Ours is a dynamic universe: given enough time, most cosmological observables such as redshift, distance, or flux will be observed to drift. One can compensate for the short careers of astronomers by seeking high precision, but measurements of parts per billion to parts per trillion are required. Nevertheless, "real-time" cosmology is now possible with precise measurement and monitoring of the locations of objects in the sky. In an accelerating universe, cosmological redshifts of objects will drift. In an expanding universe, objects will appear to shrink as they recede, providing a geometrical distance measurement. Large-scale structures of galaxies can be observed to collapse in real time. Gravitational waves will cause distant objects to appear to move in the sky. Anisotropy or violation of the Copernican Principle will create cosmic shear. The acceleration of the Sun's orbit manifests as a secular aberration drift. The motion of the Sun with respect to the Cosmic Microwave Background creates a secular parallax of galaxies in the local universe. I present theoretical predictions of – and the first application of observations to – many of these phenomena and demonstrate that we can expect to measure most of these effects within the next decade or two.
Jeremy Darling / University of Colorado Boulder
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