As the World Turns
Creationists constantly remind us that their conclusions are based on scientific evidence. But often when we examine those conclusions, we find cases of jumping to conclusions without checking the facts. One such case of a recent creation-science faux pas comes from the Midwest Center of the Institute for Creation Research, specifically the Center's director, Walter T. Brown, Ph.D. Here is what Dr. Brown writes in a pamphlet entitled Evidence that Implies a Young Earth and Solar System:
Atomic clocks, which have for the last twenty-two years measured the earth's spin rate to the nearest billionth of a second, have consistently found that the earth is slowing down at a rate of almost one second a year. If the earth were billions of years old, its initial spin rate would have been fantastically rapid—so rapid that major distortions in the shape of the earth would have occurred.
This sounds like a pretty compelling argument, and it has already been quoted by other creationists in support of their claim that the earth is very young (Chui). If one takes Brown's deceleration rate of one second loss per year each year and extrapolates 4.6 billion years into the past, one can calculate that there would have been about 53,500 days per year at that time. Each day would have been only ten minutes long.
Since satellites just above the atmosphere take about one hour to orbit the earth, it stands to reason that objects traveling six times this velocity at the equator would fly off into space. In other words, Brown is correct in asserting that, had the earth been slowing at the rate he suggests and were it as old as radioisotope decay indicates, there would have been "major distortions" of the earth's shape at the time of formation. The earth would have been shaped something like a very large rapidly spinning pizza crust. But Brown doesn't believe that this was ever the case, so he solves the apparent dilemma by assuming that the earth was formed much more recently than the widely accepted value.
Before we all join Brown as young-earthers, however, we should realize that Brown's deceleration value of one second per year per year is much greater than the accepted value of 0.005 second per year per year. Brown is off by 20,000 percent for two-hundred-fold! If one extrapolates back in time 4.6 billion years with the accepted estimate of 0.005 second per year per year, one gets a fourteen-hour day. This means that objects at the equator would have been traveling at rates considerably less than the escape velocity. The effect of such a spin rate can be seen with the planet Jupiter. It spins on its axis in ten hours and is only slightly oblate-hardly anything like the flattened earth to which Brown alludes. Hence, the earth's observed spin deceleration rate does not falsify the notion that the earth is 4.6 billion years old.
That should settle the matter. Brown used an erroneous datum to reach a faulty conclusion. But it is interesting to try to find out how the error was originally made. Did Brown make the mistake himself or did he find this error ready-made in the literature?
To answer this question, we sought the three references that Brown used. Unfortunately, one reference is an Air Force document ("Earth Motions and Their Effect on Air Force Systems," Air Force Cambridge Laboratory, November 1975, p. 6), which we were not able to locate. Perhaps the U.S. Air Force misled Brown and all the blame should be heaped onto them. However, that's not likely. In dozens of cases where we have checked references for the sources of other creationist errors, we have found that the error was not in the original paper.
Be that as it may, we were able to find the Popular Science (Fisher) and the Reader's Digest (Finchger) references. Neither of these said anything about the deceleration rate being one second per year per year. In fact, the Popular Science article even showed a graph from which one can calculate the standard 0.005 second per year per year figure. Even in the unlikely event that the error originated in the Air Force pamphlet, Brown is still accountable for failing to check out the discrepancy. If two out of three of his references either give the correct value or say nothing about the second per year per year value, then why did Brown list these references along with the Air Force pamphlet? And why didn't he list an astronomy book or a book on time keeping?
Of course, many might answer these questions by saying that creationists are deliberately exploiting a gullible public. In this case, though, we think that Brown has a better excuse. The effect of the earth's slowing spin rate on time keeping is actually quite perplexing. We are so accustomed to thinking of the length of a day and night period as being constant that it is difficult for most of us to think of time at all without equating it to the turning of the earth on its axis. So it is easy to imagine how Brown was misled when he first read about this subject.
In order to understand what is really going on, we need to be reminded of a couple of things about the principal motions of the earth. Remember, while the length of time it takes the earth to go around the sun is quite constant, the rotation of the earth on its axis is quite a different matter, due mainly to tidal friction.
It takes a lot of energy to move all that ocean water around twice a day, and the price of all this work is the earth's ever-slowing spin rate.
The slowing isn't noticeable to someone camping on a seashore, at least not to one camping without an extremely accurate time piece. But if one were to measure a day very accurately, wait a year, and then measure another day, the second day would, on the average, turn out to be about 0.000014 seconds longer than the first.
This is no big deal to the typical camper, but to a technological society that is seemingly addicted to a 86,400-second day it presents a real dilemma. We used to take care of this discrepancy by the simple expedient of making the seconds a little longer, so that 86,400 of them would just fill up a day.
But purists wanted a standard invariable second, so, about twenty years ago, an "atomic second" compromise was agreed upon. Since then, an atomic clock counts standard seconds while the earth just keeps slowing, so that each year it takes about 0.005 standard seconds more to complete 365.25 rotations. The slowdown rate is given just this way: 0.005 seconds per year each year. This is written: 0.005 sec./year/year. Thus we are really comparing two clocks-standard or atomic clock that does not slow down and a somewhat less-than-perfect clock that keeps slowing. Now let's get back to Brown's error.
Both the Reader's Digest and the Popular Science articles make much of what are called "leap seconds." To help understand the leap second, we would like to lead you through some simple calculations that you can do—and Brown should have done—with pencil and paper or calculator. We are going to add up the differences between a perfect clock and one that slows down a little each year. We will use the formula:
D: stands for the difference between the perfect clock and the earth (a clock that is gradually slowing down)
N: is the number of years that the perfect clock and the earth have been allowed to drift apart
0.005 is the measured slowing rate for the earth
Actually, the earth's deceleration rate is not a constant 0.005 sec./year/year, but that need not concern us yet. Also, we must assume that our clock keeps perfect time. (Atomic clocks come very very close to satisfying this assumption.) Now we synchronize the clock and the earth and start keeping time. At the end of the first year, we find that the earth has slowed down and is 0.005 second behind the perfect clock. There is no need yet to let the perfect clock tick off an extra "leap" second to allow the earth to catch up with the clock. The earth would now start the second year 0.005 second behind the atomic clock.
It would slow down another 0.005 second and at the end of the second year would be running at a rate that was 2 x (0.005) = 0.01 sec./year slower than the clock. By summing the first year's deficit and the loss incurred during the second year, we would get 0.005+0.010=0.015 second; still no need to have a leap second. The deficits at the ends of the succeeding years would be 0.03, 0.05, 0.075, 0.105, and so forth. The earth would find itself 1.05 seconds behind the clock after twenty years, and it would then be spinning at a rate that was 0.1 second per year slower than the atomic clock. (See, we told you it was confusing.)
Keep up with those calculations. By throwing in a leap second now, the earth could almost catch up to the atomic clock. The deficit would be reduced to 0.05 second by having the leap second, but the error would be accumulating at an even faster rate. In fact, the error would accumulate to another second in just 8 more years, in the 28th year of the standard. You would need another leap second at 35, 40, 45, 49, 53, and 57 years. The leap seconds would get increasingly common as the earth continued to spin more and more slowly. The first two leap seconds to occur just one year apart would occur in years 110 and 111 after the system had been instituted. The last skipped year when no leap second would be needed would be the year 186 of this system. By the year 214, some years would need double leap seconds.
Now remember, all of these calculations are based on an absolutely uniform slowing rate of 0.005 sec./year/year. Having a leap-second-year every year means that the earth's spin rate is 1 sec./year slower than the atomic clock, not that the earth is slowing 1 sec./year/year. Evidently Brown read that we were needing leap seconds almost every year and erroneously concluded that our spin rate was slowing 1 sec./year/year. That's what can happen if you "know" the answer before you start the problem.
Still, you might be wondering why we have had so many leap seconds already when we have only had the atomic clock system for a couple of decades. "Shouldn't we be getting ready for our first leap second," you ask, and "Shouldn't the next one be eight years down the road?" There are two reasons for such a high frequency of leap-second years in just the short time since the atomic clock standard was instituted. First, the standard was not based on the first year of its inception but rather on the earth's nineteenth-century rotation rate. Second, the earth's slowing rate is not uniform. In Greenwich Time and the Discovery of the Longitude, Derek Howse provides a graph that shows this fluctuation for the past two centuries. Time could be measured very accurately before atomic clocks, but it took laborious astronomical observations and tedious calculations to do so. The atomic clock has made accurate time keeping an everyday moment-to-moment convenience. Atomic clocks also have managed to fool young-earth advocates into thinking that they had physical evidence to support their religious convictions.
A Note About Calculations
Please don't accept on faith our calculations of the earth's primordial spin rate. Below is a simplified example of the type of calculations we did. Be a skeptic. Check it out for yourself.
Assume (for the sake of simplicity, not realism) Brown's slowing rate of 1 sec./year/year. Note also that there are about 31.6 million seconds per year.
Imagine a time 31.6 million years in the future. By this time, according to Brown, we would have added 31.6 million seconds to the year. More likely, we would add 24 leap hours to every day. That would give us 24 standard atomic clock hours plus 24 leap hours every day. It is easy to see that the day would be 48 hours long. In other words, the earth's spin rate would be one half of our current rate.
Likewise, 31.6 million years ago, the earth would have been spinning at twice the rate it is now. The day would have been 12 of our hours long. Using Brown's figure to go 4.6 billion years into the future, we find that the earth would be spinning at about 1 / 143 of its present rate, so 4.6 billion year ago it should have been spinning 143 times as fast. This gives us about a 10-minute day and a pizza-shaped earth. Too bad Brown's number is way off. It was a great young-earth argument. In fact, it sounds so good that we'll bet that creationists go right on using it anyway.
Brown, Walter T. Evidence that Implies a Young Earth and Solar System. Naperville, IL: Evidence for Creation Series, I.C.R. Midwest Center.
Chui, C. Overwhelming Evidence for a Young Earth. Irvine, CA: Creation Science Association of Orange County.
Finchger, Jack. November 1977. "And Now, Atomic Clocks." Reader's Digest. Vol. 111,
Fisher, Arthur. March 1973. "The Riddle of the Leap Second." Popular Science. Vol. 202, pp. 110-113, 164-166.
Howse, Derek. 1980. Greenwich Time and the Discovery of the Longitude. Oxford University Press.