I'm not really all that mysterious

Ptolemy and Empiricism

It’s funny how people use the example of Copernicus and the heliocentric model as the archetype for scientific progress. The fact of the matter is that, at least initially, Ptolemy’s geocentric model actually still made more accurate predictions.

This is probably because Ptolemy incorporated empirical findings into his model (eventually causing it to evolve into something exceedingly and impossibly complex) whereas Copernicus made the (now known to be very inaccurate) assumption that planetary orbits are perfectly circular.

It was Galileo (often touted as the epitome of reason triumphing over unreason), then later Lorentz, then finally Einstein who realized that there is no privileged reference frame, which is why our current theory of gravity is known as Relativity. Because of the principle of relativity, it’s actually perfectly valid to consider the Earth at rest while the rest of the universe moves around it (although the calculations are much easier to perform if you pretend that the sun is stationary while the planets orbit in ellipses, and you ignore the effects of everything outside of the solar system.)

This is why the reductionist statement that Copernicus was right and Ptolemy was wrong always irks me. That’s almost never how science really progresses.

The Great Ptolemaic Smackdown • 2013 Aug 24 • Mike Flynn • The TOF Spot

I have two things to say that might surprise you: first, geocentrism is a valid frame of reference, and second, heliocentrism is not any more or less correct.

Surprise! Of course, the details are important.

Look, I’m human: I say “The Sun rose in the east today”, and not “the rotation of the Earth relative to the rest of the Universe carried me around to a geometric vantage point where the horizon as seen from my location dropped below the Sun’s apparent position in space.” To us, sitting here on the surface of a planet, geocentrism is a perfectly valid frame of reference. Heck, astronomers use it all the time to point our telescopes. We map the sky using a projected latitude and longitude, and we talk about things rising and setting. That’s not only natural, but a very easy way to do those sorts of things. In that case, thinking geocentrically makes sense.

However, as soon as you want to send a space probe to another planet, geocentrism becomes cumbersome. In that case, it’s far easier to use the Sun as the center of the Universe and measure the rotating and revolving Earth as just another planet. The math works out better, and in fact it makes more common sense.

Geocentrism? Seriously? • 2010 Sep 14 • Phil Plait • Bad Astronomy

initially published online on:
page regenerated on: