Sonic boom

If you are interested, first watch the Youtube video linked to by the title of this post. It's a very interesting video that explains in simple terms how and why a sonic boom is caused.

Here is my attempt to explain to you and myself and understand the principles behind supersonic flight: Actually I am trying to answer this week's question in The Hindu's SciTech section's Question Corner.

As you might know, sound is pressure changes in air (that's why sound needs a medium to travel). Every moving object changes the pressure of the air it's trying to occupy as it tries to move, and this makes sound, whether or not we can hear it.

As explained in the Wikipedia article here, it's accepted by the current scientific community that the sudden drop in pressure is what causes the visible condensation cloud that surrounds an aircraft travelling at transonic speeds (speeds slightly below and above 330m/s).

As the nose of the aircraft hits a point in the plane into which it's moving, pressure of the air suddenly rises, and as the aircraft moves through the plane, it falls steadily and goes below the normal value to reach a minimum, and when the tail of the aircraft leaves the plane, it suddenly rises back to normal again. This can be thought of as tracing the letter 'N', and hence the name of the wave, N-wave. This N-wave follows the aircraft wherever it goes.

Now, in this N-wave there is a point at which the air pressure goes below a certain point, causing a corresponding sudden drop in temperature. The temperature goes below the dew point, and hence causes the water vapour to condense into water droplets, forming a condensation cloud around the tail of the aircraft.

I hope that explains the formation of condensation cloud. I still don't understand how dew point works though, I hope I can make another post out of it.