Sunday, April 29, 2007


I came along a phrase on a blog of a friend:

For example, the linguistic, traditional truth of 'the sun rises' is in contradiction with the modern, contemporary notion of heliocentrism.

Although I understand what he means by this example, I think his conclusion is not entirely true.
The rising of the sun is an observation that is done by everyone on the surface of planet Earth. This observation does not contradict heliocentrism, because heliocentrism is a possible conclusion that can follow this observation. The real contradiction is between heliocentrism and another conclusion of the observer seeing the 'sun rise', known as geocentrism, the traditional view, ie. since the Middle Ages in our Western view of the world.

Traditionaly, the observation of the sun rising led to the conclusion that the sun must revolve around planet Earth.
Planet Earth was believed to be in the centre of the Universe, with the Sun, the Moon and all planets in our solar system revolving around it. Even the stars where placed in a circular band around planet Earth.
In the sixteenth century, Copernicus stated that this model was incorrect and should be replaced by a heliocentric model, where the Sun was placed in the centre of the solar system, with planet Earth and the planets revolving around the Sun. This theory was later refined by Johannes Kepler, who based his conclusions, known as the (3) laws of Kepler, on observations made by his tutor Tycho Brahe.
Copernicus and Kepler certainly came up with novell ideas, which contradicted the contemporary view (or even doctrine) of geocentrism. However, their views are certainly not new. In ancient times, long before any big civilisation was noted in the European parts of the world, Indian and Arab scientists were already familiar with a heliocentric model.

An observer, tied to the surface of planet Earth, seeing the sun rising in the morning, travelling through the sky all day, going down in the evening and disappear at dusk, until it rises again at dawn, could come to the conclusion that the sun revolves around planet Earth, if this observer believes that planet Earth is a fixed point in the Universe. With geocentric believes, this is a logical conclusion.
The same observer, also tied to the surface of planet Earth, sees the sun rising, but believes that it is planet Earth that revolves around the sun, as propagated in the heliocentric model, can explain this too. This observer might come to the conclusion that between moments he sees the sun rise, go down and rise again, planet Earth makes a complete revolution around the sun. We know this isn't true, as planet Earth revolves around its own axis, resulting in the day-night cycle of the sun rising. Actualy, the revolution of planet Earth around the sun defines a year, where different seasons (spring, summer, autumn and winter) cycle, instead of different parts of day (morning, afternoon, evening, night) caused by the axial revolution of planet Earth.

In both models, geocentric and heliocentric, an observer tied to the surface of planet Earth can see the sun rise, but depending on the applied model, he can explain it in another way.

The contradiction lies in the models being used and not between the observation and one of the derived models.

1 comment:

Bright Smith said...

You are, of course, right, that's why I spoke of the *traditional* truth of the 'sun is rising', meaning the pre-modern notion of the sun revolving around the earth.
The contradiction is indeed not between two different observations, but between two different paradigms in which the same observation can be embedded.