Aether theories

Aether theories propose an unseen medium that fills space and carries light or electromagnetic waves. Nineteenth-century versions treated the aether as a material reference frame for wave propagation.

Luminiferous aether: A hypothetical medium proposed to carry light waves through otherwise empty space. This is the best-known aether model, developed to explain light as a wave.
Wave theory of light: The account of light as a wave rather than a stream of particles. A wave model encouraged physicists to seek a medium analogous to air or water.
Hendrik Lorentz: A Dutch physicist who developed electron theory and a mathematical account of motion relative to the aether. His transformations and contraction hypothesis made aether theory compatible with null drift experiments.
Newtonian mechanics: The classical framework describing motion through absolute space and time using Newton's laws. Its absolute reference frame offered an analogy for the preferred frame sought in aether theories.
Maxwell's equations: Four equations describing how electric and magnetic fields are generated and interact. Their wave solutions made electromagnetic waves central to later aether debates.
Christiaan Huygens: A Dutch physicist and astronomer who developed an influential wave theory of light in the seventeenth century. His wave account helped establish the problem of what light waves propagate through.
George Francis FitzGerald: An Irish physicist who proposed that bodies contract along their motion through the aether. His contraction hypothesis anticipated a key feature of Lorentz's explanation.
Corpuscular theory of light: A theory that treats light as particles rather than waves. It competed with the wave account that gave aether theories their motivation.
Electromagnetic wave: A propagating disturbance of electric and magnetic fields that transports energy through space. Aether theories proposed a medium for the propagation of these waves.
Augustin-Jean Fresnel: A French physicist whose mathematical wave theory explained diffraction, interference, and polarization of light. Fresnel developed a detailed optical aether model to support his wave theory.

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