 Hello, and welcome to our segment on special relativity. You'll recall that in our last segment on the speed of light, Michelson and Morley demonstrated that the speed of light was the same for all inertial observers. The first impact of this discovery was that the Galilean transformations that we had been using for centuries was incorrect. New transformations were needed, and these new transformations had to satisfy two key requirements—one, no matter how we add speeds, the speed of light had to come out the same, and at low speeds compared to the speed of light, we had to get the Galilean transformations. In the years following Michelson-Morley's experiment, a number of physicists and mathematicians went to work on this problem. People like George Fitzgerald, Henry Ponkari, and Hendrick Lorenz. They came up with these transformations, now called the Lorenz transformations. In this segment, we'll see how these transformations required that time was stretched, dilated, and distance was contracted in order to satisfy the two main requirements, and we'll also see how Einstein put it all together with just two postulates.