RSS Feed
iTunes Link

Episode 3: Young-Earth Creationist Claims About Comets

Download the Episode

Recap: A mainstay of young-Earth creationist arguments is that comets prove the solar system cannot be more than 10,000 years old. Listen in and find out why this claim ignores science.

Puzzler: Asteroids tend to have, overall, pretty circular orbits and they generally orbit within the rest of the plane of the solar system. Comets, though, generally have highly elliptical orbits and are generally on more inclined orbits to the planets. Why?

Solution to Episode 2's Puzzler: "No" to both. The reason is two-fold. First, once you get far enough away from an object, its angular size will be linear to its distance. This is called the "small angle theorem." The second reason uses the first: If the size we get from these objects makes them appear smaller at the same, linear rate, then it doesn't matter how far away we are, the relative sizes will always be the same. This is, of course, using the given situation in the problem that we are many light-years from the system to begin with.

Additional Materials:

Transcript of the Main Material:

Note: Clips were taken from the Institute for Creation Research's radio show from February 4, 2006. You can find the original audio on their website.

Before we really get started with this, I'm going to talk about what comets are and the structure of the solar system.

For lack of a better analogy, comets are commonly referred to as the "dirty snowballs" of the solar system. They are amalgamations of rock and ice where a significant fraction of their material is ices or "volatiles."

Volatiles are, well, volatile. They are molecules that are frozen at low temperatures, but once they reach a temperature like, say, room temperature, they melt and either turn into a liquid or directly into a gas. Water-ice and methane-ice would be considered volatiles that make up a large amount of comets, among other molecules.

The body of the comet itself - called a "nucleus" - is generally up to a few kilometers across. For example, Comet Halley's nucleus is about 7 by 15 kilometers, an oblong shape. Of the comets that spacecraft have visited, Halley was a rather large one. When the Deep Impact mission encountered comet Tempel 1, it found the average diameter to be about 6 km, while Stardust found comet Wild 2 to be 4 km. Comets can get pretty big, with Comet Hale-Bopp estimated to be about 60 km in size.

Unlike planets and most asteroids, comets do not generally stay in nice, circular orbits. Rather, they spend most of their time in the frozen outer parts of the solar system, like out beyond Pluto, and then for brief periods of just a few years they venture into the inner solar system and swing by the sun.

When they get closer to the sun than Jupiter - which is about 5x farther from the sun than Earth - the volatile elements in the comet start to melt. This is what forms the comet's coma and tail. The material continues to slowly melt or vaporize until after it swings past the sun and heads out beyond Jupiter again.

So that's the basic idea behind what a comet is, and creationists generally don't dispute that.

Now let's talk a bit about the structure of the solar system.

In the center, we have the sun, a star. Moving outwards comes the terrestrial-type planets, with Mercury, Venus, Earth, and Mars. What these have in common are that they are rocky objects with either no or a relatively thin atmosphere. Still moving outcomes a large field of asteroids which are, again, rocky, with very little "volatile" compounds.

This is an important concept in the solar system because interior to the asteroid belt, when the solar system formed, volatile compounds were not stable. Beyond the asteroid belt, they were. Hence, moving outwards, we have the two gas giant planets -Jupiter and Saturn - with ginormous gaseous atmospheres. Beyond these are the two ice giant planets - Uranus and Neptune, which also have large gaseous atmospheres but are enriched with more types of volatile compounds that Jupiter and Saturn are not --namely methane, which gives them their blue color.

Beyond the realm of the ice giants lies the Kuiper Belt; or, for the 2% of my listeners who are Brits, the Edgeworth-Kuiper Belt. This was a theoretical region of the solar system that was supposed to contain a large number of cometary nuclei --basically, very icy asteroids. I say this "was" a theoretical region because the first Kuiper Belt Object (KBO) was discovered in 1992. Since then, many more have been discovered. The Kuiper Belt is the source of comets that have orbits of less than about 200 years.

Beyond this lies another theoretical region called the "Oort Cloud." This is theoretically a vast cloud of cometary nuclei that form the comets with periods of more than 200 years. It is still a theoretical region in our solar system because we have not and cannot yet detect any of them because they are much too small and much too far away for our current technology. But, we have seen Oort Clouds around other star systems.

[Clip from ICR's radio show about not believing in the Oort Cloud.]
This is an interesting clip. From a religious person who takes the Bible on faith. Not seeing something therefore not believing it exists. Wow. It's such an incredible double-standard that I'm not really sure it deserves going into much, but I will very briefly.

No one's ever seen gravity, but we see its effects. No one's ever seen the impactor that formed Tycho crater on the moon, but we have a darn good idea of how it happened. No one's ever seen a star explode, but we have good models that make predictions about what we should see after they explode, which is what is observed.

But really, when you get right down to it, for a creationist of all people to say that they haven't seen something therefore don't believe it's there is just the height of hubris.

Anyway, the idea is that over time, through interactions with each other or passing stars, the comet nuclei will be nudged and while some may be nudged out of the solar system, others are nudged into the solar system and will begin their lifetime as a comet that we can observe.

That was a bit of a long clip, but boiling it down, there were three main points: (1) That comets lose 5% or a few feet off their size at every orbit, (2) that a comet with a 100-year orbit would die out in 10,000 years, and then (3) therefore all comets must be less than 10,000 years old so the solar system must have been recently created. We'll go in order ...

First, on the amount of material lost. If you lose 5% off your size during every orbit, the first thing to realize is that you will survive more than 20 orbits. That's because you start out at 100%, go down to 95%, but then 5% off of 95% is not 90%, it's90.25%. The next pass you'll be at 85.7%, then 81.5%, then77.4%, and so on. After 20 orbits, you're still at 35.8% your original size. It takes about 45 trips to get under 10%, and about 60 trips to get to under 5%. Not 20.

But, the other problem is that 5% is not the same as "a few feet" off of a several-mile-wide comet. Let's just take a small comet, say, 1 mile across, and be generous in that "a few feet" is 10feet. For you metric folks, that's about 1.6 km and 3 meters. "A few feet" is about 0.02% of the comet's size, not 5% ...that's a difference of a factor of 250x. Not just 2 or 3 like we found using the percentages. So now, if we lose 10 feet off a 1-mile-wide comet each orbit and it has a 100-year orbit, then it's going to last about 500 orbits, or 50,000 years. Not <10,000.

That brings us to the second point. As I just explained, if we're losing "a few" feet off of a comet during each pass of a 100-year-orbit comet, we'll last longer than 10,000 years. But, not all comets have 100-year periods. As of August 2011, there were 4329 known comets. Several hundred of these have periods measured in the tens of years. Several dozen have periods ranging in the thousands or millions of years. For example, Comet McNaught that was famous in 2006 has a period of 92,600 years. The "Comet of a Lifetime," Hale-Bopp, has a period of around 2500 years.

That brings us to the third point, where they took the simple, simple math and way, way wrong assumption that because their example was a 100-year period comet, all comets must be less than10,000 years old. That's just wrong. There's not really another way of saying it. Besides, for example, Hale-Bopp which would only complete four orbits in 10,000 years, assuming its orbit doesn't get significantly altered by Jupiter or other planets, then by even the creationists' math, it would still be a very viable comet a million years from now.

And, that ignores the Oort Cloud as a source for cometary nuclei. Now, I realize the creationists don't think it exists, as I discussed more in-depth earlier. Let's actually say it doesn't. If it doesn't, where do all of these very long-period comets live? Where do they spend most of their time? By definition, these comets spend most of their time near their farthest distance from the Sun. We've only charted a few in the last hundred years. So there must be hundreds of thousands more out there that we haven't seen yet unless you want to use some very special pleading that we've seen all the long-period, 10s of thousands of year orbit comets come by the sun in the last hundred years or so.

There's one more thing about this that I want to address, considering that this is my first podcast about young-Earth creationism.

That short clip shows you something that you will see in almost all young-Earth creation "science" products: They say that all scientists who disagree with them are evolutionists. It does not matter what the scientist actually studies -- history, geology, physics, chemistry, astronomy, biology, engineering -- they are all "evolutionists."

It's really an attempt at poisoning the well - linking a science they don't like with one they know 40% of Americans reject - in order to further try to make the listener, reader, or viewer reject the real science.

Provide Your Comments:

Comments to date: 1. Page 1 of 1.

Robert Harrington   Mineola, Texas

7:30am on Tuesday, September 13th, 2011

It seems a bit funny to me that the Creationists try to use math (a tool of science) to "Prove" their point of view. They feel threatened in their belief system, by modern science. There is no way to meld the Bible and modern science. The Bible was written 3000 to 1500 years ago to try to help a non-technological society cope with lifes spiritual problems, and there is much Good in this collection of writings. To take as an article of faith every "jot and tittle" of a book that has gone through several translations by people that had their own agenda to promote, is ludcrious,and using pseudo-science to try and disprove the observable results of the scientific method is futile.

Your Name:

Your Location:

Vote:

Your Comment:

Security check *

security image