Is the physics within the Solar system really understood?

A collection is made of presently unexplained phenomena within our Solar system and in the universe. These phenomena are (i) the Pioneer anomaly, (ii) the flyby anomaly, (iii) the increase of the Astronomical Unit, (iv) the quadrupole and octupole anomaly, and (v) Dark Energy and (vi) Dark Matter. A new data analysis of the complete set of Pioneer data is announced in order to search for systematic effects or to confirm the unexplained acceleration. We also review the mysterious flyby anomaly where the velocities of spacecraft after Earth swing--bys are larger than expected. We emphasize the scientific aspects of this anomaly and propose systematic and continuous observations and studies at the occasion of future flybys. Further anomalies within the Solar system are the increase of the Astronomical Unit and the quadrupole and octupole anomaly. We briefly mention Dark Matter and Dark Energy since in some cases a relation between them and the Solar system anomalies have been speculated.Comment: 22 pages, 3 figures, submitted for the proceedings of the 359th WE-Heraeus Seminar on "Lasers, Clocks, and Drag-Free: Technologies for Future Exploration in Space and Tests of Gravity

The 26th Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting

This document is a compilation of technical papers presented at the 26th Annual PTTI Applications and Planning Meeting. Papers are in the following categories: (1) Recent developments in rubidium, cesium, and hydrogen-based frequency standards, and in cryogenic and trapped-ion technology; (2) International and transnational applications of Precise Time and Time Interval technology with emphasis on satellite laser tracking, GLONASS timing, intercomparison of national time scales and international telecommunications; (3) Applications of Precise Time and Time Interval technology to the telecommunications, power distribution, platform positioning, and geophysical survey industries; (4) Applications of PTTI technology to evolving military communications and navigation systems; and (5) Dissemination of precise time and frequency by means of GPS, GLONASS, MILSTAR, LORAN, and synchronous communications satellites

Entanglement and quantum clocks in curved spacetime

In this thesis, we investigate how motion through a curved spacetime background affects a system's dynamics, specifically the entanglement contained between its degrees of freedom, and our ability to use the system as a clock. We incorporate both quantum theory and general relativity using quantum field theory in curved spacetime, localising the field by boundaries to describe e.g. an optical cavity. We derive the effect of boundary motion on the state of the field contained therein. A moving boundary can create particles from the vacuum in a phenomenon known as the dynamical Casimir effect; we give a description of the effect in curved spacetime. Reconsidering a common scenario, now adopting the Schwarzschild metric, we find novel particle-production resonances due to the curvature. We also discuss a potential enhancement of the effect in the phonon field of a Bose-Einstein condensate. We apply these results to a quantum model of the famous light-clock thought experiment. After motivating and reviewing the model, we show for Gaussian clock states that the discrepancy between two such clocks is state-independent, and separates into classical and quantum effects. We numerically investigate the discrepancy when one clock is held in a gravitational field and the other falls a certain distance, finding quantitative and qualitative differences from the case of classical pointlike observers. We further show that the quantum and classical effects respectively increase and decrease in magnitude with increasing gravitational field strength. We then study entanglement in a number of drop-tower scenarios, considering entanglement generated between field modes within an apparatus, and the degradation of an initially entangled state, both between spatially separated parties, and between modes contained within one apparatus. We quantify the effect via the negativity or the entanglement fidelity, as appropriate to each case. We present numerical investigations into the entanglement generated/degraded, finding novel features compared to previous investigations of non-inertial motion in flat spacetime, and discuss our results in the context of recent experiments on the subject.Open Acces

Rotational invariance of maxwell's equations

Rotational invariance of maxwell vector equation

Time metrology in Global Navigation Satellite Systems

Precise timekeeping is at the basis of any Global Navigation Satellite System. In this thesis, after an extensive introduction on time and frequency metrology, some of the basic time-related aspects of navigation systems are discussed, and new ideas and solutions are presented. In the first part of the work, the most relevant innovative contributions are related to the mathematical clock model and to the stability analysis of atomic clocks affected by frequency jumps, as well as to the development of a new averaging algorithm for the generation of a robust time scale from an ensemble of atomic clocks. In the second part, devoted to the role of timekeeping in satellite navigation systems, the innovative contributions are mainly about: a revision of the relativistic corrections; the development and testing of a new composite clock, which could be used as a system time scale for the Galileo system; a study on the impact of the light-shift effect on the timing performance of GPS rubidium clocks; the development of a new recursive clock anomalies detector, as well as a discussion about the possible implementations of a clock anomalies detector and a compensation system for on-board applications

Satellite clock time offset prediction in global navigation satellite systems

In an operational sense, satellite clock time offset prediction (SCTOP) is a fundamental requirement in global navigation satellite systems (GNSS) tech- nology. SCTOP uncertainty is a significant component of the uncertainty budget of the basic GNSS pseudorange measurements used in standard (i.e not high-precision), single-receiver applications. In real-time, this prediction uncertainty contributes directly to GNSS-based positioning, navigation and timing (PNT) uncertainty. In short, GNSS performance in intrinsically linked to satellite clock predictability. Now, satellite clock predictability is affected by two factors: (i) the clock itself (i.e. the oscillator, the frequency standard etc.) and (ii) the prediction algorithm. This research focuses on aspects of the latter. Using satellite clock data—spanning across several years, corresponding to multiple systems (GPS and GLONASS) and derived from real measurements— this thesis first presents the results of a detailed study into the characteristics of GNSS satellite clocks. This leads onto the development of strategies for modelling and estimating the time-offset of those clocks from system time better, with the final aim of predicting those offsets better. The satellite clock prediction scheme of the International GNSS Service (IGS) is analysed, and the results of this prediction scheme are used to evaluate the performance of new methods developed herein. The research presented in this thesis makes a contribution to knowledge in each of the areas of characterisation, modelling and prediction of GNSS satellite clocks. Regarding characterisation of GNSS satellite clocks, the space-borne clocks of GPS and GLONASS are studied. In terms of frequency stability—and thus predictability—it is generally the case that the GPS clocks out-perform GLONASS clocks at prediction lengths ranging from several minutes up to one day ahead. There are three features in the GPS clocks—linear frequency drift, periodic signals and and complex underlying noise processes—that are not observable in the GLONASS clocks. The standard clock model does not capture these features. This study shows that better prediction accuracy can be obtained by an extension to the standard clock model. The results of the characterisation and modelling study are combined in a Kalman filter framework, set up to output satellite clock predictions at a range of prediction intervals. In this part of the study, only GPS satellite clocks are considered. In most, but not all cases, the developed prediction method out- performs the IGS prediction scheme, by between 10% to 30%. The magnitude of the improvement is mainly dependent upon clock type

Quantum Times: Physics, Philosophy, and Time in the Postwar United States

The concept of time in physics underwent significant changes in the decades following World War II. This dissertation considers several ways in which American physicists grappled with these changes, analyzing the extent to which philosophical methods and questions played a role in physicists' engagement with time. Two lines of questioning run through the dissertation. The first asks about the professional identities of postwar American physicists in relation to philosophy, as exemplified by their engagement with the concept of time. The second analyzes the heterogeneous nature of time in physics, and the range of presuppositions and assumptions that have constituted this "fundamental" physical concept. The first chapter looks to the development of atomic clocks and atomic time standards from 1948-1958, and the ways in which new timekeeping technologies placed concepts such as “clock”, “second,” and “measure of time” in a state of flux. The second chapter looks to the experimental discovery of CP violation by particle physicists in the early 1960s, raising questions about nature of time understood as the variable “t” in the equations of quantum mechanics. The third chapter considers attempts to unify quantum mechanics and general relativity in the late 1960s, which prompted physicists to question the “existence” of time in relation to the universe as a whole. In each episode considered, physicists engaged with the concept of time in a variety of ways, revealing a multiplicity of relationships between physics, philosophy, and time. Further, in each case physicists brought a unique set of assumptions to their concepts of time, revealing the variety ways in which fundamental conceptsfunctioned and changed in late twentieth century physics. The result is a heterogeneous picture of the practice of physics, as well as one of physics’ most basic concepts.History of Scienc

Nanosatellites for quantum science and technology

Bringing quantum science and technology to the space frontier offers exciting prospects for both fundamental physics and applications such as long-range secure communication and space-borne quantum probes for inertial sensing with enhanced accuracy and sensitivity. But despite important terrestrial pathfinding precursors on common microgravity platforms and promising proposals to exploit the significant advantages of space quantum missions, large-scale quantum testbeds in space are yet to be realized due to the high costs and leadtimes of traditional “Big Space” satellite development. But the “small space” revolution, spearheaded by the rise of nanosatellites such as CubeSats, is an opportunity to greatly accelerate the progress of quantum space missions by providing easy and affordable access to space and encouraging agile development. We review space quantum science and technology, CubeSats and their rapidly developing capabilities, and how they can be used to advance quantum satellite systems