Dark Energy & Its Discontents
Peter Coles, University of Sussex
BRLSI Friday 24th April 2015
Notes by William Gaskell AMInstP
Parsec is about 3 lightyears
Calcium “doublet” signature on spectrum is marker used to measure Doppler shift with red/blue shifted light from galaxy/star indicaates relative velocity galaxy/star is moving away/towards us.
Hubble’s law is:
Which describes how Universe is expanding but Hubble never wrote about it and he got his constant wrong by a factor of 10.
Alexander Friedman took Einstein’s Theory of Relativity and developed a more comprehensive model from it “The Freedman Model” – or The Big Bang Model.
Dark Energy is something that creates gravity but is not stuff – it’s like pressure that the vacuum of space exerts on matter.
Dark Energy increases as space expands, as it is a constant like the Hubble constant, but space expands in order to spread out the energy density of matter evenly.
Photosphere is the visible edge of the Sun, where gas density falls past the visible threshold where it is no longer opaque, which is a similar concept to the edge of the cosmos.
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