Caption:
Diagram showing the relative ordering of the five elements proposed by Robert Fludd: 1. Terra (Earth); 2. Aqua (Water); 3. Aer (Air); 4. Ignis (Fire); 5. Aether (Ether). According to ancient and medieval science, ether is the material that fills the region of the universe above the terrestrial sphere. The concept of ether was used in several theories to explain several natural phenomena, such as the traveling of light and gravity. Robert Fludd stated that the ether was of the character that it was subtler than light. Fludd cites the 3rd century view of Plotinus, concerning the ether as penetrative and non-material. Robert Fludd, also known as Robertus de Fluctibus (January 17, 1574 - September 8, 1637) was a prominent English Paracelsian physician. He is remembered as an astrologer, mathematician, cosmologist, Qabalist, and Rosicrucian apologist. Illustration appeared in Utriusque cosmi historia, 1617.