evolution of the universe
- Generation X (Wikipedia)
Generation X (often shortened to Gen X) is the demographic cohort following the Baby Boomers and preceding Millennials. Researchers and popular media often use the mid-1960s as its starting birth years and the late 1970s as its ending birth years, with the generation being generally defined as people born from 1965 to 1980. By this definition and U.S. Census data, there are 65.2 million Gen Xers in the United States as of 2019. Most of Generation X are the children of the Silent Generation and early Baby Boomers; Xers are also often the parents of Millennials and Generation Z.
- Galaxy (Wikipedia)
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. The word is derived from the Greek galaxias (γαλαξίας), literally ‘milky’, a reference to the Milky Way galaxy that contains the Solar System. Galaxies, averaging an estimated 100 million stars, range in size from dwarfs with less than a hundred million stars, to the largest galaxies known – supergiants with one hundred trillion stars, each orbiting its galaxy’s center of mass. Most of the mass in a typical galaxy is in the form of dark matter, with only a few percent of that mass visible in the form of stars and nebulae. Supermassive black holes are a common feature at the centres of galaxies.
