Oftentimes we can know how old something is.  Not just though written history as some have gotten stuck into.  It is entirely possible to find out the age of things with natural scientific methods too.  They date with an error margin varying from method to method.  I will now explain some which I have personal knowledge about.  There are of cause more methods.  However, I am not familiar with how they work.

The most exact dating method is called dendrochronology.  In areas with clear seasonal differences trees from an outer ring per year.  Under exceptional weather conditions an extra such ring can form.  But the extra one is then less distinct than normal yearly rings.  I don’t think it is possible for trees to form more than two such rings per year.  Those growing at the border of where trees can grow can to the opposite lack certain years.  Differently thick yearly rings form depending on weather conditions.  The pattern of such are matched to other wood from the same species.  Samples can be drilled out from the trunk of living trees.  This way wood can be dated with an error margin of a year.  Long chains of overlapping pieces have been puzzled together by scientists.  The longest one covers more than 13,900 years.  Please note that specific trees only live for a few hundred or thousand years.  Their overlapping lifetimes have made such long chains possible.

A different method is radiocarbon dating which is used on organic material.  The substance carbon-14 is constantly formed form nitrogen in the Earth’s atmosphere.  Life-forms then absorb this substance as long as they live.  In dead life-forms it is not replaced but gradually decays into nitrogen.  After 5,730 years half the substance has decayed.  After 11,460 years 3/4 has decayed and so on.  By measuring the fraction which is left the point in time when the life-form died can be dated.  However, it has turned out the amount of carbin-14 forming has varied over the ages.  This is dues to how much cosmic radiation is hitting the Earth’s atmosphere.  The method has therefore been calibrated with the help of dendrochronology.  Layering with yearly variation can be used for this purpose too.  The resulting calibration curve has made the dating more exact.  The individuals making the measurements state the size of the error margin.  Generally the error margin is larger the older the tested sample is.  It is determined by the sensitivity of the measuring instruments to the dwindling fraction which is left.

Larger variation than before has occurred after 1945.  On one hand, nuclear weapons tests in the atmosphere have formed large amounts of carbon-14.  On the other hand, emissions from fossil fuels have increased enormously since then.  These contain almost no carbon-14.  What little they contain is due to radioactive decay in surrounding rock types.  When they are burned the carbon dioxide is mixed with the one made by live organisms.  The result is an unnaturally low rate of carbon-14 in the atmosphere.  Scientists are aware of this and have used it in some cases.  Not in order to fool others but to find out things.  Carbon-14 from nuclear tests has been used to date the cells of our bodies.  Then it can be found out how often they are replaced.

Other forms of radiometric dating don’t have the problems of carbon-14.  The processes forming these substances don’t vary over time.  Instead certain substances occur in specific proportions when some types of rock form.  These substances decay into others at a certain pace.  This pace can be used to date the rock layer.  If I understand it correctly this only works on volcanic rock.  Samples are drilled out of rock layers to avoid the effect of weathering.  Then the proportions of different substances in the sample are measured.  The result is an age which has a certain error margin.  I think this method works in 97% of the cases.  In the case it does not work there are now explanations for this.

There is good reason to think that the pace of decay is constant.  The pace has been directly measured for more than a century now.  The changes which have been measured are all within the error margin.  Moreover, the pace is determined by fundamental natural forces.  The strength of these natural forces has to be at least fairly constant.  If they varied greatly over time this would have other consequences too.  These effects would in turn make life on Earth impossible.

Uploaded on the 5th of April 2024.