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==The Brans-Dicke Theory of Gravitation==

==The Brans-Dicke Theory of Gravitation==

While Dicke accepted [[Theory of Relativity|Relativity]], both special and general, he believed that plain General Relativity did not fully explain gravity.  Along with his former student Carl Brans, he formulated the Brans-Dicke theory, which includes a scalar field in addition to the tensor field defined by general relativity.  This "scalar-tensor theory" (as opposed to plain relativity, which is just a "tensor theory") included a scalar field, usually denoted &omega;, which, when assigned a certain value, they believed matched experimental data better.  (When &omega; is set to infinity, the Brans-Dicke theory becomes equivalent to plain General Relativity.)  Brans and Dicke suggested a value of about 5.  The observable differences between Brans-Dicke and general relativity are extremely tiny, but the Mariner and Cassini spacecraft (below) clearly detected this<ref name="exper1">http://content.time.com/time/magazine/article/0,9171,943324,00.html This is currently behind a "paywall". Before that, the theme of the full article was the demise of Brans-Dicke, and it explained that the Mariner measurements supported plain relativity and refuted Brans-Dicke.</ref> <ref name="exper2">http://www.jpl.nasa.gov/releases/70s/release_1970_0566.html</ref> <ref name="exper3">[https://books.google.com/books?id=9ZuP9JQzc00C&pg=PA157&lpg=PA157&dq=brans-dicke%2Bmariner&source=bl&ots=Y2jhf2OjcU&sig=C8qWD1E5ukCe_5DiKObCiWjAEKg&hl=en&sa=X&ei=cCw9VcfBE8HksASynoHICw&ved=0CDkQ6AEwBQ#v=onepage&q=brans-dicke%2Bmariner&f=false The Rise and Fall of the Brans-Dicke Theory]</ref>.

While Dicke accepted [[Theory of Relativity|Relativity]], both special and general, he believed that plain General Relativity did not fully explain gravity.  Along with his former student Carl Brans, he formulated the Brans-Dicke theory, which includes a scalar field in addition to the tensor field defined by general relativity.  This "scalar-tensor theory" (as opposed to plain relativity, which is just a "tensor theory") included a scalar field, usually denoted &omega;, which, when assigned a certain value, they believed matched experimental data better.  (When &omega; is set to infinity, the Brans-Dicke theory becomes equivalent to plain General Relativity.)  Brans and Dicke suggested a value of about 5.  The observable differences between Brans-Dicke and general relativity are extremely tiny, but the Mariner and Cassini spacecraft (below) clearly detected this<ref name="exper">Multiple references:

*Time magazine article, Nov. 23, 1970, explaining how the Mariner space probe supported plain relativity and refuted Brans-Dicke.  Currently behind a "paywall". [http://content.time.com/time/magazine/article/0,9171,943324,00.html Science: A Victory for Relativity].

*Jet Propulsion Laboratory memo, Nov. 13, 1970. [http://www.jpl.nasa.gov/releases/70s/release_1970_0566.html]

*[https://books.google.com/books?id=9ZuP9JQzc00C&pg=PA157&lpg=PA157&dq=brans-dicke%2Bmariner&source=bl&ots=Y2jhf2OjcU&sig=C8qWD1E5ukCe_5DiKObCiWjAEKg&hl=en&sa=X&ei=cCw9VcfBE8HksASynoHICw&ved=0CDkQ6AEwBQ#v=onepage&q=brans-dicke%2Bmariner&f=false The Rise and Fall of the Brans-Dicke Theory]</ref>

.

Dicke was instrumental in proposing extremely sensitive tests of General Relativity.  Modern measurements of the various tests, specifically from the Mariner 6 spacecraft in 1969 and the Cassini spacecraft in 2004, show that plain Einsteinian relativity, not the Brans-Dicke theory, agrees with observation<ref name="exper1"/> <ref name="exper2"/> <ref name="exper3"/>.  Nevertheless, interest in the Brans-Dicke formulation has recently revived, in the context of dark matter / dark energy investigations.

Dicke was instrumental in proposing extremely sensitive tests of General Relativity.  Modern measurements of the various tests, specifically from the Mariner 6 spacecraft in 1969 and the Cassini spacecraft in 2004, show that plain Einsteinian relativity, not the Brans-Dicke theory, agrees with observation<ref name="exper"/>.  Nevertheless, interest in the Brans-Dicke formulation has recently revived, in the context of dark matter / dark energy investigations.

==No Nobel Prize==

==No Nobel Prize==