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Size (left) and distance (right) of a few well-known galaxies put to scale. There are an estimated 100 billion galaxies in all of the observable universe. [1] On the order of 100,000 galaxies make up the Local Supercluster, and about 51 galaxies are in the Local Group (see list of nearest galaxies for a complete list).
1989 – Margaret Geller and John Huchra discover the "Great Wall", a sheet of galaxies more than 500 million light years long and 200 million wide, but only 15 million light years thick. 1990 – Michael Rowan-Robinson and Tom Broadhurst discover that the IRAS galaxy IRAS F10214+4724 is the brightest known object in the Universe.
Mission name Ref(s). 1903 Publication of Exploration of the Universe with Rocket-Propelled Vehicles [1] that showed physical space exploration was theoretically possible, including the Tsiolkovsky rocket equation, multi staged rockets and using liquid oxygen and liquid hydrogen in liquid propellant Russia Konstantin Tsiolkovsky [2] 1914
This is a timeline of Solar System exploration ordering events in the exploration of the Solar System by date of spacecraft launch. It includes: It includes: All spacecraft that have left Earth orbit for the purposes of Solar System exploration (or were launched with that intention but failed), including lunar probes .
The chronology of the universe describes the history and future of the universe according to Big Bang cosmology.. Research published in 2015 estimates the earliest stages of the universe's existence as taking place 13.8 billion years ago, with an uncertainty of around 21 million years at the 68% confidence level.
c. 2nd century BCE–3rd century CE – In Hindu cosmology, the Manusmriti (1.67–80) and Puranas describe time as cyclical, with a new universe (planets and life) created by Brahma every 8.64 billion years. The universe is created, maintained, and destroyed within a kalpa (day of Brahma) period lasting for 4.32 billion years, and is followed ...
The timeline of the Universe lists events from its creation to its ultimate final state. For a timeline of the universe from the present to its presumed conclusion, see: Timeline of the far future; Chronology of the universe; Timeline of the universe
The principal change was to space leap years differently so as to make the average calendar year 365.2425 days long, more closely approximating the 365.2422-day 'tropical' or 'solar' year that is determined by the Earth's revolution around the Sun. The reform advanced the date by 10 days: Thursday 4 October 1582 was followed by Friday 15 ...