Observations represent the truth, models…

In the last year during a larger meeting I had made a comment, which let a lot of attendees shake their head and others just smile. The statement was:

“Observations represent the truth, models the state of our understanding.”

Like I have said before, on the first sight it is of cause rubbish that observations have anything to do with the truth. Indeed, truth is a great word with many different meanings and implications. In the context above “truth” (which anyhow should always set between quotation marks) describes the possible best estimation of the real world by the current available technology in real case situations. When I personally write things up, I usually use a measurement operator to make this clear that observations are never able to describe the full reality. How much effort observers might put at it (and they usually do an amazing job), the real physical state of a physical system can only be approximated.

Nevertheless, since this is the case, we use in our daily job observations as truth. The values, together with their uncertainty are the basis of every analysis. Additional information, like physical understanding or knowledge on the measurement conditions lead afterwards to an interpretation, which will be compared to models.

Models itself are basing on the understanding of the natural processes. They use simplifications, approximations and parametrisations to create a virtual picture of the real world. This can be afterwards used to get a better understanding of the reality and compared to those information we gather from it: the observations. That is why I describe them as our understanding of the real world. With these model building steps we acknowledge that our knowledge is limited. Its not only the computers who limit us, it might be simple chaos. A model itself, without testing and calibrating it to data derived from observations, is nice to have, but tells us not much about reality. Nevertheless, they might still be helpful for theoretical considerations.

All in all, yes, the statement above is a quite bold expression on how we handle the different type of data in our daily work. The models can not be better as the observations permit (at least in most of the cases). Especially in earth sciences, models are calibrated and verified at the hand of observations. So they are seen and used as an uncertain truth.


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