Welcome to the American Journal of Physics (AJP). AJP publishes papers that meet the needs and intellectual interests of college and university physics teachers and students. This Journal was established in 1933 under the title the American Physics Teacher, which covers Volumes 1 through 7. The name was changed to the American Journal of Physics in 1940.
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We give an introduction to the QBist interpretation of quantum mechanics, which removes the paradoxes, conundra, and pseudoproblems that have plagued quantum foundations for the past nine decades. As an example, we show in detail how this interpretation eliminates “quantum nonlocality.”

A particle in hyperbolic motion produces electric fields that appear to terminate in midair, violating Gauss's law. The resolution to this paradox has been known for sixty years but exactly why the naive approach fails is not so clear.

In the coherent state of the harmonic oscillator, the probability density is that of the ground state subjected to an oscillation along a classical trajectory. Senitzky and others pointed out that there are states of the harmonic oscillator corresponding to an identical oscillatory displacement of the probability density of any energy eigenstate. These generalizations of the coherent state are rarely discussed, yet they furnish an interesting set of quantum states of light that combine features of number states and coherent states. Here, we give an elementary account of the quantum optics of generalized coherent states.

We discuss the design of a simple experiment that reproduces the operation of the Michelson stellar interferometer. The emission of stellar sources has been simulated using light emerging from circular endfaces of stepindex polymer optical fibers and from diffuse reflections of laser beams. Interference fringes have been acquired using a digital camera, coupled to a telescope obscured by a double aperture lid. The experiment is analogous to the classical determination of stellar sizes by Michelson and can be used during the day. Using this experimental setup, we can determine the size of extended sources, located at a distance of about 75 m from our telescope, with errors less than 25%.

A rattleback is a canoeshaped body that, when spun on a smooth surface, rotates stably in one direction only; when spun in the reverse direction it oscillates violently (i.e., it “rattles”) and reverses its direction of spin. This behavior can be traced to the misalignment of the principal axes of the body with respect to the symmetry axis of its bottom surface. Although analyses of the phenomenon exist in the literature, there is not a clear, direct presentation of the basic mechanism responsible for the reversal of direction. The goal of this paper is to present, as clearly as possible, a treatment of the phenomenon by focusing on the geometry of the usual rattleback. Two initial conditions are considered: rotation about the vertical axis with no oscillation, and oscillation about a horizontal axis with no rotation. For the first initial state, oscillatory motion about the two horizontal axes is analyzed using a combination of linearization and reasonable assumptions. The reversal is then analyzed using energy considerations. The analysis for the second initial state is more direct and elementary. In combination, these analyses explain the transitions from rotation to oscillation to rotation in the opposite direction. The nonreversal for the rotation opposite initial rotation is also accounted for. We also comment on how the rattleback might be modified allowing it to reverse in both directions and thus to repeatedly reverse its direction of rotation.