The nebular hypothesis is the most widely accepted model in cosmogony
explaining the formation and evolution of the Solar System, which
suggests that it formed from nebulous material in space. The hypothesis
offers explanations for some of the Solar System's properties, including
the nearly circular and coplanar orbits of the planets, and their motion
in the same direction as the Sun's rotation. According to the
hypothesis, Sun-like stars form over about 100 million years, in
massive, gravitationally unstable clouds of molecular hydrogen (giant
molecular clouds). Matter coalesces to smaller, denser clumps within,
which then proceed to both rotate and collapse, forming stars. Star
formation produces a gaseous protoplanetary disk around the young star,
which may give birth to planets (protoplanetary disk pictured in the
Orion Nebula). The formation of planetary systems is thought to be a
natural result of star formation, with dense terrestrial planets forming
closer to the star and colder giant planets forming further away, beyond
the so-called frost line. Originally applied only to our own Solar
System, the nebular hypothesis is now thought to be at work throughout
the universe.
Read more: <https://en.wikipedia.org/wiki/Nebular_hypothesis>
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Today's selected anniversaries:
1774:
In response to the British Parliament enacting the Intolerable
Acts, representatives from twelve of Britain's North American colonies
convened the First Continental Congress at Carpenters' Hall in
Philadelphia.
<https://en.wikipedia.org/wiki/First_Continental_Congress>
1793:
French Revolution: The National Convention began the Reign of
Terror, a ten-month period of systematic repression and mass executions
by guillotine of perceived enemies within the country.
<https://en.wikipedia.org/wiki/Reign_of_Terror>
1914:
World War I: The First Battle of the Marne began with French
forces engaging the advancing German army at the Marne River near Paris.
<https://en.wikipedia.org/wiki/First_Battle_of_the_Marne>
1945:
Cold War: Soviet cipher clerk Igor Gouzenko defected to Canada
with over 100 documents on Soviet espionage activities and sleeper
agents.
<https://en.wikipedia.org/wiki/Igor_Gouzenko>
1977:
NASA launched the robotic space probe Voyager 1 (pictured),
currently the farthest spacecraft from Earth.
<https://en.wikipedia.org/wiki/Voyager_1>
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Wiktionary's word of the day:
canard:
A false or misleading report or story, especially if deliberately so.
<https://en.wiktionary.org/wiki/canard>
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Wikiquote quote of the day:
I succeeded by saying what everyone else is thinking.
In the mystic traditions of the different religions we
have a remarkable unity of spirit. Whatever religion they may profess,
they are spiritual kinsmen. While the different religions in their
historic forms bind us to limited groups and militate against the
development of loyalty to the world community, the mystics have already
stood for the fellowship of humanity in harmony with the spirit of the
mystics of ages gone by.
--Sarvepalli Radhakrishnan
<https://en.wikiquote.org/wiki/Sarvepalli_Radhakrishnan>