It’s About Time to learn the “Truth” about TIME! I have been called, “Mr. Time.” I am not; but, I know Who is! Also, being 84 years old this month (25 September 2020), and remembering the wonderful colleagues I have been privileged to work with over the years, I felt impressed to write some interesting insights regarding TIME from both a scientific and religious point of view. I use the above Biblical phrase to catch our attention to the enormous increase in timekeeping accuracy we have enjoyed over the years in contrast to this scripture, and the benefits have been enormous; GPS is a classic example. The title may appear contradictory, but you will see at the end, it is not.
Timekeeping accuracy has increased a billion fold in my lifetime. It has been so exciting to work with and know many of the players in this rapidly advancing field over my sixty years doing time and frequency metrology (the science of measurement). Many of them are Nobel laureates and their contributions have been enormous. Many have passed on.
Here I will share some fascinating scientific aspects of time development, and then conclude with what is really most important — the religious truths about TIME. We have before us the 2020 autumnal equinox (22 September 1331 UTC (7:30 a.m. MDT)), when the spin axis of the earth is exactly at 90 degrees to the line from the center of the earth to the sun. And the time for that changes every year because the time for an earth orbit around the sun is out of sync with the spin rate of once per day of the earth with respect to the sun. Everyone knows the number of days in a year is not a whole number bringing about the leap year phenomena. Interestingly and in contrast, If you were on the unique planet Mercury, you would see that the Mercury day and year are harmonically synchronized.
Starting With Solar Time
As science came of age following the renaissance, we started out with solar time, where the length of the second was 60 seconds in a minute, 60 minutes in an hour, and 24 hours in a day — making the length of the second 1/86400 of an average mean solar day (60 x 60 x 24 = 86400 seconds in a day). Then astronomers noticed random variations in solar time. Because of these variations, in 1956, the ephemeris second became the next definition as decided by the International Bureau of Weights and Measures (BIPM): the second was defined as the, “fraction 1/31,556,925.9747 of the tropical year for 1900 January 0 at 12 hours ephemeris time.” A tropical year is the time between one vernal equinox and the next (365.24219 ephemeris days in the year 2000). Earth time (solar-time) has slowed down about 60 seconds since the year 1900. Astronomical time accuracy is like +/- 0.0002 of a second of error in a day. This seems small, but for a system like GPS, this error is enormous where GPS needs about a billionth of a second level of accuracy using atomic clocks to work as it does.
In the 1940s Nobel Laureate, I. I. Rabi, thought of atomic clocks. I had breakfast with him in 1983 in Philadelphia, PA, when he received the first Frequency Control Symposium Rabi Award named after him. I felt greatly honored a year later to be the second recipient of the Rabi Award. Based on Rabi’s concepts the first atomic clock was invented in 1948-49 by Harold Lyons, et. al. at NBS in Washington, D.C., based on an ammonia-molecule microwave resonance, but its accuracy was not significantly better than astronomical time.
However, because of its excellent short-term frequency stability, the first atomic clock I worked on in 1960 was an ammonia maser (microwave amplification by stimulated emission of radiation). Shimoda, Wang, and Townes wrote a pioneering paper on ammonia masers. I got to know all three of these gentlemen and great scientists from Japan, China, and the USA, respectively. Charles Townes went on to invent the LASER (Light Amplification of Stimulated Emission of Radiation).
Can you imagine how many billion laser scanners there are now in the world — every grocery store checkout counter, etc.? And now also, lasers are fundamental building blocks for the most accurate clocks in the world. The uses of lasers are enormous, laser ranging, and it goes on and on. It is fun to think that lasers were given birth in time and frequency metrology.
Essen and Perry at the National Physical Laboratory (NPL) in Teddington, England, began atomic-clock timekeeping in June 1955 using a resonance in the cesium-133 atom (not radioactive). The accuracies increased and in 1967 on Friday the 13th of October that year the second was again re-defined and the definition remains with us to this day:
“the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom” (at a temperature of 0 K)”.
One may ask where that number came from — tying the astronomical measurement of time to that of an atom?
The Role of Standards Laboratories
The National Bureau of Standards (NBS), where I worked, had a standard-time transmission radio station (WWV) in Beltsville, Maryland. That signal was received at the United States Naval Observatory (USN0) and at NPL in the UK. Following several years of work, Essen and William Markowitz from the United States Naval Observatory (USNO) determined the relationship between the hyperfine transition frequency of the cesium atom and the ephemeris second. Using a common-view measurement method based on the received signals from radio station WWV commonly received at NPL and USNO, and gave us 9,192,631,770 Hz (cycles per second) for the cesium frequency with respect to the ephemeris second.
Markowitz, an astronomer in charge of time at the USNO, was an interesting guy. He told me one time that physicists don’t understand time. He is right, but neither do astronomers.
The famous Greenwich (zero) meridian-line goes through the Royal Greenwich Observatory. Later, for timekeeping purposes, RGO moved down to Herstmonceux Castle in southern England. Humphrey Smith, who was the director of time services there, tells a little bit about that in this audio link. This is the meridian line used by all navigation systems and for mapping.
Before atomic clocks, quartz-crystal oscillator-clocks were our timekeepers, and every laboratory and observatory had some of these in a very good environment to provide the best frequency stability and hence timekeeping ability. James A. Barnes as part of his Ph.D thesis had developed the NBS-A time-scale algorithm to calibrate three quartz-crystal clocks using Roger Beehler’s (NBS) primary cesium-beam standard across the hall at the NBS-Boulder, CO, laboratories. Then Jim and Lowell Fey carried one of those quartz clocks to WWV in 1965 to transfer the time from Beltsville to Boulder to set the time for the NBS-A time-scale algorithm, and to improve the timekeeping for the USA.
Best Atomic Clocks
I was working on my master’s thesis at the same time as Jim. That fall we invited the makers of the best atomic-clocks to do a comparison at our lab in Boulder. The two-sample variance, which was named the Allan variance and which came out of my thesis, became the analysis tool to compare all these new and exciting atomic-clock timekeeping devices.
I had used this tool to characterize some unusual time variations in two of the NBS radio stations: WWVL and WWVB, and I prepared a paper on same, which was to be given in Ankara, Turkey. So in August 1967, I arranged to visit the primary timekeeping centers on my way to Ankara.
James Steele was my kind host at NPL and Humphrey Smith at RGO (Herstmonceux Castle). I was greatly impressed with their work. My next visit was with Bernard Guinot, at the Paris Observatory (OP). We became good friends over the years and had many great discussions regarding time-scale algorithms, clocks, astronomy, and the like. He was then head of the BIH (Bureau of the hour) and responsible for generating time for the world.
Jim Barnes became Section Chief and turned over the timekeeping responsible to me. I then had an ensemble of eight commercial atomic clocks, and I wrote the AT-1 algorithm in 1968, to combine their readings in an optimized way using the Allan variance to characterize their varying timekeeping performances.
Dr. Guinot sent Michael Granveaud to Boulder to work with me, and then Michael returned and wrote ALGOS, which still keeps time for the world. AT-1 is a better algorithm, but ALGOS is more politically correct working with all the nations who contribute across the globe. With significant improvements by my colleagues, AT-1 is still keeping official time for the USA today.
Guinot was particularly intrigued by the paper that Helmut Hellwig, Dave Glaze, and I gave in Cagliari, Italy, on “An Accuracy Algorithm for an Atomic Time Scale.” This paper shows how to combine accuracy and stability nicely. It is highly relevant today with the amazing accuracies and stabilities of optical clocks. In simple terms, accuracy can be thought of as agreement with some standard, and stability means minimal changes over time.
How Accurate can Clocks Be?
One of my colleagues and a dear friend, Dr. Elizabeth Donley (now Chief of the NIST Time and Frequency Division in Boulder, CO), has written an equation, which shows the potential accuracy and stability of atomic clocks in terms of the square-root of the Allan variance. From it, she shows that the potential accuracy can improve with the frequency of the resonance, with the signal-to-noise, which improves as the square-root of the averaging time used to determine the frequency, and with the line-width of the atomic resonance. From this equation, one can see why optical clocks now being researched are reaching eighteen-digits of potential accuracy and stability. Optical atomic clock frequencies are about 100,000 times higher than the cesium microwave frequency.
The accuracies now being achieved are like measuring the distance to the sun (93 million miles) to 0.003 of the width of a human hair. I pulled out one of mine to measure it, and I don’t have many to spare! This is like 0.1 picosecond/day. GPS operates at the billionth of a second accuracy level (nanosecond); a picosecond is a thousand times smaller than a nanosecond! And the end is not in sight with things improving by about a factor of ten every seven years — Moore’s Law. It has been a great privilege to know some of the scientists helping make this continued incredible progress.
Variations always occur in nature and in all timekeeping devices. There is no perfect clock! With the help of colleagues over the years, we have developed statistical techniques (Allan variance, the Modified Allan variance, and the Time variance) giving a full spectrum of colors of these variations. All three of these have become IEEE international standards, and are broadly used in time and frequency metrology, in navigation, and in telecom systems.
We have shown that using the classical variance that one learns about in a college statistics class is like taking a black-and-white picture of a rainbow; you get intensity, but no color. The above three variances give you both intensity and full color for the common power-law spectral variations we see in clocks. Hewlett Packard asked me to write an application note for them, “The Science of Timekeeping.” In it is a description of the spectrum of variations in timekeeping devices:
The different slopes denote different colors of time variations. This application note was published in 1997, and the clocks now are about a thousand times better than the best shown here. I prepared a tutorial for the IEEE web site on the development of these three variances: The ordinate on this chart is the square-root of the Allan variance times the prediction or timekeeping interval. Notice that the variations in the earth’s spin rate are one of the most divergent time-varying slopes of all in the long-term.
A lot of the above information is also contained in my IEEE ORAL HISTORY, which Dr. Donley came to our home and recorded on 5-6 November 2018. I wrote this application note with the help of my good friends, Prof. Neil Ashby, who did the relativity equations for GPS, and with Cliff Hodge, of NPL, who is a space clock expert.
Where Are We Going From Here?
As technology continues to escalate, and morality is declining due to increasing secularism and materialism. Where are we going? I believe we live in the most exciting time in history, but I also believe in the above scripture with exciting promises associated therewith. Another translation reads, “that no more time should intervene and there should be no more waiting or delay.” (Amplified Bible) The last five chapters of my book, “It’s About Time”, deal with this question, and I show the difference between man’s time and God’s time. The basic premise of the book is that if something is true in science, and something is true in religion, they must agree. Hence, the subtitle is “Science harmonized with religion.”
“It’s About Time” to know the truth about who we are and where we are in God’s time.
On 25 September 2020 the VIRTUAL EXPO, I will be sharing details on where we are in God’s TIME.
On 26 September 2020 join in national and international prayer to “heal” our land and forgive our sins.
On 27 September 2020, let us make it a sacred Sabbath drawing our selves and as many as we can closer to God.
We now have proof that America is the “Promise Land” spoken of in the Book of Mormon, and it is critical for the inhabitants there of to serve God or they will be”Sept off.”
The evidence of God’s love is profound for those who have eyes to see and hearts to feel. He is inviting us to graduate into His millennial paradisaical glory with a new heaven and a new earth — exciting, but the end of worldliness has to come first. when the above scripture and the Amplified version take on great significance. We are greatly blessed to live at this TIME in history.
Most look to the dark, but let us look to the light; IT IS GLORIOUS. The ride home to celestial realms of glory will be more spectacular than anything we can imagine. There we will be ONE with God in fullness of joy.
David W. Allan