Astrofísica

LAS TEORÍAS DE LOS UNIVERSOS PULSANTES O EL MODELO CÍCLICO, ES UN PARADIGMA ALTERNATIVO A LOS CLÁSICOS ENFOQUES DE LOS UNIVERSOS ESTACIONARIOS Y LOS UNIVERSOS INFLACIONARIOS (EN ESTA OCASIÓN DEJAREMOS DE LADO EL ENFOQUE DE LOS UNIVERSOS AUTOCREADOS)...
ESTA PROPUESTA (EL MODELO CÍCLICO),  FUE ELABORADO FORMAL Y PUBLICAMENTE EN 1930, POR RICHARD TOLMAN,  QUIEN DICE: QUE EL UNIVERSO SERÍA ETERNO (NO TIENE PRINCIPIO NI FIN); Y QUE CONSTANTEMENTE SE ENCUENTRA RE INICIÁNDOSE, DESPUÉS DE PASAR POR UNOS “CICLOS” O “PERIODOS” LARGOS DE VDE “VIDA”, EN QUE ESTOS COSMOS, PRIMERO SE EXPANDEN, Y LUEGO SE CONTRAEN…. SE INFLAN PRODUCTO DE UN BIG BANG, Y DESPUÉS, SE “COMPRIMEN”, HASTA GENERAR UN BIG CRUNCH....
A ESTOS DOS EVENTOS: EL BIG BANG Y EL BIG CRUNCH; CONJUNTAMENTE SE LOS LLAMA TAMBIÉN “BIG BOUNCE”, O GRAN REBOTE. POR QUE SI BIEN, DESTRUYEN UN UNIVERSO (CON EL BIG CRUNCH), INMEDIATAMENTE,, EMPIEZAN CON EL DISEÑO DE OTRO, MEDIANTE UN BIG BANG. PODRÍAMOS INCLUSO CONSIDERAR, QUE SOLO SE TRATARÍA DE UNA SOLA “GRAN EXPLOSIÓN”, QUE HACE REINICIARSE AL SISTEMA. ES DECIR, EL BIG CRUNCH Y EL BIG BANG, SERÍA UN SOLO EVENTO, QUE EN ESTE CASO SE LLAMARÍA “GRAN REBOTE”.
ESTO, DE REINICIAR EL UNIVERSO CADA CIERTO PERIODO DE TIEMPO, SE DEBE, A QUE DE ACUERDO A LAS TEORÍAS DE LA TERMODINÁMICA, EN EL FINAL DE SUS VIDAS, CADA UNO DE ESTOS COSMOS, TERMINAN CON ALTÍSIMOS NIVELES DE ENTROPIA O DESORDEN.
ESTOS NIVELES DE ENTROPIA SOLO PUEDEN BAJAR A “0”,  SI HACEMOS QUE EL COSMOS EMPIECE DE NUEVO, DESDE “0”. SOLO DE ESTA MANERA, SERIA POSIBLE, LA EXISTENCIA DE OTRO UNIVERSO, DESPUEÉS DE LA MUERTE DE UNO.
DESDE UNA PERSPECTIVA HISTÓRICA O DIACRÓNICA, ESTE TIPO DE UNIVERSOS, TENDRIAN UNA FORMA ESFÉRICA EN SU EVOLUCION, POR LA CONTRACCIÓN QUE TIENEN, A DIFERENCIA DE LOS UNIVERSOS INFLACIONARIOS, QUE POR LO GENERAL TIENEN FORMA DE PIRAMIDE INVERTIDA.
SIN OTRO PARTICULAR, ESPERANDO QUE NUESTRO TRABAJO LES SEA DE AYUDA NOS DESPEDIMOS DE USTEDES MUY CORDIALMENTE. GRACIAS…

Spitzer data at 24, 70, and 160 μm and ground-based Hα images are analyzed for a sample of 189 nearby star-forming and starburst galaxies to investigate whether reliable star formation rate (SFR) indicators can be defined using the monochromatic infrared dust emission centered at 70 and 160 μm. We compare recently published recipes for SFR measures using combinations of the 24 μm and observed Hα luminosities with those using 24 μm luminosity alone. From these comparisons, we derive a reference SFR indicator for use in our analysis. Linear correlations between SFR and the 70 μm and 160 μm luminosity are found for L(70) 1.4 × 10 42 erg s −1 and L(160) 2 × 10 42 erg s −1 , corresponding to SFR 0.1-0.3 M yr −1 , and calibrations of SFRs based on L(70) and L(160) are proposed. Below those two luminosity limits, the relation between SFR and 70 μm (160 μm) luminosity is nonlinear and SFR calibrations become problematic. A more important limitation is the dispersion of the data around the mean trend, which increases for increasing wavelength. The scatter of the 70 μm (160 μm) data around the mean is about 25% (factor ∼2) larger than the scatter of the 24 μm data. We interpret this increasing dispersion as an effect of the increasing contribution to the infrared emission of dust heated by stellar populations not associated with the current star formation. Thus, the 70 (160) μm luminosity can be reliably used to trace SFRs in large galaxy samples, but will be of limited utility for individual objects, with the exception of infrared-dominated galaxies. The nonlinear relation between SFR and the 70 and 160 μm emission at faint galaxy luminosities suggests a variety of mechanisms affecting the infrared emission for decreasing luminosity, such as increasing transparency of the interstellar medium, decreasing effective dust temperature, and decreasing filling factor of star-forming regions across the galaxy. In all cases, the calibrations hold for galaxies with oxygen abundance higher than roughly 12 + log(O/H) ∼ 8.1. At lower metallicity, the infrared luminosity no longer reliably traces the SFR because galaxies are less dusty and more transparent.

Energy-dependent patterns in the arrival directions of cosmic rays are searched for using data of the Pierre Auger Observatory. We investigate local regions around the highest-energy cosmic rays with E ≥ 6×10 19 eV by analyzing cosmic rays with energies above E ≥ 5×10 18 eV arriving within an angular separation of approximately 15 •. We characterize the energy distributions inside these regions by two independent methods, one searching for angular dependence of energy-energy correlations and one searching for collimation of energy along the local system of principal axes of the energy distribution. No significant patterns are found with this analysis. The comparison of these measurements with astrophysical scenarios can therefore be used to obtain constraints on related model parameters such as strength of cosmic-ray deflection and density of point sources.

Nuevos modelos de información geográfica guían a los paleontólogos,  MEDICINA Inmunoterapia contra el cáncer, INGENIERÍA Avances en el diseño flexible, MEDIOAMBIENTE Muerte anunciada de los corales, FÍSICA DE PARTÍCULAS Las ideas que condujeron al bosón de Higgs

Aims. Lyα emitters (LAEs) can be detected out to very high redshifts during the epoch of reionization. The evolution of the LAE luminosity function with redshift is a direct probe of the Lyα transmission of the intergalactic medium (IGM), and therefore of the IGM neutral-hydrogen fraction. Measuring the Lyα luminosity function (LF) of Lyα emitters at redshift z = 7.7 therefore allows us to constrain the ionizing state of the Universe at this redshift. Methods. We observed three 7. 5 × 7. 5 fields with the HAWK-I instrument at the VLT with a narrow band filter centred at 1.06 μm and targeting Lyα emitters at redshift z ∼ 7.7. The fields were chosen for the availability of multiwavelength data. One field is a galaxy cluster, the Bullet Cluster, which allowed us to use gravitational amplification to probe luminosities that are fainter than in the field. The two other fields are subareas of the GOODS Chandra Deep Field South and CFHTLS-D4 deep field. We selected z = 7.7 LAE candidates from a variety of colour criteria, in particular from the absence of detection in the optical bands. Results. We do not find any LAE candidates at z = 7.7 in ∼2.4 × 10 4 Mpc 3 down to a narrow band AB magnitude of ∼26, which allows us to infer robust constraints on the Lyα LAE luminosity function at this redshift. Conclusions. The predicted mean number of objects at z = 6.5, derived from somewhat different luminosity functions of Hu et al.

There is an increasing interest of scientists on climate extremes. A progressively larger number of papers dealing with climate issues have been produced in the past 15 yr, and those dealing with extremes have increased at an even faster pace. The number of papers on extremes in the Mediterranean follows this overall trend and confirms how extremes are perceived to be important by the scientific community and by society. This special issue (which is mainly related to activities of the MedCLIVAR (Mediterranean CLImate VARiability and Predictability) and CIRCE (Climate Change and Impact Research: the Mediterranean Environment) projects), contains thirteen papers that are representative of current research on extremes in the Mediterranean region. Five have precipitation as its main target, four temperature (one paper addresses both variables), and two droughts; the remaining papers consider sea level, winds and impacts on society. Results are quite clear concerning climate evolution toward progressively hotter temperature extremes, but more controversial for precipitation, though in the published literature there are indications for a future increasing intensity of hydrological extremes (intense precipitation events and droughts). Scenario simulations suggest an attenuation of extreme storms, winds, waves and surges, but more results are requested for confirming this future change.

Questão de Fermi, mais conhecida como "Paradoxo de Fermi", analisa o paradoxo aparente seguinte: "Se existem muitas civilizações tecnológicas alienígenas na Via Láctea e no Universo, por que não descobrimos sinais ou vestígios de nenhuma delas.

Context. After more than 50 years, astronomical research still struggles to reconstruct the history of lithium enrichment in the Galaxy and to establish the relative importance of the various 7Li sources in enriching the interstellar medium (ISM) with this fragile element. Aims. To better trace the evolution of lithium in the Milky Way discs, we exploit the unique characteristics of a sample of open clusters (OCs) and field stars for which high-precision 7Li abundances and stellar parameters are homogeneously derived by the Gaia-ESO Survey (GES). Methods. We derive possibly un-depleted 7Li abundances for 26 OCs and star forming regions with ages from young (∼3 Myr) to old (∼4.5 Gyr), spanning a large range of galactocentric distances, 5 < RGC/kpc < 15, which allows us to reconstruct the local late Galactic evolution of lithium as well as its current abundance gradient along the disc. Field stars are added to look further back in time and to constrain 7Li evolution in other Gal...

The Advanced LIGO and Advanced Virgo observatories recently discovered gravitational waves from a binary neutron star inspiral. A short gamma-ray burst (GRB) that followed the merger of this binary was also recorded by the Fermi Gamma-ray Burst Monitor (Fermi-GBM), and the Anti-Coincidence Shield for the Spectrometer for the International Gamma-Ray Astrophysics Laboratory (INTEGRAL), indicating particle acceleration by the source. The precise location of the event was determined by optical detections of emission following the merger. We searched for high-energy neutrinos from the merger in the GeV-EeV energy range using the ANTARES, IceCube, and Pierre Auger Observatories. No neutrinos directionally coincident with the source were detected within ±500 s around the merger time. Additionally, no MeV neutrino burst signal was detected coincident with the merger. We further carried out an extended search in the direction of the source for high-energy neutrinos within the 14 day period following the merger, but found no evidence of emission. We used these results to probe dissipation mechanisms in relativistic outflows driven by the binary neutron star merger. The non-detection is consistent with model predictions of short GRBs observed at a large off-axis angle.

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of 1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg 2 at a luminosity distance of 40 8 8-+ Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 M . An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at 40 Mpc) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ∼10 days. Following early non-detections, X-ray and radio emission were discovered at the transient's position 9 and 16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta.

We present evidence for the discovery of a protocluster of starburst galaxies (Lyα emitters, or LAEs) near the end of the epoch of reionization. The recent trend in the search for high-redshift protoclusters focuses on utilizing bias tracers, such as luminous starburst galaxies, as signposts of overdensities. Thus, we conducted a photometric selection of LAE candidates around a pair of spatially close, luminous LAEs at z=6.5 in the Subaru/XMM-Newton Deep Survey field, using OSIRIS in its imaging mode at the 10.4 m Gran Telescopio Canarias in La Palma, Spain. The spectroscopic follow-up was done with OSIRIS in its multiobject spectroscopy capability. We have spectroscopically confirmed 10 LAEs via their recognizable Lyα emission feature. The redshifts of these LAEs shed light on their 3D distributions within the observing window defined by the photometric selection. We have derived the galaxy number density contrast of 3.18  , comparable to the Coma cluster. Thus, our careful analysis has pointed to evidence that this protocluster would evolve into a Coma-analog cluster in the present-day universe.

Este artigo investiga a interseção fascinante entre teologia e ufologia, utilizando a passagem de 2 Reis 2:11 como ponto de partida para compreender as experiências de avistamentos de UAPs (Fenômenos Aéreos Não Identificados) e as tecnologias exóticas desenvolvidas por humanos.
Através da análise do desenvolvimento de tecnologias avançadas, especialmente na física quântica, abordamos como esses conceitos podem iluminar a compreensão de fenômenos extraordinários que transcendem a experiência humana.

Un evento di grande rilievo culturale e scientifico, organizzato dalla Fondazione Maddalena Ferraro, che da anni semina sapere attraverso iniziative dedicate alla divulgazione. La giornata di oggi vede la partecipazione di numerosi studenti provenienti da tutta la Campania, impegnati in un concorso che unisce tradizione e innovazione. Oltre

Las estrellas de tipo FU Orionis son estrellas de Pre-secuencia Principal que incurren de forma periódica en un aumento de brillo de hasta ∼ 6 magnitudes en un lapso de unos pocos años, y que luego decae paulatinamente al cabo de un par de décadas o siglos a su brillo original. Este estallido se debe a un incremento en la tasa de acreción de material hacia la estrella. El evento tipo FU Orionis (FUOR) genera profundos cambios físicos que afectan a la posterior evolución del disco y de la estrella central. Los granos de polvo que componen el disco son de distinta especies, y a lo largo de la formación de la estrella van sufriendo una serie de transformaciones. En este trabajo se estudia la mineralogía de dichos granos. Para realizar este estudio, se dispone de observaciones espectroscópicas entre 8 y 13 µm tomadas con los instrumentos Michelle y T-ReCS de los telescopios Gemini Norte y Sur, respectivamente. Palabras claves: discos circunestelares, discos proto-planetarios, FU Orionis, procesamiento del polvo interestelar, estrellas de Pre-secuencia Principal. Clasificación: 97.82.Jw Infrared excess, debris disks, protoplanetaru disks, exozodiacal dust. Í ndice general Introducción 4 Perspectivas futuras 98 Referencias 99 Capítulo 1 El Fenómeno FU Orionis 1.1. Formación de estrellas de masa baja En lasúltimas décadas se ha acumulado evidencia que muestra que las estrellas de masa baja, se forman mediante un proceso de acreción de gas y polvo de las nubes moleculares. Estas nubes contienen, básicamente, hidrógeno molecular H 2 con densidades de ∼10 2 cm −3 y tienen temperaturas de ∼10 K. El perfil de la densidad de estas nubes no es uniforme sino que presenta zonas de mayor densidad (10 4-10 5 cm −3) que constituyen los llamados núcleos moleculares densos (o "dense cores").

Nel 1887 è stato eseguito l'esperimento di Michelson e Morley, che avrebbe dovuto rilevare il moto della Terra rispetto all'etere (che corrisponde allo spazio) e cioè al mezzo nel quale si manifesterebbe la luce, e quindi il solo rispetto al quale la sua velocità potrebbe essere realmente la stessa in tutte le direzioni, e cioè realmente isotropa. Ma l'esperimento ha rilevato che la velocità della luce risulta isotropa anche rispetto alla Terra e, quindi, non ha rilevato alcun moto rispetto all'etere. Per giustificare questo risultato negativo, Lorentz ha ipotizzato che tutti gli oggetti che si muovono nell'etere, subiscano un rallentamento del tempo ed una contrazione della lunghezza nella direzione del moto, facendo così risultare la velocità della luce isotropa, anche se in realtà non lo è. Invece Einstein ha giustificato detto risultato sostenendo che la luce si propaga nel vuoto e che la sua velocità è isotropa in tutti i sistemi di riferimento, qualunque sia il moto tra di essi, precisando però che si tratta di una convenzione e, quindi, non di un fenomeno reale, per cui l'isotropia può essere solo apparente. Ma in seguito Einstein ha considerato detta isotropia come reale e così la considera ancora la comunità scientifica, prepotentemente, dato che non accetta di mettere in discussione questa sua tesi. In verità è proprio grazie al reale rallentamento del tempo e alla reale contrazione della materia, che la velocità della luce appare isotropa. Ed è un'apparenza molto utile, perché in base ad essa è possibile di far funzionare il sistema GPS. Che non può funzionare in base alla realtà, perché non si conosce la velocità precisa della Terra rispetto all'etere e, quindi, neanche la reale velocità della luce rispetto alla Terra, che servirebbe per far funzionare il GPS. Ma detta apparenza non consente di calcolare correttamente anche velocità e distanze degli oggetti celesti, per cui, usandola ugualmente, la comunità scientifica ha ottenuto un modello di Universo complicato e incompatibile con le osservazioni, la cui espansione risulta in accelerazione, anziché in decelerazione, come dovrebbe essere in base alla realtà.

Este artigo revisa e analisa as principais teorias que exploram a ausência de contato com civilizações extraterrestres. Analisamos o famoso ``SINAL WOW´´, o Paradoxo de Fermi, e outras hipóteses como a Teoria da Floresta Negra e a hipótese de que vivemos em uma simulação. Este estudo fornece uma visão abrangente sobre alguns motivos pelo qual não temos contato com vidas inteligentes fora da Terra, utilizando uma revisão crítica sobre teorias que tentam explicar esta ausência.

Este artigo revisa e analisa as principais teorias que exploram a ausência de contato com civilizações extraterrestres. Analisamos o famoso ``SINAL WOW´´, o Paradoxo de Fermi, e outras hipóteses como a Teoria da Floresta Negra e a hipótese de que vivemos em uma simulação. Este estudo fornece uma visão abrangente sobre alguns motivos pelo qual não temos contato com vidas inteligentes fora da Terra, utilizando uma revisão crítica sobre teorias que tentam explicar esta ausência.

Aprovechando los eventos astronómicos de los meses agosto, septiembre y  octubre,  nuestra revista decide sacar una edición especial sobre todos los acontecimientos más importantes, en qué y como nos afectan estos cambios y las tormentas solares que en este momento están sucediendo en nuestro sistema estelar, esperamos que todo nuestro publico pueda disfrutar de el.

During recent decades, the use of probabilistic forecasting methods has increased markedly. However, these predictions still need improvement in uncertainty quantification and predictability analysis. For this reason, the main aim of this paper is to develop tools for quantifying uncertainty and predictability of wind speed over the Iberian Peninsula. To achieve this goal, several spread indexes extracted from an ensemble prediction system are defined in this paper. Subsequently, these indexes were evaluated with the aim of selecting the most appropriate for the characterization of uncertainty associated to the forecasting. Selection is based on comparison of the average magnitude of ensemble spread (ES) and mean absolute percentage error (MAPE). MAPE is estimated by comparing the ensemble mean with wind speed values from different databases. Later, correlation between MAPE and ES was evaluated. Furthermore, probability distribution functions (PDFs) of spread indexes are analyzed to select the index with greater similarity to MAPE PDFs. Then, the spread index selected as optimal is used to carry out a spatiotemporal analysis of model uncertainty in wind forecasting. The results indicate that mountainous regions and the Mediterranean coast are characterized by strong uncertainty, and the spread increases more rapidly in areas affected by strong winds. Finally, a predictability index is proposed for obtaining a tool capable of providing information on whether the predictability is higher or lower than average. The applications developed may be useful in the forecasting of wind potential several days in advance, with substantial importance for estimating wind energy production.

Questa teoria accetta l'apparente isotropia della velocità della luce in tutti i sistemi di riferimento, per la gravitazione della Relatività Generale e per il sistema GPS, ma si basa sulla realtà per spiegare l'espansione dell'Universo e per il calcolo delle distanze degli oggetti celesti. E così ottiene un modello di Universo molto semplice, la cui espansione risulta essere sempre stata in decelerazione.

The performance of the Weather Research and Forecasting (WRF) model to reproduce the surface wind circulations over complex terrain is examined. The atmospheric evolution is simulated using two versions of the WRF model during an over 13 year period (1992 to 2005) over a complex terrain region located in the northeast of the Iberian Peninsula. A high horizontal resolution of 2 km is used to provide an accurate representation of the terrain features. The multiyear evaluation focuses on the analysis of the accuracy displayed by the WRF simulations to reproduce the wind field of the six typical wind patterns (WPs) identified over the area in a previous observational work. Each pattern contains a high number of days which allows one to reach solid conclusions regarding the model performance. The accuracy of the simulations to reproduce the wind field under representative synoptic situations, or pressure patterns (PPs), of the Iberian Peninsula is also inspected in order to diagnose errors as a function of the large-scale situation. The evaluation is accomplished using daily averages in order to inspect the ability of WRF to reproduce the surface flow as a result of the interaction between the synoptic scale and the regional topography. Results indicate that model errors can originate from problems in the initial and lateral boundary conditions, misrepresentations at the synoptic scale, or the realism of the topographic features.

MEGARA (Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía) is an optical Integral-Field Unit (IFU) and Multi-Object Spectrograph (MOS) designed for the GTC 10.4m telescope in La Palma. MEGARA offers two IFU fiber bundles, one covering 12.5x11.3 arcsec 2 with a spaxel size of 0.62 arcsec (Large Compact Bundle; LCB) and another one covering 8.5x6.7 arcsec 2 with a spaxel size of 0.42 arcsec (Small Compact Bundle; SCB). The MEGARA MOS mode will allow observing up to 100 objects in a region of 3.5x3.5 arcmin 2 around the two IFU bundles. Both the LCB IFU and MOS capabilities of MEGARA will provide intermediate-to-high spectral resolutions (R FWHM~6 ,000, 12,000 and 18,700, respectively for the low-, mid-and high-resolution Volume Phase Holographic gratings) in the range 3650-9700ÅÅ. These values become R FWHM~7 ,000, 13,500, and 21,500 when the SCB is used. A mechanism placed at the pseudo-slit position allows exchanging the three observing modes and also acts as focusing mechanism. The spectrograph is a collimator-camera system that has a total of 11 VPHs simultaneously available (out of the 18 VPHs designed and being built) that are placed in the pupil by means of a wheel and an insertion mechanism. The custom-made cryostat hosts an E2V231-84 4kx4k CCD. The UCM (Spain) leads the MEGARA Consortium that also includes INAOE (Mexico), IAA-CSIC (Spain), and UPM (Spain). MEGARA is being developed under a contract between GRANTECAN and UCM. The detailed design, construction and AIV phases are now funded and the instrument should be delivered to GTC before the end of 2016.

Resumo Descreve-se a evolução do Observatório Astronómico da Universidade de Coimbra de 1930 a 1970, destacando- se o exercício das funções de diretor por Manuel dos Reis (1900-1992), de 1934 a 1970. Fonte primordial é o espólio documental de Manuel dos Reis à guarda do Arquivo da Universidade de Coimbra, que inclui programas, lições, problemas, exames, estudos e notas, e outros manuscritos sobre História da Astronomia, Astronomia (Geral, Mecânica, Esférica e Geodésica), Astronomia Medieval, e Astronomia Náutica dos Descobrimentos. Engloba ainda listas bibliográficas, rascunhos das comunicações e discursos sobre Astronomia Náutica proferidos na Academia das Ciências de Lisboa. Apresenta-se, em particular, um documento datilografado, inédito, provavelmente da década de 30, com o título “Reorganização do ensino da Astronomia e da investigação astronómica”, onde Reis, após descrever brevemente a história da Astronomia, refere a Astrofísica como o “novo ...

En 1905 un joven desconocido llamado Albert Einstein publico cinco articulos que cambiaron la fisica. La teoria de la relatividad destruyo el espacio y tiempo absolutos que habian caracterizado a la fisica moderna desde los tiempos de Newton. La relatividad general sustituyo a la cosmologia moderna, el universo estatico e infinito fue reemplazado por el universo finito y en expansion de la teoria del Big bang. La mecanica cuantica elimino el principio de causalidad estricto sobre el que se habia afirmado la representacion determinista de la Naturaleza. La revolucion cientifica del siglo XX cambio nuestra representacion de la Naturaleza y los presupuestos epistemologicos sobre los que se asentaba la Razon moderna de la civilizacion occidental. Einstein desempeno un papel protagonista en dicha revolucion, aunque el caracter probabilista de la teoria cuantica, a la que habia realizado contribuciones esenciales, le desagrado profundamente.

Los filósofos griegos de la antigüedad fueron los primeros en abordar el análisis del ser y el devenir racionalmente explicándolos de forma natural. Así, para Parménides el ser es lo que es, es decir, lo que existe en la realidad, y lo que no es, no es ni puede ser. El ser y la nada son permanentes. Para Heráclito, sin embargo, todo cambia, excepto el devenir, es decir, la