Quantum probe of space-time curvature

An atom interferometer measures the quantum phase due to gravitational time dilation

Time to imagine moving: Simulated motor activity affects time perception

Sensing the passage of time is important for countless daily tasks, yet time perception is easily influenced by perception, cognition, and emotion. Mechanistic accounts of time perception have traditionally regarded time perception as part of central cognition. Since proprioception, action execution, and sensorimotor contingencies also affect time perception, perception-action integration theories suggest motor processes are central to the experience of the passage of time. We investigated whether sensory information and motor activity may interactively affect the perception of the passage of time. Two prospective timing tasks involved timing a visual stimulus display conveying optical flow at increasing or decreasing velocity. While doing the timing tasks, participants were instructed to imagine themselves moving at increasing or decreasing speed, independently of the optical flow. In the direct-estimation task, the duration of the visual display was explicitly judged in seconds while in the motor-timing task, participants were asked to keep a constant pace of tapping. The direct-estimation task showed imagining accelerating movement resulted in relative overestimation of time, or time dilation, while decelerating movement elicited relative underestimation, or time compression. In the motor-timing task, imagined accelerating movement also accelerated tapping speed, replicating the time-dilation effect. The experiments show imagined movement affects time perception, suggesting a causal role of simulated motor activity. We argue that imagined movements and optical flow are integrated by temporal unfolding of sensorimotor contingencies. Consequently, as physical time is relative to spatial motion, so too is perception of time relative to imaginary motion.

The Relation between General Relativity’s Metrics and Special Relativity’s Gravitational Scalar Generalized Potentials and Case Studies on the Schwarzschild Metric, Teleparallel Gravity, and Newtonian Potential

This paper shows that gravitational results of general relativity (GR) can be reached by using special relativity (SR) via a SR Lagrangian that derives from the corresponding GR time dilation and vice versa. It also presents a new SR gravitational central scalar generalized potential V=V(r,r.,ϕ.), where r is the distance from the center of gravity and r.,ϕ. are the radial and angular velocity, respectively. This is associated with the Schwarzschild GR time dilation from where a SR scalar generalized potential is obtained, which is exactly equivalent to the Schwarzschild metric. Thus, the Precession of Mercury’s Perihelion, the Gravitational Deflection of Light, the Shapiro time delay, the Gravitational Red Shift, etc., are explained with the use of SR only. The techniques used in this paper can be applied to any GR spacetime metric, Teleparallel Gravity, etc., in order to obtain the corresponding SR gravitational scalar generalized potential and vice versa. Thus, the case study of Newtonian Gravitational Potential according to SR leads to the corresponding non-Riemannian metric of GR. Finally, it is shown that the mainstream consideration of the Gravitational Red Shift contains two approximations, which are valid in weak gravitational fields only.

Life in a rotating world

We imagine a group of people living on the inner surface of a huge rotating cylinder in flat spacetime. Their experiences are described and calculated. Thus we introduce gravimagnetic effects and the connection between gravitational time dilation and gravitational acceleration. Gravimagnetic effects such as the force on moving particles and the precession of gyroscopes are derived. The Thomas precession is obtained. These observations illustrate GR ideas that are applicable more generally. Some properties of the general stationary metric are introduced.

3. Philosophical implications of relativity

‘Philosophical implications of relativity’ looks at the counterintuitive implications of the special theory of relativity. It begins with time dilation and length contraction, wherein the measurements of spatial distances and temporal intervals appear to vary with the motion of the observer. The question of whether relativity allows for the possibility of time travel is raised and the so-called paradoxes of time travel are explored.

Derivation of general relativistic gravitational potential energy using principle of equivalence and gravitational time dilation

Einstein’s theory of general relativity which has been experimentally proved to be true theory of gravity doesn’t need gravitational potential energy to predict trajectory of particles in space. This is because general relativity is a purely geometric theory. Objects move along the geodesics in the curved space-time. The energy-momentum tensor that warps the space-time as per Einstein’s field equations takes into account only the energy/momentum of matter and radiation. Thus, gravitational potential energy doesn’t come into picture in Einstein’s theory of gravity and its role is taken over by curvature of space-time. However, general relativistically correct expression for gravitational potential energy is required for energy conservation and some energy-based approaches in physics. Conventionally, correct form of gravitational potential energy is derived by using full mathematical formality of general relativity. In this paper, we describe an event by which we derive the same general relativistic expression for gravitational potential energy simply by using the principle of equivalence and gravitational time dilation.