Fundamentals III - The Unseen Universe (some philosophical considerations)

"The most perfect philosophy of the natural kind only staves off our ignorance a little longer, as perhaps the most perfect philosophy of the moral or metaphysical kind serves only to discover larger portions of it. Thus the observation of human blindness and weakness is the result of all philosophy, and meets us at every turn, in spite of our endeavours to elude or avoid it." David Hume (An Enquiry Concerning Human Understanding, 1772)

Even though the scope of this page is not philosophical, it is interesting to realize that deep philosophical questions are behind the fact that most of our universe is invisible and that we are confined to a very limited sensorial realm.

Such questions arise when one considers the existence of objects external to us, the objects of 'human enquiry' and how one can be certain about their existence. We know that science has developed its own procedures in order to explain natural phenomena. Today we known that there are many invisible things in our Universe, things that do not interact with our sensory organs. How do we know that they exist ? 

Non-observed and invisible phenomena are understood in terms of theories that first explain how the intermediary devices or methods, used to make such facts visible, can work. In order to build or develop such equipments or methods, we need to understand the theory and strongly believe the existence of the things they are design to show.

In this sense, we must broaden our view, considering not only what is 'observable' and 'visible' as part of the Universe. We must be guided by procedures and tacit considerations in order not to neglect what is not directly observable, for these things might possess a rich ontological content (they may exist independent of us and represent a new reality) and they may be identified as the cause of many phenomena yet unexplained. 

Science has unveil the existence of unobservable things along its history, and this is hardly a finished process.

Fundamentals II - The Unseen Universe (Examples)

Some examples of the 'empirical' classification presented in our past post are given below. Not all phenomena are observable as we see. Many of them are non-observable and cannot be sensed in any way.

Observable and cyclic: 

• Conspicuous astronomical events: apparent movement of celestial bodies, eclipses of the sun, moon, tides - rise and fall of sea level; 
• Seasonal ocurrrences: change of color of leaves in the beginning of autumn, the menstrual cycle;

Observable and noncyclic:

A large category of natural ocurrences such as:

• Weather and climate: storms, lightning, hurricanes; 
• Life (biology): an interesting example are bat´s sounds at the threshold of what can be heard by humans (below 20KHz). Most of bat´s interaction with the environment is ultrasonic and, therefore (according to our nomenclature) 'invisible' (non-audible), almost all life occurrences are noncyclic and shows a strong cause and effect link; 
• Geology: vulcanic eruptions (including geysers) and earthquakes. Other geological occurrences are too slow to be witnessed during the human life interval; 
• Astronomy: the sudden appearance of a bright supernova (ex. SN1987A); 
• Medicine: many symptons are observables and are related to (nonobservable) causes. 

Nonobservale, Visible and Cyclic

• Astronomy: the observation through a telescope of Jupiter´s moons transits or eclipses; 
• Biology: observation  of the cyclic cell division through microscopes; 

Nonobservable, Visible and noncyclic

• Astronomy: observation of solar prominences. Interesting enough, solar prominences are observable only during total solar eclipses.In normal conditions, the sun bright photosphere outshines their appearance that can only be observed with the use of special equipments. In general, all nonperiodic astronomical events (such as supernavas in distant galaxies) share the same features; 
• Biology: observation though microscope of all types of nonperiodic biological phenomena; 
• General: low amplitude sound effects: throught the use of amplifiers, unhearble sounds can become hearable; 
• Medical techniques: Positron emission tomography. A remarkable example of something hidden (observable body structures) that can become visible through a PET scan device. 

Nonobservable, invisible and cyclic

Radioastronomy:radio waves of periodic pulsars can become audible using radio telescopes.

Nonobservable, invisible and noncyclic

• Thermophysics, optics: Schlieren imaging reveals very small changes in the refraction index of transparent media.  Thermal plumes rising from human bodies can not be seen in any way, but are visible throught Schlieren imaging tecniques  (intervening medium). The technique also allows the visualization of sound waves; 
• Radio: all sorts of electromagnetic phenomena can become audible using a radio. The range of frequencies is very wide; 
• Astronomy: X-ray, infrared, Ultraviolet astronomy revealing an universe we are totally blind to; 
• Astrophysics and Cosmology: ~74% of what exists in the universe is invisible (and nonobservable), the so called dark energy. Dark matter is the term used to describe another special matter state that respond for 22% of what exist.The remaining 4% is made up of atoms and, therefore, matter of our ordinary knowledge. 

How do we know about the existence of non-observable, invisible and sporadic events ? The secret lies in the theories or rational structures that provide ways to experimentally access them.