Good Math/Bad Math

Friday, May 05, 2006

Creationists and Extra-solar planets

I had so much fun with the AiG pseudo-relativity argument, I decided to prowl around their site looking for other fun things to shred. Todays article is Extrasolar planets suggest our solar system is unique and young. This has the advantage of being incredibly stupid, and of also demonstrating some of the statistical errors that I just talked about the other day.

Here's the basic idea of their argument:
Much excitement concerns the star 55 Cancri. Apparently, it has a Jupiter-like planet orbiting further out—at about 5.9 AU with a mass about 4.05 M_Jupiter. (AU, stands for astronomical unit, the unit of length for solar-system-scale measurement, and equals the average distance of the Earth from the sun. The mass unit, M_Jupiter, is based on the mass of the planet Jupiter, about 318 times the mass of the Earth.) Because this exoplanet with 55 Cancri exists, so the thinking goes, other exoplanets must exist much farther out from their host stars. If so, our solar system would not be unique.

Evolutionists hope that many stars will be discovered with habitable Earth-like planets and gas-giant planets orbiting far from their host stars—similar to our solar system configuration. It’s interesting that this latest speculation has arisen from extrapolating a single observation with both mass and measured orbital eccentricity (e = 0.16) much greater than Jupiter’s (e = 0.05). The reports also reveal that 55 Cancri apparently has two other Jovian-mass planets orbiting much closer (< 0.3 AU). Obviously the planetary system for 55 Cancri is not particularly similar to our solar system.
Basically, they want to argue that our solar system is special. The way that they're going to do that is to look at what we know about other solar systems, and argue that because those solar systems aren't much like ours, that therefore our solar systems is special and unique.

Before I hit them for anything else, I have to point out one piece of general linguistic bogosity. Throughout this article, they refer to the astronomers and other scientists looking for extra-solar planets as "evolutionists". Of course, none of this has anything to do with evolution. It's just a knee-jerk thing with them: anything which seems to suggest that their biblical doctrine doesn't match physical reality is automatically put under the banner of evolution.

Once they're done with the introduction, they present a bunch of statistics about the extrasolar planets that we've discovered so far:
A simple statistical analysis of some of the data for the exoplanets listed to date3 yields the following averages:
  • Mean semimajor axis, a = 1.24 AU
  • Mean eccentricity, e = 0.274 (larger than Pluto’s e = 0.244, the most eccentric of our solar system)
  • Mean mass = 3.295 M_Jupiter
If this average gas-giant planet were orbiting in our solar system it would have a perihelion, (q) of 0.90 AU and aphelion, (Q) of 1.58 AU and continually cut across Earth’s orbit. We need to keep in mind that the masses reported are a minimum estimate, not a maximum.

In our solar system, the average values of the nine planets for the same three properties are:
  • Mean semimajor axis, a = 11.902 AU
  • Mean eccentricity, e = 0.081
  • Mean mass = 0.156 M_Jupiter
The ‘average’ perihelion, q is 10.938 AU and the aphelion, Q is 12.866 AU, which is well removed from the Earth’s orbit.
The extrasolar-planet data suggests our solar system is special, which is difficult to explain from a naturalistic evolutionary perspective. For some reason, when our solar system formed, the sun managed to avoid the more common ‘fate’ of other star systems. Specifically, we do not have gas-giant planets orbiting from 0.1 to 3.0 AU from the sun, like 75% of the stars with planets so far listed.3 The other planets in our solar system are well clear of the Earth’s orbit.
Here's where we start seeing the problem. Superficially, this all looks fine. So what's the catch?

How is the sample that was used to compute the averages for extra-solar planets selected? Well, it's the (very small) set of planets that had been discovered three years ago (when this article was written). And what properties does that sampling method have? Well, all of the planets were discovered using astronomical techniques based on how the mass of the planet perturbed the motion of its star. We do not know much about the solar systems with these large planets, except that they have large planets. Do they have smaller planets in closer or farther orbits? We can't tell. Are there other stars with smaller planets? We don't know.

There's the key. The way that we find extrasolar planets orbiting distant stars only works for extremely massive planets; and it works better for massive planets in close orbits; and it works better for planets with eccentric orbits (because eccentric orbits have a more pronounced effect on the star).

So if we can only find planetary systems with extremely large planets; and the only planets we can detect are the large ones (so even in a system with large planets, we can't tell if there are also small ones); and our method for finding these systems is better and finding systems with eccentric orbits... Then, by putting together statistics about what we know about these systems, we can conclude that other solar systems we know about tend to have larger planets in more eccentric orbits than our solar system.

Wow. Deep, huh?

And now it gets really funny.
The data is easy to understand from a young-earth creation model. Since Creation Week ended (Genesis 2:1–3) some 6,000 years ago as measured on earth, the sun and nearby spectral class G stars have completed much less than one galactic rotation. Certainly, since Creation Week, these nearby star systems have experienced little stellar evolution. The creation interpretation affects our understanding of the origin of our solar system and of extrasolar planets.

I wonder if evolutionists thank their lucky stars and random particle collisions for the unique configuration of our solar system and our habitable earth. Modern secularists cannot consider that the Creator had anything to do with it. Such thinking would violate a central tenet of modern science—methodological naturalism.8

From a creation perspective, God, during the Creation week, predetermined the initial conditions of our solar system to provide a habitable earth. We know from Genesis 1:31, that at the end of Creation Week God’s creation was ‘very good’. It is hard to imagine that gas-giant planets orbiting near the Earth and gravitationally interacting with it would fit the description of ‘very good’. Such interaction would cause the Earth to become as volcanically active as Jupiter’s moon Io, even if the orbits were stable.
Y'see, we know that earth is special because it's different from those other systems. The reason that it's different is because God said that his creation of earth was "very good", and if our solar system looked like the ones that they're comparing to, it wouldn't be very good. Therefore, God must have created the solar system this way, because it is very good.

Oh, and we know that the solar system is young, because, well, umm... Because if it were older, then it would have completed several galatic rotations which would have.. umm.., well, it would have messed stuff up. They can't really say how, or why.. just that it means that our solar system has experienced "little stellar evolution".


  • Wow! AiG must be right, Mark. The universe is very young because otherwise the "merry-go-round effect" would have screwed up the planetary systems. Just think of any playground: When you spin the merry-go-round several times, kids and toys and junk go flying in all directions. Clearly the galaxy hasn't spun around very much or all those nice neat planetary orbits would be askew. It's simple science. (Very, very, very simple!)

    You're right. This nonsense is on a par with their other arguments. It must be hard work to be this dim.

    By Blogger Zeno, at 9:46 PM  

  • Hey, when you're a cretinist, you can't be choosey: you have to grab at whatever straws happen to flutter your way.

    The fact that the argument makes no sense is irrelevent. Nothing about AiG makes any sense to begin with.

    By Anonymous Ray, at 9:59 PM  

  • This comment has been removed by a blog administrator.

    By Blogger Ketsuban, at 8:03 AM  

  • This comment has been removed by a blog administrator.

    By Blogger Ketsuban, at 8:04 AM  

  • You erroneously state that the technique used to detect exoplanets only works on large planets. The technique works for all planets since they all exert a force on their host star just like the star exerts a force on them (conservation of momentum, don't you know). It's just much BETTER at detecting big planets close to the star since then the force exerted on the star is that much bigger and more obvious.

    By Blogger Ketsuban, at 8:05 AM  

  • The AiG folks have some of the best comedy writers in the country. How do they think of this stuff?

    By Anonymous frank, at 10:16 AM  

  • Ketsuban:

    The technique that astronomers currently use for finding planets requires a fairly significant pertubation in the motion of the star; while smaller planets certainly do affect the star, at the distances we're talking about, the effect isn't large enough to be measurable. That's what I meant by the method only really detecting very large planets; given the current precision of our measurements, we're far more likely to find large planets than small ones, even for relatively close stars; and for distant stars, we haven't a chance of detecting small planets through gravitational effect.

    By Blogger MarkCC, at 10:41 AM  

  • "Stellar evolution"? Weren't the solar systems and galaxies intelligently designed? I've always assumed that supernovae were just the evidence of the FSM having a really bad noodle day.

    By Blogger Bob Munck, at 1:06 PM  

  • Does anyone else find the phrase 'Creation Week' rather silly? It sounds like the name of a small town fair or some political awareness event at a liberal arts college.

    By Anonymous Stormy Dragon, at 1:53 PM  

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