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Robert P Kirshner

Publications and source records attributed to Robert P Kirshner.

3 recordsLinked to original sources

Hubble's diagram and cosmic expansion.

Edwin Hubble's classic article on the expanding universe appeared in PNAS in 1929 [Hubble, E. P. (1929) Proc. Natl. Acad. Sci. USA 15, 168-173]. The chief result, that a galaxy's distance is proportional to its redshift, is so well known and so deeply embedded into the language of astronomy through the Hubble diagram, the Hubble constant, Hubble's Law, and the Hubble time, that the article itself is rarely referenced. Even though Hubble's distances have a large systematic error, Hubble's velocities come chiefly from Vesto Melvin Slipher, and the interpretation in terms of the de Sitter effect is out of the mainstream of modern cosmology, this article opened the way to investigation of the expanding, evolving, and accelerating universe that engages today's burgeoning field of cosmology.

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Throwing light on dark energy.

Supernova observations show that the expansion of the universe has been speeding up. This unexpected acceleration is ascribed to a dark energy that pervades space. Supernova data, combined with other observations, indicate that the universe is about 14 billion years old and is composed of about 30%matter and 70%dark energy. New observational programs can trace the history of cosmic expansion more precisely and over a larger span of time than has been done to date to learn whether the dark energy is a modern version of Einstein's cosmological constant or another form of dark energy that changes with time. Either conclusion is an enigma that points to gaps in our fundamental understanding of gravity.

Journal Article↗