Gravity Experiments Research Articles

Constraint of d = 8 Lorentz Invariance Violation with New Experimental Design

Short-range gravity experiments are more suitable for the testing of high-order Lorentz symmetry breaking effects. In our previous work, we proposed a new experimental design based on precision torsion balance technology to test the Lorentz violation force effect that varies inversely with the fourth power of distance (corresponding to mass dimension d = 6 term), and the corresponding experiment is currently underway. In this paper, we focus on analyzing the potential of this experimental scheme to test the Lorentz violation force that varies inversely with the sixth power of distance (corresponding to mass dimension d = 8 term). The results show that, compared with the current best limit, the new experimental scheme can improve the constraints on the Lorentz violation coefficients with d = 8 by at least one order of magnitude.

An inverse gravity experiment supports the theory of an internal gravity model in the central nervous system

An inverse gravity experiment supports the theory of an internal gravity model in the central nervous system

Coupled System of Dual-Axis Clinostat and Helmholtz Cage for Simulated Microgravity Experiments

The experimental investigation of plant growth under space conditions is a necessary prerequisite of long-term space missions. Besides experiments in space, many studies are performed under simulated microgravity, using a clinostat. However, the Earth magnetic field is usually not taken into account in such investigations. Here, a self-designed and constructed system of coupled devices—a clinostat and a Helmholtz cage—is presented. The clinostat can, on average, cancel the effective gravity field by using two independent rotations, enabling simulated zero-valued gravity experiments. Additionally, an appropriately symmetrically mounted Helmholtz cage can be used to cancel the natural Earth magnetic field in the volume where the clinostat is located. The combination of these two devices offers the opportunity, e.g., for bio-inspired experiments in which plant cultivation can be carried out in conditions that imitate a space environment. We provide information about the experimental setup and show first experimental results of growth tests.

Observable strong field effects of extra spacetime dimension in the braneworld black hole

Inspired by the string theory, the braneworld picture introduces extra dimensions beyond the four that may have observable non-trivial effects in short distance (strong field) gravity experiments. A case in point is the Randall–Sundrum braneworld picture that projects the 5d bulk Weyl tensor onto the 3d brane providing a stress tensor in the effective Einstein field equations on the brane. Dadhich, Maartens, Papadopoulos and Rezania (DMPR) derived an exact braneworld black hole solution of the brane vacuum field equations. The solution formally resembles that of Reissner–Nordström but is physically different from it since the ”tidal charge” Υ in the solution is not the electric charge but an imprint from the fifth dimension allowing both signs in the power law modification ±Υ2r2 to the Schwarzschild metric Υ=0. The corresponding black holes are designated as DMPR±. We study here the effect of Υ on strong field lensing observables and compare in the eikonal limit the ring down quasinormal mode (QNM) frequencies of DMPR− with those of DMPR＋ , the two variants of tidal charge modified Schwarzschild black hole (Υ=0). It turns out that the tidal charge can significantly modify the Schwarzschild lensing observables and QNM frequencies. In particular, we find that the Pretorius–Khurana critical exponent γ of circular null orbits in the DMPR− black hole has a lower value than that for the Schwarzschild black hole, which indicates a stronger Lyapunov instability suggesting that the accretion disks of DMPR− black holes would appear brighter. The case of the SgrA* black hole is considered for a possible constraint on Υ from the EHT observation of its shadow size.

Erosion rate of lunar soil under a landing rocket, part 1: Identifying the rate-limiting physics

Multiple nations are planning activity on the Moon's surface, and to deconflict lunar operations we must understand the sandblasting damage from rocket exhaust blowing soil. Prior research disagreed over the scaling of the erosion rate, which determines the magnitude of the damage. Reduced gravity experiments and two other lines of evidence now indicate that the erosion rate scales with the kinetic energy flux at the bottom of the laminar sublayer of the gas. Because the rocket exhaust is so fast, eroded particles lifted higher in the boundary layer do not impact the surface for kilometers (if at all; some leave the Moon entirely), so there is no saltation in the vicinity of the gas. As a result, there is little transport of gas kinetic energy from higher in the boundary layer down to the surface, so the emission of soil into the gas is a surprisingly low energy process. In low lunar gravity, a dominant source of resistance to this small energy flux turns out to be the cohesive energy density of the lunar soil, which arises primarily from particles in the 0.3 to 3 μm size range. These particles constitute only a tiny fraction of the mass of lunar soil and have been largely ignored in most studies, so they are poorly characterized.

On Improving Water-Based Drilling Mud Swelling Control Using Modified Poly(Vinyl Alcohol)s.

One of the most challenging issues when drilling under high-temperature, high-pressure (HT/HP) conditions is wellbore instability caused by clay swelling and fluid loss of the drilling mud. One of the most difficult issues when drilling under high-temperature, high-pressure (HT/HP) conditions is wellbore instability caused by clay swelling and fluid loss in drilling mud. Two modified PVOHs, nonionic and cationic polymers made from sodium bentonite clay and deionized water at concentrations of 0.08, 0.28, and 0.49 wt.%, were introduced to WBM percent. A series of specific gravity and mud rheology experiments at 25, 55, and 85 °C indicated that both values drop monotonically with increasing temperature, regardless of PVOH addition or concentration. A temperature increase of 30 °C decreases the mud viscosity of WBM (without PVOH) by 18% from its starting value, on average. Only 0.1% of cationic and nonionic polymer reduces viscosity by 10% and 0%, respectively. Experimenting with mud samples for 5 h revealed that adding nonionic polymers enhances mud filtration by up to 34.7%, 1.25 times more than that achieved from cationic polymers under the same filtration circumstances. Increasing the filtration temperature moderately affects mud cake generation due to increased mud swelling index and preferential adsorption by nonionic polymer. The latter observation was corroborated by determining the polymer content of the filtrates. Therefore, it was shown that nonionic polymers adsorbed more (118.9 mg/g) than cationic polymers (84.51 mg/g). Increased filtration temperature moderately affects mud cake generation due to increased mud swelling index and preferential adsorption by nonionic polymer. The latter observation was corroborated by testing the filtrates for the polymer content. As a result, it was discovered that nonionic polymer adsorbed more (118.9 mg/g) than cationic polymer (84.51 mg/g). Thermogravimetry analysis (TGA) finally tested the thermal stability of polymers.

Constraining light scalar field with torsion-balance gravity experiments

The light scalar field with a coupling to standard model particles provide a possible source of the long-range Yukawa forces or violation of the weak equivalence principle, which can be potentially explored by precision gravity experiments. We describe the searches for such light scalar fields with the three types of gravity experiments, including the G-measurement experiments, Inverse-Square Law (ISL) experiments, and equivalence principle experiments. We investigate the potential influences of the scalar field as a function of its mass, and focus on the experimental constraints from torsion-balance gravity experiments. HUST-18 G-measurement torsion-balance experiments place bounds on the photon coupling and electron coupling at up to Λγ=7×1017 GeV and Λe=1×1017 GeV in the mass ranges 10−9–10−4eV. Results from the ISL experiments by the Universities of Washington, Stanford, IUPUI, HUST, Colorado, Irvine, Yale and others allow us to set limits on the photon coupling and electron coupling at up to Λγ=5×1017 GeV and Λe=3×1016 GeV for scalar field mass ranges between 10−5 and 10−1eV. Additionally, we also discuss the limits from equivalence principle experiments, and MICROSCOPE final result updates the constrains on the coupling parameters at up to Λγ=7×1022 GeV and Λe=4×1021 GeV for mass ranges ≲10−13eV. These results contribute experimental constraints to relatively unexplored mass regions of light scalar field parameter space and improve upon previous limits in some mass ranges. This work paves the way for long-range Yukawa forces mediated by light scalar fields in future high-precision gravity experiments.

Spatiotemporal distribution of groundwater drought using GRACE-based satellite estimates: a case study of Lower Gangetic Basin, India.

Droughts frequently occurring in India have significant societal, economic, and environmental effects. The lack of direct measurements of groundwater in location and time hinders quantitative methods to analyse the intricate nature of groundwater drought. This work used the datasets derived from the Gravity and Climate Experiment (GRACE and GRACE-FO) and Global Land Data Assimilation System (GLDAS) to extensively analyse Groundwater Storage changes in the Lower Gangetic Basin (LGB) using unique hydrological parameters between the years 2003 and 2022. The analysis highlights that the GRACE-derived terrestrial water storage anomaly in the LGB decreased significantly (-12.12 mm/yr), and the amount of Groundwater Storage Anomaly (GWSA) decreased similarly (-10.80 mm/yr), while in the GRACE-FO period, a positive trend has been noticed in TWSA (33.96 mm/yr) and GWSA (64.8 mm/yr) respectively. A drought indicator called the GRACE-derived groundwater drought index (GGDI) has been computed for the entire LGB region. A traditional drought study viz. Standardised Precipitation Index (SPI) was performed over LGB to justify the results of the GGDI. The results from GGDI study effectively matched the periods of significant drought occurrences with the 12-month SPI time series. From the GGDI, this study examined groundwater drought's spatial distribution, temporal evolution, and trend (Modified Mann Kendall trend) aspects. According to research findings, the LGB experienced three major drought periods between 2009-2010, 2019 (moderate), and 2015-2016 (severe). The study offers reliable quantitative data on the evolution of GRACE-derived groundwater drought, which may add a new perspective to additional drought research in the densely populated study area, which depends majorly on agriculture, livestock and less skilled water-intensive industries such as leather and textile industries in a sub-tropical climate. This paradigm incorporates changes in groundwater resources caused by human activities and climate change, paving the way for measuring progress towards sustainable use and water security.

Experimental study on subcooled pool boiling of FC-72 on a flat plate in normal and microgravity

A series of experimental studies on the heat transfer characteristics of pool boiling were conducted aboard the Chinese satellite SJ-10 in April 2016. Ground comparative experiments under the same conditions were carried out using the same apparatus. FC-72 was used as the working fluid containing non-condensable gas. The total quasi-stable-state acceleration aboard satellite SJ-10 during its in-orbit flight is approximately 2 × 10−6 g0. The integrated microheater fabricated by the microelectromechanical system (MEMS) technique was used to investigate the boiling characteristics. The boiling surface of the integrated microheater is on top of a flat plate quartz glass wafer substrate 2 mm thick, heated by a serpentine Pt thin film (main heater) below the substrate. The effective area of the boiling surface in direct contact with FC-72 is 5.5 mm in diameter. Ten temperature sensors are located around the boiling surface center and uniformly distributed in the circumferential direction. The experimental results show that single-phase convection could still be maintained under lower Rayleigh number conditions, showing consistency with the predictions based on the available correlations. The generated bubble volume determines the boiling state. At high liquid subcooling, the bubbles formed after the liquid vaporizes are relatively small, and steam condensation at the bubble cap promotes the phase change efficiency, which maintains nucleate boiling in microgravity. When subcooling is low, bubbles are larger and cover most of the heating surface, nucleate boiling is difficult to maintain, and the boiling becomes transition boiling. High liquid subcooling improves the heat transfer efficiency, thereby contributing to maintaining the progress of nucleate boiling in microgravity. However, boiling is less affected by liquid subcooling on the ground than in microgravity. A comparison of pool boiling curves between microgravity and normal gravity experiments indicates that nucleate boiling curves under the same subcooling partially overlap, while the heat flux corresponding to the initiation of the nucleate state is lower than that on the ground. In microgravity, lower liquid subcooling and higher heating power will result in larger bubble volumes and easier complete coverage of the heating surface, resulting in an easier transition from nucleate boiling to film boiling.

Spacetime-emergent ring toward tabletop quantum gravity experiments

We propose a way to discover, in tabletop experiments, spacetime-emergent materials, that is, materials holographically dual to higher-dimensional quantum gravity systems under the AdS/CFT. The emergence of the holographic spacetime is verified by a mathematical imaging transform of the response function on the material. We consider theories on a one-dimensional ring-shaped material and compute the response to a scalar source locally put at a point on the ring. When the theory on the material has a gravity dual, the imaging in the low-temperature phase exhibits a distinct difference from the ordinary materials: The spacetime-emergent material can look into the holographically emergent higher-dimensional curved spacetime and provides an image as if a wave had propagated there. Therefore the image is an experimental signature of the spacetime emergence. We also estimate the temperature, ring size, and source frequency usable in experiments, with an example of a quantum critical material, ${\mathrm{TlCuCl}}_{3}$.

An Experiment on Apparent Specific Gravity and Settleable Degree of Fire Extinguishing Agent according to Durable Years of Regional Powder Extinguisher

For powder extinguishing agents based on the useful life of the powder extinguisher, a powder extinguisher with a elapsed life of 6-10 years was collected from market, factory, and apartment houses to experiment with changes in volume by appearance and sedimentation, and to examine digestive characteristics. As a result of the study, the first, second, and third arithmetic mean analysis of the apparent specific gravity experiments from 6 to 10 years of use, showed that the total arithmetic average of three experiments in the market area with an 8-year useful life was 127mL. In 2012, the average arithmetic average of three experiments in multi-family housing with a 10-year useful life was 131mL, which was found to be inappropriate. Second, in the experimental value for sedimentation, it was found to be unsuitable in the 2012 sedimentation experiment on samples in the apartment area. In other words, the sedimentation test of the powder extinguishing agent should not occur within an hour, but the sample in the apartment complex area in 2012 was found to be defective. Third, the fire extinguisher needs to be strengthened to enable fire extinguisher maintenance and inspection because problems that cannot be used during initial fire suppression occur depending on the place of deployment, surrounding environment, age of use, and maintenance status.

Quantum gravitational sensor for space debris

Matter-wave interferometers have fundamental applications for gravity experiments such as testing the equivalence principle and the quantum nature of gravity. In addition, matter-wave interferometers can be used as quantum sensors to measure the local gravitational acceleration caused by external massive moving objects, thus lending itself for technological applications. In this paper, we will establish a three dimensional model to describe the gravity gradient signal from an external moving object, and theoretically investigate the achievable sensitivities using the matter-wave interferometer based on the Stern-Gerlach set-up. As an application we will consider the Mesoscopic Interference for Metric and Curvature (MIMAC) and Gravitational wave detection scheme [New J. Phys. 22, 083012 (2020)] and quantify its sensitivity to gravity gradients using frequency-space analysis. We will consider objects near Earth-based experiments and space debris in proximity of satellites and estimate the minimum detectable mass of the object as a function of their distance, velocity, and orientation.

Electroadhesive robotics experiment in simulated microgravity

Canada has a strong presence in space robotics, and Mission SpaceWalker (MSW) is a group of ambitious young women who are leaning into Canadian robotics excellence through their investigation of how electroadhesive (EA) robots behave in reduced gravity, all while introducing a new testing procedure for rovers and adhesive space robotics. As an undergraduate student team at the University of Alberta, MSW has been chosen to fly their payload as part of the Canadian Reduced Gravity Experiment Challenge (CAN-RGX) organized by Students for the Exploration and Development of Space Canada (SEDS-Canada), the National Research Council of Canada, and the Canadian Space Agency. The annual competition is open nationwide to university students, soliciting participating groups to create a payload to be tested onboard a parabolic flight. The experiment will consist of an automated system contained within a Pelican case, featuring a mechanical design that will obtain footage of two robots on conductive and nonconductive surfaces. It will log data from onboard sensors to provide insight into the performance of the EA pads on both surfaces. The payload is expected to be flown on a parabolic flight during the CAN-RGX campaign in the 2023 calendar year.

Optimization of an Active Leveling Scheme for a Short-Range Gravity Experiment

At Cal Poly Humboldt, undergraduate researchers and faculty have constructed a torsion-pendulum experiment that seeks to measure gravitational interactions below test mass separations of 100 microns. The aim of this experiment is to look for deviations in the weak equivalence principle (WEP) and inverse-square law (ISL). The scale at which this experiment operates is within an untested range at the submillimeter scale. This apparatus’s torsion pendulum consists of equal masses with differing materials arranged as a composition dipole. The twist of this configuration is measured as an attractor mass oscillates in a parallel-plate arrangement nearby. The oscillation creates a time-dependent torque on the pendulum which can be studied for deviations in the WEP and ISL. At present, an active leveling scheme has been implemented to mediate the apparatus’s long-term tilt variations. This scheme has been optimized through the use of a power supply and proportional-integral-derivative (PID) loop that mitigates the variations in tilt by applying a voltage to a resistor attached to one of the apparatus legs. The applied voltage causes thermal expansion of the apparatus leg support structure, thus correcting and modulating the tilt of this experiment.

Lab-on-a-Chip Technologies for Microgravity Simulation and Space Applications.

Gravity plays an important role in the development of life on earth. The effect of gravity on living organisms can be investigated by controlling the magnitude of gravity. Most reduced gravity experiments are conducted on the Lower Earth Orbit (LEO) in the International Space Station (ISS). However, running experiments in ISS face challenges such as high cost, extreme condition, lack of direct accessibility, and long waiting period. Therefore, researchers have developed various ground-based devices and methods to perform reduced gravity experiments. However, the advantage of space conditions for developing new drugs, vaccines, and chemical applications requires more attention and new research. Advancements in conventional methods and the development of new methods are necessary to fulfil these demands. The advantages of Lab-on-a-Chip (LOC) devices make them an attractive option for simulating microgravity. This paper briefly reviews the advancement of LOC technologies for simulating microgravity in an earth-based laboratory.

Analogy of the Lorentz-violating fermion-gravity and fermion photon couplings

By adopting a methodology proposed by R.J. Adler \etl, we study the interesting analogy between the fermion-gravity and the fermion-electromagnetic interactions in the presence of the minimal Lorentz-violating (LV) fermion coefficients. The one-fermion matrix elements of gravitational interaction (OMEGI) are obtained with a prescribed Lense-Thirring (LT) metric assuming test particle assumption. Quite distinct from the extensively studied linear gravitational potential, the LT metric is an essentially curved metric, and thus reveals the anomalous LV matter-gravity couplings as a manifestation of the so-called gravito-magnetic effects, which go beyond the conventional equivalence principle predictions. By collecting all the spin-dependent operators from the OMEGI with some reasonable assumptions, we get a LV non-relativistic Hamiltonian, from which we derive the anomalous spin precession and gravitational acceleration due to LV. Combined these results with certain spin gravity experiments, we get some rough bounds on several LV parameters, such as $|3\vec{\tilde{H}}-2\vec{b}|\leq1.46\times10^{-5}\mathrm{eV}$, with some ad hoc assumptions.

Mechanical parametric feedback-cooling for pendulum-based gravity experiments

Gravitational forces that oscillate at audio-band frequencies are measured with masses suspended as pendulums that have resonance frequencies even lower. If the pendulum is excited by thermal energy or by seismic motion of the environment, the measurement sensitivity is reduced. Conventionally, this problem is mitigated by seismic isolation, potentially combined with cryogenic cooling. Here, we propose mechanical parametric cooling of the pendulum motion, continuously even during the measurements. Different from linear damping, the actuator of our approach does not need a mechanically stable reference point. We report a proof of principle demonstration in the seismic noise dominated regime and achieve a damping factor of the pendulum motion of 5.7. We find a model system for which mechanical parametric feedback cooling reaches the quantum mechanical regime near the ground state. Gravitational-wave detectors would already be improved with much lower cooling factors.

Examining the influence of turbulence on viscosity measurements of molten germanium under reduced gravity

The thermophysical properties of liquid germanium were recently measured both in parabolic flight experiments and on the ISS in the ISS-EML facility. The viscosity measurements differed between the reduced gravity experiments and the literature values. Since the oscillating drop method has been widely used in EML, further exploration into this phenomenon was of interest. Models of the magnetohydrodynamic flow indicated that turbulence was present during the measurement in the ISS-EML facility, which accounts for the observed difference.

Design and Implementation of Virtual Physics Based on Unity and Visual Programming

Based on the Unity3D physical simulation characteristics and PlayMaker visual programming as the programming means, this paper designs and realizes the virtual experiment suitable for junior high school physics teaching. The purpose is to transform the serious physical experiment into an intuitive and vivid virtual interactive animation, so as to stimulate students' interest in physics learning and improve the learning quality.This design is mainly designed for the elastic realization and gravity experiment in the middle school physics curriculum.In addition, the use of visual programming tools can reduce the development threshold, and some non-computer major students can also complete the design and implementation of the experiment in practice.

Gravitational signal propagation in the double pulsar studied with the MeerKAT telescope

The double pulsar PSR J0737−3039A/B has offered a wealth of gravitational experiments in the strong-field regime, all of which general relativity has passed with flying colours. In particular, among current gravity experiments that test photon propagation, the double pulsar probes the strongest spacetime curvature. Observations with MeerKAT and, in the future, the Square Kilometre Array (SKA) can greatly improve the accuracy of current tests and facilitate tests of next-to-leading-order (NLO) contributions in both orbital motion and signal propagation. We present our timing analysis of new observations of PSR J0737−3039A, made using the MeerKAT telescope over the last three years. The increased timing precision offered by MeerKAT yields a measurement of Shapiro delay parameter s that it twice as good, and an improved mass measurements compared to previous studies. In addition, our results provide an independent confirmation of the NLO signal propagation effects and already surpass the previous measurement from 16 yr data by a factor of 1.65. These effects include the retardation effect due to the movement of the companion and the deflection of the signal by the gravitational field of the companion. We also investigate the novel effects that have been expected. For instance, we search for potential profile variations near superior conjunctions caused by shifts of the line of sight due to latitudinal signal deflection, and we find insignificant evidence with our current data. With simulations, we find that the latitudinal deflection delay is unlikely to be measured with timing because of its correlation with Shapiro delay. Furthermore, although it is currently not possible to detect the expected lensing correction to the Shapiro delay, our simulations suggest that this effect may be measured with the full SKA. Finally, we provide an improved analytical description for the signal propagation in the double pulsar system that meets the timing precision expected from future instruments such as the full SKA.