evolution of the universe
- SeaTac — Thumbnail History (historylink.org)
The City of SeaTac was incorporated in 1989 and named after the Seattle-Tacoma International Airport, which it surrounds. Native Americans had occupied the region roughly midway between present-day Seattle and Tacoma for millennia before the arrival of the first Euro-American settlers in the mid-1850s. The area is centered on the Highline ridge separating Puget Sound and the valley of the Duwamish and Green rivers…
- 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.
