The definition of the meter (m), which is the international unit of length, was once defined by a physical artifact - two marks inscribes on a bar of platinum-iridium. Today, the meter (m) is defined in terms of constant of nature: the length of the path traveled by the light in vacuum during a time interval of 1/299, 792, 458 of a second. The Length - Evolution from Measurement Standard to a Fundamental Constant explains the evolution of the definition of the meter.
Rainbow flag (LGBT movement) For other uses, see rainbow flag. The rainbow flag is a symbol of lesbian, gay, bisexual, and transgender (LGBT) pride and LGBT social movements in use since the 1970s. LGBT symbols. The rainbow flag, commonly the gay pride flag and LGBT pride flag, is a symbol of lesbian, gay, bisexual, and transgender (LGBT) pride and LGBT social movements.
Use of the rainbow flag by the gay community began in 1978 when it first appeared in the San Francisco Gay and Lesbian Freedom Day Parade. Inverted Triangles. The pink triangle is easily one of the more popular and widely-recognized symbols for the gay community.