scholarly journals New horizons in black hole astrophysics

2021 ◽  
Vol 52 (1) ◽  
pp. 12-14
Author(s):  
Roger Blandford

Black holes, a seemingly inevitable consequence of Einstein’s general theory of relativity and stellar and galactic evolution are being observed in many new ways with masses ranging from roughly three to ten billion solar masses. Their masses and spins determine how they power the most luminous objects in the universe and impact their environments.

Author(s):  
Purujit Malik

A black hole is a region of space from which nothing, not even light, can escape. According to the general theory of relativity[2], it starts existing when spacetime gets curved by a huge mass. There is a sphere around the black hole. If something goes inside the sphere, it can not leave. This sphere is called the event horizon. A black hole is black because it absorbs all the light that hits it. It reflects nothing, just like a perfect black body in thermodynamics. Under quantum mechanics, black holes have a temperature and emit Hawking radiation, which makes them slowly get smaller.Because black holes are very hard to see, people trying to see them look for them by the way they affect other things near them. The place where there is a black hole can be found by tracking the movement of stars that orbit somewhere in space. Or people can find it when gas falls into a black hole, because the gas heats up and is very bright[1].However besides all these theories we still do not know what a black hole and dark matter is because all these theories rely on the much physical aspect of things and not on a unified understanding of creation.


2016 ◽  
Vol 4 (1) ◽  
Author(s):  
Bhanu Pratap Singh

The purpose of this article is not to present a popular history of mathematical physics nor even to display for the general reader some of the result of research in the history of science, Rather the intention is to explore one important aspect of the great scientific revaluation of recent times which proves the existence of Gravitational wave, predicted by Dr. Albert Einstein about a hundred years ago in his general theory of relativity. Gravitational waves are ripples in the fabric of space time caused by some of the most violent and energetic processes in the universe. They are produced by catastrophic events such as colliding Black hole as well as the collapse of stellar super nova.


2021 ◽  
Vol 58 (4) ◽  
pp. 175-195
Author(s):  
Vladimir P. Vizgin ◽  

The article is based on the concepts of epistemic virtues and epistemic vices and explores A. Einstein’s contribution to the creation of fundamental physical theories, namely the special theory of relativity and general theory of relativity, as well as to the development of a unified field theory on the basis of the geometric field program, which never led to success. Among the main epistemic virtues that led Einstein to success in the construction of the special theory of relativity are the following: a unique physical intuition based on the method of thought experiment and the need for an experimental justification of space-time concepts; striving for simplicity and elegance of theory; scientific courage, rebelliousness, signifying the readiness to engage in confrontation with scientific conventional dogmas and authorities. In the creation of general theory of relativity, another intellectual virtue was added to these virtues: the belief in the heuristic power of the mathematical aspect of physics. At the same time, he had to overcome his initial underestimation of the H. Minkowski’s four-dimensional concept of space and time, which has manifested in a distinctive flexibility of thinking typical for Einstein in his early years. The creative role of Einstein’s mistakes on the way to general relativity was emphasized. These mistakes were mostly related to the difficulties of harmonizing the mathematical and physical aspects of theory, less so to epistemic vices. The ambivalence of the concept of epistemic virtues, which can be transformed into epistemic vices, is noted. This transformation happened in the second half of Einstein’s life, when he for more than thirty years unsuccessfully tried to build a unified geometric field theory and to find an alternative to quantum mechanics with their probabilistic and Copenhagen interpretation In this case, we can talk about the following epistemic vices: the revaluation of mathematical aspect and underestimation of experimentally – empirical aspect of the theory; adopting the concepts general relativity is based on (continualism, classical causality, geometric nature of fundamental interactions) as fundamental; unprecedented persistence in defending the GFP (geometrical field program), despite its failures, and a certain loss of the flexibility of thinking. A cosmological history that is associated both with the application of GTR (general theory of relativity) to the structure of the Universe, and with the missed possibility of discovering the theory of the expanding Universe is intermediate in relation to Einstein’s epistemic virtues and vices. This opportunity was realized by A.A. Friedmann, who defeated Einstein in the dispute about if the Universe was stationary or nonstationary. In this dispute some of Einstein’s vices were revealed, which Friedman did not have. The connection between epistemic virtues and the methodological principles of physics and also with the “fallibilist” concept of scientific knowledge development has been noted.


2020 ◽  
Vol 29 (11) ◽  
pp. 10-16
Author(s):  
Wontae KIM ◽  
Mu-In PARK

A black hole is a theoretical prediction of Einstein’s general theory of relativity, differently from Newtonian gravity, which is a non-relativistic gravity. In recent few years, its direct detection via gravitational waves and other multi-messenger observations have made it possible to test the prediction and hence its associated general relativity. From purely theoretical points of view, general relativity cannot be a complete description due to its not being compatible with quantum mechanics, which is a successful description of microscopic objects. In this article, we introduce the conceptional development of quantum-gravity theories and give brief sketches of fundamental problems in quantum black holes. As an interesting model of quantum black holes, we consider a collapsing shell of matter to form a Hayward black hole and investigate semiclassically quantum radiation from the shell. By using the Israel’s formulation and the functional Schrödinger formulation for massless quantum radiation, we find that the Hawking temperature can be deduced from the occupation number of excited states when the shell approaches its own horizon.


Science ◽  
2019 ◽  
Vol 365 (6454) ◽  
pp. 664-668 ◽  
Author(s):  
Tuan Do ◽  
Aurelien Hees ◽  
Andrea Ghez ◽  
Gregory D. Martinez ◽  
Devin S. Chu ◽  
...  

The general theory of relativity predicts that a star passing close to a supermassive black hole should exhibit a relativistic redshift. In this study, we used observations of the Galactic Center star S0-2 to test this prediction. We combined existing spectroscopic and astrometric measurements from 1995–2017, which cover S0-2’s 16-year orbit, with measurements from March to September 2018, which cover three events during S0-2’s closest approach to the black hole. We detected a combination of special relativistic and gravitational redshift, quantified using the redshift parameter ϒ. Our result, ϒ = 0.88 ± 0.17, is consistent with general relativity (ϒ = 1) and excludes a Newtonian model (ϒ = 0) with a statistical significance of 5σ.


2017 ◽  
Vol 9 (2) ◽  
pp. 87
Author(s):  
Mehmet Bora Cilek

General Theory of Relativity constitutes the framework for our understanding of the universe, with an emphasis on gravity. Many of Einstein’s predictions have been verified experimentally but General and Special Theories of Relativity contain several anomalies and paradoxes, yet to be answered. Also, there are serious conflicts with Quantum Mechanics; gravity being the weakest and least understood force, is a major problem.Supported by clear experimental evidence, it is theorised that gravity is not a field or spacetime curvature effect, but rather has a flow mechanism. This is not an alternative theory of gravity with an alternative metric. Established laws and equations from Newton and Einstein are essentially left unchanged. However, spacetime curvature is replaced with flow, producing a refined and compatible theory.


Author(s):  
Serge L. Parnovsky ◽  

The Nobel Prize in Physics in 2020 was awarded to the famous British physicist, mathematician, philosopher of science Roger Penrose “for the discovery that black hole formation is a robust prediction of the general theory of relativity” as well as German astrophysicist Reinhard Genzel and American astronomer Andrea Ghez “for the discovery of a supermassive compact object at the center of our galaxy.”


2012 ◽  
Vol 18 (3) ◽  
pp. 175-184
Author(s):  
Vo Van On

In this paper, based on the vector model for gravitational field we deduce an equation to determinate the metric of space-time. This equation is similar to equation of Einstein. The metric of space-time outside a static spherically symmetric body is also determined. It gives a small supplementation to the Schwarzschild metric in General theory of relativity but the singularity does not exist. Especially, this model predicts the existence of a new universal body after a black hole.


2008 ◽  
Vol 08 (02) ◽  
pp. L141-L153
Author(s):  
THEO M. NIEUWENHUIZEN

Within the Relativistic Theory of Gravitation it is shown that the equation of state p = ρ holds near the center of a black hole. For the stiff equation of state p = ρ − ρc the interior metric is solved exactly. It is matched with the Schwarzschild metric, which is deformed in a narrow range beyond the horizon. The solution is regular everywhere, with a specific shape at the origin. The gravitational redshift at the horizon remains finite but is large, z ~ 1023 M⊙/M. Time keeps its standard role also in the interior. The energy of the Schwarzschild metric, shown to be minus infinity in the General Theory of Relativity, is regularized in this setup, resulting in E = Mc2.


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