Weighing planets and stars

(September 2000)

According to a report posted on the Internet
during September, a University of Washington group has reduced the uncertainty
in the value of G, the universal gravitational constant, by almost a factor of
ten. Their preliminary value is G = 6.67390 x 10-11 m3/kg/s2, with an
uncertainty of 0.0014%.

Combining this new value of G with
measurements made with the Lageos satellite (which uses laser ranging to keep
track of its orbital position to within a millimeter) permits the calculation
of a brand new, highest precision mass for the earth of

5.97223 (+/- 0.00008) x 1024 kg

Similarly, the new mass of the sun becomes
1.98843 (+/- 0.00003) x 1030 kg.

For more detail, see http://gravity.phys.psu.edu/mog/mog15/mog15.html and http://gravity.phys.psu.edu/mog/mog15/node12.html