Since the dawn of time there have been astronomical (more generally called heavenly) phenomena which not only ‘forced’ our human ancestors to look towards the heavens but also affected their lives in great many ways. To mention a few of these phenomena, one should point to the never- ending succession of night by day and vice versa, the four seasons spanning across a whole year, the bright stellar constellations covering the whole of the night sky. To be a bit more specific, the four seasons would affect the humans nutrition while the stellar constellations would facilitate navigation around the then-known world (hence increase trading and the profits made from it).
Many of the very first civilisations (Egyptians, Assyrians, etc.)
glorified heavenly objects such as the sun or the moon to a point where
they considered them as the upper gods in their deities’ pantheon. One
of the first applications of astronomy appearing in the history of
human civilisation (circa 4000-1000 BC) is the adaptation of the moon
calendar to the solar year which was a bit larger than the
corresponding lunar periods. This adaptation was realised for
agricultural reasons. Another characteristic example of a civilisation
adapting its calendar to its agricultural needs is the Jews (their
calendar became solar based instead of the lunar based calendar they
originally used).
Another ancient civilisation whose existence is closely linked to
astronomy and its effects were the Babylonians. Their measurements
regarding appearance and disappearance of heavenly bodies and the
extremely accurate position monitoring of other bright planets of our
solar system (e.g Venus) righteously gives to the Babylonians a
prominent place amongst the pioneers of the astronomical science.
The Assyrians on the other hand were more cruel and crude compared to
the Babylonians even if these two share more or less the same time slot
in human history. The Assyrians treated the sun and the moon as deities
like many of the Mesopotamian people at the time, but also demonstrated
a vibrant interest in astrology and not so much in astronomy. One of
the primary reasons that they used a calendar was not for astronomical
observations or other reasons, but for astrological predictions;
Assyrians deeply believed that the effect of the stars and heavenly
bodies on the behaviour and thought of the man was quite significant.
What is even more interesting is that Assyrians in their effort to
discover and interpret omens regarding kingdoms, kings, empires etc.,
observed more closely the moon and the stars rather than the sun. This
‘preference’ was due to the fact that the sun does not present any
variations in his colour or trajectory throughout the time that he is
observable from the earth. The planets and the moon in the dark sky on
the other hand appear to have multiple trajectories (relative to the
earth of course) depending on the time of year, etc. The Assyrians’
kingdom however was dismantled by a combined effort of the Babylonians
and their allies in the late 7th century BC. This conquest marks a new
era for the science of astronomy. No more omens are exclusively sought
after in the night skies, but scientific observations and mapping
efforts of the night sky and its objects is beginning to be realised.
The town of Babylon itself which is the centre of this cultural and
scientific revolution will pass from the hands of many
conquerors…stability however is ensured throughout those transitions
and this city will become the epicentre of this astronomical evolution
up until the time of the deat of Alexander the Great roughly three
centuries afterwards.
However, it should not be forgotten that the main driving force behind
the evolution of astronomy in Babylon were the priests who, locked
inside their temple they made their observations but this situation had
one inherent disadvantage: their knowledge and scientific methods are
not documented anywhere; instead, the knowledge passed on from templar
to templar most likely.
In the years after the decay of Babylon, the Chaldeans appear and take
over further advancing the astronomical science. Greek mathematicians
at the time also use for the first time elliptical coordinates systems
to fully describe the motion of a planet inside space and not only on a
two-dimensional area (as the Babylonian priests did up to that time).
The Chaldeans created the now-famous Chaldean tables which are
essentially a whole collection of various data on motion of the planets
inside a 3-D elliptical world which is cut in two parts: an upper and a
lower part which is smaller.
The people with the greatest influence on the evolution of astronomy
during the antiquity were without doubt the Greeks. In classical plays
such as the Iliad and the Odyssey, Homer clearly mentions a series of
constellations and stars known at the time such as the Great Bear,
Orion, etc. Some of the early settlers of Greece were also forced to
migrate to the islands of the Aegean or to Asia Minor due to the harsh
morphology of mainland Greece; a side effect of this migration were
the commercial bonds developed between those various towns. Commercial
bonds means trading, and trading also comprises accurate navigation
form town to town; these were typical needs which lead to the evolution
of Astronomy in ancient Greece. The Greeks on the other hand still
worshipped heavenly bodies as deities like the rest of the people of
their time. Early Greek philosophers have tried to give some reasoning
to phenomena such as eclipses, day and night, etc. Their reasoning
however hardly had any practical value. The first to express an opinion
of value was Thales who foretold within a year an actual solar eclipse.
It is worth noticing at this point that a few Greek philosophers were
the very first to express the opinion that the earth is of spherical
shape and the moon rotates around it: they were Timaeus, Aristoteles
and Plato. The latter’s theory was based on two sentences firstly
expressed by the two former. The fact remains that by the 4th century
BC, astronomy had evolved in Greece up to a point where for example the
elliptical trajectories of individual planets were easy to be observed
throughout the year; this evolution however was nothing compared to the
corresponding revolution of other arts and philosophy of the time.
In the second century A.D Ptolemy extended the idea of the ancient
Greeks for the universe and he proposed a model where the earth was
stationary at the center surrounded by eight spheres which carries the
sun, the moon, the five know at that time planets and the stars. The
planets moved on their respective spheres and the stars which were at
the last and eighth sphere, would always stay at the same positions
relative to each other and rotate across the sky; beyond those stars it
wasn’t clear what existed. Ptolemy’s model was accurate to predict the
position of the planets, while it fails to describe accurately the
orbit of the moon. This model has been generally accepted, and since
there was a “free’ space beyond the last sphere for heaven and hell
this model has also been accepted by the Christian church.
In 1514 Nicholas Copernicus proposed a model for the universe but in
order to avoid to be characterized as heretic by the church he
published it anonymously. According to his model, the sun was
stationary at the center and the earth and the planets where moving
around it in circular motion. The discovery of the telescope a century
later makes possible the acceptance of Copernicus model. The Italian
astronomer Galileo Galilee observed that Juniper’s moon was orbiting
around Juniper and not as according to Ptolemy’s model around the
earth, while the German astronomer Johannes Kepler observed that
planets move around sun in elliptical and not circular orbits. Those
observations confirm Copernicus model for the universe, but the
explanation for the elliptical and not circular motion of the planets
came later in 1687. At this time a great publication came to life from
Sir Isaac Newton who in his published work explained the motion of the
objects with time and he put mathematical expression for those, as well
as defining the law of universal gravitation. According to him, each
body in the universe will be attracted by any other body by a force
known as gravity; this force is proportional to the mass of the bodies
and inversely proportional to the square of the distance between them.
Newton’s law of gravity gave proof that the orbits of the planets
around the sun will be elliptical as so the orbit of the moon around
the earth. The law of gravity gave a reasonable explanation on the
motion of the planets but created a paradox at the same time; since
gravity is an attractive force therefore will it cause the planets to
collide at some point with each other? Newton argued on this by
defining the universe as static and infinite; at that point, no one
thought about the possibility that the universe will expand or
contract, but they where trying to modify the law of gravity in order
to complete the “picture”. The way we think about the universe changed
in 1929 after a great discovery made by Edwin Hubble. Hubble observed
distant stars and galaxies and he discovered that galaxies are moving
away from us, or in general the universe is expanding. For an expanding
universe there was a time where the universe was still infinitesimally
dense and infinitely small, this time has been named as the Big Bang.
At that point in time the general laws of physics broke down, and if
there was time of the universe before the big bang, we are not able to
know it since there is nothing left from them. The idea of a static
universe collapsed!
The discovery of the electromagnetic theory by James Clerk Maxwell
in 1865 brought the idea that light is a wave disturbance of the
electromagnetic spectrum, which travels at fixed speeds. Albert
Einstein introduced that in the theory of relativity in 1905, according
to his theory all the laws of physics are the same independently from
the speed of the observer. The law of relativity put an end to the idea
of absolute time, since it confirmed both Newton’s and Maxwell’s
theories. In 1915 Einstein extended his theory and produced the general
theory of relativity; he found out that the universe is a four
dimensional space where time is the fourth dimension, thus the
space-time universe is not flat but it is curved by the disturbance
which is caused by the mass of any object. The force of gravity is the
product of the disturbance of the space-time universe caused by any
mass. For example the mass of the sun curves the space-time domain
while the earth is moving in a straight path in the space time domain
it appear from earth (a three dimensional space) that is orbiting in an
elliptical path. According to the law of relativity, the path of the
light is affected by the wrapped space time universe; it bends its path
so it doesn’t travel in straight line. When the light from a distant
star passes near the sun the light is bended because of the distortion
of space time universe by the mass, so for an observer on earth the
star will appear in a different position in the sky, the prediction of
general relativity confirmed by the observations made in 1919 measuring
the position of a star during an eclipse. Before the theory of general
relativity space and time was thought as static, events happening there
wouldn’t have an affect on them, after 1915 things changed the universe
defined as a dynamic quantity of space and time where each action taken
place affects it.
Essay Bibliography
- A. Pannekoek, “A HISTORY OF ASTRONOMY”, Ruskin House, George Allen and Unwin Ltd.
- J.D. North, “ the Fontana history of Astronomy and Csmology”, Fontana Press
- I.D. Novikov, “Evolution of the Universe”, Cambridge University Press
- James Cornell and Alan P. Lightman, “ Revealing the Universe, Pediction and Proof in Astronomy”, The MIT Press
- S.W.Hawking, “A Brief History of Time”, Bantam Press 1988
- J.J.C. Smart, “Problems of Space and Time”, Macmillan Pub. Co, 1964
- S.F. Mason, “A History of Sciences”, Colier, 1962
- M. Kaku & J. Thompson, “Beyond Einstein”, Oxford University Press, 1999