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This article is a list of notable unsolved problems in astronomy.Problems may be theoretical or experimental. Theoretical problems result from inability of current theories to explain observed phenomena or experimental results.
Daniel is initially troubled, and he is reassured by the king. Daniel then expresses the hope that the dream applied to someone else - those who hate the king - but he goes on to explain: the king himself is the tree, and by the decree of God he will lose his human mind for the mind of an animal, and live with wild animals and eat grass like an ox.
For example, gamma rays that require 1 cm (0.4 inch) of lead to reduce their intensity by 50% will also have their intensity reduced in half by 4.1 cm of granite rock, 6 cm (2.5 inches) of concrete, or 9 cm (3.5 inches) of packed soil. However, the mass of this much concrete or soil is only 20–30% greater than that of lead with the same ...
Long before experiments could detect gamma rays emitted by cosmic sources, scientists had known that the universe should be producing them. Work by Eugene Feenberg and Henry Primakoff in 1948, Sachio Hayakawa and I.B. Hutchinson in 1952, and, especially, Philip Morrison in 1958 [6] had led scientists to believe that a number of different processes which were occurring in the universe would ...
Daniel Wayne Hooper (born December 16, 1976) is an American cosmologist and particle physicist specializing in the areas of dark matter, cosmic rays, and neutrino astrophysics. He is a professor of physics at the University of Wisconsin–Madison [ 1 ] and the director of the Wisconsin IceCube Particle Astrophysics Center (WIPAC).
Future cosmic ray observatories, such as the Cherenkov Telescope Array, will use advanced techniques to detect gamma rays produced by cosmic ray interactions in Earth's atmosphere. Since these gamma rays will be the most sensitive means to study cosmic rays near their source, these observatories will enable astronomers to study cosmic rays with ...
Originally, the electromagnetic radiation emitted by X-ray tubes had a longer wavelength than the radiation emitted by radioactive nuclei (gamma rays). [18] So older literature distinguished between X- and gamma radiation on the basis of wavelength, with radiation shorter than some arbitrary wavelength, such as 10 −11 m, defined as gamma rays ...
The difference between gamma rays and X-rays is somewhat blurred. Gamma rays arise from transitions between nuclear energy levels and are monoenergetic, whereas X-rays are either related to transitions between atomic energy levels ( characteristic X rays , which are monoenergetic), or are electrically generated (X-ray tube, linear accelerator ...