Unprecedented accuracy levels will be achieved using cold atoms in free-fall to probe the gravitational field, surpassing thus the state-of-art measurements based on torsion balance
and simple pendulum.in parallel, megante will provide results that go far beyond the pure metrological interest.
At the Main Astronomical Observatory of National Academy of Sciences in Kiev, Ukraine, a high-sensitive torsion balance
with a new design (termed "torsind", refering to the device's function as a torsion indicator) has been quasi-continuously measuring fluctuations of its angular deflection since 2009.
Kesling & Crafts (1962) outlined the physics of the torsion balance
. In our version of the balance the beam and lengths of wire are used are shorter and piano wire was replaced with thinner wire of stainless steel, tungsten or silicon carbide with a central core of tungsten, all of which were found to be less affected by seawater.
The scientists placed four meticulously shaped 10-gram pieces of material -- two Earth-like, two Moon-like -- onto a spinning torsion balance
, which twists if the Sun attracts one kind of material more strongly than another.
Heckel, suspended objects with compositions similar to that of the Earth and of the moon in a rotating torsion balance
. That extremely sensitive device detects twisting forces.
Since weight is a force, such a torsion balance
could be used
Instead, he used the torsion balance
, which he was using in other experiments at the same time in order to investigate possible gravity gradients due to effects such as spatial orientation, terrestrial magnetism, etc.
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As is the case for most measurements of G, the apparatus for the present experimental idea is also a variation of a torsion balance
. Before describing the modifications needed so that a torsion balance
can measure through-the-center motion, let's consider the context in which we find this gap in experimentation.
Fitzgerald and his coworkers at the Measurement Standards Laboratory in Lower Hutt, New Zealand, used a torsion balance
, which consists of a copper bar dangling horizontally from a thin, tungsten wire fastened to the bar's midpoint (SN: 3/12/94, p.376).
The master stroke that made G measurable was the 1785 use of the torsion balance
by Charles Coulomb, who first employed it to measure small electrostatic forces.
The torsion balance
apparatus was first used by Cavendish in 1798 in a very simple form which permitted him to reach an unexpected accuracy.