and when (and by who) was it thought that is was closed?
before now that we think that it's flat...
before now that we think that it's flat...
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I think you're asking a slightly unanswerable question. It's not like one person proposed one idea and another person proposed the other. However I can give you some background information as a launching point for your research.
General Relativity is a hugely important theory. It literally enables to you come up with the Equation of the Universe. The most popular model (and the one that allows for open, closed, and flat universes) is known as the Friedmann-Lemaitre-Robertson-Walker (FLRW) Model. This model is one particular solution of the equations in GR and was developed by all those men (not necessarily together). From their model the immensely important Friedmann (yes it has two n's) Equation was derived. This is the "Equation of the Universe" that I was referring to. It describes the motion, evolution, shape and much more about the universe. It is this equation which allows us to calculate the shape of the universe and it was this equation that gave us the idea that the universe might be open, closed, or flat.
Which one it was was up for debate. It all depended on the composition of the universe and that information came from COBE and WMAP (and soon to be Planck) mostly. It has only been recently (within the past decade or so) that we had decisive enough information to say which of the three was correct.
Hope that helps.
EDIT: Like I said, that debate is going to be hard to find. Not many people took sides. That just isn't the way of science. Before people decided, they took measurements. Then they came up with the answer that it is flat. No self respecting scientist would claim something is true with no evidence (especially if the theory states all three are equally plausible). After a cursory search though I did find one thing. As I said, the universe appears to be flat. The problem is a flat universe is a very finely tuned thing. The conditions must be EXACT. As of now, it appears flat (it may be that our measurements are slightly off and it is really just very very very slightly bent). So many scientists scratched their heads and went, why does the universe meet these immensely precise conditions which enable it to be flat? This is known as the "Flatness Problem". One such stance is to claim that the universe is infinite in size and is only flat in this general region. It may be curved elsewhere, where we can't measure it. This stance is put forth by John Barrow, Frank Tipler, and John Wheeler and is described in their book The Anthropic Cosmological Principle. Not sure if that helps you any more or not, but I feel as if you're trying to research something that doesn't really exist.
http://www.amazon.com/Anthropic-Cosmolog…
General Relativity is a hugely important theory. It literally enables to you come up with the Equation of the Universe. The most popular model (and the one that allows for open, closed, and flat universes) is known as the Friedmann-Lemaitre-Robertson-Walker (FLRW) Model. This model is one particular solution of the equations in GR and was developed by all those men (not necessarily together). From their model the immensely important Friedmann (yes it has two n's) Equation was derived. This is the "Equation of the Universe" that I was referring to. It describes the motion, evolution, shape and much more about the universe. It is this equation which allows us to calculate the shape of the universe and it was this equation that gave us the idea that the universe might be open, closed, or flat.
Which one it was was up for debate. It all depended on the composition of the universe and that information came from COBE and WMAP (and soon to be Planck) mostly. It has only been recently (within the past decade or so) that we had decisive enough information to say which of the three was correct.
Hope that helps.
EDIT: Like I said, that debate is going to be hard to find. Not many people took sides. That just isn't the way of science. Before people decided, they took measurements. Then they came up with the answer that it is flat. No self respecting scientist would claim something is true with no evidence (especially if the theory states all three are equally plausible). After a cursory search though I did find one thing. As I said, the universe appears to be flat. The problem is a flat universe is a very finely tuned thing. The conditions must be EXACT. As of now, it appears flat (it may be that our measurements are slightly off and it is really just very very very slightly bent). So many scientists scratched their heads and went, why does the universe meet these immensely precise conditions which enable it to be flat? This is known as the "Flatness Problem". One such stance is to claim that the universe is infinite in size and is only flat in this general region. It may be curved elsewhere, where we can't measure it. This stance is put forth by John Barrow, Frank Tipler, and John Wheeler and is described in their book The Anthropic Cosmological Principle. Not sure if that helps you any more or not, but I feel as if you're trying to research something that doesn't really exist.
http://www.amazon.com/Anthropic-Cosmolog…
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Olbers' Paradox doesn't require a finite universe - it just has to have a beginning in time. I don't know of anyone who's proposed that the universe was open or closed. Big bang models allow for open, flat or closed universes but I don't know of anyone who's said the universe *is* open or closed - all the indicators show that it's flat.