Special & General Relativity Questions and Answers
How do distant objects get magnified by space curvature?
General relativity predicts that gravitational fields curve space. This leads to collections of matter in distant galaxies acting as 'gravitational lenses'. The farther out you look in space, the more galaxies are located along your line of sight, and so the more of this 'cosmological lensing' can occur. The precise amount depends on which of several cosmological models for the large-scale geometry of space are correct. Open, hyperbolic universes and closed 'spherical' universes have different degrees of space curvature once you begin to look at galaxies 5 - 15 billion light years away. The principle way that this cosmological space curvature works is to make the angular sizes of objects with a fixed linear size, appear to diminish out to some critical distance near a redshift of 1.0, then the angular sizes begin to increase the further out you go beyond this redshift. It is a very important test of cosmological models IF you can identify objects with a fixed linear size in light years. Galaxies themselves have linear sizes that vary too much.
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All answers are provided by Dr. Sten Odenwald (Raytheon STX) for the NASA Astronomy Cafe, part of the NASA Education and Public Outreach program.