Or not, as the case may be. If you haven’t already heard Comet ISON – once hailed as a potential “comet of the century” – has almost certainly fragmented after rounding the Sun and will not be spectacularly gracing our skies over the new year, nor returning to the outer reaches of the solar system intact. In more hopeful times back in late June Brian Thomas published an article called “Ison–The Comet of the Century,” which opened:
In September 2012, a Russian and a Belarusian astronomer using the Kislovodsk Observatory co-discovered a comet heading our way. Comet Ison should become visible to Earth viewers in December 2013 after passing perilously close to the Sun during November. It may even appear brighter than the moon, triggering discussions about when and how comets formed.
Thomas, who paid no attention to what was even then a very real possibility that ISON would break up during its “perilous” perihelion approach, used the comet as a launching pad to promote the young-Earth creationist view that comets prove that the universe is young. But even before fragmenting ISON was not a particularly good poster-boy for this cause.
When comets pass the Sun in their highly-elliptical orbit they lose mass, and after enough orbits they will eventually cease to be. The rule of thumb sometimes used by creationists is that this process will take around a hundred orbits, meaning that a comet with a period of around a hundred years, like Haley’s comet, could be expected to be only 10,000 or so years old and fitting with their 6000 year age for Earth and universe as a whole. This logic of course doesn’t work – calculating how long a comet will last from now on doesn’t tell you how old it is – but positing that Haley was originally a large ice-planet that has been slowly whittled down over the last few billion years to its present relatively diminutive size is not the correct solution to this problem.
Instead, consider another comet that you may have seen in the news recently: Comet Encke, which passed its own perihelion about a week ago. Encke has the shortest period of any comet known, with an orbit that doesn’t even take it as far out as Jupiter. This comet passes the Sun every ~3.3 years, which is one reason why it didn’t make so much of a news splash, and by using the previously explained creationist reasoning we can conclude from this information that the universe can be little more than 300 years old. This is an unacceptably low result for everybody, at least as far as I am aware, so the conclusion we must draw is that this is not a reliable or useful method for estimating the age of the Earth or anything else.
The real reason for Encke’s existence and short period, as everyone should be able to accept, is that it originally had a longer period but orbital interactions have caused it to reduce (perhaps it was part of a larger comet that broke up). The same explanation of comets with longer periods becoming shorter works for all comets – whether they be Haley, ISON, or the proto-Encke – and the original source is hypothesised to be the Kuiper belt and the Oort cloud.
The Kuiper belt itself was originally only hypothesised, but has since been definitively observed, while the Oort cloud has yet to be seen as the objects that make it up are small, faint and very far away. Because of this young-Earth creationists feel free to deny that the latter bunch of iceballs exists at all. Thomas said in his June article:
Unfortunately, nobody has yet witnessed a single one of those “trillions and trillions of chunks.” Going strictly with observational science, the “so-called Oort cloud” may exist only in the reservoir of the human mind.
Clearly, secular astronomers invented the Oort cloud to rescue their billions-of-years dogma from a disintegration process that limits a comet’s age—and thus the age of the Solar System—to thousands of years.
But while we have never knowingly detected a single photon from the Oort cloud – and we would not expect to have done so – that doesn’t mean we can’t observe other evidence for its existence. Like ISON, for example.
This doomed orbit appears to have been the first time that ISON has approached the Sun. It’s orbit seems to be a borderline case between one that would lead to it returning in a few hundred thousand years or for it to never come back at all, but with its fragmentation such speculation is moot. The “secular” explanation, as Thomas calls it, is that ISON was relatively recently perturbed from its far distant Oort cloud position and began to fall towards the Sun for the first time, eventually coming too close and falling apart. Importantly, comets like ISON show that there is indeed a regular supply of fresh comets replacing those vaporised by the Sun. This one in particular may have done something else, but it is evidence that the comets that are supposed to be coming from the Oort cloud really are doing so, contrary to what the creationists require.
In contrast YECs must believe that when He created the heavens their god also created a small collection of iceballs, with orbits that they would never have time to fully complete, which would pass by the Earth in a single blaze of glory for reasons known only to Him. Indeed, Steve Austin once noted that the Bible doesn’t talk about comets much, suggesting that this might be because they are often seen by pagans as a symbol and that true Christians shouldn’t pay them any heed. But Thomas concluded his article by saying:
When Ison becomes visible later this year, perhaps it will remind thoughtful viewers that the universe is quite young, just as Scripture teaches.
The orbits of comets are deterministic, and Thomas’ god is supposed to be all-knowing and all-powerful, so clearly He had other ideas about the purpose of His comet than to aid the goals of the creationists. I wonder if Thomas will write a follow-up article with the bad news?