Shock wave

In physics, a shock wave or shock is a type of propagating disturbance. When a wave moves faster than the local speed of sound in a fluid it is a shock wave. Like an ordinary wave, a shock wave carries energy, and can propagate through a medium; however it is characterized by an abrupt, nearly discontinuous change in pressure, temperature and density of the medium. In supersonic flows, expansion is achieved through an expansion fan also known as a Prandtl-Meyer expansion fan.

Unlike solitons (another kind of nonlinear wave), the energy of a shock wave dissipates relatively quickly with distance. Also, the accompanying expansion wave approaches and eventually merges with the shock wave, partially cancelling it out. Thus the sonic boom associated with the passage of a supersonic aircraft is the sound wave resulting from the degradation and merging of the shock wave and the expansion wave produced by the aircraft.

When a shock wave passes through matter, energy is preserved but entropy increases. This change in the matter's properties manifests itself as a decrease in the energy which can be extracted as work, and as a drag force on supersonic objects; shock waves are strongly irreversible processes.

Transformers (toy line)

The Transformers (トランスフォーマー, Toransufomā) is a line of toys produced by the Japanese company Takara (now known as Takara Tomy) and American toy company Hasbro. The Transformers toyline was created from toy molds mostly produced by Japanese company Takara in the toylines Diaclone and Microman. Other toy molds from other companies such as Bandai were used as well. In 1984, Hasbro bought the distribution rights to the molds and rebranded them as the Transformers for distribution in North America. Hasbro would go on to buy the entire toy line from Takara, giving them sole ownership of the Transformers toy-line, branding rights, and copyrights, while in exchange, Takara was given the rights to produce the toys and the rights to distribute them in the Japanese market. The premise behind the Transformers toyline is that an individual toy's parts can be shifted about to change it from a vehicle, a device, or an animal, to a robot action figure and back again. The taglines "More Than Meets The Eye" and "Robots In Disguise" reflect this ability.