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This article is a list of notable unsolved problems in astronomy.Problems may be theoretical or experimental. Theoretical problems result from inability of current theories to explain observed phenomena or experimental results.
Was there ever a collision of the Earth with another planet Theia, giving birth to the Moon? [1] There is compelling evidence, such as measures of a shorter duration of the Earth's rotation and lunar month in the past, pointing to a Moon much closer to Earth during the early stages of the Solar System. [2] What is the long-term heat balance of ...
The faint young Sun paradox or faint young Sun problem describes the apparent contradiction between observations of liquid water early in Earth's history and the astrophysical expectation that the Sun's output would have been only 70 percent as intense during that epoch as it is during the modern epoch. [1]
CMEs typically reach Earth one to five days after leaving the Sun. The strongest deceleration or acceleration occurs close to the Sun, but it can continue even beyond Earth orbit (1 AU), which was observed using measurements at Mars [21] and by the Ulysses spacecraft. [22] ICMEs faster than about 500 km/s (310 mi/s) eventually drive a shock ...
This is an accepted version of this page This is the latest accepted revision, reviewed on 8 February 2025. Discrepancy of the lack of evidence for alien life despite its apparent likelihood This article is about the absence of clear evidence of extraterrestrial life. For a type of estimation problem, see Fermi problem. Enrico Fermi (Los Alamos 1945) The Fermi paradox is the discrepancy ...
Earth Day is on April 22, but really, it should be every day—saving the planet should be a daily occurrence! From conservation to wildlife to politics, test your environmental and historical ...
The following is a list of notable unsolved problems grouped into broad areas of physics. [1]Some of the major unsolved problems in physics are theoretical, meaning that existing theories seem incapable of explaining a certain observed phenomenon or experimental result.
Several unanswered questions remain, including whether Earth was a full "snowball" or a "slushball" with a thin equatorial band of open (or seasonally open) water. The Snowball Earth episodes are proposed to have occurred before the sudden radiations of multicellular bioforms known as the Avalon and Cambrian explosions ; the most recent ...