What exactly is THUNDER?

[NYSportsGuy210]

As I am looking and hearing outside my window tonight and the rain is coming down I hear loud "booming" noises raising above from the heavens. It seems louder and more close to the ground than normal too. It's almost as if a big train is gonna come down and shatter my whole neighborhood any second now.....

.....so it bears me to ask all the scientists in the audience, what exactly is thunder? (I know it used to be Brandon Jacobs in his prime....but I'd like a serious factual answer this time)

How is it produced? Can it cause earthquakes too?

[falconticket]

Sonic shockwave from superheated air traveling faster than the speed of sound. Earthquake no

[JuicedUp]

Thunder is the sound made by lightning. Depending on the nature of the lightning and distance of the listener, thunder can range from a sharp, loud crack to a long, low rumble (brontide). The sudden increase in pressure and temperature from lightning produces rapid expansion of the air surrounding and within a bolt of lightning. In turn, this expansion of air creates a sonic shock wave which produces the sound of thunder, often referred to as a clap, crack, or peal of thunder. The distance of the lightning can be calculated by the listener depending on when the sound is heard vs. the vision of the lightning strike.

Cumulonimbus clouds often form thunderstorms.
The cause of thunder has been the subject of centuries of speculation and scientific inquiry. The first recorded theory is attributed to The Greek philosopher Aristotle in the third century BC, and an early speculation was that it was caused by the collision of clouds. Subsequently, numerous other theories have been proposed. By the mid-19th century, the accepted theory was that lightning produced a vacuum. In the 20th century a consensus evolved that thunder must begin with a shock wave in the air due to the sudden thermal expansion of the plasma in the lightning channel. The temperature inside the lightning channel, measured by spectral analysis, varies during its 50 μs existence, rising sharply from an initial temperature of about 20,000*K to about 30,000*K, then dropping away gradually to about 10,000*K. The average is about 20,400*K (20,100*°C; 36,300*°F).[1] This heating causes it to expand outward, plowing into the surrounding cooler air at a speed faster than sound would travel in that cooler air. The outward-moving pulse that results is a shock wave,[2] similar in principle to the shock wave formed by an explosion, or at the front of a supersonic aircraft. More recently, the consensus around the cause of the shock wave has been eroded by the observation that measured overpressures in simulated lightning are greater than what could be achieved by the amount of heating found. Alternative proposals rely on electrodynamic effects of the massive current acting on the plasma in the bolt of lightning.

[NYSportsGuy210]

So it's basically one big sonic boom of oxygen particles?

[falconticket]

Just like a bullwhip.