'Einstein: Ether and Relativity' http://www-groups.dcs.st-and.ac.uk/~history/Extras/Einstein_ether.html "Think of waves on the surface of water. Here we can describe two entirely different things. Either we may observe how the undulatory surface forming the boundary between water and air alters in the course of time; or else-with the help of small floats, for instance - we can observe how the position of the separate particles of water alters in the course of time. If the existence of such floats for tracking the motion of the particles of a fluid were a fundamental impossibility in physics - if, in fact nothing else whatever were observable than the shape of the space occupied by the water as it varies in time, we should have no ground for the assumption that water consists of movable particles. But all the same we could characterise it as a medium." if, in fact nothing else whatever were observable than the shape of the space occupied by the aether as it varies in time, we should have no ground for the assumption that aether consists of movable particles. But all the same we could characterise it as a medium having mass which is displaced by the particles of matter which exist in it and move through it. Watch the following video starting at 0:45 to see a visual representation of the state of the aether. What is referred to as a twist in spacetime is the state of displacement of the aether. [video=youtube;s9ITt44-EHE]https://www.youtube.com/watch?v=s9ITt44-EHE[/video] "Imagine the Earth as if it were immersed in honey," says Francis Everitt of Stanford University in California, the mission's chief scientist. "As the planet rotates, the honey around it would swirl, and it's the same with space and time." The 'swirl' is more correctly described as the state of displacement of the aether.