- #51

marcus

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Actually I have seen curved models invoked many times, my point is that none of those models ever gave us the value, the bang for the buck, that the flat model does. Indeed those models can now be seen to be largely a source of unnecessary complication. Almost all cosmology textbooks, for example, start out with the three possible geometries, and go to great lengths describing their differences, only to throw it all away when they come to describing the currently favored model! It's so much wasted overhead...

Ah. This is where your personal attitude comes in. I remember in another thread you were urging that students not be exposed to the spatially curved versions of the model. You are campaigning for a kind of educational reform, in effect. Cosmology textbooks and curriculum should not WASTE STUDENT'S TIME by introducing the slightly curved case, or cases. It is "unnecessary complication"

The course outline, in effect, should focus exclusively on the flat case.

But not because flat is BELIEVED by any kind of mainstream majority or consensus.

Indeed to illustrate, in a central paper like the 2010 WMAP5 report by Komatsu et al they were keeping their options open and calculated up front with THREE versions of LCDM showing their results already on page 3 as I recall, Table 2, I think. A central paper with a dozen big name cosmologists reporting on a flagship project. Not fringe.

You are advocating a curriculum reform, to save "overhead", which would render students incapable of undertanding the options being kept open by core top professionals in the field.

It strikes me as a bit short sighted, a false "economy". It seems to have no logical basis, since we do not KNOW curvature is zero, and we may in future discover that it is on the positive or negative side of today's rather broad 95% confidence interval.

There is no logical basis for you to insist on this change in the course outline. It seems to have more to do with PERSONAL AESTHETIC.

I guess if we are going to talk at the level of personal aesthetics, prejudices etc. I will state my own, about what beginning cosmology students should be taught.

I would wish the course to present and explain the current confidence interval for Ω

_{k}from the WMAP7 report (also Komatsu et al) and, assuming today's best estimate for the cosmological constant, describe the two basic kinds of universe contained in that confidence interval, both indefinitely expanding, one with slight positive curvature and the other with zero or slight negative. One model spatially finite (now and at the start of expansion) and the other infinite (now and at the start) or topologically rather intricate.

I'll go get that confidence interval for Ω

_{k}Just google "komatsu wmap 7" and you get

http://arxiv.org/abs/1001.4538 and page 3 says:

−0.0133 < Ω

_{k}< 0.0084

which means:

0.9916 < Ω < 1.0133

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