum rate of 10 trillion frames per second, are able to capture light in progress in its one-way transit. The clip referenced was filmed using the slower of the two cameras and yet it captures the laser beam's one-way journey through the bottle!
One of the philosophy of science books by award-winning physicist Max Jammer, who was personally acquainted with Einstein at Princeton, is directly on our topic, Concepts of Simultaneity: From antiquity to Einstein and beyond. Written thirteen years before the fast-camera light-in-the-bottle recording, Jammer concluded that the conventionality thesis remains an open question, and thus, whether the one-way speed of light can be measured may seem theoretically impossible, but it might just be that we haven't figured out how to do it.
Thus according to this Berlin-born Israeli physicist who became close to Einstein, as of 2006, no experiment had falsified a potentially infinite one-way speed of light. But Jammer, who passed away in 2010, never saw this 2019 Caltech bottle video.
The astounding technical achievement of the CIT researchers has been popularized by YouTube's The Slo Mo Guys. (We've previously utilized two of their videos in our answer to creationist Michael Oard to explain why there is a linear crack, called the mid-oceanic ridge, that circles the Earth like the seam on a baseball.) The March 17, 2019 Slo Mo Guys' video is called Filming the Speed of Light at 10 Trillion FPS. The slower of CIT's two fastest cameras used to "film" the "bottle" segment of their video was operating at 100 billion FBS, that is, each frame equaled 10 picoseconds (ten trillionths of a second) and it took about 2,000 picoseconds (two billionths of a second) for the light to travel through the length of the bottle. On our Real Science Radio program my co-host Fred Williams and I briefly discussed this and argued that this video may have measured the one-way speed of light.
A second measurement appears at 5:40 into the same video. At the same 100 billion frames per second, the CIT technician recorded light bouncing around inside of a water-vapor filled mirrored device they call a chaotic cavity. (See image, left.) Light propagates in a vacuum only three hundredths of 1% faster than it travels through "air". (On average, about two percent of the molecules in Earth's atmosphere are water vapor, and "for applications with less than five digits of accuracy, the index of refraction of air is the same as that of vacuum...") So the light beam in this cavity traveling through nothing but air and water vapor must be traveling at very close to the speed of light in a vacuum. The videotaped light pulse bouncing around within this chamber demonstrates that it travels at no discernable difference in its speed in any direction, including when it bounces back and forth essentially in a "roundtrip" pattern. It certainly never appears to have moved at infinite speed by disappearing and instantly popping up across the chamber. Prof. emeritus Michael Tooley from the University of Colorado, argued in his 2000 Time, Tense, and Causation that the many attempts to measure the one-way speed of light had all failed. And of course that too was concluded before Caltech researchers made possible this 2019 Filming the Speed of Light video. (We would be remiss in not warning the public, and the professor himself regarding the horrific consequences in this life, and eternally, about his vile arguments in defense not only of killing unborn children but also in Tooley's denial even that newborn babies have a right to life.)
The third measurement appears at 10:50 into the video using Caltech's fastest camera. A researcher records at ten trillion frames per second a pulse of light traveling about ten millimeters through a milky vile. (See image, right.) See that segment of the video also at rsr.org/asc#camera (or just click play here):