The World (Descartes) - Cartesian Theory On Light

Cartesian Theory On Light

With his laws of motion set forth and the universe operating under these laws, Descartes next begins to describe his theory on the nature of light. Descartes believed that light traveled instantaneously - a common belief at the time – as an impulse across all the adjacent particles in nature, since Descartes believed nature was without a void. To illustrate this, Descartes used the example of a stick being pushed against some body. Just as the force which is felt at one end of the stick is instantly transferred and felt at the other end, so is the impulse of light that is sent across the heavens and through the atmosphere from luminous bodies to our eyes. Descartes attributed light to have 12 distinct properties:

1. Light extends circularly in all direction from luminous bodies
2. Light extends out to any distance
3. Light travels instantaneously
4. Light travels ordinarily in straight lines or rays
5. Several rays can come from different points and meet at the same point
6. Several rays can start at the same point and travel in different directions
7. Several rays can pass through the same point without impeding each other
8. If the rays are of very unequal force, then they can sometimes impede one another

Also:

• 9) and 10) Rays can be diverted by reflection or by refraction
• 11) and 12) The force of a ray can be augmented or diminished by the disposition of the matter that receives it.