Thursday, October 13, 2022

Science Is Self-Correcting

Environmental & Science Education, STEM, Astronomy, Astrophysics, Cosmology, Nature of Science

Ed Hessler

In their research and its reporting, scientists think a lot about and spend time trying to get the science right. This is the goal.  For those of us who are not scientists this can be a daunting task. When this doesn't happen scientists  make the proper corrections, i.e., science is a self-correcting process.

An interesting example is reported in NatureNews on data from the James Webb Space Telescope (JWST). and has to do with the "limitations of early data from Webb." It is about calibrating this new instrument available to space scientists. Ensuring that the JWST provided accurate results had occupied the work of scientists for many years,  e.g., John Mather in a 2010 technical paper written for a workshop considering JWST calibration drew attention to this issue and closed his presentation with why. It is because of its "ability to observe sources that are far fainter than any calibration standards." Many of the problems were resolved.

However, as Alexandra Witze nicely puts it in the Nature article, the current calibration  issue includes a difference from one that is technical. It is human. She writes "Astronomers have been so keen to use the new James Webb Space Telescope that some have got a little ahead of themselves. Many started analysing Webb data right after the first batch was released, on 14 July, and quickly posted their results on preprint servers — but are now having to revise them. The telescope’s detectors had not been calibrated thoroughly when the first data were made available, and that fact slipped past some astronomers in their excitement."  

Another way of looking at this is that science is very much a human enterprise. Who doesn't want to use a new instrument right "out of the box"?  And now the corrections have begun.  Redoing the work, according to astronomer, Marco Castellano is both "'thorny and annoying.'"

Witze notes that "the STScI  made it clear that the initial calibrations to the telescope were rough and that it is a new telescope whose details are still being worked out." She describes how telescopes are calibrated  and points out that "working with Webb data involves several types of calibration, but (that)  the current controversy is around one of the telescope’s main instruments, the Near Infra Red Camera (NIRCam). 

Because of early demands on the use of the JWST, researchers only had "enough time to point it at one or two calibration stars, and to take data using just one of NIRCam’s ten detectors. They then estimated the calibrations for the other nine detectors." Martha Boyer who is working on calibration efforts, told Witze “That’s where there was a problem. Each detector will be a little bit different.'”

In late July, "STScI released an updated set of calibrations that were substantially different from what astronomers had been working with." In what struck me, a stereotype, as a typical British understatement, Nathan Adams said "'This caused a little bit of panic.'"  He also added this, “'For those including myself who had written a paper within the first two weeks, it was a bit of — ‘Oh no, is everything that we’ve done wrong, does it all need to go in the bin?’” It turns out "no" and that things were not as bad as feared. 

New calibrations for the Webb are forthcoming which Witze indicates "should shrink the error bars on the telescope’s calibrations from the tens of percentage points that have been bedevilling astronomers in some areas, down to just a few percentage points. And data accuracy will continue to improve as calibration efforts proceed over the coming months."

This is a story of science-in-action and I hope you will read Witze's story for the full picture she paints. I've taken only a few snapshots with little attention to richness. It is short, ~5 m read, and has a great title, too.

Science works!

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