Creationists and Leap-Seconds
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[edit] Introduction
One popular creationist argument against an old Earth involves the slowing of the Earth's rotation and the insertion of "leap-seconds" into our calendar.
[edit] Why are there leap seconds?
Before we get on to the creationist argument, we should explain what a leap-second is.
The rate at which the Earth rotates is slowing down: the mean solar day is getting longer at a rate of about 1.4 milliseconds per day per century[1] (that is, over the course of a century, the length of a day gets longer by about 1.4 milliseconds). This means that if we want to define a second as having a constant duration (which is highly desirable for scientific purposes) we cannot simply define it as being one 86400th part of a day, because days are slowly and surely getting longer.
In fact, the standard second is one 86400th part of the duration of a day in approximately the year 1820. The slight slowing of the Earth's rotation since then means that nowadays a day is around 86400.002 seconds long: whereas our clocks measure out days exactly 86400 seconds long.
This discrepancy may not be large, but it accumulates: it means that after 1000 days, our clocks will have gained around two seconds on astronomical time, so that they will register 12 noon two seconds before it is actually mid-day. And this error, left unchecked, would of course accumulate: after 2000 days the discrepancy would be about 4 seconds, and so on, until eventually our clocks would say it was noon when it was actually midnight.
The solution that scientists have come up with is something of a kludge. Every now and then (a little less than once a year) they arrange for the official clocks to reckon a day with 86401 seconds in it: the extra second being called a "leap second". By this means, our clocks are kept from getting ahead of the natural "clock" of the Earth's rotation.
[edit] The creationist argument
The reader unfamiliar with creationism may at this point be wondering what in the world leap-seconds can have to do with creationism. However, the reader who has studied the habits of creationists will recall that more or less any mistake about science can be turned into a creationist argument.
The mistake that creationists have made in this instance is a doozie. Having vaguely grasped the idea that a leap-second is added approximately once a year, and that the insertion of leap seconds has something to do with the fact that the Earth's rotation is slowing down, they have leapt to the bizarre conclusion that the Earth is slowing down by one second per day per year, rather than the true figure of 0.0014 seconds per day per century.
From this, they deduce that at this rate, the Earth a billion years or so ago would have been spinning so fast that centrifugal force would have distorted the Earth into a pancake shape and flung loose objects off into space.
Prominent creationist fraudster Kent Hovind explains this thesis in his own inimitable style:
- Another factor. The earth is spinning—we are turning around. How many knew that already? We are turning around. You know the earth is going a little over 1,000 miles an hour at the equator, but the earth is slowing down. It is actually slowing down 1000th of a second everyday. Pensacola News Journal, 1990, said on December 6, “Earth’s rotation is slowing down, June will be one second longer than normal. The earth is slowing down 1000th of a second every day.” Astronomy magazine announced, 1992 in the June edition, “Earth’s rotation is slowing down, June is going to be one second longer than normal.” We will have to have a “leap second.” A leap second? Most people have heard of leap year, but lots of folks have never heard of leap second. Did you know we have a leap second about every year and a half now because the earth is slowing down? Now kids this is going to be kind of complicated so listen carefully. The earth is spinning but it is slowing down. So that means that it used to be going faster. How many can figure that out with no help? Okay several. Well, now if the earth is only 6,000 years old that is not a problem. It was probably spinning a little faster when Adam was here. Maybe they had 23 and 1/2 hours in a day. They would not notice, they did not have a watch anyway. Some of these folks want you to believe that the earth is billions of years old. Now that would make a problem. If you go back a few billion years, the earth was spinning real fast. Your days and nights would be pretty quick! Get up, go to bed! Get up, go to bed! Get up, go to bed! You would never get anything done. And a centrifugal force would have been enormous, would have flattened the earth like a pancake. The winds would have been 5,000 miles an hour from the Coriolis effect. You think the dinosaurs lived 70 million years ago? I know what happened to them? I know what happened to them... they got blown off! No they did not live 70 million years ago, folks; it simply cannot possibly be true.[2]
Now, if the creationists' figure for the slowing of the Earth was accurate, their conclusions would be correct. As Thwaites and Awbrey point out in their article As the World Turns: Can Creationists Keep Time?:
- 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.
The problem with the creationist argument is that the figure on which it is based is totally wrong. The Earth is not "slowing down 1000th of a second everyday": the reason for the existence of leap-seconds, as we have noted, is that the Earth is slowing down by 1.4 milliseconds per century. This is the figure provided by the United States Naval Observatory[3], the body responsible for timekeeping in the United States, who add:
- Confusion sometimes arises over the misconception that the regular insertion of leap seconds every few years indicates that the Earth should stop rotating within a few millennia. The confusion arises because some mistake leap seconds for a measure of the rate at which the Earth is slowing. The 1 second increments are, however, indications of the accumulated difference in time between the two systems. (United States Naval Observatory, emphasis in the orginal.[4])
This perfectly describes the creationist blunder: they have mistaken the accumulated difference between our clocks and the Earth (about 1 second per day per year) with the rate at which the Earth is slowing (0.0014 seconds per day per century).
This blunder renders their argument worthless: their calculations are a classic instance of the computer programmers' proverb: "Garbage In, Garbage Out".
[edit] The zombie walks
Some creationists have been persuaded that they are wrong about the rate at which the Earth is slowing: for example, the originator of the leap-second blunder, Walt Brown, no longer uses this claim in his propaganda.
However, in a peculiar turn of events, some creationists, having acknowledged that the Earth is only slowing down at 1.4 milliseconds per day per century, continue to draw from this accurate figure the same conclusion as their more deluded brethren who put the figure at one second per day per year. That is, those creationists who accept the true figure for the Earth's deceleration still claim that it follows from this accurate figure that a billion years ago the Earth would have been spinning at impossibly high speeds, would flatten itself out like a pancake, would have thrown loose objects off into space, and so forth --- as though they could draw exactly the same conclusions from a figure for the slowing of the Earth which is several orders of magnitude smaller than the figure on which the creationist argument was originally based.
This is, of course, nonsense. Using real figures and the real physics relating to the dynamics of the Earth-Moon system, scientists have been able to calculate how fast the Earth would actually have rotated in the past, yielding a figure of a thirteen hour day 4.5 billion years ago when the Earth was first formed.
This fairly modest speed of rotation is not sufficient to justify creationist fantasies about the effects of centrifugal force. This can be verified by considering Jupiter, which has a day lasting a little under ten hours[5], but is not noticeably pancake-shaped.
[edit] Creationism gets a shot in the foot
If creationists were a little bit smarter, they would keep quiet about the slowing of the Earth's rotation. For it is possible, using real figures and real physics, to calculate the speed of the Earth in times gone past: for example, it is possible to calculate that the Earth should have had a 21-hour day in the Devonian period. Remarkably, it is possible to demonstrate that it did, which provides a nice piece of confirmatory evidence for an old Earth.
For details of how the early Earth's rate of rotation can be demonstrated, consult our main article on Sclerochronology.
