Historians Rediscover Einstein's Forgotten Model of the Universe 35
KentuckyFC writes In 1931, after a 3- month visit to the U.S., Einstein penned a little known paper that attempted to show how his theory of general relativity could account for some of the latest scientific evidence. In particular, Einstein had met Edwin Hubble during his trip and so was aware of the latter's data indicating that the universe must be expanding. The resulting model is of a universe that expands and then contracts with a singularity at each end. In other words, Einstein was studying a universe that starts with a big bang and ends in a big crunch. What's extraordinary about the paper is that Einstein misspells Hubble's name throughout and makes a number of numerical errors in his calculations. That's probably because he wrote the paper in only 4 days, say the historians who have translated it into English for the time. This model was ultimately superseded by the Einstein-de Sitter model published the following year which improves on this in various ways and has since become the workhorse of modern cosmology.
In the case you wonder (Score:5, Informative)
He spelled Hubble as "Hubbel", german way. Hubbel [wiktionary.org] is also a german word meaning "bump".
Re:But we ain't gonna have a Big Cruch, right ? (Score:5, Informative)
The Hindu's have some mindbogglingly long number they came up with like 12000 years ago that's supposed to be how long the Universe spends between Big Bangs, before it's reborn. As in the Hindu religion there is no death, no end of the world, everything cycles on, in a perpetual reincarnation way. I think it's one of the biggest numbers that humans ever came up with, bigger than Aristotle's cattle problem, but not sure. I'm too lazy to research it and look up references and substantiate claims for it right now, but there you have it, a fleeting idea.
Einstein-de Sitter (Score:5, Informative)
The EdS model is not "the workhorse of modern cosmology", no matter what the author of this summary wants you to think. If any model could be described thus it would be the Friedman-Lemaitre-Robertson-Walker model, which was already known (thanks to Friedman and Lemaitre who developed it in the 20s) by 1931. The EdS model is a specialisation of the FLRW to a universe containing pure pressureless matter, and an expansion is necessarily decelerating. As such not only can it not describe the early universe, when the existence of the CMB and the expansion of the universe together imply a period where the universe was instead dominated by radiation, nor the late universe, where observations imply that expansion is instead accelerating. EdS was used as an approximation to the late time universe until the 90s when it was obvious that it was in conflict with observation. It's sometimes still used for rough approximations thanks to the simple solutions one can find for linear perturbations, but those are only valid up to redshifts of approximately 1, and no later.
Re:Einstein-de Sitter (Score:4, Informative)
But the Friedman-Lemaitre-Robertson-Walker model is based on the Einstein-DeSitter model:
http://en.wikipedia.org/wiki/E... [wikipedia.org]
They're even credited and referred to multiple times.
Re:Einstein-de Sitter (Score:2, Informative)
Other way round, the EdS is a specialisation of the FLRW, and Friedman and Lemaitre both developed their models before 1932. These weren't the final forms of what we now call FLRW models -- otherwise it wouldn't be necessary to put the RW on the end -- but technically their models did precede the EdS, and are a superset. I have absolutely no idea how well that was appreciated at the time, mind you.
Basically, an FLRW is a metric composed of completely homogeneous and isotropic 3-surfaces, all stacked one on top of the other. You can have any kind of matter you like on the surfaces, just so long as it's also distributed completely homogeneously and isotropically. For instance, a de Sitter model (not Einstein-de Sitter; this is a different thing) is an FLRW filled only with a cosmological constant and which therefore expands exponentially; models of inflation are quasi-de Sitter because they mimic a de Sitter expansion but with a scalar field that almost, but not quite, behaves in the same way. An Einstein-de Sitter model is filled with pressureless "dust", which expands as t^2/3. So far as I know there isn't a name for the FLRW filled only with radiation, but if you set one up it expands as t^1/3 -- the slower expansion coming from the additional gravitational "mass" contributed by the radiation pressure. (The gravitational "mass" is density plus pressure (times c^2 but we habitually set c = 1 so that we measure time in metres or distance in seconds); so a cosmological constant has zero gravitational "mass" since by definition its pressure is exactly minus its density, while radiation (pressure = density / 3, so density + pressure = (4/3) * density) has a higher gravitational "mass" than dust (density + pressure = density).)
-- boristhespider