The Citizen Scientist

These are a few familiar quotations that we encounter throughout our lives, but what exactly is time?

We live in a world of technological marvels, and because of that we sometimes forget from whence we came. One of these marvels is that of timekeeping. With a modern day atomic clock we can know time accurately to within a few nanoseconds or so per century. But did you ever stop to wonder relative to what? For example, if it's 3:00 P.M. in New York City , then it is 12:00 P.M. in California and 10:00 A.M. in Alaska. Who is right? Well, they all are. For to know what time it is, you need to know where you are.

If I ask you the time, you will look at your watch or a nearby clock and state the indicated time. Does this response answer my question? It depends. In reality, you cannot simply state the time without an awareness of some reference. Does this sound confusing? Well, it certainly can be. My intent in writing this article is to purge away all our misconceived, long held prejudices about time and provide a new outlook on one of our most fundamental and misunderstood beliefs.

How often have we set out to perform some specific task, only to find ourselves someplace that at first thought seemed totally unrelated? That's how it is sometimes when doing scientific research. You start out planning to go directly from “A” to “B”, only to find yourself on a strangely circuitous route leading to some hither to unexpected discovery.

This happened to me about a year ago when I purchased a Sun & Sky Monitoring Station, designed for Radio Shack® by SAS's own Forrest M. Mims III . Forrest has done extensive research into atmospheric studies involving haze, water vapor, ozone, and smoke. Another senior SAS member, Sheldon Greaves, published a review of the Sun & Sky Monitoring Station in The Citizen Scientist.

While reading through the Sun & Sky Monitoring Station's beautifully written 64-page manual, I was inspired to create a set of Excel worksheets to be used when operating the device. In doing so, (without thinking as we sometimes do) I placed some “dummy” values in the cells of the live worksheet to indicate to someone how to fill out the sheet. One of these “dummy” variables was time. To make things easy, I copied 12:00 P.M. in every cell. This led me to think about the origin of two terms that we use when talking about time, A.M. and P.M. The technical definition for determining noon is when the sun is crossing the observer's local meridian, from this we have A.M. (ante meridiem), meaning before mid-day, and P.M. (post meridiem), meaning after the mid-day.

One possible point of confusion for “mid-day” is that we have a condition where A.M. proceeds immediately into P.M. What happened to mid-day? It has become commonplace to refer to mid-day as simply “noon,” with “afternoon” considered after 12:00 P.M. Noon is commonly relegated to one of those “sort of” times where most people are perfectly content with the several minutes before or after noon to be considered as noon.

Some might argue that as we approach noon the time proceeds from 11:58 A.M. to 11:59 A.M. and then to 12:00 A.M. But this is like saying that noon just became midnight! Applying the same logic, when we are approaching midnight we proceed from 11:58 P.M. to 11:59 P.M. and then to 12:00 P.M, and midnight becomes noon. By common agreement noon is understood to be 12:00 P.M., while midnight is considered 12:00 A.M.

To avoid confusion, some plane and train schedules deliberately avoid using the midnight time (12:00 A.M.) and use 11:59 P.M. for arrivals and 12:01 A.M. for departures. Some legal contracts start or end at 12:01 A.M. on a specific day. It is much less confusing if we use a 24-hour time format.

Everyone understands north and south, but what about east and west? Fortunately, there are two international standards for determining this. The first is the Prime Meridian, the longitude line for Greenwich, England. This line is designated 0º longitude. The second is on the opposite side of the Earth and is known as the International Date Line. It is roughly 180º longitude. I say “roughly,” because the International Date Line doesn't exactly follow the 180º longitude line due to geographical and political reasons. Between these two lines we reference what is considered the Earth's Western and Eastern hemispheres.

Starting from Greenwich (0º longitude), anything to the left (assuming that you are facing North) is considered west, while anything to the right is considered east until you get to the International Date line (180º longitude). Then the opposite is true. This East-West delineation makes a difference to time, also. When you cross the International Date Line (180º longitude), depending upon which way you go, you can gain or lose a day! If you cross the International Date Line going west, then you add a day, while if you cross it going east, you lose a day.

I should point out that at any moment on the Earth, it is both today and tomorrow, or if you are on the opposite (East-West) hemisphere of the Earth, it would be both yesterday and today. Either way, there are two different “days” happening at any time. Technically you could argue that at the instant of midnight at the International Date Line, there is only one day on Earth. But at one second after midnight, there are now two days again.

To help illustrate this concept, consider the following. If we divide the Earth into several sections, say 24 because the Earth rotates once in 24 hours, each section equals 15 º. This means that each section contains a time interval of 1 hour or 60 minutes, leaving us with four minutes per degree or rotation. If the sun is at its apex in the sky, then it is where its light will travel the least distance through the atmosphere to the surface below. When correlating measurements of sunlight to the atmospheric thickness, or air mass, this is an important point. The sun will be at its apex at noon, right? Well, that all depends on where you are, and when you are there.

Most of us know by experience that at noon a shadow cast by a vertical object will be at its shortest length for that particular day. If we use this information to determine when the sun is at its highest point in the sky, then that is when we have the minimum amount of air mass between us and the sun. We will assume that the height of the atmosphere remains constant throughout our little thought experiment and signify this distance as D atm throughout Figs. 1-3. Each observer is standing near a short vertical pole. All the vertical poles are exactly the same height above the ground.

Figure 1. The relative positions of three observers in the same time zone and their relation to the sun.

Figure 1 shows the relative positions of three observers in the same time zone. At the moment the sun crosses the line between time zones 1 and 2, all three observers look at their vertical indicator poles and note the length of the shadow. Observer 3 will see the shortest shadow, with observer 1 noting the greatest shadow length. Some basic trigonometry will show that the farthest distance that sunlight traverses the atmosphere will be distance 1 and the shortest distance will be distance 3.

Figure 2. The relative positions of three observers in the same time zone and their relation to the sun a short time after the situation depicted in Fig.1.

If you ask a person when the sun is at its highest point, they will most likely say noon. Sometimes they will be correct – but only sometimes! If we examine Fig. 2, we see that the sun appears in a different part of the sky relative to each observer, even when their watches indicate noon. Yet only the shadow of Observer 2 is at its shortest length for the day.

Figure 3. The relative positions of three observers in the same time zone and their relation to the sun a short time a short time after the situation depicted in Fig. 2.

Figure 3 shows the position of the sun relative to the observers a short time later. Now Observer 1's shadow indicates noon, even though his watch indicates a time well past noon. What is going on here? Shouldn't noon be at 12:00 P.M.?

There is a term known as local noon, the exact time when the sun reaches its highest point in the sky relative to an observer's meridian. Therefore, local noon varies throughout each time zone. Think of how confusing it would be if we didn't have an accepted concept of time and time zones. If Observers 1, 2, and 3 all had identical sundials (not corrected for longitude), then they could not come to an agreement for the exact time of noon. If our observers agree to meet at exactly noon, then each would arrive at their own noon, either too early or too late depending upon who you ask!

Nevertheless, the position of the sun provides an approximation of the time, and solar noon provides a means by which watches and clocks can be set. This works okay in a small town, but towns that are separated by some distance will each have their own local time. If a meeting at noon were to be held between two distant towns situated on different longitudes, then the participants would assume that their local noon was the correct noon. Both sides would arrive at different times.

We can look at two US continental cities in the same time zone to illustrate some peculiarities of our conception (or misconception) of time. Let's select two cities at approximately the same latitude, but spaced apart by almost 15 degrees. Boston, Massachusetts, is at 71.1° W longitude and 42.3° N latitude. Detroit, Michigan, is at 83.1° W longitude and 42.4° N latitude. Both cities are in the Eastern Time Zone.

The longitudinal separation between the two cities is 12 degrees. From our previous discussion, we know that for every degree difference there is a 4 minute difference in time. For our 12 degrees we should note a 48-minute (sundial) time difference. Thus, local noon for each city would occur at the following times on 16 April 2006:

(Note: Daylight Saving Time in the United States begins 2 April 2006, so there is a one-hour discrepancy when compared to a clock.)

Even though the two cities are in the same time zone, there is almost an hour's difference (48 Minutes) between the local noon times when referenced to the sun. One thousand years ago this would not have been any concern, as there was no high speed mass transportation or communication. Bear in mind that all time zones are not spaced apart by exactly 1 hour, some use fractional amounts of time. Today, if we were to use only solar time for time keeping, things would grind to a halt in short order! As an aside, If you want to experience a quantum state, then go to either of the two geographic poles of the Earth and stand there – you will now be in every time zone at once! What time will it be there?

Now bear in mind that I took some liberties and used a perfectly idealized situation. If you look at a map of actual time zones, then the situation is much more complex. Political and geographical obstacles alter the time zone boundaries and, as a result, uniform arrangements of time zone delineations don't exist in the real world.

Another drawback to using the sun to tell time is that it doesn't do you much good at night or when the sky if overcast!.We need a better method of time keeping, or at least a way to supplement sun time.

Keeping time by the position of the sun was implemented by vertical pillar or obelisk whose shadow indicated the passage of time. Sundials followed these simple methods.

If you needed to determine time throughout the entire day (rain or shine, day or night), then other methods were used, including the water clock, measured candle, burning incense, or an hour glass.

The water clock is a simple device in which a known amount of water would pour from a spout or small orifice over a specific time interval.

The measured candle is simply a large candle with regular intervals of markings to mark the passage of time.

Burning incense is a thin, circuitous length of material that burns at a specific rate to indicate the passage of time.

The hour glass is usually filled with fine sand, which flows from one section to another in a known period of time.

All these methods are not true clocks; instead, they are timers. They measure intervals of time, not actual time. If you started a candle burning, then your time accuracy is dependant upon whether or not you knew the time you started the flame.

Astronomical methods were also used to mark the passage of time. One was an Egyptian Merkhet . It dates to around 600 BC, and a pair was used to establish a north-south reference (meridian) by alignment with the Pole star. Once this is done, the night time hours could be measured by examining the passage of other known stars across the meridian.

To simply state that 3 hours has passed, is meaningless unless you can say that you knew what time it was 3 hours ago. It is possible to use combinations of sundials, and the aforementioned methods to tell time throughout the entire day. I am sure people did indeed utilize combinations of methods to determine time. Of course whoever uses specific methods to determine time must also define what they mean by time. Is the length of a day 18 hours? 24 hours? 30 hours? Once everyone agrees on a uniform system of time, then they can finally start relating to one another.

But these methods are not equivalent to clocks, which have two basic requirements:

1. A regular, constant or repetitive process or action to mark off equal increments of time.

2. A means of keeping track of the increments of time and displaying the result.

1 : a device other than a watch for indicating or measuring time commonly by means of hands moving on a dial; broadly : any periodic system by which time is measured

The word clock comes from Medieval Latin clocca, meaning a bell. Early clocks had a bell that rang without the need of the familiar hands.

We need a better method by which to determine time. Even a broken clock is correct twice a day, but the trick is knowing when it is correct! One of the best time keeping methods occurred as a result of boredom. This is ironic, because usually people become more or less bored when they know what time it is and how much time there is to go before they begin some predetermined task or event. You are less likely to be bored if you know that there are only a few minutes left before you reach a destination, as opposed to having several hours to go.

Incidentally, did you ever wonder why the hands of a clock move clockwise? The sundial was used for thousands of years, and gained prominence in the Northern Hemisphere. Because of this a shadow cast by a vertical stick in the ground moves from left to right, or what we now call clockwise. If the sundial were first used predominantly in the Southern Hemisphere, then what we call clockwise would be in the opposite direction.

Galileo contributed much to science, and one of his observations made while bored in a church was to watch a swinging lantern. He noted that the interval between swings was exceptionally periodic. Although Galileo never constructed a pendulum clock, his idea led other people to construct such clocks to mark the passage of time.

One of those people who took Galileo's swinging lantern periodicity observation to the next level was Christian Huygens. Before Christian Huygens, most clocks were basic sundials or large weight driven mechanical clocks which did not contain a pendulum. The basic mechanism was that of a verge-and-foliot mechanism. These continued in popularity for more than 300 years. All verge-and-foliot clock mechanisms had the same inherent problem: The oscillation period of the escapement depended heavily on the attached weight and the amount of friction in the drive. These clocks were difficult to regulate.

With the addition of a swinging pendulum in 1656 to help regulate the escapement, Christian Huygens ushered in a new era in time keeping. His early clocks were accurate to an unheard of one minute per day. Clocks of that period not using a pendulum were typically accurate to approximately fifteen minutes per day. Later refinements in clock construction enabled an accuracy or around one second or so per day.

A further refinement in clock design came as a result of the need for better marine navigation. In 1714, the British Parliament put up a £20,000 cash award for anyone coming up with a clock that was able to be used on ships at sea and remain accurate. At that time, many ships were lost at sea because they were unable to find their exact coordinates and avoid treacherous rocky shores. It is fairly obvious that a standard pendulum based clock would not work on a ship at sea due to the pitching back and forth.

John Harrison (a cabinet maker, musician, and self taught clock maker) stunned the world by making a pendulum operated clock that did work on a ship. The clever inventor used a pair of balanced pendulums that swung in opposing directions, connected to compensation springs. His clock worked perfectly during sea trials, and although it was a success, John Harrison thought it as being unwieldy and too large.

Harrison took great strides to compensate for the rolling and pitching motion of the ship, but he never took into consideration the effect of the ships yawing motion. After much investigation, he was able to add many refinements to further improve accuracy. Four clock designs later, he came up with a compact, spring wound, time keeping device that was accurate to within five seconds in six and one half weeks. For several decades, John Harrison was in a constant battle with the Board of Longitude and the advocates of using astronomical observations to determine time. Newton himself was an advocate of the astronomical method.

Figure 4 shows two iterations of Harrisons clock, H1 (his first) on the left, and H4 on the right. H1 weighed about 75 pounds, and occupied a space of about four foot square. H4 was 3 pounds, and could be handheld being only 5 inches in diameter. After much frustration and frequent discouragement caused by constant additional amendments from the Board of Longitude, John Harrison, now eighty, was finally awarded the long overdue £20,000 cash award. One might say that after several decades of frustration in dealing with the Board of Longitude, Harrison might well have been “Bored of Longitude." Harrison could also be considered the first person to be able to claim that “Time is money,” specifically £20,000.

There is considerable information on the web about clocks, escapement mechanisms and clock history, so I won't bore you with clock trivia. But I will point out that at one time, owning a clock was something that only the wealthiest could afford. You could probably equate clock ownership to that of computer ownership several decades ago. To see how commonplace clocks are today, just look around. You might be surprised how many you will see and how much we take them for granted.

It really is pretty amazing how a cheap watch bought today for fewer than ten dollars can outperform a fairly expensive clock from just a hundred years ago. We take our perception of time in a fairly cavalier manor.

When did we start using time zones? Before I answer that, let's go back to our previous example of the three observers in the same time zone. Recall that in Fig. 1 each observer has his own unique local noon, the time when their vertical stick is casting its shortest shadow. If they all agreed to meet at a specific place at noon, then they would have to agree upon which noon they were talking about. Which noon is the right noon? They all are, but as more people began to live in larger areas with faster modes of transportation and communication, bad things start to happen.

If everyone had to walk, or ride a horse to get where they are going, then there is not any dire need to have a uniform time zone. Enter the era of the train. A train can carry large groups of people across great distances in a relatively short amount of time. Some of these trains traveled across several states, and because of economics, had to share the same track. If two trains had to use the same track and travel in opposite directions, then you can imagine what could happen if someone makes a mistake. Therefore the railroads were keenly interested in keeping accurate time.

On 18 November 1883 the US railroads established standard time zones. This was known as railroad time. Time was so important to a railroad worker that the pocket watch they carried had to be at least a 21 jeweled watch, and an official “Watch Inspector” would check these watches periodically for accuracy and condition.

One method of checking the pocket watch for accuracy was to use something called a heliochronometer . This highly accurate device is a very precise adjustable sundial that uses a fine piece of wire or small pinhole to indicate compensated mean solar time as opposed to apparent solar time (sundial time). By aligning a pin point of light on an inscribed analemma on the heliochronometer, an accurate mean solar time (clock time) can be realized throughout the entire year. A variation of approximately +/-15 minutes will be noted for any standard sundial, while a Heliochronometer will compensate for this. An example of how to use a Heliochronometer with animations can be found on the web at http://www.draysonbeckett.co.uk/gunning.sundials/works/heliochronome t er/index.html .

England, Scotland, and Wales had initiated standard railroad time in the 1840s. It caused much controversy in areas. To understand why people objected to no longer operating under sun time, you have to remember that many people had been using sundials, with maybe a single large clock tower in the town square or church. Until the beginning of the 20th century, people set their pocket watches to sun dials.

A conference was held in 1884 in Washington D.C. to formalize acceptance of the meridian line passing through Greenwich, England, as the prime meridian. But it was only thirty five years later that the U.S., by an act of Congress, made official the acceptance of standardized time zones.

Daylight Saving Time

Now is a good time to discuss Daylight Saving Time (DST). (Notice I did not use the common but incorrect “Daylight Savings Time.") When does Daylight Saving Time start? In the United States, it starts on the first Sunday of April at 2:00 A.M., and ends on the last Sunday of October at 2:00 A.M. This is easy to remember, but the government decided to make it more confusing. As of March 2007, with the passage of the 2005 Energy Policy Act ( Pub.L. no. 109-58, 119 Stat 594, 2005), Daylight Saving Time will be extended in the United States to begin on the second Sunday of March, and end on the first Sunday of November.

If you were to watch the transition from standard time to DST on a capable digital clock, the time will go immediately from 1:59.59 A.M. on 2 April 2006 to 3:00.00 A.M, completely bypassing the 2:00 A.M. hour. The minutes from 2:00 A.M. to 2:59 A.M. simply do not exist! Bear in mind that not everyone conforms to DST, and in the United States, Arizona, Indiana and Hawaii do not recognize it.

Benjamin Franklin considered the idea of Daylight Saving Time or Daylight Time while he was in Paris, but the idea was not seriously proposed until 1907 in a pamphlet entitled “Waste of Daylight ” by William Willett. It was not officially enacted in the United States until World War I. The law was later repealed, due to its unpopularity, and was then reinstated in February 1942, and then repealed again in September 1945. Daylight Saving Time was reinstated again in 1967. Even today there is much debate about Daylight Saving Time and Standard Time.

In the places that use Daylight Saving Time, we can have an odd occurrence where we will have one day out of the year that will be 23 hours, and one day out of the year will be 25 hours, depending if we are “Springing Ahead” (going to DST) or “Falling Back” (going from DST to Standard Time). This will be apparent when we compare clock time to that of the rotation time of the Earth, i.e. from a local noon to a local noon.

I should point out that next year every electronic time keeping device that automatically adjusts for Daylight Saving Time will be off by one hour from the second Sunday in March until the first Sunday in April and also from the last Sunday in October until the first Sunday in November. This means that when we adjust for DST on 11 March 2007, the electronic devices (programmable thermostats, watches, automated lighting systems, older electronic time clocks and computers, older fire panels and alarm systems, etc.) will have to be manually adjusted, and then readjusted on the first Sunday in April. This same procedure will have to take place when we revert back to Standard Time. All the electronic time keeping devices will revert back to Standard Time on the last Sunday in October, when it will have to be changed again on the first Sunday of November.

In a sense, this could be a mini Y2K-type bug. Did they consider this when they passed the new law? I also wonder how different computer operating systems and Internet servers will deal with this. Windows allows one to perform online updates through Microsoft's web site. There is also a way to manually edit the start and stop of Daylight Saving Time.

In Part 2 Mike Dziekan will continue his journey through the world of time with more about sundials, a discussion of the equation of time and much more. Editor.