Clock hypothesis

Abstract: We describe a new fault-tolerant algorithm for solving a variant of Lamport's clock synchronization problem. The algorithm is designed for a system of distributed processes that communicate by sending messages. Each process has its own read-only physical clock whose drift rate from real time is very small. By adding a value to its physical clock time, the process obtaines its local time. The algorithm solves the problem of maintaining closely synchronized local times, assuming that processes' local times are closely synchronized initially. The algorithm is able to tolerate the failure of just under one-third of the participating processes. It maintains synchronization to within a small constant, whose magnitude depends upon the rate of clock drift, the message delivery time and its uncertainty, and the initial closeness of synchronization. We also give a characterization of how far the clocks drift from real time. Reintegration of a repaired process can be accomplished using a slight modification of the basic alborithm. A similar style algorithm can also be used to achieve synchronization initially.

Abstract: First-order tests of special relativity are based on a comparison of clocks synchronized with the help of slow clock transport with those synchronized by the Einstein procedure. This comparison enables the measurement of the one-way velocity of light and is equivalent to a measurement of the time dilatation factor. The accuracy of present measurements is of the order 10−7, yielding an upper limit of 3 cm/sec for the ether drift.

Abstract: This study explores the rate of molecular evolution in mammals. Various methods of comparative analysis have been applied to different kinds of molecular data in attempts to resolve the issue. The choice of molecular data, and more importantly, the different assumptions made in the analysis, have resulted in contrasting conclusions being drawn. These assumptions are critically evaluated and the conclusion is drawn that, for "silent" DNA, the molecular clock hypothesis cannot be rejected. For amino acids, the clock hypothesis is rejected, and this appears to reflect the action of natural selection. The implications of the DNA clock in relation to the pattern of mammalian evolution and the process of mutation are discussed.

Abstract: We extend the mathematical model based on stochastic differential equations describing the error gained by an atomic clock to the cases of anomalous behavior including jumps and an increase of instability. We prove an exact iterative solution that can be useful for clock simulation, prediction, and interpretation, as well as for the understanding of the impact of clock error in the overall system in which clocks may be inserted as, for example, the Global Satellite Navigation Systems.