Light velocity at zero degrees Kelvin was examined. Major results of previous reports were replicated  . First, light speed was zero at low vacuum energy (1-state bit) densities. That is, the hypothesis that the lowest vacuum densities are opaque to light transmission  was confirmed with improved measurement methods. Second, light speed decreased from its maximum velocity as energy density decreased. Third, light velocity was approximately equal to 1/π in bit velocity units , where bit velocity is d/t and d and t are the quantized fundamental length and time constants respectively. These results (1) change the status of Einstein's Special Relativity statement of constant light speed c in a vacuum independent of signal source velocity from postulate to known mechanism and (2) limit the vacuum density range in which light speed c may, in fact, be constant  and (3) highlight issues in light speed measurement methods.
Methods and Results
Legend: Bit density: energy (1-state bit) density as proportion of maximum possible energy density. Light speed expressed in bit velocity units.
Zero Kelvin Input System States. In a previous study , system states in 48x48x48 spot volumes at zero Kelvin were prepared and saved as *.mat files with the Binary Mechanics Lab Simulator (BMLS) v1.38. The 23 saved zero Kelvin system states ranging from approximately 0.07 to 0.20 bit densities were examined and found to contain zero electromagnetic (EM) radiation and zero particle motion (kinetic energy). An objective of the present study was to measure light velocity c. Hence, the present study used these 23 files as initial states hoping that measurement accuracy might be improved if there was initially no particle motion or EM radiation that might interfere with light signal transmission.
In each velocity test, (1) a zero Kelvin file was loaded, (2) the VSUF (default) bit operations order  was chosen, (3) a run limit of 150 BMLS Ticks was entered, (4) during the first display (Tick = 0), the "3" key was pressed to select Experiment 3 , and (5) during the second display (Tick = 1), the "b" key was pressed to turn off Box Mode. Optionally, during the Tick = 2 display, the "x" key may be pressed to change to X-Ray display.
BMLS Experiment 3. In step 4 above, Experiment 3 enables Box Mode (turned off in step 5 above) and the left-pointing bit gun for 21 BMLS Ticks (the duration of one proton bit cycle). With the simulated cubic space dimension of 48 spots, 6048 1-state bits are fired into the simulated volume on the right side (21 Ticks x 242 / 2). Bit detectors on the left side of the simulated cube recorded signal arrival (*xL variable in output *.cvs).
Light Speed Calculation. *xL vs Tick plots show the Tick at which the first bit(s) arrive at the detectors (Onset Tick) and the Tick at which the arriving waveform peaks (Peak Tick). In this report, the average of the Onset and Peak Tick values was the light travel time (see Figs. 3 and 4). Distance traveled was 96d (2d x 48 spots). Time elapsed was travel time in BMLS Ticks x 4t per Tick. Light velocity was then expressed in bit velocity units: 96d / (4t x travel time in Ticks).
Light Transmission Requires a Minimum Vacuum Energy Density. Fig. 1 summarizes results for the 23 tests. Each point is one test except the far right point which is the average of 7 tests with similar initial state bit densities (0.194 to 0.196). For the distance and signal intensity used, no light transmission was detected below about 0.124 vacuum density. Starting at 0.124 density, the signal was detected with velocities increasing almost linearly and peaking at about 0.180 density.
Legend: Bit density: energy (1-state bit) density as proportion of maximum possible energy density. Light speed expressed in bit velocity units. Far right point is mean and SEM of N = 7 tests.
Light Speed Equals 1/π in Bit Velocity Units. Fig. 2 shows detail of data on the right in Fig. 1. As mentioned above, the far right point is the mean and SEM of 7 tested initial states (input files). The observed velocity was not significantly different from the predicted velocity of 1/π . The one-sample t = (0.31822 - 0.31831) / 0.00140 = -0.06429. That is, the measured velocity equaled 1/π within about 3 parts in 10,000 with a very small N = 7 with average initial density of 0.195.
Three tests showed higher velocities in the 0.165 to 0.180 density range. Four tests showed lower velocities in the 0.124 to 0.148 density range. From the velocity peak at 0.180, light speed decreased almost linearly to the lowest value at 0.124 density.
Tick Travel Time Raw Data. Fig. 3 plots the signal travel time Tick counts -- Onset Tick, Peak Tick and their Average. Of course, for slower velocities, the Tick counts increase. The three Tick counts -- Onset, Peak and Average -- converge at lower initial bit densities where much fewer bits from the signal source arrive at the bit detectors.
Legend: Onset (blue), Peak (pink) and Average (yellow) Tick counts vs initial bit density.
Pilot Study Results Confirmed. The present report replicates with improved methods the general results of a pilot study on light velocity c . First, the prediction that absolute vacuum is opaque to light transmission  was confirmed again. Indeed, for the travel distance and vacuum energy densities used, no signal was detected below 0.124 bit density. Second, the speculation that light velocity c equals 1/π in bit velocity units  was further supported by the present data, repeating previous results  . Third, the Special Relativity postulate of "constant light speed c in a vacuum" is partially supported, but with severe limitations regarding applicable vacuum energy density range.
The previous and present data appear to indicate that the time-development laws (bit operations)  and fundamental constants d and t of binary mechanics  determine light velocity c. This interpretation is equivalent to the first-ever calculation of light velocity c from postulates of a coherent, comprehensive, fundamental physical theory and its basic constants.
Improved Methods. Compared to the pilot study, the present method included a greater distance, a signal source where intensity and duration can be exactly quantified, and zero Kelvin initial states without EM radiation and particle motion which could interfere with the experimental signal transmission. Hence, some key results could presumably be obtained with less noise and greater precision. What could be more precise than the ability to detect a single 1-state bit, the smallest unit of energy?
New Results. Perhaps the major new result was that light transmission and velocity properties were basically the same at zero degrees Kelvin compared to much higher temperatures in the pilot study. In addition, the present methods and results highlight a potentially important question: which velocity measurement (e.g, Onset, Peak or Average) is the "real" light speed c?
Will the Real Light Speed Please Stand Up? Which velocity in Figs. 2 and 3 is the correct light speed?
1. The decreased velocities at and below 0.148 bit density in Fig. 2 are thought to reflect a delay in which signal bits "fill the vacuum" to raise its density to support light transmission. As a result, observed velocity is decreased as well as detected signal intensity. This phenomenon was cited as a possible mechanism for some red shifts in signals from distant cosmological objects where light might travel through possible vast lower vacuum density regions of outer space, which might put expanding universe questions back on the table .
2. Is the peak velocity at 0.180 density the real light velocity? If so, then the slower light speeds above 0.18 density might represent refraction as light passes through denser materials. On the other hand, the time-evolution laws of binary mechanics predict faster-than-light bit motion  . Under certain conditions, an accelerated speed would most probably be seen naturally only over relatively short distances, which would include the present data. If this prediction is correct, then it may provide the mechanism for the apparently faster-than-light Onset Tick counts in Fig. 3. Consistent with this possibility, Fig. 4 shows 5 bits over 3 Ticks arriving early before the apparent arrival of the main wave front. Thus, in this test, the Onset Tick count may be seen as distorted by a few instances of faster-than-light bit motion, maybe by 3 or even more Ticks less than it would otherwise have been. This would artificially boost the calculated velocity based on the average of Onset and Peak Tick counts.
3. In this context, it might seem amazing that the CODATA value for light speed c is said to be "exact" . If binary mechanics is the first to propose that light velocity can be calculated from first principles, then this "exact" value must be based on empirical measurements. What exactly has been measured? Let us assume that signal detectors are not sensitive enough to detect a single 1-state bit. If this is correct, then what was detected to measure light speed? It is fair to say that light detector sensitivity in terms of 1-state energy quanta is unknown. So how many bits is required for a lab photon detector to generate a output? Also unknown. In any case, Fig. 4 may illustrate an instance of the real appearance of a photon, compared to the cartoon-like images in most physics literature.
Special Relativity Update. The pilot and present data suggest some updates to Einstein's postulate that light speed c in vacuum is constant, as discussed previously in some detail . First, as vacuum energy density decreases, light speed slows and is essentially zero at the lowest densities. That is, absolute vacuum is opaque. Strictly speaking, these results are a major violation of the constant light speed postulate. Thus, further work is required to specify more clearly the energy density range in which light speed is constant, if such exists. Second, these data appear to change the status of light velocity c from a postulate to a known mechanism detailed in the time-evolution laws by which light energy travels through space.
Finally, these results exclude any physical theory that depends specifically on constant light speed c in vacuum, regardless of vacuum energy density. Further, future investigations might better speak of some more physically correct description of the constant, such as fastest light speed or light speed based on waveform peak or light speed at a benchmark energy density.
 Keene, J. J. "Light speed amendment" J. Bin. Mech. March, 2015.
 Keene, J. J. "Binary Mechanics Lab Simulator update" J. Bin. Mech. December, 2015.
 Keene, J. J. "Physics glossary" J. Bin. Mech. May, 2011.
 Keene, J. J. "Intrinsic electron spin and fundamental constants" J. Bin. Mech. January, 2015.
 Keene, J. J. "Zero degrees Kelvin" J. Bin. Mech. January, 2016.
 Keene, J. J. "Bit operations order" J. Bin. Mech. May, 2011.
 Keene, J. J. "Fundamental forces in physics" J. Bin. Mech. October, 2014.
 Keene, J. J. "Expanding universe questions" J. Bin. Mech. April, 2015.
 Keene, J. J. "Physics news: faster than light" J. Bin. Mech. September, 2011.
 Keene, J. J. "Faster than light" J. Bin. Mech. January, 2016.
 NIST CODATA "Fundamental physical constants -- complete listing"
© 2016 James J Keene