A quark is an elementary particle and a fundamental constituent of
matter. Quarks combine to form composite particles called hadrons, the
best-known of which are protons and neutrons, the components of atomic
nuclei. Due to a phenomenon known as color confinement, quarks are
never found in isolation; they can only be found within hadrons. For
this reason, much of what is known about quarks has been drawn from
observations of the hadrons themselves. There are six different types
of quarks, known as flavors: up, down, charm, strange, top, and bottom.
Up and down quarks are generally stable and the most common in the
universe, whereas charm, strange, top, and bottom quarks can only be
produced in high energy collisions (such as those involving cosmic rays
and in particle accelerators). Quarks are the only elementary particles
in the Standard Model of particle physics to experience all four
fundamental interactions.
Read the rest of this article:
<http://en.wikipedia.org/wiki/Quark>
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Today's selected anniversaries:
1830:
During the opening of the Liverpool and Manchester Railway , one of the
world's first intercity passenger railways in which all the trains were
timetabled and operated for most of the distance solely by steam
locomotives, British Member of Parliament William Huskisson was struck
and killed by the locomotive engine Rocket.
<http://en.wikipedia.org/wiki/Liverpool_and_Manchester_Railway>
1831:
The John Bull, currently the oldest operable steam locomotive in the
world, ran for the first time in New Jersey on the Camden and Amboy
Railroad.
<http://en.wikipedia.org/wiki/John_Bull_%28locomotive%29>
1835:
During the second voyage of HMS Beagle, Charles Darwin reached the
Galápagos Islands, where he further developed his theories of
evolution.
<http://en.wikipedia.org/wiki/Gal%C3%A1pagos_Islands>
1935:
Nazi Germany enacted the Nuremberg Laws, which deprived German Jews of
citizenship, and adopted a new national flag emblazoned with a
swastika.
<http://en.wikipedia.org/wiki/Nuremberg_Laws>
2008:
The financial crisis of 2007–2009: The global financial-services firm
Lehman Brothers filed for bankruptcy while holding over US$600 billion
in assets, the largest such filing in U.S. history.
<http://en.wikipedia.org/wiki/Bankruptcy_of_Lehman_Brothers>
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Wiktionary's word of the day:
wherewithal (n):
The ability and the financial means required to accomplish some task
<http://en.wiktionary.org/wiki/wherewithal>
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Wikiquote quote of the day:
If we had no faults we should not take so much pleasure in noting those
of others.
--François de La Rochefoucauld
<http://en.wikiquote.org/wiki/Fran%C3%A7ois_de_La_Rochefoucauld>
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