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报告内容摘要
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1、In June 2015
published the Task Group on Fundamental Constants (TGFC) in the Committee on
Data for Science and Technology a new value for the Newtonian Constant of
Gravitation, G. Its value now is G=(6,67408±0,00031)×10-11 m3 kg-1 s-2,
i.e. G is currently known with a relative standard uncertainty of 4.7x10-5.
This uncertainty is just half of the 2010-CODATA uncertainty, which sounds
very positive. However, taking into account that this constant is one of the
first ever measured, but still remains the one with highest uncertainty of
all fundamental physical constants, it is quite disappointing for scientists
and metrologists. New ways have to be gone to overcome this issue.
The first part of
the talk focuses on the current status of the measurement of G and the
international efforts that are made to overcome this dilemma. The second part
presents a new proposal of a measurement that is based on a laboratory
free-fall experiment.
2、Free-fall
absolute gravimeters are devices that measure the absolute acceleration due
to gravity, g. They find applications in many different areas of science and
technology. Just to name some, a gravimeter is used in geodesy to define the
geoid, in geophysics to study volcanic activities or postglacial rebound.
Recently it plays also a fundamental role in metrology, namely the
redefinition of the SI unit kilogram. In the so-called watt-balance
experiment, which measures Planck’s constant, the local value of g is needed
to be known to better than one part in 10-8. However, gravimeters are
sophisticated instruments which are subject to many kinds of possible
systematic errors.
In this talk I will
discuss some of those possible error sources of classical free-fall absolute
gravimeters, which includes corner cube rotation and the so-called
speed-of-light correction.
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