Exposing PseudoAstronomy

September 4, 2008

Why Comets Are NOT Evidence for a Young Solar System

Filed under: comets,creationism — Stuart Robbins @ 4:47 am
Tags: , , ,

This post is in regards to the Institute for Creation Research’s February 4, 2006 program about Comets.  You can listen to the audio here.

The beginning of this program is actually fairly decent, talking about how comets are “dirty icebergs” that orbit the Sun, and when they get too close, they begin to lose material because the Sun’s heat and wind both melt and erode material from its surface.  I don’t know precisely if the number “5%” of it gets removed, but that’s not a huge issue for me (is for them, and I’ll explain why).

The first real mistake in this piece comes at about 2 min 30 seconds in.  The host makes the point that, “Since matter is being stripped away from comets, how long do they survive in the solar system?”  Their expert, Dr. Falkner (not sure on that spelling), replies that most comets are only a few miles across and that each time they come close to the Sun, they may “lose a few feet off of that size.”

This contradicts what they said above about the 5% number.  Let’s say for argument that a comet is 1 mile in diameter (probably fairly small).  And a “few feet” amounts to a generous 10 feet.  If it loses 10 feet off its diameter every pass, it would need to go through about 528 passes of the Sun to disintegrate … not after “probably maybe 100 trips around the Sun it eventually dissipates.”  If comets have orbits of 100 years (as they then generalize), then that’s nearly 53,000 years!  NOT 10,000 years.

Then let’s examine the claim of 5%.  If a comet is again 1 mile in diameter, then it doesn’t simply have to approach the Sun 20 times (20*5 = 100) to die off.  5% is multiplicative.  So the first pass it would have 95% of its original material, but the next pass would reduce it to 90.25% of its original material (0.95*(1-0.5)).  This continues iteratively.  So the third pass would leave it with 85.7375% (0.9025*(1-0.05)), and so on.

But this is again a huge over-generalization, but they use it to say it’s evidence for recent creation.  Well, yes, IF you assume that all comets started orbiting the Sun on orbits that took them close to the Sun when the solar system was formed, IF you assume that all comets have 100-year orbits, IF you assume that all comets are only 1 mile in diameter and lose a few feet or 5% (which are NOT equivalent) of material after every orbit, then sure, this may be evidence for a recent creation.  But this is NOT the case.

And it’s not even the biggest mistake they make.  The host then says that, “Many evolutionists answer this question by hypothesizing that a large cloud of orbiting comets (dirty snowballs) exists in the outer reaches of the solar system.”  So there’s the association fallacy at work, I’m an “evolutionist” and therefore I’m wrong about other things simply by that association.

Well this claim that that’s what astronomers believe is mostly true.  They are referring specifically to the Oort Cloud, a very large (2-light-year-radius) cloud of comets that is believed to contain trillions of bodies in the outer reaches of the solar system, extending half-way to the nearest star (4.3 light-years away).  It is believed to be the source of long-period comets (comets that have a “year” of more than 250 Earth-years).  But there’s another region of comets interior to the Oort Cloud that starts just outside Neptune – the Kuiper Belt.  This is another region of space believed to have billions of comets that is the source for short-period comets (those with years less than 250 Earth years).  The Kuiper Belt was first observed in 1992 (when the first object was discovered in it).  The Oort Cloud remains the subject of theory simply because the objects in it are so far away and so small that they are too faint to be detected with current technology.  But it is still a falsifiable theory.

Now that you have a brief understanding for what these are, on with the ICR claims (at about 4 min in):  [host] “However, there is a small problem with the Oort Cloud Theory.”  [scientist] “All this sounds very complicated, but the bottom line is nobody’s ever seen the Oort Cloud.  We see what looks like an Oort Cloud around other systems, but we don’t see it in our own vicinity.  So I have my doubts that it exists …” [emphasis mine]

So let’s think about this for a bit.  “Nobody’s ever seen the Oort Cloud … so I have my doubts that it exists.”  Alright.  No one’s ever seen gravity, but we see its effects.  No one has ever seen a crater form on a planetary surface, but we have a very good idea of how it happens and we can model it.  No one has ever seen a star explode (this is a good thing) but we have good models that make predictions about what we should see after they explode, which have been observed.

The Oort Cloud is hypothetical, and it is not possible to actually observe it with our technology.  But, it is the best science-based explanation for long-period comets.  The Kuiper Belt was hypothetical, but it was later verified and we have now cataloged many hundreds of members of it.

And they even miss the point that even if the Oort Cloud does NOT exist, then (a) there’s no source for long-period comets, but (b) it STILL does not mean that the solar system was created 10000 years ago or less.  That’s because it’s actually fairly few comets that enter the inner solar system at any given time, the Belt has to be perturbed by a passing object to knock a comet into the inner solar system.  That takes time.  And so any object in the Kuiper Belt today could get knocked into an orbit that takes it close to the Sun and makes it a comet to us.  That starts the clock on that particular comet at 0.  So the fact that we still see comets today says ABSOLUTELY NOTHING about the solar system having been created recently.

The creation scientist then goes on to talk about some other stuff, but around 5 min 30 sec basically sums up the point of the broadcast episode:  “Comets are fragile.  During their orbits around the Sun, they shrink, or melt, some occasionally hit the Sun or Jupiter, and some comets leave the solar system all together.  Yet, there’s the continued presence today of hundreds of known comets … each and every comet is a witness to a supernatural, created solar system that is just thousands of years old, not billions.”

As I have hopefully convincingly shown, this is simply not true.  It is based on gross generalizations, assumptions, and outright disregard for the consensus of the structure of the solar system.

But, it’s difficult to argue with faith, when the announcer says (8 min 30 sec):  “As creationists, we know that comets, along with the rest of the Universe, were made by God on Day 4 of Creation Week.”

This is why I am not trying to convince you that creationism is or is not true.  I am simply illustrating that the scientific claims that creationism makes are flawed, not true, or outright denials of evidence.



  1. good presentation of faith…lol….gravity can be observed,,,,oort cloud CAN NOT!!!

    Comment by mhykz — August 16, 2011 @ 11:05 pm | Reply

  2. […] magnetic field strength last time, this time I’ll choose comets and simply link to my blog (here, or here), or podcast […]

    Pingback by A Follow-Up on How Science Works versus Creationism « Exposing PseudoAstronomy — November 30, 2011 @ 5:25 pm | Reply

  3. While I agree with most of the points, I think the use of “can’t see it but it’s still there” is flawed… People of religion will often comment that just because you can’t “see” god doesn’t mean god doesn’t exist. I think it would be better phrased that we may not be able to see gravity, we can still measure it’s effects.

    Comment by flip — August 13, 2012 @ 4:30 am | Reply

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