The attracting masses in measurements of G: an overview of physical characteristics and performance.

Simple spheres and cylinders have been the geometries employed most frequently, but not uniquely, for the attracting masses used historically in measurements of the Newtonian gravitational constant G. We present a brief overview of the range of sizes, materials and configurations of the attracting masses found in several representative experimental arrangements. As one particular case in point, we present details of the large tungsten spheres designed originally by Beams, which have been incorporated into several different apparatuses for measuring G over the past 50 years. We also consider the question of possible systematic dependence of the results and their precision on the size of the large masses/mass systems that have been employed to date. We close with some considerations for possible future work.

Comment on "observation of matter wave beat phenomena in the macrodomain for electrons moving along a magnetic field".

I show that the claim of the observation of matter wave beat phenomena in the classical macrodomain by Varma et al. [Phys. Rev. E 65, 026503 (2002)] is based on a mistaken interpretation of effects arising from multiple focusing of an electron beam in an axial magnetic field. I present the basic physical facts that mimic wavelike phenomena and suggest a classical explanation of modulations reported by Varma et al. Realization that the macroscopic "de Broglie wavelength" used by Varma et al. is the same as the focusing distance of a monoenergetic electron beam in the uniform magnetic field leads to a full classical explanation of all the effects reported by Varma et al. The reported observations are not evidence for any quantumlike phenomenon in the macrodomain, and their results do not indicate any violation of the Lorentz equation of motion.

Bose-Einstein condensation of metastable helium.

We have observed a Bose-Einstein condensate in a dilute gas of 4He in the (3)2S(1) metastable state. We find a critical temperature of (4.7+/-0.5) microK and a typical number of atoms at the threshold of 8 x 10(6). The maximum number of atoms in our condensate is about 5 x 10(5). An approximate value for the scattering length a = (16+/-8) nm is measured. The mean elastic collision rate at threshold is then estimated to be about 2 x 10(4) s(-1), indicating that we are deeply in the hydrodynamic regime. The typical decay time of the condensate is 2 s, which places an upper bound on the rate constants for two-body and three-body inelastic collisions.