This is the best animation that I have seen of the ancient Earth centered system for calculating the positions of the planets in the sky. Smaller circles on the main orbits called epicycles correct for the fact that planets don't actually revolve around the Earth. It's cool to see the whole system in motion at once.

Contrary to popular opinion, there never were 'epicycles upon epicycles' needed to produce further corrections, and when Kepler finally proposed his elliptical sun centered system, he had found that the Ptolmeic model was about as accurate as the circular Earth centered Copernican model - both accurate to a few arcminutes. Another interesting fact is that the Copernican model also included small epicycles called 'epicyclets'. Both systems were mathematically quite difficult to work with.

The Copernican model was ironically praised for the fact that it adhered better to Aristotelian theory in that heavenly bodies move at a constant speed, which does not occur in Ptolemy's model - a problem that he made apologies for. Many astronomers were simply impressed that two radically different models could give accurate planetary positions.

The driving economic interest behind creating these models was the production of natal charts giving the positions of the planets at the time of birth, useful for making astrological predictions - a practice that paid the bills for the Renaissance astronomers.

Great Animation of the Ptolmeic Model of the Solar System

A South Korean woman paralyzed for 20 years is walking again after scientists say they repaired her damaged spine using stem cells derived from umbilical cord blood.

This appears to be the first case of successful spinal cord therapy using stem cells. This should increase the pressure towards allowing stem cell research.

Paralyzed woman walks again after stem cell therapy

Imagine two people standing about 500 feet from a car that is against wall around a bend. One is holding binoculars, the other a piece of paper. One looks through his binoculars at the car and says, "Someone was driving that car too fast, skidded out, and slammed into the wall."

The other person says, "I don't believe that, the police report says that it was placed there by God."

"I know that the report says that, but I can pretty clearly see skid marks on the road, the car is smashed, the windows shattered, and there is broken glass on the road."

"I don't necessarily agree. I see what you mean about the marks, but they don't look that clear to me. I am also not sure that the stuff on the road is glass. To me it looks like it could be water. Besides, I believe Officer Joe, he is a good man."

"I know that Officer Joe is honest, but I think he is mistaken. Through my binoculars it looks pretty clear that the car was driven into the wall. It looks like a man drove it there, the skid marks are clear, that is definitely say that the stuff on the road is broken glass and not water. I also think I see the man's head leaning against the steering column. It looks to me like an accident."

"That is fine. It is just your opinion though. I believe the report that God put it there. You know, binoculars often produce optical distortions, there is no such thing as a perfectly accurate lens. In addition, you aren't entirely sure about the man's head, it may not be that there is a man in the car, you said that you aren't sure. If there is not a man in the car, then how could it have gotten there? The police report says it was placed there by God, and if no one was driving it..."

"Ok, ok, I know about distortions and all, but I use these binoculars all the time and I know what is and is not a distortion. Besides, to say that the car was put there by God just sounds a little..."

"A little what?"

"I mean, come on. The car was driven into the wall. This is a stupid argument. I can see that..."

"Can you see the driver?"

"Well I can sort of make out..."

"No, you can't say for sure. But you are calling me stupid. Why can't you admit that you have your opinion and that I have mine?"

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If you are a scientist, this is what the creationist argument looks like. The scientist isn't smarter or better than the other person, he just has a set of mathematical and instrumental tools, the binoculars, that he is skilled at using with knowledge of their limitations.

With the techniques of modern biology, the evolution argument is about that obvious. The scientist sees an incredible amount of evidence that people descended from primates. Just like in the metaphor, the creationist seems to be lacking binoculars. The only difference is that in reality the toolset is differential equations, statistics, technology, chemistry, and complex instrumentation. Unfortunately, this i... [ Read More (0.1k in body) ]