Tuesday, June 15, 2010

Will A Mis-Calibration Using Jupiter Mess Up Cosmology?

Some of you may have heard of a recent paper stating that there may be a problem with the WMAP results. (But I'm sure it is not.)  From the press release:
New research by astronomers in the Physics Department at Durham University suggests that the conventional wisdom about the content of the Universe may be wrong. Graduate student Utane Sawangwit and Professor Tom Shanks looked at observations from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite to study the remnant heat from the Big Bang. The two scientists find evidence that the errors in its data may be much larger than previously thought, which in turn makes the standard model of the Universe open to question. The team publish their results in a letter to the journal Monthly Notices of the Royal Astronomical Society.
Here is essentially the problem, from what I can tell:
  1. Experiments don't have perfect resolution.
  2. The measure of angular resolution is very important for WMAP's cosmology results.
  3. Specifically, the true resolution has a powerful effect on the shape of the angular power spectrum.  (Pictured above.) Small deviations and the best-fit cosmology changes.
  4. WMAP uses the bright object Jupiter to calibrate their angular resolution.
  5. This paper calls into question the accuracy of that calibration.
  6. They show if the calibration is off as much as they think it can be, then the standard flat Lambda-CDM universe may not be the best fit cosmology anymore.
Okay.  A few thoughts.
  1. Though this article did get published, I have a lot more faith in the WMAP team who's work has been scrutinized and reverified by several groups for years.
  2. I'm sure the WMAP team will respond, and when they do I'm sure they will provide ample evidence nothing in their calculations are wrong.
  3. Many groups have used separate data and techniques and have all arrived at the same conclusion as WMAP.
So I'm sure there is no need to question WMAP's results.  That said, I am glad people force groups like WMAP to be very careful, especially when slight errors cause major problems.  


  1. So what happens if it is wrong? Will the Universe implode?

  2. Stan,

    Actually, this is another reason to trust the WMAP results. If the universe wasn't flat, it might do something like either implode or go through some runaway expansion. And the WMAP team finds the best fit is for a flat universe so it seems that their results make sense with the idea that we are still alive.


To add a link to text:
<a href="URL">Text</a>