3,743 research outputs found
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
Solar system tests of scalar field models with an exponential potential
We consider a scenario where a scalar field has dynamics ruled by an
exponential potential, such as those arising from some quintessence type
models, and aim at obtaining phenomenological manifestations of this entity
within our Solar System. To do so, we assume a perturbative regime, derive the
perturbed Schwarzschild metric, and extract the relevant post-Newtonian
parameters.Comment: 5 page
Long range gravity tests and the Pioneer anomaly
Experimental tests of gravity performed in the solar system show a good
agreement with general relativity. The latter is however challenged by the
Pioneer anomaly which might be pointing at some modification of gravity law at
ranges of the order of the size of the solar system. As this question could be
related to the puzzles of ``dark matter'' or ``dark energy'', it is important
to test it with care. There exist metric extensions of general relativity which
preserve the well verified equivalence principle while possibly changing the
metric solution in the solar system. Such extensions have the capability to
preserve compatibility with existing gravity tests while opening free space for
the Pioneer anomaly. They constitute arguments for new mission designs and new
space technologies as well as for having a new look at data of already
performed experiments.Comment: 8 page
On The 5D Extra-Force according to Basini-Capozziello-Leon Formalism and five important features: Kar-Sinha Gravitational Bending of Light, Chung-Freese Superluminal Behaviour, Maartens-Clarkson Black Strings, Experimental measures of Extra Dimensions on board International Space Station(ISS) and the existence of the Particle due to a Higher Dimensional spacetime
We use the Conformal Metric as described in Kar-Sinha work on Gravitational
Bending of Light in a 5D Spacetime to recompute the equations of the 5D Force
in Basini-Capozziello-Leon Formalism and we arrive at a result that possesses
some advantages. The equations of the Extra Force as proposed by Leon are now
more elegant in Conformal Formalism and many algebraic terms can be simplified
or even suppressed. Also we recompute the Kar-Sinha Gravitational Bending of
Light affected by the presence of the Extra Dimension and analyze the
Superluminal Chung-Freese Features of this Formalism describing the advantages
of the Chung-Freese BraneWorld when compared to other Superluminal spacetime
metrics(eg:Warp Drive) and we describe why the Extra Dimension is invisible and
how the Extra Dimension could be made visible at least in theory.We also
examine the Maartens-Clarkson Black Holes in 5D(Black Strings) coupled to
massive Kaluza-Klein graviton modes predicted by Extra Dimensions theories and
we study experimental detection of Extra Dimensions on-board LIGO and LISA
Space Telescopes.We also propose the use of International Space Station(ISS) to
measure the additional terms(resulting from the presence of Extra Dimensions)
in the Kar-Sinha Gravitational Bending of Light in Outer Space to verify if we
really lives in a Higher Dimensional Spacetime.Also we demonstrate that
Particle can only exists if the 5D spacetime exists.Comment: Withdrawn: author no longer wishes to post work on arXi
Paper Session I-C - Drop Tower Bremen -Short Time Microgravity Experiments During Free Fall
In September 1990, the Center of Applied Space Technology and Microgravity (ZARM) of the University of Bremen, West, Germany, will start the operations for the Drop Tower Bremen . Drop Towers enable short time experiments under microgravity condititons, and are thus lowcost research facilities complementing the existing and, projected space laboratories for microgravity research. Developed by ZARM in close cooperation with the Bremen based companies MBB/ERNO Raumfahrttechnik, OHB-System and Krupp Atlas Elektronik, the tower will realize up to several times per day to produce microgravitational condititons for approximately 4.7 s in free fall over 110 m. A powerful pumping system by which, the drop tube can, be evacuated to a pressure of 1 Pa, reduces the air drag to a negligible level,, By using a special release system, the rotation and vibration of the experiment capsule during drop can be minimized. In constructing the tower system, gireat efforts were made to detect and to eliminate \u27further disturbance effects,. Experimental studies were carried out on a 18 m high, drop tower at ZARM during the last 2 years* These studies are complemented by theoretical, investigations and calculations of drop capsule models and, platforms used for mounting the experimental equipment inside the drop capsule,, The results of these studies and considerations show that the rates of the residual disturbing accelerations, to be attained during free fall at the Drop Tower Bremen in the interesting frequency range from 0.2 Hz to 1 kHz can be reduced to a level of 10 g [1]. As a result of these extremely low residual disturbing accelerations, the Drop Tower Bremen is not only a lowcost, but also a very high quality microgravity laboratory
On Doppler tracking in cosmological spacetimes
We give a rigorous derivation of the general-relativistic formula for the
two-way Doppler tracking of a spacecraft in Friedmann-Lemaitre-Robertson-Walker
and in McVittie spacetimes. The leading order corrections of the so-determined
acceleration to the Newtonian acceleration are due to special-relativistic
effects and cosmological expansion. The latter, although linear in the Hubble
constant, is negligible in typical applications within the Solar System.Comment: 10 pages, 1 figure. Journal versio
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A multiregion assessment of observed changes in the areal extent of temperature and precipitation extremes
This study examines trends in the area affected by temperature and precipitation extremes across five large-scale regions using the climate extremes index (CEI) framework. Analyzing changes in temperature and precipitation extremes in terms of areal fraction provides information from a different perspective and can be useful for climate monitoring. Trends in five temperature and precipitation components are analyzed, calculated using a new method based on standard extreme indices. These indices, derived from daily meteorological station data, are obtained from two global land-based gridded extreme indices datasets. The four continental-scale regions of Europe, North America, Asia, and Australia are analyzed over the period from 1951 to 2010, where sufficient data coverage is available. These components are also computed for the entire Northern Hemisphere, providing the first CEI results at the hemispheric scale. Results show statistically significant increases in the percentage area experiencing much-above-average warm days and nights and much-below-average cool days and nights for all regions, with the exception of North America for maximum temperature extremes. Increases in the area affected by precipitation extremes are also found for the Northern Hemisphere regions, particularly Europe and North America
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A multiregion model evaluation and attribution study of historical changes in the area affected by temperature and precipitation extremes
The skill of eight climate models in simulating the variability and trends in the observed areal extent of daily temperature and precipitation extremes is evaluated across five large-scale regions, using the climate extremes index (CEI) framework. Focusing on Europe, North America, Asia, Australia, and the Northern Hemisphere, results show that overall the models are generally able to simulate the decadal variability and trends of the observed temperature and precipitation components over the period 1951–2005. Climate models are able to reproduce observed increasing trends in the area experiencing warm maximum and minimum temperature extremes, as well as, to a lesser extent, increasing trends in the areas experiencing an extreme contribution of heavy precipitation to total annual precipitation for the Northern Hemisphere regions. Using simulations performed under different radiative forcing scenarios, the causes of simulated and observed trends are investigated. A clear anthropogenic signal is found in the trends in the maximum and minimum temperature components for all regions. In North America, a strong anthropogenically forced trend in the maximum temperature component is simulated despite no significant trend in the gridded observations, although a trend is detected in a reanalysis product. A distinct anthropogenic influence is also found for trends in the area affected by a much-above-average contribution of heavy precipitation to annual precipitation totals for Europe in a majority of models and to varying degrees in other Northern Hemisphere regions. However, observed trends in the area experiencing extreme total annual precipitation and extreme number of wet and dry days are not reproduced by climate models under any forcing scenario
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Understanding the role of sea surface temperature-forcing for variability in global temperature and precipitation extremes
The oceans are a well-known source of natural variability in the climate system, although their ability to account for inter-annual variations of temperature and precipitation extremes over land remains unclear. In this study, the role of sea-surface temperature (SST)-forcing is investigated for variability and trends in a range of commonly used temperature and precipitation extreme indices over the period 1959 to 2013. Using atmospheric simulations forced by observed SST and sea-ice concentrations (SIC) from three models participating in the Climate of the Twentieth Century Plus (C20C+) Project, results show that oceanic boundary conditions drive a substantial fraction of inter-annual variability in global average temperature extreme indices, as well as, to a lower extent, for precipitation extremes. The observed trends in temperature extremes are generally well captured by the SST-forced simulations although some regional features such as the lack of warming in daytime warm temperature extremes over South America are not reproduced in the model simulations. Furthermore, the models simulate too strong increases in warm day frequency compared to observations over North America. For extreme precipitation trends, the accuracy of the simulated trend pattern is regionally variable, and a thorough assessment is difficult due to the lack of locally significant trends in the observations. This study shows that prescribing SST and SIC holds potential predictability for extremes in some (mainly tropical) regions at the inter-annual time-scale
On the possibility of measuring relativistic gravitational effects with a LAGEOS-LAGEOS II-OPTIS-mission
In this paper we wish to preliminary investigate if it would be possible to
use the orbital data from the proposed OPTIS mission together with those from
the existing geodetic passive SLR LAGEOS and LAGEOS II satellites in order to
perform precise measurements of some general relativistic
gravitoelectromagnetic effects, with particular emphasis on the Lense-Thirring
effect.Comment: Abridged version. 16 pages, no figures, 1 table. First results from
the GGM01C Earth gravity model. GRACE data include
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