Tuesday, 10 December 2013

Common Sense and the Laws of Nature (Part 1)

Common sense is what we humans live by – it is kind of wisdom gained from experience over many generations. Humans experience the world through the five senses, but importantly we also use our intelligence to perform cause and effect analysis of what has been happening around us to understand how the world behaves. 
Common sense has worked very well and has ensured the survival of the human race; particularly, in the avoidance of dangerous and harmful situations.  Human societies evolved to preserve and enhance the species.  Shared knowledge and effort proved useful in meeting adverse situations and quality of life improved rapidly as humans started to live together in social groups.  
Survival of human societies is a multifaceted situation; they not only have to guard against the hostile physical environment around them but also against other fellow humans who are driven by greed, violence and other undesirable traits.  Humans have always enjoyed exercising power and control over others around them. This is a classic example of conflicting requirements – living in societies is beneficial but at the same time exposes one to potentially dangerous elements of oppression and exploitation.  How humans dealt with this is fascinating and will be discussed in a future blog.
How does our common sense relate to the laws of nature is what we wish to look at first.  The difference is in the scope of the evidence available.

Laws of nature are deduced from experimental observations at all possible levels of space and time.  As human ability improves to expand such observations to wider regions of space and time, laws of nature are modified or even replaced by a different set of laws.  Fine-tuning of the laws is fundamental to their authenticity and acceptance.  The current set is the best available to make sense of what the empirical evidence tells us. 

Common sense is much more restricted in terms of empirical evidence at its disposal.  Without technological aids - and most human experiences have been in such conditions - humans really occupy a small region roughly in the middle of space-time expanse.   Their experiences are limited in size, speed, time, colour, frequency etc.  Quantitatively: We experience

Physical dimensions from ~0.01 mm to a few hundred km. 
Speeds vary from rest to a few tens of km/hour.
Time is restricted to our reaction time of the order of 10 ms to a few hundred years.
Colour is perceived in the narrow wavelength range of 0.4 to 0.8 micron                                       (1 micron = 0.001 mm)
Perception of sound is limited to frequencies less than about 20 kHz.

Animal species do better in colour and sound perception due to the evolutionary need to protect themselves against predators etc.

Humans mainly perceive the world around them through light which travels at the fantastic speed of 300,000 km per second; this gives the feeling of instantaneous communication – things are happening as we see them.

Natural phenomena like rain, thunder, lightening, tides, storms, earthquakes, motion of heavenly bodies, infectious/mental and other diseases etc. were mediated by causes outside the range of human perception.  Theories and explanations were put forward – of course different in different societies – to make sense of such events.  This can give rise to beliefs, customs, rituals, superstitions etc. 
We shall return to this later.

Limited scope of human experience, nevertheless, provided some quite sensible and workable theories about the way the world operates – kind of ‘limited’ laws of nature.  In good true scientific spirit a law would get modified when the evidence against it became overwhelming.  Sometimes it would require great sacrifices as changing a law might encumber on the interests/dogma of the powerful in the society. 

Situation started to improve about 500 years ago with the acceptance that experiment based evidence could not be ignored and must be taken into account in formulating so called laws of nature.  Technological advances helped in removing many of the limits to observations – in space, time and other areas.  Common sense inspired laws of nature started to be replaced by the new physics at the turn of the 20th century and in the short span of 25 years the acceptance of the new laws of relativistic and quantum physics was overwhelming. 

While common sense laws are arrived at through observations, mostly visual, and rely on the behaviour of matter around us at the macroscopic scale of dimensions greater than about 1 micron (0.001 mm), laws of nature (physics) are determined in the way elementary particles, typically of dimensions less than 0.001 micron, interact with each other.  These interactions are of four types:

gravitational (G), 

electromagnetic (EM), 

strong nuclear (SN) and 

weak nuclear (WN).  

G and EM are long range and affect matter at all distances. SN and WN are relevant only at nuclear dimensions with distances of the order of a billionth of a micron or less!   
Chemical and biological properties are determined by EM forces acting between atoms and molecules at distances of the order of 0.001 microns and may not be properly understood through evidence from everyday experience. Old theories based on human experiences have been unable to make good sense of chemistry and life sciences.
Motion of heavenly bodies is governed by gravitational forces but mostly involves distances far greater than our senses can be sensitive to.  That is why there has been so much confusion about this subject in historical accounts.  Newton's laws of gravitational attraction explained the way heavenly bodies are organised in the sky but a proper understanding of the Universe had to wait for the theories of relativity and the development of nuclear sciences. 

The world of atoms and nuclei was latent to our ancestors as the distances involved were unimaginably small and even their existence could not be contemplated. Understanding the true nature of atoms and nuclei only started at the turn of the 20th century and this has created the atmosphere in which modern industry could start.  Nuclear energy, Nanotechnology, Computers, Biotechnology, Space Exploration all owe their success to the laws of nature enunciated through empirical evidence acquired through development in technology in the 19th and 20th centuries.  Without this mind-set, modern industry would not even be science fiction.

Another interesting aspect of this discussion is the emergence of paradoxes.  A language that is weakly developed will be unable to describe a situation that is highly complex – the vocabulary is just not there.  A good example of a paradox is the wave-particle duality in classical physics (mostly based on common sense observations).  In our daily lives we see objects behave like material particles or as undulating waves in motion.  We do not have objects that switch between being waves and particles at different times.  This was the situation until the end of the 19th century when light was observed to exhibit properties akin to waves in some experiments but behaved exactly like a stream of particles in others.  The situation was resolved and explained by quantum description of light in 1925.  Now, we know that everything in the universe shows wave-particle duality and it is just our attempt to classify things as either waves or particles that is flawed.  We are using the wrong language for our description.

It is not that there are no paradoxes in the modern theories.  There are many and this simply points to the fact that, while we have a much better understanding of the world we live in, we have more to learn and the laws of nature will be rewritten differently in the future. 

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