Abstract
Galaxies are gigantic physical systems having a typical size of many tens of thousands of light years. Thus, any change at the center of the galaxy will affect the rim only tens of millennia later. Those retardation effects seem to be ignored in present day modelling used to calculate rotational velocities of matter in the outskirts of the galaxy and the surrounding gas. The significant discrepancies between the velocities predicted by Newtonian theory and observed velocities are usually handled by either assuming an unobservable type of matter denoted “dark matter” or by modifying the laws of gravity (MOND as an example). Here, we will show that considering general relativistic effects without neglecting retardation can explain the apparent excess matter leading to gravitational lensing in both galaxies and galaxy clusters.
Highlights
We have deduced from general relativity a linear approximation
This was followed by a discussion on the retardation effects on light ray trajectories, deriving an expression for “dark matter” which is the same as the one obtained in [15] for slowly moving bodies
Justifying results reported in the literature of the equivalence of “dark matter” for both galaxy rotation curve and gravitational lensing
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Fritz Zwicky noticed, in 1933, that the velocities of Galaxies within the Comma Cluster are much higher than those predicted by the virial calculation that assumes Newtonian theory [7]. A gravitational lens is some form of matter (for example a cluster of galaxies) between a distant source of light and the observer, that is, bending the light as it travels towards the observer This effect is denoted gravitational lensing, the amount of bending is one of the predictions of GR [19,20,21]. Strong lensing is the distortion of background galaxies into arcs when their light passes through a gravitational lens This has been observed around many clusters such as Abell. We discuss the effect of retardation on the lensing phenomena and show in what way can retardation cause a “dark matter” phenomena
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