The Infinite Cosmos: Questions from the Frontiers of Cosmology
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From time immemorial, poets and philosophers have looked in awe and wonder at the Universe. Such awe is shared by astrophysicists, too as they seek to understand its nature, and whether it has any limits. In he Infinite Cosmos, Joseph Silk, Savillian Professor of Astronomy at Oxford University, cosmologist and well-known science writer, brings together the modern understanding of the Universe, its structure, its evolution, and its possible fate, combining the latest from theory and observation. The narrative is peppered with quotations from literature and philosophy, and reflects too on the process of scientific discovery and the implications of our discoveries.
Witness to exotic physics that occurs in the nuclei of the most active galaxies. Conditions are surely extreme in the vicinities of supermassive black holes. It is likely that only near very massive black holes are the conditions sufﬁciently favourable to be able to accelerate the cosmic rays to the highest energies that are observed. 7 Supermassive Black Holes and Galaxy Formation . . . time is the longest distance between two places. Tennessee Williams I have been a stranger in a strange.
Would be generated than can be accounted for. The power source of quasars is also conjectured to be accretion on to a supermassive black hole. Most galaxies may have undergone an active phase in their past, and should therefore possess massive black holes in their nuclei. Nowadays 99 per cent of galaxies have faint and unremarkable nuclei: their central supermassive black holes must be completely inert, with no matter falling into them. Quasars are rare in the nearby universe, but were common.
Isotropic space. If space is ﬂat (Euclidean), or negatively curved (hyperbolic), like the surface of a saddle, it must be inﬁnite. Only if space is curved positively, like the surface of a sphere, can SPACE IS NEARLY FLAT 77 it be ﬁnite. Einstein’s theory of general relativity predicts that gravity is in effect a curvature of space. Replace the gravity ﬁeld of the sun by a slight curvature in the surrounding Euclidean space. The effect is that straight lines, as traced by light rays from.
Dwarf galaxies, which are everywhere dark matter dominated, cannot readily be explained. This is studied via the rotation of the galaxies, and generally soft cores are found. The dark matter simulations invariably ﬁnd a strong central concentration, which looks quite unlike the inferred dark matter content of the observed galaxies. The theory fails to explain the observed cores of the low surface brightness dwarfs. It may be that resolution of this problem just requires more detailed, higher.
Background photons by electrons. Gravity waves are non-compressive: they only produce a shearing effect as they pass by, and the density is left unchanged. The slight shearing motions of the electrons produce the polarization, and differ from the symmetric compressive motions generated by density perturbations. The net result of the gravity waves is an antisymmetric polarization signal in the microwave background, a unique large angular scale testimony to the action of gravity waves. A somewhat.