Interferometer

An interferometer was devised to precisely split a beam of light and bring it back together, enabling measurements of the light's phase differences. This experiment contributed significantly by disproving the existence of the supposed luminiferous ether.
 Albert Abraham Michelson United States 1881 Interferometer

An interferometer was devised to precisely split a beam of light and bring it back together, enabling measurements of the light's phase differences. This experiment contributed significantly by disproving the existence of the supposed luminiferous ether.