 Analysis of the two slit experiment, where you put things through two slits, they arrive on the detector one by one, and then only over time, doing that lots of times you get an interference pattern, is an excellent way to talk about the core conceptual changes that happen when quantum mechanics arrive in its final, modern form. But it's not actually the experiment that quantum mechanics was invented to explain. Quantum mechanics was invented to solve a whole bunch of problems that had been growing over the latter half of the 19th century. It doesn't even explain the name quantum mechanics, why is it called quantum? Now, the history of quantum mechanics is connected with the odd properties of light, and the way light interacts with matter. So quantum mechanics started with the idea of photons. In 1807, Young publishes double slit experiment for light. But it wasn't until about 1818, where Poisson's spot had been observed, that people really believed that light was indeed a wave. But it was nearly 50 years later that Max will combine the equations for electricity and magnetism together, and discover that there was a possibility of an electromagnetic wave that would propagate. And he also realized that that wave would propagate the speed of light, and made the large jump that maybe light was indeed an electromagnetic wave. And if you understand that light is an electromagnetic wave, then you understand how much energy it carries, you understand how it interacts with charged particles. And over the following decades, people started to realize that basically all matter was made of charged particles. At a microscopic level, you had a nucleus in the middle, and then a cloud of electrons around the outside, which people still sort of visualized as particles, because the wave theory of matter hadn't been invented at that stage. And so if you understand electromagnetism, and you understand that matter is made of charged particles moving in particular ways, then basically you can figure out exactly how they interact and exactly what should happen. In the late 1800s it was certainly felt that people were really closing in on the truth of the matter. They were figuring out the fundamental physics, the fundamental laws of the universe, and it was all coming together. They decided to work out a few details. Now unfortunately, some of those supposedly small details were starting to cause some really big problems. Now historically the first of those details arose when people tried to marry their understanding of light as an electromagnetic wave with the other great success of physics, which was thermodynamics. Thermodynamics was the physics behind the industrial revolution. It told us how energy could be transformed between different forms, and how we could manage temperature to build engines and machines that would eventually let us use so much more energy than we could produce with our own hands. And this is effectively what transformed technology for humans.