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These days, no one with a clear mind questions facts like
roundness of the earth or it’s rotation around the sun.
It seems easy and obvious when
we can watch it on pictures like that.
Lots of people can’t get over fact that our ancestors
could believe that Earth isn’t globe.
But sciences like Physics are based on the facts that can be verified through experiment.
And simple experiment based on looking far away…
... suggests ...
... the Earth is flat.
I think this opinion wasn’t supported by members of the expedition
which commenced 10th August Anno Domini 1519.
10 August 1519 – Ferdinand Magellan's journey begins
21 April 1521 – Magellan dies on Mactan island in the Philippine archipelago killed by natives
6 September 1522 – expedition led by first officer Juana Sebastian Elcano returns to Spain after traveling around 60.5 thousand kilometers during three years.
No one could have any more doubts if the Earth is globe.
Although indications pointing to this conclusion have been spotted much earlier.
You don’t need any specialized equipment nor much physics knowledge to observe
ship fading over horizon or Moon with Earth shadow cast over it during the eclipse.
Thanks to this it was already possible to conclude what’s Earth shape in ancient times.
Earth perimeter was measured around year 230 B.C. by Eratosthenes by comparing length of
shadows casted at noon, during summer solstice between Syene, currently Aswan in Egypt next to Nil, and Alexandria.
He assumed that both citied lay on same meridian which is close enough to reality
and sunrays reaching Earth are almost parallel.
Sunrays were falling exactly upright on the Earth surface in Syene
while in Alexandria there was 7.2 degree angle which is 1/50 of full angle.
Based on this results Eratosthenes concluded that distance between Syene and Alexadria is equal to 1/50 of earth perimeter
giving its value of approximately 40 000 km.
Today we know that Earth, which isn’t perfect globe, average perimeter value is 40 041 km.
Therefore Eratosthenes result is surprisingly accurate.
So called geocentric model was created based on knowledge that Earth is globe and simple
conclusions from observing surrounding us celestial bodies.
It assumed that the Earth is placed in center of the universe and everything else is travelling around it.
Discovery it’s otherwise we owe to Nicolaus Copernicus.
Born 19th February 1473 in Toruń started studies at Cracow Academy in 1491
where in year 1495 he received Master of Science title.
In his studies, Nicolaus Copernicus observed the movements of the stars at the sky
which after only a short moment looks like this.
Plotting the observed celestial bodies trajectories in the perspective of months, further complicates the situation.
Creating a model that would determine the positions of stars and planets, understand their
movements and role of the Sun was one of interesting research goals at that time.
Such model would allow to reform generally used Julian calendar
and solve time measurement problems. Other theories tried to
explain why we see so strange trajectories of stars,
until fresh and revolutionary model was proposed by Copernicus.
In the middle of everything is the Sun,
Thus indeed, as though seated on a royal throne,
the Sun governs the family of planets revolving around it.
Pope was initially interested in the Copernicus theory, which was explained to him on special meetings.
However arguments taken both from biblical cosmology and science were brought up
as contradiction to heliocentrism.
Regarding Scripture arguments, it should be noted
that opponents of the heliocentric theory were not only among the dignitaries of the Catholic Church.
The great reformers Martin Luther and John Calvin considered Copernicus theory an insult to God.
Passage where Joshua stops the movement of the Sun in the sky was brought up as one of argument.
Galileo fought stubbornly with those ideas, explaining
that Joshua goal was to show power of the Lord God to people instead of trying
to explain them stars movement on the sky.
As for scientific arguments, the biggest heliocentrism problem
was so-called parallax effect.
Prominent Danish astronomer Tycho Brahe decided to deal with this issue.
If the Earth revolves around the Sun, then it occupies different position in space during different seasons.
Based on that fact, stars should be visible in a slightly different locations on the sky
depending on the season. Half of the angle between the straight lines indicating the location
of the star from the Earth perspective, as shown in the animation, is called the parallax angle.
However, over the years stars were seen always in the same place!
Parallax effects turned out not to exist. Thus Copernicus theory had to be false.
Thus Copernicus theory had to be false.
Was it so strange that the Church was not pleased with the work that was in conflict
with general Christian understanding of the universe structure?
What should have been done with the theory that not only was incompatible with Scripture
but also with scientific experiment?
Index librorum prohibitorum -- records of works banned for their harmful content, conducted by the Supreme Sacred Congregation
of the Roman and Universal Inquisition.
God's mills grind slowly, and the Church has never been hasty to condemn.
Therefore 73 years have passed since The Revolutions of Heavenly Spheres appeared in print,
until the work was prohibited.
Unfortunately, Copernicus died without having seen the solution to the problem of parallax.
And what’s the solution? Well, parallax angle exist, but back then it was immeasurably small
because of distance from sun to nearest star, which is Alpha Centauri, its value is 0.76 arc second.
Then it was hard to accept fact that stars are so unimaginably far away.
Alpha Centauri is about 4.3 light years, which is 300 000 times farther then the Sun.
What kind of devices were available to Copernicus that he wasn’t able to measure such small angles?
Probably to most of us lunette seems as basic working tool for astronomer.
However lunettes weren’t created until seventeenth century.
We’re currently in Jagiellonian University Museum Collegium Maius,
where copies of instruments on which Copernicus worked can be found. Let's take a look at them.
Quadrant was used to measure the height of sun or moon above the horizon.
Watching the shadow cast by pin called the gnomon it was possible to read the angle.
For more accurate angle measurements of other celestial bodies, Copernicus used triquetrum,
called Lineal Ptolemy. It’s an isosceles triangle, with adjustable base length.
Pinpointing of observed object was conducted through peep sights placed on the top bar.
Then we check the base length on the scale.
To determine the size of the angle, at which the object is seen in relation to the zenith,
we have to use values from table, which were calculated by Copernicus.
Today we would call this calculation the value of trigonometric sine function,
but at the time of Copernicus, trigonometric functions were still unknown.
The most complex device was armillary sphere or spherical astrolabe.
It’s a celestial sphere model, which is apparent sphere seen by an observer from the Earth.
It’s composed of six rings with scales.
These rings were adjusted in characteristic corresponding planes, like for example
equator or illusory Sun path across the sky. Then pinpointing through the peep sights,
in the same way as using triquetrum, coordinates could be read in reference systems
used by astronomers.
Apparatus able to measure real parallax angle appeared in the nineteenth century,
and it was measured just in 1839 while Kepler's laws and the theory of gravity,
buried geocentrism much earlier.
In the history of the heliocentric theory the most interesting fact is that at the time of its creation
remained less consistent with the experiment than the false geocentric theory.
Still, some scholars have insisted on it, and the scientific intuition told them to promote
Copernicus theory as the right one.
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Ok I have to go cuz he’s coming.