What was the "ether" theory?

By the end of the nineteenth century, the general thought concerning ether was that it pervaded space. Ether was considered to be the medium through which waves of light and radio traveled. Scientists believed they could measure ether's elasticity and that this would help them more aptly describe the laws of nature. This theory finally broke apart in 1905 when Einstein penned an article that argued against the idea of ether as a medium.