Stanton Friedman reckons that the transistor was developed in 1947.

Also the Sound Barrier was experienced that year as I found out :

From Wikipedia, the free encyclopedia.

http://en.wikipedia.org/wiki/Sound_barrier

U.S. Navy F/A-18 at transonic speed. The cloud is due to the Prandtl-Glauert Singularity.In aerodynamics, the sound barrier is the apparent physical boundary stopping large objects from becoming supersonic. The term came into use during World War II when a number of aircraft started to encounter the effects of compressibility, a grab-bag of unrelated aerodynamic effects, and fell out of use in the 1950s when aircraft started to routinely "break" the sound barrier.

As a plane approaches the speed of sound, the way air flows around its surfaces changes and it becomes a compressible fluid. Along with a number of changes in the way that lift is generated, this change also gives rise to a rapid increase in drag, known as the wave drag.

At first the exact nature of the wave drag was not well understood. It appeared that it increased exponentially, as it does for a limited range of speeds. With only the limited power of piston engines to drive them, planes could not overcome this rapid increase in drag, and even large increases in power would result in only tiny increases in performance. It appeared that an infinite amount of power would be needed to reach supersonic speeds, and thus everyone started talking about the sound barrier.

Artillerymen knew better. Starting with Ernst Mach in the 19th century, they were aware that after a point the drag no longer increased, and in fact dropped again. The challenge then became how to provide this amount of power. With the introduction of the swept wing to lower drag, and the jet engine to provide the power, by the 1950s a number of aircraft were able to fly supersonically with relative ease.

Charles Elwood Yeager was the first person to break the sound barrier on October 14, 1947, flying the experimental Bell X-1 at Mach 1 at an altitude of 45,000 feet.

Hans Guido Mutke claimed to have broken the sound barrier before Yeager, on April 9, 1945 in a Messerschmitt Me 262. However, this claim is disputed by most experts and lacks a scientific foundation.

The Prandtl-Glauert singularity, at which point a sudden drop in air pressure occurs, is generally accepted as the cause of the visible condensation cloud when an airplane breaks the sound barrier, though there remains some debate. It is an example of a mathematical singularity in aerodynamics.

One view of this phenomenon is that is exhibits the effect of compressibility and the so-called N-wave. The N-wave is the time variant pressure profile seen by a static observer as a sonic compression wave passes. The overall three-dimensional shock wave is in the form of a cone with its apex at the supersonic aircraft. This wave follows the aircraft. The pressure profile of the wave is composed of a leading compression component (the initial upward stroke of the "N"), followed by a pressure descent forming a rarification of the air (the downward diagnonal of the "N"), followed by a return to the normal ambient pressure (the final upward stroke of the "N"). The rarefaction may be thought of as the "rebounding" of the compression due to inertial effects.

Since heat does not leave the affected air mass, this is an adiabatic change of pressure, with an associated change of temperature. Under humid air conditions, the drop in temperature in the most rarified portion of the shock wave (close to the aircraft) can bring the air temperature below its dew point. At this temperature, moisture condenses to form visible microscopic water droplets. As the pressure effect of the wave is reduced by its expansion (the same pressure effect is spread over a larger radius), the vapor effect also has a limited radius.