Gravity Chapter
2: Reality and Natural Forces
The real world outside of our bodies is experienced only by means
of our senses and these senses define reality for each of us as individuals.
These sensory capabilities were developed by the process of natural
selection over millions of years of evolutionary progression and were
developed to cope with a primitive existence in a natural environment.
The human senses in a roughly ascending order of importance
are:
Taste - The cells on the surface of the tongue activate
the sensation of taste and these cells essentially determine
the acidity or otherwise of the matter that it comes into
contact with. It is a combination of these that determine the specific
taste sensation.
This sense was important for prehistoric man to be able
to test the safety or the palatability of food, but today
this sense is mainly utilised for pleasure.
Smell - the cells within the nose, which are somewhat similar
to those on the tongue, are stimulated by some particles
of matter that are borne in the air. This of course was
a vital sense for prehistoric man but this is hardly of
importance to survival today.
Hearing - within the ear the eardrums vibrate in concert
with the minute variations of pressure transmitted by the
air, which fluctuations are described as sound waves.
This sense was vital for survival in prehistory, but today
mainly used for lingual communication, or as in the case
of music for pleasure.
Touch - The skin is the largest organ of the human body
and reacts to changes in temperature, or in other words
as to whether the matter of the environment around the
body is attempting to extract energy from it or emit energy
to it. The skin is also very sensitive to changes in pressure.
This sense is perhaps as important now as it was then,
but its importance is perhaps underestimated.
Vision - Of all the senses vision is, and was, by far the
most important, commanding 70 percent of all the sensory
receptors of the human body. The retina of the eye is stimulated
by light and more specifically by the variations in its
frequency, which we sense as the colours of the rainbow
or of the spectrum of light.
If a sense is defined as a reaction to external stimuli
or signals, then there is in fact a sixth sense, the sense
of balance, which is influenced by the force of gravity.
This of course is a vital factor in the control of movement.
The organ of balance is also situated within the ear, (the
three semi-circular canals) and senses any alteration in
the inclination of the head with reference to the force
of the Earth’s gravity.
It is with these six senses we learn to ‘know’ about the
world directly outside our bodies, and, in our lifetimes,
to progressively accumulate knowledge or experience of
the physical world that we personally and literally come
into contact with by means of the sensory receptors of
our body. This is the only way that we can truly ‘experience’
the reality of this world and it is the only way that we
can ‘know’ with any absolute certainty.
But before we can examine how the senses enable us to deal
with reality we need briefly to consider another ‘reality’
that is often presented to us as being real as this has
a bearing on current scientific beliefs.
Metaphysics
For centuries now it has been generally taught that another
world, or another reality, exists besides this physical
world that we experience directly via our senses, the
‘meta’physical world or the spiritual world of, for example,
Gods, heaven and hell.
From birth we learn to cope with the real physical world
with the aid of our senses but we have no access to and
no perception of, i.e. our senses cannot perceive, other
worlds and other realities and any understanding of these
concepts are only learnt through association with other people.
The Greek philosopher Plato suggested that we are born
with knowledge, and to some extent this must be true as
in the animal world a Wildebeest calf will struggle to
its feet within minutes of birth and walk with no assistance
or instruction from the mother.
However Plato went further and suggested that we humans
are fully endowed with knowledge before we are born and
that all we need to do is to recall that knowledge that
is sitting dormant in our unconscious mind and that learning
is the process of the effort of recollecting this. This
idea has been largely rejected by philosophers (notably
Locke) since but of course is still of interest to those who believe
in a separate world as this, if true, would give this concept some
credibility.
This problem of credibility for those who promote the idea
of a separate existence is that only those people who from
an early age are consistently guided or instructed in it
come to accept it. The vast majority of those who are not
‘guided’ to any belief in the superstitious or in a metaphysical
existence, or who have only a passing acquaintance with
this concept, generally ignore it and have no need of it
in their lives.
Further it can be argued that only those who are guided
to believe in the ‘true god’ believe in ‘him’, while the
billions of people around the world who are guided to believe
in other ‘false gods’ do not believe in ‘him’.
Of course for those who wish to believe in a metaphysical
or spiritual existence that is their business, but believing
in something, for which there is no tangible evidence or
other sensory indication, leads to a state of mind where
it’s easier to accept and believe statements by others
on other issues and concepts which have no sound basis
in fact.
Instilling belief in a mystical all-powerful being or creator,
who for some inexplicable reason does not actually deign
to exercise his powers for the good of ‘his’ people, (for
example to prevent large scale atrocities) is a useful
ploy to gain control of large numbers of people, as the
humans who promote this concept gain status as the ‘beings’
representative on earth and as the only ones who can interpret
‘his’ will.
The development of this idea led to the accumulation of
enormous power and wealth by the Holy Roman Empire, which,
for a thousand years, effectively ruled, and taxed, all
of Western Europe during the Dark Ages.
Instilling such a belief also leads to an unquestioning
acceptance of an intangible authority and of that authority’s
definition of what is right and wrong, interpreted of course
by ‘his’ representatives. Also acceptance of a set of rules
or a doctrine of concepts of ‘right and wrong’ means that
an individual does not have to go through the often painful
process of coming to terms with their own definition of
these concepts.
Incidentally this is very handy for any secular government,
as it tends to lead the population into accepting its authority
as well. Which is why rulers of all ages have suggested
that the gods are on their side when they seek to gain
acceptance of the public for any large political enterprise
or crusade, and they of course continue to do so today.
There are a number of other problems with the idea of the
existence of a creator; the simplest and most obvious is
the question; who created the creator?
Another is more of a practical question, when the idea
of a single god that fashioned the earth was developed,
it was easier to present the earth as being the centre
of everything and that the sun and the planets and stars
revolved around it. Today we are aware that the earth is
a very minor planet orbiting around a minor star in an
average galaxy that is just one of billions of galaxies
in a universe, the size of just the portion that is ‘visible’
to us, is incomprehensibly large. In this context the earth is so
small that it is bordering on the infinite or non-existence.
In the other direction it is known now that the building
blocks, the atomic particles, of the matter that we are
comprised of and that we come into contact with are of
a similarly comparable dimension. With this in mind, the
idea of a god in the sky that achieved this incredible
feat of engineering and also created man in his own likeness
becomes unbelievable to anyone of a rational persuasion.
Faced with this information, some religious leaders have
backed off from a strictly literal interpretation of creation
in such books as the Bible.
There have been other suggestions by philosophers, such
as Hume in the 18th century, that the matter that we experience
via our senses is a figment of our imagination or mind,
however these are questions that are not of any real interest
to rational and practical people, and we will return to
the real world.
This is not intended to deny the possibility of the existence
of other sensory influences on us, which may have so lapsed
into disuse that we are not aware of them, (for example
a sensitivity to the earth’s magnetic field) but simply
to say that any supposed reality that cannot at present
be perceived directly by the senses cannot be considered
in our examination of the reality presented by human perception.
Perceptions
Having briefly considered other worlds we need to look
at how we perceive the outside world with our senses
and what are the limitations of those senses. Then to look
at how we understand the world that is beyond the direct personal experience
of our senses and how relevant the senses are in understanding
it.
As stated the visual senses command 70% of all the sensory
receptors in the human body. It is the main source of information
from the external environment and it is suggested that 90 percent
of information stored in the brain is of visual origin. It is therefore
the main influence in our relationship with the natural world in
controlling actions in it and our reactions to it.
Thus of all the senses this is the dominant sense and all
the other senses generally refer to this sense. For example
when we hear something in a natural environment it is instinctive
to turn and look in the direction of the noise to identify it, even
if you have some idea of what the cause of this is, and when you
touch something unseen and unexpected with your hand, your eyes are
drawn to this object to check on it.
In humans the clear focus of the eyes is a cone of a few
degrees in width, however the total cone of visual perception
is, in most people, very wide. This cone of perception, or rather
combined cones of each eye, covers a total arc of 180° to 200° in
a horizontal plane and up to about 145° in the vertical plane. This
cone of visual perception is the total external area from which rays
of light are directly received, through the cornea and the lens,
by the retina of the eye.
To demonstrate this sensitivity and also the wider horizontal
arc of perception, consider a person standing in the middle
of the halfway line of an empty football field focusing his eyes
straight ahead at the goal posts. If a second person on the sideline
to his right or left, say 50 metres away, walks from a position behind
him and moves into a position on the halfway line, at about 90° to
his line of vision, the eye of the first person will then detect
this movement. In other words, while the focus of the eyes is at
right angles to this image, the brain has received a visual signal
through the eyes and is aware of the incursion into this space.
The natural, primaeval instinct would then be to turn and
focus on this perceived movement to establish what this
object is and whether it is a potential danger or otherwise
worthy of interest.
If the focus is returned to the front then the eye can
track any subsequent movement of this object to a remarkable
degree of accuracy.
Every moment that we have our eyes open our brain is receiving
and processing a huge amount of information from all parts
of this total visual field. This relationship between the
retina of the eye, where rays of light are received from outside
the body, and the brain, is extremely complex, and we are usually
unaware, or rather unconscious of, the fact that our brain is processing
the vast amount of information that is received by it, and often
as to what is ultimately stored, or retained by it in long term memory.
The main use to which this sense is put and was developed
to its present acute level is to control and instruct,
or coordinate, the movement of our body and our limbs.
This ability to perceive depth or distance is made possible by the
positioning of our eyes in the head, inclined in the same direction,
at about 70 mm apart. This gives us what we call binocular vision
whereby the eyes (or rather the brain) has the ability to detect
a minute difference in angle in the light received in one eye in
relation to the light received from the same object in the other
eye and make a judgement of distance from this information.
We use this capability continuously, for example the precise
control of movement needed for picking up a simple object
such as a cup from a table would be difficult without this
visual-mental capability. To test how important this ability is,
try judging the distance to a horizontal line held in front of your
eyes about an arms length away, such as a clothes line, you will
find it very difficult to place your hand on the line as there is
no binocular perspective. If the line is now held vertically the
positioning of the hand will be precise.
This capability to perceive depth and judge distance is
very accurate at short range but progressively declines
away from the eyes, however this still enables us to have
some degree of judgement of the distance of an object up to a kilometre
or so away.
To understand the acute sensitivity of the visual senses
in this respect consider that the angle subtended by an
object that measures two or three metres in width, at say
1 km distance. This angle is an arc of less than 0.2°, or about 10
seconds of arc. This is a remarkable sensitivity that has been developed
over millions of years of evolutionary, natural selection. However
because of the narrow reference points, in other words the small
distance between both eyes, as objects recede into the distance the
accuracy of any spatial or distance judgments declines proportionately.
‘excellent accuracy of positional judgements performed
by the (human) visual system (are) of the order of 10 seconds
of arc, comparable to vernier acuity’ 1
Thus our ability to judge the distance of an object with
any accuracy is limited to an area of a few kilometres
from our present position.
Here it is important to differentiate between the visual
senses alone and the combination of the visual senses with
memory or experience. For example when we observe a tree
at some distance or a ship on the horizon, experience tells
us that this will be of a certain size, and this experience or memory
helps the visual senses to make a judgment of the distance to it.
Thus while we can see stars that are many light years away
from us, our ability to mentally interpret the distance
of an object, or our spatial ability, is limited to a range
of a few kilometres. This then is the yardstick, or the
reference by which we try to interpret or understand distances
that are greater than our own local experience.
With this in mind we can examine our understanding of distance
or space in a wider context.
Spatial Perception
The planet on which we live is a minor planet orbiting
around a minor star that is itself orbiting around the
centre of an average galaxy that sits in space amongst,
it is said, billions of other galaxies in the visible universe.
To put our position, and our isolation, in some sort of
perspective, even if we could build a spaceship that could
travel at the presently unimaginable velocity of tens of
thousands of kilometres per second it would take us thousands of
years to travel to the nearest star and back again.
Therefore, while it may be an interesting diversion or
indulgence for those who consider these matters, for the
foreseeable future speculation about the nature of the
universe outside our own solar system is of no practical
value to humankind.
Let us return then from heaven and put our feet on the
ground on earth and take a look at our existence there.
The earth’s surface is a thin crust of solid matter that
is between 40 and 70 km thick and which is supported, some
geologists suggest that it is floating, on a much deeper
layer of matter called the magma.
Much of this crust, about
70 percent, is covered by the water of the oceans. Extending
out into space from the surface of the oceans and the continents
is an atmosphere of gas. This gas decreases in density
progressively with altitude and above about 8 km it is so rarefied
so as to be unable to support human life.
As the radius of the earth is about 6400 km the crust would
represent about 0.5 percent of this and the atmosphere
in which we can live less than 0.2 percent. To put this
into some sort of context or perspective, the crust and
the liveable atmosphere combined could be compared to the
skin on an apple. On this delicately thin crust in this
narrow film of gas we exist and live our lives.
We human beings are between 1.5 and 2 metres tall and our
walking pace is about 0.5 metres. When walking we can travel
at a speed of between 50 to 100 metres in one minute, 3-6
kilometres in one hour. However most people in industrialised
countries these days rarely travel on foot and accordingly
they would have difficulty relating to how far this distance
is in practical terms. In other words the experience of
the actual physical effort combined with the time involved in walking
such distances.
For example our interpretation of the distance of 10 km
is that it takes 15 to 20 minutes travelling in a car or
a bus or a train. But to have any real concept of this
distance you would have to walk it and for a fit person
this would normally take about two hours.
The Atlantic Ocean is about 3000 kilometres across between
Ireland and Newfoundland and to walk this distance non-stop
would take around 25 days or alternatively about 75 days
of walking eight hours a day. Accordingly, if it is difficult
for most people to relate to the distance represented by
a 10 km walk, they will find it difficult to conceive the
actual size of the oceans or the Sahara Desert.
It could be suggested perhaps, that only those individuals
who have actually rowed or walked across these could be
said to have any real perception of these relatively vast
distances.
Taking this even further the circumference of the earth
is 40,000 kilometres and its radius about 6400 km, while
the sun is, in contrast, 700,000 kilometres in radius,
or over 100 times the size of the earth. The average radius
of the earth’s elliptical orbit around the sun is about
150 million km.
It is quite clear that these sorts of distances are impossible
to relate to our local perception of distance, and to understand
them, or at least to try and understand them, we need to
somehow compare these to our personal yardsticks, and the
best way that we can do this is by putting these figures
into some sort of perspective that we can relate to.
Accordingly let us reduce the sun from a diameter of about
1,300,000 kilometres to the size of a basketball at, say,
a diameter of 250 mm.
If we place this basketball at one end of an airport runway,
on this scale the earth would be a tiny ball 2.3 mm in
diameter over 50 metres away and it would take you nearly
a minute to walk to it (and have very great difficulty
in finding it). You could attempt to walk on to the outermost
planet in the solar system, Pluto, on our runway, which
in this perspective would be a particle 0.5 mm in diameter
over 2 km further away, and the walk would take you 20-30
minutes. But you would have no chance whatever of finding
it on the surface of the runway.
It is however possible that you might stumble across Jupiter
and Saturn on your way. Jupiter would be 25 mm (1 inch)
in diameter at 270 metres (four minutes walk) away from
our basketball sun and Saturn at 22 mm at 500 metres (8
minutes) away.
It is clear from this that these distances, of millions
of kilometres, are well beyond the ability of the human
mind to relate to or to grasp, as we simply have no mental
yardstick or reference to compare them to, moreover these
huge distances, incomprehensible to us are less than miniscule
in terms of the size of, even our galaxy, let alone the
size of the universe.
Thus our senses and our minds have evolved to cope with
a local environment and both are incapable of fully understanding
the dimensions of what is beyond our personal horizons.
Continued >
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