Comments on: WMAP results — cosmology makes sense!

By: From Quantum to Cosmos-II | Cosmic Variance

From Quantum to Cosmos-II | Cosmic Variance — Thu, 29 Jun 2006 15:02:48 +0000

[...] Since I’m focusing on cosmology in this post, I’ll skip past great talks by Alan Kostelecky and Tom Weiler and jump right to the Monday evening session in which David Spergel gave a tight and crystal clear review of the WMAP3 results, and then Sean spoke on Cosmological Constraints on Modified Gravity. I will be deliberately sketchy about Sean’s talk because most of it described work which will appear in a couple of papers, one of which we are writing together with our graduate students, within the next week. But a broader part of the talk concerned how one might differentiate between dark energy and modified gravity as explanations for cosmic acceleration. Sean discussed how, in modified gravity, Newtonian potentials can grow differently than in General Relativity (GR) (even sometimes at different rates on different scales), and how this might be used not only to distinguish it from dark energy, but to distinguish between different suggestions for modifying gravity. [...]

By: The Future of Theoretical Cosmology | Cosmic Variance

The Future of Theoretical Cosmology | Cosmic Variance — Tue, 25 Apr 2006 14:39:49 +0000

[...] Origins Questions. Where did the universe come from, and why do we find it in this particular configuration? Inflation, which received an important boost from the recent WMAP results, is a crucial ingredient in our current picture, but I stressed that there is a lot that we don’t yet understand. In particular, we need to understand the pre-inflationary universe to know whether inflation really provides a robust theory of initial conditions. Thinking about inflation naturally leads us to the multiverse, and I argued that untestable predictions of a theory are perfectly legitimate science, so long as the theory makes other testable predictions. We don’t yet have a theory of quantum gravity that does that, and I prevaricated about whether one hundred years would be sufficient time to establish one. (Naive extrapolation predicts that we won’t be doing Planck-scale experiments until two hundred years from now.) [...]

By: Everything I know about the universe I did not learn from newspaper headlines | Cosmic Variance

Mon, 27 Mar 2006 16:51:36 +0000

[...] The new WMAP results have told us a lot about the universe. The basic findings are: [...]

By: Spaceman

Spaceman — Mon, 27 Mar 2006 01:54:33 +0000

Like Dumb biologist, I am also interested in the age-old question: is the universe finite or infinite? In my opinion, this is one of the most important questions ever asked. I know this question can only be answered definitively if the universe is smaller than the horizon. Unfortunately, I have a feeling that those in favor of the small universe idea will never accept any data which concludes that non-trivial topology, if it exists, must be on a super-horizon scale.

I have several questions related to the finite or infinite issue which I am hoping a cosmologist could help answer.

1). The low CMB quadrupole is in sharp contradiction with the infinite universe prediction for the quadrupole. Wouldn’t any infinite universe model which tries to accommodate this observation be considered an unnatural stretch?

2). Luminet et al (2004) and Aurich et al (2005) and others have written highly critical papers regarding the topology conclusion reached by Spergel et al (2004). A lot of this criticism is two-pronged: they basically say that (i) the 1st year sky-maps have too much noise in them for Spergel et al to have reached the conclusion they did, and (ii), the methodology itself is in some way flawed. Who is correct? Do the WMAP 3-year sky-maps have a high enough signal-to-noise ratio for one to look for a topological signiture in them, or, will it take another satellite (i.e. the Planck Surveyor) to resolve this issue?

3). Do Spergel et al have plans to write a paper to counter the recent criticisms that have been leveled against their “circles in the sky” analysis?

By: Spaceman

Spaceman — Mon, 27 Mar 2006 00:57:12 +0000

From what I can tell based on critical reading skills and a trust of the WMAP team, the superbly accurate 3-year results are the product of an exhaustive and painstakingly detailed search for systematic errors and foreground contamination. A number of new techniques were employed to see if the data is of high enough quality to be used for a cosmological analysis. So, the combination of longer integration time and a more thorough analysis assures us the new results are giving us a solid picture/understanding of cosmic evolution. I certainly don’t think cosmology is solved, as there are still mysteries and cosmophenomena that need to be explained, but at least we now have a rough outline of cosmic evolution. I have a feeling that the standard model of cosmology is basically correct even though it may take decades before we fill in all of the details. Think about it like this: we knew the size and shape of the earth before we knew what it was made out of and had it all mapped; similarly, we now almost surely know the size, expansion rate, and shape (i.e, flatness) of the universe even though we do not yet know what is the dark energy and the dark matter. Humanity has little to be proud of these days on Earth, as neo-liberalism allows billionaire tourists to fly into space while billions remain without the basics. Nevertheless, we should be proud of the fact that we’ve come as far as we have in recent years in terms of being able to read the “universe story” in the sky.

By: Slacker Astronomy Show Notes » WMAP’s Anistrophy Trophy (Show #47)

Slacker Astronomy Show Notes » WMAP’s Anistrophy Trophy (Show #47) — Wed, 22 Mar 2006 03:57:23 +0000

[...] WMAP results â€” cosmology makes sense! via Cosmic Variance Blog [...]

By: Scott O

Scott O — Sun, 19 Mar 2006 21:18:03 +0000

Thanks for the comments, David (#50). I’m looking forward to seeing Mark Halpern’s astro seminar tomorrow at UBC, in order to learn more.

By: Savya

Savya — Sun, 19 Mar 2006 20:41:50 +0000

Thanks, Hiranya.

By: Sean

Sean — Sun, 19 Mar 2006 17:40:47 +0000

That’s right — only the 4% of the universe that is “ordinary matter” is described by the Standard Model.

By: Arun

Arun — Sun, 19 Mar 2006 14:09:01 +0000

So does the Standard Model – electroweak, QCD – apply to only 4% of the stuff in the universe?