A wake is sufficient to locate a small boat from the air. You can even tell us something about their size and speed. And a trail of bubbles can afford to visualize the invisible movement of subatomic particles. How
see something so tiny that it escapes any optical or electronic microscope? How to know the trajectory of particles which travel near the speed of light? This was the problem they had physicists in the mid-twentieth century. The truth is that there was a new problem, but their instruments were limited to discover everything they wanted. His best tool was then the cloud chamber. The basic idea was simple, you're detecting something tiny uses an unstable system that can change state with a tiny amount of energy.
The most basic cloud chamber consists of a container filled with a mixture of air and saturated water vapor, ie with a relative humidity greater than one hundred percent. To achieve this mix is \u200b\u200bexpanding the mixture into a cylinder which is cooled and ready to let the steam condense quickly. In real life a condensation causing moisture as high as the morning dew.
The brainchild of Charles Thomson Rees Wilson, a Scottish physicist of the early twentieth century, it was noted that the ions also act as excellent condensation nuclei. And the radiation falling on the generating mix these ions. The tiny droplets of liquid that is formed along the path of the radiation could be photographed making it possible to detect the radiation. And, if in addition the camera is in a electric or magnetic field, the trajectories were bent by the field and it was possible to know the burden of the incident radiation. It was an ingenious invention of the century XIX it worked fine without need for sophisticated electronic detectors that nobody had yet invented. And even been able to discover new particles as the positron that appears in this picture.
The original version was used only intermittently since it was necessary to return the camera to its initial position after a short space of time. More sophisticated variants used different designs and vapors of other elements to improve its performance and sensitivity. The latest variant, the diffusion cloud chamber, could be used continuously and even now can be purchased models such as Photo
as educational tools. 
To improve the detection capability was necessary to look even more unstable systems. In the next text we will see two other ideas born in the twentieth century. Using bubbles instead of drops or cause an "avalanche" of electrons.
Category: Physical
