Do Comets Indicate a Young Earth?

Comet_WestOne of the common arguments made for a young creation has to do with the age of comets. While the arguments seem reasonable at first, it’s pretty easy to see how they miss some key information. The interesting thing about this is that it not only becomes a good example of the oversimplified arguments that are commonly used, but also the importance of testing.

Comets are small bodies orbiting the sun, made up of rock and ice. When they get near the sun, its heat causes the ice to melt and boil away. The resulting gases make the characteristic tail that we see on earth. Thus, comets lose a little material each time they get near the sun because some gets boiled away.

Some comets orbit the sun every 200 years or less, and these are considered short-term comets. Others take much longer, and these are called long-term comets.

The YEC argument is that, since comets lose a little material each visit, they would eventually run out of material to boil, and no longer have tails. The calculations for the amount of material lost each time are pretty straight-forward, and it’s easy to show that short-term comets cannot have been orbiting the sun for billions of years because they would have lost all material that was not solid rock.

So the simple claim is that, since we still have short-term comets around, creation cannot be billions of years old.

Seems clear, but this assumes that comets have been in the same orbit for their entire existence. It turns out that this is not true; comets are known to change orbits because the planets can affect them. The YEC conclusion only makes sense if one ignores real-world observations.

A great example of this is comet 67P/ Churyumov-Gerasimenko. In 2014, the Rosetta mission landed a probe on the comet. During the time the probe was analyzing the comet, it approached the sun and began to give off gases to form a tail. With the data from the probe, scientists were able to measure the amount of material given off. This allowed the YEC arguments to be directly applied, which seemed to show that the comet cannot be very old.

However, it turns out that NASA calculated the comet’s orbit in reverse, to see what it had been doing in the past. NASA is very, very good at this sort of calculation; it’s what allows them to send probes all over the solar system across billions of miles.

A summary of their calculations can be found here, but basically, they found that the comet had been nudged out of a different orbit by some encounters with a couple planets. Before that, it had been staying far away from the sun. It had been so far from the sun that nothing would have boiled off of the comet, and it had been there for a very long time. In other words, comet 67P clearly shows how today’s active comets could still be billions of years old.

Unfortunately, this simple test was ignored by Institute for Creation Research’s (ICR’s) science writer, Brian Thomas, when he attempted to show that comet 67P indicated a young creation. Thomas simply stated the party line, apparently without checking the conclusion himself. He stated this opinion as scientific fact, and because he is a very public figure, many people would have seen this teaching.

I don’t know how many people tested his statements, but from some of the rhetoric I’ve read concerning this false teaching, quite a few people accepted what he said as fact, without practicing any discernment whatsoever. (For one careful test of Thomas’ article, and many others, see this article on Naturalis Historia.)

Perhaps this is why the Bible teaches us to test the spirits, to test everything and hold onto the good. While it may be practically hard to check every teaching we hear, we should have the sensitivity to validate a teaching at least a little before repeating it or using it to judge others, especially on controversial topics. The fact that teachers like Brian Thomas can make strong claims without checking out the basic facts, and get away with it over and over, means that his readers are not practicing Biblical discernment.


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