Method for measuring retarded light through very long baseline interferometry and natural or artifical diffraction effects

Methods are provided for measuring retarded light that takes longer than x/c time to travel through a vacuum to a detector x distance from the source. The method exploits the frame invariance of in vacuo light speed c and the quantum mechanical nature of photons. It includes placing instrumentation packages consisting of detectors, broadband recording devices and atomic clocks at large distances from each other and from the source of an electromagnetic signal, such that the detectors are located at the extreme sidebands of light that has been diffracted by natural or artificial processes. The data are combined and analyzed using the standard techniques of very long baseline interferometry. This method is useful for providing on the order of a half minute of extra data from the past for distant astronomical events. The method is also useful for providing on the order of tenths of microseconds of extra data from the past for electric meteorological events.

TECHNICAL FIELD 
The present invention relates generally to methods for measuring 
electromagnetic radiation that has taken longer than x/c time to travel 
through a vacuum to a detector x distance from the source (retarded 
light). More particularly the present invention relates to the combination 
of very long baseline interferometry and natural or artificial diffraction 
effects to measure in vacuo light that has traveled an extra distance to 
the detector at the frame-invariant speed c. 
BACKGROUND OF THE INVENTION 
Any imaging device detects past events due to the finite speed c of light 
in a vacuum. Astronomers necessarily detect light from events in the 
distant past because of the great distances light must travel from a star 
to a detector on or near the Earth. Some science fiction authors, such as 
Isaac Asimov, have imagined cameras capable of photographing events that 
occurred in the Earth's distant past without being at a significant 
distance from the Earth. Of course, these authors attempt no explanation 
of how such a camera would work. The present invention can at least image 
events in the relatively recent past. This would be useful for many fields 
of research. 
Suppose, for example, that at a particular point in time astronomers on 
Earth see a new supernova begin to explode. If we could see the star even 
a half minute before the explosion were noticeable on Earth, it could be 
useful in elucidating the stellar processes that lead to supernovae. Or 
suppose meteorologists could see what was going on in a thunderhead two 
tenths of a microsecond before a lightning discharge of that same duration 
began. This could be instructive in modeling the complex processes that 
occur during lightning bolts. 
The measurement of such retarded light is made possible by the following 
proven principles, all of which are well understood by those in the art: 
1. The speed of light c in a vacuum is frame independent. This, for 
instance, alters temporal durations for moving and stationary observers. 
2. Unlike massive particles, quantum mechanical particles, including 
photons, do not have classical trajectories but instead have a probability 
density current. Due to the increasing uncertainty product .DELTA.p.sub.x 
.DELTA.x between momentum p.sub.x and position x,p.sub.x fixed, any wave 
packet broadens in coordinate space as time progresses. A 0.22 caliber 
bullet, for instance, is localized to 0.1 millimeter and can maintain its 
shape in coordinate space for about 10.sup.24 seconds. But an electron 
localized to an angstrom retains its form for only about 10.sup.-16 
seconds. 
3. The bands in a diffraction pattern reflect the amplitude of the light 
wave in various regions of space and, as such, reflect the probability 
.vertline..PSI.(x, t.vertline..sup.2 of detecting a photon in that region. 
4. The outcome of a quantum mechanical experiment can be determined by the 
way we prepare a measurement. If, for example, we use any means to 
determine which of two slits in a double-slit diffraction experiment a 
particle moves through, then the double-slit diffraction pattern will 
vanish. 
Consider the diffraction pattern shown in FIG. 1. The high-amplitude 
central-band photons travel to the detector in time 
EQU t=.tau.+.DELTA.x/c, (1) 
where .tau. is the light travel time to the diffraction slit. If the speed 
c were not frame invariant, the low-amplitude sideband photons, many 
wavelengths out from the central band at distance .DELTA.y, would travel 
at a higher speed to catch up to the central-band photons, as in 
Bernoulli's principle. However, since c is frame invariant, the sideband 
photons must travel to the detector in time 
EQU t'=.tau.+(.DELTA.x.sup.2 +.DELTA.y.sup.2).sup.1/2 /c, (2) 
such that the difference in travel times is, 
EQU 0&lt;.DELTA.t=t'-t=(.DELTA.x.sup.2 +.DELTA.y.sup.2).sup.1/2 
-.DELTA.x!c.sup.-1. (3) 
It is apparent from equation (3) that for the delay .DELTA.t in travel 
times to be significant for the scale of the experiment, .DELTA.y must be 
more than a small fraction of .DELTA.x. If we have .DELTA.x=.DELTA.y, for 
instance, then .DELTA.t has the same order of magnitude as .DELTA.x/c, 
EQU .DELTA.t=(.sqroot.2-1).DELTA.x/c. (4) 
This means that retarded photons will be in the extreme sidebands, and will 
have low amplitude and a low probability of detection. However, we can 
compel detection of the retarded photons by placing a pair of detectors at 
those sidebands and nowhere else. Of course, this will destroy the 
diffraction pattern. But it will not alter the position where the photons 
are detected; thus, equation (3) will still hold. In other words, this 
placement of the detectors is equivalent to blocking off the imaginary 
middle segments that become the source for secondary wavelets when a wave 
crest passes through a diffraction slit. 
BRIEF SUMMARY OF THE INVENTION 
It is apparent from equations (3)-(4) that for the delay .DELTA.t in travel 
times to be significant for the scale of the experiment, .DELTA.x/c must 
have a significant magnitude. It is, therefore, an objective of the 
present invention to detect naturally diffracted or artificially 
diffracted photons at extreme sidebands over long distances. Due to the 
inverse square law, this requires detecting light that has a very low 
luminous intensity. A proven technique for achieving this objective is 
very long baseline interferometry (VLBI). 
Radio astronomers use VLBI to detect ultra-low intensity signals with 
resolutions on the order of 10.sup.-3 arc-second, equivalent to resolving 
a basketball on the moon. The data from the distant detectors has to be 
recorded on broadband tapes and analyzed off-line. An atomic clock is used 
with each detector to synchronize the data for coherence and can produce 
synchronization somewhat better than 10.sup.-6 second. Of course, radio 
astronomers are already detecting light from the past in that have 
traveled far from its source. For that very reason, the routine use of 
VLBI does not detect past light in the sense of equation (2). VLBI dish 
antennas are typically thousands of kilometers apart, which is an 
insignificant distance when the source of the radiation is light years 
away. The novelty of the present method is in using the techniques of VLBI 
for purposes of equation (2) so we can detect past light from a relatively 
close distance. 
One particular objective of the present invention is to detect retarded 
light that has been diffracted through natural processes by placing two or 
more VLBI type instrumentation packages at the extreme sidebands of the 
light. Another objective is to detect retarded light that has been 
artificially diffracted by placing two or more VLBI type instrumentation 
packages at the extreme sidebands produced by a diffraction device that 
selects monochromatic wavelengths from naturally occurring light with 
source slits and lenses. 
The foregoing has outlined some of the more pertinent objects of the 
present invention. These objects should be construed to be merely 
illustrative of some of the more prominent features and applications of 
the invention. Many other beneficial results can be attained by applying 
the disclosed invention in a different manner or by modifying the 
invention. Accordingly, other objects and a fuller understanding of the 
invention may be had by referring to the following Detailed Description of 
the preferred embodiment.

DETAILED DESCRIPTION 
By way of brief background, it is well known that the speed of light is 
frame invariant. Yet, the effect of this on diffraction is not obvious 
until after it has been disclosed. Whereas dispersion and refraction arise 
from a refractive index larger than unity, diffraction through a vacuum 
also alters the path of light but must do so with a transformation of 
time, just as when an observer is in motion. 
FIG. 1 is a schematic representation of the diffraction of light. The 
high-amplitude central-band photons from the source 10 travel to the 
detector in time 
EQU t=.tau.+.DELTA.x/c, (1) 
where .tau. is the light travel time to the diffraction slit 20. If the 
speed c were not frame invariant, the low-amplitude sideband photons 30, 
many wavelengths out from the central band 40 at distance .DELTA.y, would 
travel at a higher speed to catch up to the central-band photons, as in 
Bernoulli's principle. However, since c is frame invariant, the sideband 
photons must travel to the detector in time 
EQU t'=.tau.+(.DELTA.x.sup.2 +.DELTA.y.sup.2).sup.1/2 /c, (2) 
such that the difference in travel times is, 
EQU 0&lt;.DELTA.t=t'-t=(.DELTA.x.sup.2 +.DELTA.y.sup.2).sup.1/2 
-.DELTA.x!c.sup.-1. (3) 
It is apparent from equation (3) that the delay .DELTA..tau. in travel 
times will be significant for the scale of the experiment when .DELTA.y is 
more than a small fraction of .DELTA.x. If we have .DELTA.x=.DELTA.y, for 
instance, then .DELTA..tau. has the same magnitude as .DELTA.x/c, 
##EQU1## 
It is well known that the various amplitudes of the various bands in the 
diffraction pattern reflect various probabilities of detecting a photon in 
that region. Photons for which .DELTA..tau. is significant in equation 
(3), that is, retarded photons, will be in the extreme sidebands. 
Consequently, they will have low amplitude and a low probability of 
detection. However, it is also well known that we can compel detection of 
the retarded photons by placing a pair of detectors at those sidebands and 
nowhere else. This will destroy the diffraction pattern but it will not 
alter the position where the photons are detected; thus, equation (3) will 
still hold. In other words, this placement of the detectors is equivalent 
to blocking off the imaginary middle segments that become the source for 
secondary wavelets when a wave crest passes through a diffraction slit. 
It is apparent from equation (3) that we want .DELTA.y to be of significant 
magnitude in comparison to .DELTA.x, as in equation (4) where 
.DELTA.y=.DELTA.x, and we want .DELTA.x/c to be of significant magnitude. 
Although not meant to be limiting, it is convenient to accomplish these 
objectives by placing two or more VLBI instrumentation packages in space. 
FIG. 2 illustrates the general method of having a pair of VLBI 
instrumentation packages 50 in orbit. The instrumentation packages 50 will 
include exterior instruments such as a parabolic antenna 60 for collecting 
radio signals and a high-gear antenna 70 for telemetry. The detectors 80 
in the instrumentation packages will collect data to be stored in a 
recorder 90 which will be time coded by an atomic clock 100. The recorded 
data can be transmitted back to Earth or, for near Earth orbits, retrieved 
by space mission. Once the data is collected, it can be synchronized by 
the atomic clocks to maintain coherence at which point the data can be 
combined and analyzed by VLBI data analysis 110. 
FIG. 3 is a schematic showing the detection of a retarded radio signal 120 
that originates beyond Saturn 130 and diffracts through the rings of 
Saturn 140. The VLBI instrumentation packages 50 are two astronomical 
units (AU) apart in the orbit of the Earth 150, approximately 
1,285.35.times.10.sup.-6 km from Saturn (mean distance from sun=9.569 AU). 
Parabolic antennae on the satellites are aligned to the extreme sidebands 
of the distant radio event and the receiver is tuned to the monochromatic 
frequency of the natural diffraction process. In this example the radio 
signal arrives late by about 29 seconds. If the event in question is rare 
and rapidly evolving, an extra half minute or so of past data transmitted 
back to Earth could be useful in understanding the physical processes that 
underlie the radio event. 
FIG. 4 is a schematic showing the detection of retarded light from a 
lightning jet or sprite using artificial diffraction. In this example the 
pair of VLBI instrumentation satellites 50 carry visible light detectors 
in geostationary orbit 150 kilometers above the Earth. The detectors are 
separated by 300 kilometers and Los Alamos, N. Mex. is centered between 
them. During a nighttime thunderstorm over Los Alamos, balloons or 
aircraft carry a large opaque foil 160 with a Fraunhofer type diffraction 
apparatus in its center over the top of the thunderheads. A lightning jet 
170 flashes under the foil and monochromatic light diffracts through the 
airborne foil, arriving at the orbiting detectors after 7.times.10.sup.-4 
seconds. This is 2.times.10.sup.-4 seconds late since the contemporaneous 
light travel time is only 5.times.10.sup.-4 seconds, the rest of the 
travel time coming from equations (3) and (4). The delay in this case 
could be about as long as the event itself. Typically, a lightning flash 
is comprised of some 50 individual bolts lasting for about 
2.times.10.sup.-4 seconds each with an interval of 2.times.10.sup.-2 
seconds between bolts. Once the data have been transmitted to Earth or 
retrieved during a space mission, data analysis can help us elucidate the 
ultrabrief processes that occur in lightning flashes. 
FIG. 5 illustrates a diffraction device 180 that will obtain monochromatic 
wavelengths. The device will have two slits for the passage of light 
waves, the source slit 190 and the diffracting slit 200. Sandwiching these 
slits will be lenses 210 which will adjust the light waves accordingly. 
Thus, as illustrated by the above embodiments, the present invention 
exploits the invariance of light speed and the quantum-mechanical nature 
of photons to combine VLBI with natural or artificial diffraction 
processes as a novel method of detecting retarded light, thereby providing 
scientists in a variety of fields with experimental data that would not 
otherwise be available.