The Protocol on Blinding Laser Weapons, Protocol IV of the 1980 Convention on Certain Conventional Weapons, was issued by the United Nations on 13 October 1995. It came into force on 30 July 1998. As of May 2015, the protocol had been agreed to by 105 states. == History == The Convention on Certain Conventional Weapons and three annexed protocols were adopted on 10 October 1980 and opened for signature on 10 April 1981. In 1986, Sweden and Switzerland pushed for the Blinding Laser Protocol. During 1989–91, the International Committee of the Red Cross (ICRC) held four international meeting...

A fire balloon (風船爆弾, fūsen bakudan, lit. "balloon bomb"), or Fu-Go (ふ号[兵器], fugō [heiki], lit. "Code Fu [Weapon]"), was a weapon launched by Japan during World War II. A hydrogen balloon with a load varying from a 15 kg (33 lb) antipersonnel bomb to one 12-kilogram (26 lb) incendiary bomb and four 5 kg (11 lb) incendiary devices attached, it was designed as a cheap weapon intended to make use of the jet stream over the Pacific Ocean and drop bombs on American and Canadian cities, forests, and farmland. The Japanese fire balloon was the first ever weapon possessing intercontinental range (the second...

In relativity, rapidity is an alternative to speed as a measure of rate of motion. On parallel velocities (say, in one-dimensional space) rapidities are simply additive, unlike speeds at relativistic velocities. For low speeds, rapidity and speed are proportional, but for high speeds, rapidity takes a larger value. The rapidity of light is infinite. Using the inverse hyperbolic function artanh, the rapidity w corresponding to velocity v is w = artanh(v / c). For low speeds, w is approximately v / c. The speed of light c being finite, any velocity v is constrained to the interval −c < v < c and...