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TOPIC: The universe is expanding


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RE: The universe is expanding
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Title: Cosmology when living near the Great Attractor
Authors: Wessel Valkenburg, Ole Eggers Bjaelde

If we live in the vicinity of the hypothesized Great Attractor, the age of the universe as inferred from the local expansion rate can be off by three per cent. We study the effect that living inside or near a massive overdensity has on cosmological parameters induced from observations of supernovae, the Hubble parameter and the Cosmic Microwave Background. We compare the results to those for an observer in a perfectly homogeneous LCDM universe. We find that for instance the inferred value for the global Hubble parameter changes by around three per cent if we happen to live inside a massive overdensity such as the hypothesized Great Attractor. Taking into account the effect of such structures on our perception of the universe makes cosmology perhaps less precise, but more accurate.

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Title: Who discovered the expanding universe?
Authors: Harry Nussbaumer, Lydia Bieri

Who discovered the expanding universe? Was it Hubble, or Lemaitre, or was it just the end result of a long series of investigations? In this article we summarise the main steps and contributions that led to one of the most exciting discoveries ever made, of which Lemaitre was the principal architect. In 1927 he combined his dynamical solutions of the Einstein equations with astronomical observations to conclude that the universe is expanding. He derived the linear velocity-distance relationship and calculated the first numerical value of what later was called the "Hubble constant". His discovery paper of 1927 was written in French and in 1931 it was translated into English and published in Monthly Notices. However, the translation omits the section where Lemaitre computed the "Hubble constant". Why was that done, and who was responsible? We do not speculate on this question, but present in a very condensed way the facts along the path of discovery. The documented details from primary sources can be found in our book "Discovering the Expanding Universe".

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Expansion of the Universe
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Expansion of the Universe

Credit The Open University



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Linear redshift-distance relationship
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Title: The linear redshift-distance relationship: Lemaître beats Hubble by two years
Authors: M.J. Way (NASA/GISS), Harry Nussbaumer (ETH, Switzerland)

Edwin Hubble is often credited with discovering the expanding Universe based on spectra taken by him. There are several errors in this statement and we feel that it is the responsibility of those who are aware of the historical facts to set the record straight.

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RE: The universe is expanding
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Our Universe started off in a hot, dense and almost uniform state. As it expanded and cooled, the first atoms formed.
Structures then emerged, leading to the formation of galaxies, stars and planets. Thanks to the use of ever more powerful telescopes on the ground and in space (allied to more powerful computers) astronomers are starting to understand the properties of the complex cosmos in which we live.

Martin Rees is Professor of Cosmology and Astrophysics at the
University of Cambridge, Astronomer Royal, and President of
the Royal Society.

This video presentation, part of the Opening Ceremony of the International Year of Astronomy 2009 held in UNESCO, Paris is featured on the IAF channel courtesy of the International Astronomical Union and UNESCO. The event was co-ordinated by the Observatoire de Paris.


Video production by University of Strasbourg/Canalc2 (www.canalc2.tv)

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Posts: 129960
Date:
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Date:
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