by Robert Brecha

The second entry of our Putting Observational Science to the Test series comes from Dr. Robert Brecha, Professor of Physics and Research Director for the Hanley Sustainability Institute at the University of Dayton.  In this post, Robert questions observational science’s treatment of time, especially its overwhelming reliance on the present. 

Ken Ham proposes an interesting view of science as being divided into two realms: that of “observational science” dealing with the “scientific method” and events in the present, and that of “historical science” which is concerned with the past and therefore not available for observers now. The clear goal of this division is to remove from the realm of science any statements about the past, including the age of the earth. As the hosts of this blog explain earlier the strictness of this definition is very problematic partly because it also implies a distinction between the “truth” of observational science and mere “conjectures” available to historical science.  

Ham’s distinction between “observational science” and “historical science” raises some basic questions for scientists.  For one thing, what counts as “observation”?  Are telescopes and microscopes allowed, or are we only to trust the naked eye?  What, in the case of a sharp division between past and present, exactly defines “the past”? If I make a measurement today, does that mean I have to start over tomorrow since I cannot say anything about the past?

Without reference to observations of the past, how can we be so confident in the observations of the present?  If we recognize that Laws of science remain constant over time, does that not mean that we can indeed infer something about the past based on those theories?  It is a truly radical re-definition of science to claim that we cannot look further backward using the same physical theories that we have seen acting consistently over decades or centuries.  

Let’s look at one example.  I can directly measure the amount of carbon dioxide in the atmosphere as a percentage of the total amount of gases in the air.  At the same time, I can look at air bubbles that form as snow falls and builds up on Antarctica and measure the carbon dioxide concentration.   Comparing these, I see that the observations match, and since I am a careful (and long-serving) scientist, I keep a notebook with my observations over a fifty-year period.  They agree very well, so I decide that I will go back to 51, or 60, or 100 years ago by digging down into the accumulated ice on Antarctica and read off the years by looking at snowfall layers – the way others might count tree rings.  I don’t have the direct measurements for those earlier years since I was a pre-scientist, or not even born.  For each year I examine the air bubbles trapped in the ice and measure how much carbon dioxide is in the air bubble.  I am in my lab, making measurements that are exactly the same as the ones I had been carefully, and currently, making each year for the past half-century.  Is it really now not a matter of science to say that, given decades of agreement between the measurement techniques, extending the ice measurements backwards will give me an idea of actual carbon dioxide levels in the atmosphere?  If not, when did the correspondence stop?  At year 51?  Why?  

Clearly we encounter increasing uncertainty as we move back in time.  Did I miscount the layers and am I therefore off by a year?  Was there a year with no snow and therefore a layer was skipped?  But that’s why my friends in Greenland are also making measurements there as a check on my work.  And then another group of friends, more biologically oriented, are counting tree rings, or looking at characteristics of pollen, or seashells of creatures that absorb carbon dioxide or oxygen, and so on.  When all of these independent techniques give the same answers, we begin to think we understand that bit of nature somewhat better.  

In the end, if we cannot say anything about the past through our scientific endeavors, we cannot say anything about the future either.  If the laws of physical science, the theories (and I mean this in the sense in which scientists use the term, not as an “uneducated guess,” as is sometimes implied) we use to underpin all of technological civilization, are not constant, then we can have no faith that the apple we drop to the floor today won’t fall twice as fast tomorrow, or maybe even jump upwards out of our hands.  If, on the other hand, we can project our theories forward and find them to hold, then it would make for a strange, asymmetrical, and cruel world in which a constant shifting of these laws would render them invalid to make inferences about the past.