scholarly journals Does gravity operate between galaxies? Observational evidence re-examined

Author(s):  
Francis J. M. Farley

The redshifts and luminosities of type 1A supernovae are conventionally fitted with the current paradigm, which holds that the galaxies are locally stationary in an expanding metric. The fit fails unless the expansion is accelerating; driven perhaps by ‘dark energy’. Is the recession of the galaxies slowed down by gravity or speeded up by some repulsive force? To shed light on this question the redshifts and apparent magnitudes of type 1A supernovae are re-analysed in a cartesian frame of reference omitting gravitational effects. The redshift is ascribed to the relativistic Doppler effect which gives the recession velocity when the light was emitted; if this has not changed, the distance reached and the luminosity follow immediately. This simple concept fits the observations surprisingly well with the Hubble constant H 0 =62.9±0.3 km s −1  Mpc −1 . It appears that the galaxies recede at unchanging velocities, so on the largest scale there is no significant intergalactic force. Reasons for the apparent absence of an intergalactic force are discussed.

2021 ◽  
Vol 13 (4) ◽  
pp. 1608
Author(s):  
Rubén Cordera ◽  
Soledad Nogués ◽  
Esther González-González ◽  
José Luis Moura

Autonomous vehicles (AVs) can generate major changes in urban systems due to their ability to use road infrastructures more efficiently and shorten trip times. However, there is great uncertainty about these effects and about whether the use of these vehicles will continue to be private, in continuity with the current paradigm, or whether they will become shared (carsharing/ridesharing). In order to try to shed light on these matters, the use of a scenario-based methodology and the evaluation of the scenarios using a land use–transport interaction model (LUTI model TRANSPACE) is proposed. This model allows simulating the impacts that changes in the transport system can generate on the location of households and companies oriented to local demand and accessibility conditions. The obtained results allow us to state that, if AVs would generate a significant increase in the capacity of urban and interurban road infrastructures, the impacts on mobility and on the location of activities could be positive, with a decrease in the distances traveled, trip times, and no evidence of significant urban sprawl processes. However, if these increases in capacity are accompanied by a large augment in the demand for shared journeys by new users (young, elderly) or empty journeys, the positive effects could disappear. Thus, this scenario would imply an increase in trip times, reduced accessibilities, and longer average distances traveled, all of which could cause the unwanted effect of expelling activities from the consolidated urban center.


Author(s):  
Ramón Maruri Villanueva

La fiesta en la España Moderna, con acusada preferencia la pública y barroca, tía venido siendo, desde 1980 fundamentalmente, un campo histohográfico bien frecuentado por los investigadores. Enmarcado en él, el presente trabajo se centra en cómo fue percibida por un conjunto de extranjeros que recorrieron la España del siglo XVIII. Sus percepciones, que hemos llamado mirada ajena, nos son conocidas a través de la denominada literatura de viajes y hablan de la fiesta pública y privada, profana y religiosa, civil y política. Dicha literatura, que no había sido utilizada con carácter sistemático en monografías sobre la fiesta, hemos considerado que podía iluminar tanto aspectos de ésta como de la mentalidad de quienes la recrearon en sus diarios y cartas: cuáles llamaron su atención; qué juicios les merecieron; en qué medida algunos de éstos sirvieron para construir, perpetuar o atemperar estereotipos; qué cambios pudieron producirse en los rituales festivos y de qué cambios en la realidad social podían dar cuenta; en qué se desviaba, o no, la percepción de los viajeros de la de españoles de la época o de la imagen recuperada por la investigación histórica contemporánea.Since about 1980 festivities in Spain of the Ancien Régime, with a marked preference for public and baroque festivities, have been a historiographic field frequently studied by researchers. Set in the frame of reference of this field, this work centers on how festivities were perceived by a group of foreigners who traveled around Spain in the eighteenth century. Their perceptions, which we call the foreign perspective, are known to us through what is called travel literature, and speak about various kinds of festivities: public and prívate, secular and religious, civilian and political. We believed that this literature, which had not been used systematically in studies of festivities, could shed light not only on facets of the festivities themselves but also on aspects of the mentality of those that described them in their diaries and letters: which festivities captured their attention; what judgments they made about them; to what extent these judgments served to construct, perpetúate or modérate stereotypes; what changos might have taken place in the festivo rituals and what changos in the social reality they could reveal; in what respects the perception of the travelers differed from that of Spaniards of the time or from the image recovered by contemporary historie research.


Science ◽  
2019 ◽  
Vol 365 (6458) ◽  
pp. 1134-1138 ◽  
Author(s):  
Inh Jee ◽  
Sherry H. Suyu ◽  
Eiichiro Komatsu ◽  
Christopher D. Fassnacht ◽  
Stefan Hilbert ◽  
...  

The local expansion rate of the Universe is parametrized by the Hubble constant, H0, the ratio between recession velocity and distance. Different techniques lead to inconsistent estimates of H0. Observations of Type Ia supernovae (SNe) can be used to measure H0, but this requires an external calibrator to convert relative distances to absolute ones. We use the angular diameter distance to strong gravitational lenses as a suitable calibrator, which is only weakly sensitive to cosmological assumptions. We determine the angular diameter distances to two gravitational lenses, 810−130+160 and 1230−150+180 megaparsec, at redshifts z=0.295 and 0.6304. Using these absolute distances to calibrate 740 previously measured relative distances to SNe, we measure the Hubble constant to be H0=82.4−8.3+8.4 kilometers per second per megaparsec.


Author(s):  
Chris L. Fryer

Super-novas (SNs) are one of the most powerful explosions in the universe and astronomers have invoked the collapse of a stellar core down to a neutron star as a potential power source behind these cosmic blasts. The current paradigm behind core-collapse SN relies on convection in the region just above the newly formed neutron star. This engine was driven and confirmed by observations. We review this observational evidence, and the potential for further observational constraints in this paper.


Author(s):  
Josephine Wapakabulo Thomas

Data-exchange standards adoption research is important to both the SC4 community and the IT standards research community. Chapter Five and Six presented case studies of four standards to assess the factors and barriers critical to the adoption of standards. Two models were developed and these models sought to shed light on the relationships between factors and barriers critical to the adoption of dataexchange standards. However, as part of this research it was deemed important to develop two novel standards ‘Adoption Checklists’ from both an innovation- and adopter-centric point of view. The purpose of these checklists is to act as a frame of reference to support the decision-making process in the development and adoption of new and emerging data-exchange standards. The checklists are a series of ques-tions that can be used to assess the adoptability of a data-exchange standard. The checklists have been developed so that positive answers to the series of questions indicate that a standard is more likely to be adopted. In addition, these checklists act as a foundation for the action research into the adoption of PLCS, which is detailed in Chapters Eight and Nine. This chapter begins by chronicling the development of the innovation-centric ‘Adoption Checklist’. Following on from that is the development of the adopter-centric ‘Adoption Checklist.’ The final section summaries and concludes this chapter.


2020 ◽  
Vol 29 (14) ◽  
pp. 2043010
Author(s):  
Jose Beltrán Jiménez ◽  
Dario Bettoni ◽  
Philippe Brax

This Essay explores consequences of a dark nonlinear electromagnetic sector in a universe with a net dark charge for matter. The cosmological dynamics can be described by a Lemaître model and can be understood, thanks to a screening mechanism driven by the electromagnetic nonlinearities that suppress the dark force on small scales. Only at low redshift, when the screening scale enters the Hubble horizon, do cosmological structures commence to feel the dark repulsion. This repulsive force enhances the local value of the Hubble constant, thus providing a promising scenario for solving the Hubble tension. Remarkably, the dark electromagnetic interaction can have a crucial impact on peculiar velocities, i.e. introducing a bias in their reconstruction methods, and having the potential to explain the presence of a dark flow.


1966 ◽  
Vol 25 ◽  
pp. 363-371
Author(s):  
P. Sconzo

In this paper an orbit computation program for artificial satellites is presented. This program is operational and it has already been used to compute the orbits of several satellites.After an introductory discussion on the subject of artificial satellite orbit computations, the features of this program are thoroughly explained. In order to achieve the representation of the orbital elements over short intervals of time a drag-free perturbation theory coupled with a differential correction procedure is used, while the long range behavior is obtained empirically. The empirical treatment of the non-gravitational effects upon the satellite motion seems to be very satisfactory. Numerical analysis procedures supporting this treatment and experience gained in using our program are also objects of discussion.


1976 ◽  
Vol 32 ◽  
pp. 233-254
Author(s):  
H. M. Maitzen

Ap stars are peculiar in many aspects. During this century astronomers have been trying to collect data about these and have found a confusing variety of peculiar behaviour even from star to star that Struve stated in 1942 that at least we know that these phenomena are not supernatural. A real push to start deeper theoretical work on Ap stars was given by an additional observational evidence, namely the discovery of magnetic fields on these stars by Babcock (1947). This originated the concept that magnetic fields are the cause for spectroscopic and photometric peculiarities. Great leaps for the astronomical mankind were the Oblique Rotator model by Stibbs (1950) and Deutsch (1954), which by the way provided mathematical tools for the later handling pulsar geometries, anti the discovery of phase coincidence of the extrema of magnetic field, spectrum and photometric variations (e.g. Jarzebowski, 1960).


Author(s):  
Dhruba K. Chattoraj ◽  
Ross B. Inman

Electron microscopy of replicating intermediates has been quite useful in understanding the mechanism of DNA replication in DNA molecules of bacteriophage, mitochondria and plasmids. The use of partial denaturation mapping has made the tool more powerful by providing a frame of reference by which the position of the replicating forks in bacteriophage DNA can be determined on the circular replicating molecules. This provided an easy means to find the origin and direction of replication in λ and P2 phage DNA molecules. DNA of temperate E. coli phage 186 was found to have an unique denaturation map and encouraged us to look into its mode of replication.


Author(s):  
L. Fei

Scanned probe microscopes (SPM) have been widely used for studying the structure of a variety material surfaces and thin films. Interpretation of SPM images, however, remains a debatable subject at best. Unlike electron microscopes (EMs) where diffraction patterns and images regularly provide data on lattice spacings and angles within 1-2% and ∽1° accuracy, our experience indicates that lattice distances and angles in raw SPM images can be off by as much as 10% and ∽6°, respectively. Because SPM images can be affected by processes like the coupling between fast and slow scan direction, hysteresis of piezoelectric scanner, thermal drift, anisotropic tip and sample interaction, etc., the causes for such a large discrepancy maybe complex even though manufacturers suggest that the correction can be done through only instrument calibration.We show here that scanning repulsive force microscope (SFM or AFM) images of freshly cleaved mica, a substrate material used for thin film studies as well as for SFM instrument calibration, are distorted compared with the lattice structure expected for mica.


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