From Pot-Boy in a Tavern to Imperial Mathematician and Astronomer
Johann Kepler was a pot-boy in a tavern, his parents were both of noble families.
But Johann got a very bad start in life. His parents had degraded themselves; they had come down in
the world. The last straw seems to have been that Johann's father had become security for a friend,
and this friend had absconded, leaving Johann's father to pay the piper. It was then that he sold
off all of value that he possessed and became a tavern-keeper, and it was in this tavern the son
worked for several years.
There was no happy home life for the boy. His mother was a woman with a terrible temper, so much so
that her husband was glad to go abroad as a soldier. Just when Johann should have been sent to
school he became a victim to smallpox. On his recovery he went to school, but after two years of
irregular attendance he was withdrawn so that he might act as pot-boy in his father's tavern. He
seems to have been kept at this menial work for five years, by which time he would be fourteen years
of age. He then returned to school, but only for a very short time, as he developed a severe
illness, while his parents, at the same time, were both suffering from smallpox.
We see that Kepler had passed the ordinary school age without any proper schooling. How different
from Tycho Brahé who had entered the University at thirteen years of age. But at the age of fifteen
years Kepler was admitted to a monastery which prepared students for the University at Tubingen.
We have been picturing this unfortunate boy without placing him in any particular part of the world,
except for the preceding paragraph. The name Johann will probably have placed him in his native land
of Germany. It is usual to speak of Kepler as John Kepler, but this has always seemed to me
unfortunate; indeed, I have found some young friends thinking of Kepler as an Englishman. Probably
this error has arisen through these young people only hearing of Kepler in connection with Sir Isaac
Newton's work. However, the birthplace of Johann Kepler was a small town about ten miles from
Stuttgart, and he was born prematurely a few days before the Christmas of 1571. He remained delicate
His time at the University was interrupted not only by repeated illnesses, but by family troubles.
It was at this time that the mother's violent temper drove the father to a foreign land, where he
died. It is reported that the mother quarrelled with every one of her relations. It is to Johann
Kepler's credit that, despite all these troubles, he succeeded in gaining his degree of Bachelor,
coming out second in the examination.
It is interesting to note that when Kepler was about twenty years of age he became a convert to the
Copernican theory, which brought the Sun to a standstill and set the Earth in motion. His conversion was
due to a lecture on the subject delivered in the University. Galileo's conversion to this theory is
supposed to have taken place about this time also, but we must remember that the surroundings of the
two men were very different. Kepler was allowed perfect freedom of thought in Germany, whereas
Galileo had no such liberty in Italy. It is interesting to note that when Galileo first heard of the
Copernican theory, he thought it was "a piece of solemn folly." However, we shall hear more of him
in the succeeding chapters.
At the age of twenty-three years Kepler became Professor of Astronomy at Gratz, but this Science was
not accounted of much importance in these days, except so far as it was of value to Astrology.
Kepler was not physically fit to become an Astronomer such as old Tycho was in Denmark at that time.
Kepler suffered from weak eyes, and his delicate constitution prohibited him exposing himself to the
night air. Neither was it as a Mathematician that Kepler excelled, but he had a wonderfully vivid
imagination, and so his strength lay in devising theories concerning the motions of the heavenly
bodies. Some people think that theories are mere guesses at the truth, but unless a "guess" or
hypothesis can be supported by established facts it is not allowed to remain. Kepler made many very
wild guesses, he has left us a record of some of these, but he did not stop there. He put all his
theories to the test. Sometimes he thought he had established them, but when he found out some error
later, he never failed to make it known, and to demolish his own theory.
But when considering the theories of others Kepler sometimes became very sarcastic. For instance,
when a new or temporary star appeared, similar to that seen by Tycho Brahé some thirty years
previously, those philosophers who were known as Epicureans put forward a theory that the new star
was due to a fortuitous concourse of atoms. Kepler wrote a good deal of sarcastic nonsense about
this, finishing up in the following fashion: "I will tell those disputants, not my own opinion, but
my wife's. Yesterday, when weary with writing, and my mind quite dusty with considering these atoms,
I was called to supper, and a salad I had asked for was set before me. 'It seems then,' said I,
aloud, 'that if pewter dishes, leaves of lettuce, grains of salt, drops of water, vinegar, and oil,
and slices of egg had been flying about in the air from all eternity, it might at last happen by
chance that there would come a salad.' 'Yes,' says my wife, 'but not so nice and well dressed as
this of mine.'"
As Kepler was not capable of being an active observer of the heavens, it was necessary that he
should rely upon the observations of others in constructing his theories. For this reason Kepler
paid a visit to Tycho Brahé at Prague, to which I referred in the preceding chapter. At that time
Tycho would be about fifty-four years of age, while Kepler would be twenty-nine. After returning
home from that visit, Kepler received a pressing invitation from Tycho to become his assistant, and
so Kepler and his wife set out for Prague. Again misfortune overtook our hero. He fell ill on the
journey and was delayed for seven months. During that time all his savings disappeared, and he had
to ask Tycho for financial assistance.
Tycho and Kepler became the best of friends. They undertook to compute a new set of Astronomical
Tables, which would entail an enormous amount of labour, but Tycho died in that same year.
Kepler was appointed to Tycho's post of Imperial Mathematician, and he was promised a liberal salary
by the Emperor, but unfortunately the Treasury was already overtaxed by heavy war expenses, and
Kepler's salary was always in arrears. Indeed, Kepler did not receive enough to keep him and his
family, and he had to set up as an Astrologer, while he continued his real astronomical work in
earnest. He was not in earnest about Astrology; we saw that Tycho Brahé was a real Astrologer,
believing in his own predictions. Kepler was only an Astrologer in the same sense as we have
fortune-tellers at country fairs to-day; merely as a means of livelihood. There was this difference,
that the modern Astrologer often knows nothing of Astronomy.
Kepler did not like to resort to this means of making money. A few years later, when he had to raise
funds in a similar manner, he wrote: "I have been obliged to compose a vile prophesying Almanac,
which is scarcely more respectable than begging." Kepler was scarcely ever free from money
difficulties, and it is all the more creditable to him that he did such excellent work.
The most outstanding of Kepler's discoveries are those truths known to the student as Kepler's
Laws. The first of these laws states that the planets move in ellipses, with the Sun in one
focus. This was a truly great discovery. The famous philosopher Aristotle had said that the heavenly
bodies moved in circles, and we have seen that there was no doubt in Aristotle's mind, for the
the only perfect and natural motion. And because Aristotle had declared this long ago, generation
after generation accepted the statement as an established fact. Astronomers could not get the
motions of the planets to agree with a simple circular motion. They made an elaborate system of one
circle carrying another circle. Then, believing the earth to be the centre around which the planets
moved, they placed the Earth at some distance from the true centre in order to try and account for
the different positions of the planets at different times. All this arrangement developed by
Ptolemy, and known as the Ptolemaic System, was very much complicated.
How, then, did Kepler discover that the path of a planet is of an oval or elliptic form? Simply by
guessing one thing, and when he found that would not do, guessing another possible solution. But it
required a strong mind to break away from the universally accepted doctrine of Aristotle.
As we are considering only the life of Kepler, we need not detail the other two laws which he
discovered. We are more concerned about the welfare of our hero, whose scientific ardour could not
be extinguished by all the worries of this life.
About this time his wife became very seriously ill, and before she had recovered, their three
children were attacked by smallpox, which caused the death of his favourite son.
There seemed little use in Kepler remaining at Prague, as mere promises of payment of salary would
not meet his household bills. And so he set out for Austria, where he believed he might obtain a
Chair of Mathematics. On his return home he found his wife in a very despondent
condition, and not long afterwards she was attacked by an infectious fever which proved fatal.
Kepler felt that his son and daughter required the care of a mother, so he decided to marry again.
He asked his friends to select a suitable wife for him. Why he adopted this plan is not quite clear.
To suppose that it was because he was too engrossed with his studies to trouble about the details of
such an affair does not explain matters, for he had to consider no less than eleven different
The first candidate was a widow, who had been a family friend, but when Kepler, who had not seen the
lady for some years, heard that she had decided in the end not to accept his offer, his description
of her was that "there is no single pleasing part about her." This lady had two marriageable
daughters, and later on these young ladies were added to Kepler's list. His reason for refusing one
of the other candidates was that she had learned nothing but showy accomplishments. Another was too
old, while another was "too proud of her birth and quarterings." In one case the courtship lasted
several months, but in the end the lady jilted him.
Kepler's description of another selected candidate makes amusing reading: "She has, undoubtedly, a
good fortune, is of good family, and of economical habits; but her physiognomy is most horribly
ugly; she would be stared at in the streets, not to mention the striking disproportion of our
figures. I am lank, lean, and spare; she is short and thick: in a family notorious for fullness, she
is superfluously fat."
Kepler was at this time a little over forty years of age, but he refused the eleventh selection of
because of her excessive youth. The final result was that he went back to number five on his list,
and declared that she was the one he had really been in love with all the time. Kepler says of her:
"Her person and manners are suitable to mine, no pride, no extravagance. She can bear to work; she
has a tolerable knowledge how to manage a family; middle-aged, and of a disposition and capability
to acquire what she still wants."
Kepler had settled down with his new wife, when he received the offer of a professorship in Italy.
This offer was respectfully declined; his reason was that he would not have the freedom of speech to
which he was accustomed. The wisdom of this decision will become apparent when we consider the life
of Galileo in the succeeding chapter.
Kepler's financial troubles were not at an end yet, the Government were always far in arrears with
It is interesting to note that he dedicated one of his books to King James I of England. But why he
did so is not quite clear. Possibly because King James had shown interest in the work of Tycho
Brahé. Of this book Kepler wrote: "The die is cast; the book is written, to be read either now or by
posterity, I care not which. It may well wait a century for a reader, as God has waited six thousand
years for an observer." However, not long after the publication of his Harmonies of the
World Kepler received a visit from the English Ambassador at Vienna, and we may presume
that this visit was owing to the dedication of the book to King James. The Ambassador urged Kepler
to take up his residence in England, but Kepler declined this invitation. To those of us living in
these Islands it is amusing to read that one of Kepler's
reasons was that he "dreaded the confinement of an island." One wonders if Kepler's geography were
Kepler received a very handsome offer from the Duke of Friedland, one of the most distinguished men
of that day, to take up his residence in Silesia. At last Kepler's misfortunes seemed to be at an
end. The Duke treated him liberally. He provided him with an assistant for his calculations, and he
presented him with a printing press. He also obtained for Kepler a professorship.
Later we find Kepler making one more attempt to get his arrears of pension paid by the Imperial
Assembly. Probably Kepler thought to provide for his wife and family; he was now fifty-eight years
of age. However, his mission was useless, and this seems to have worried him. His health, never
good, was weakened by over-study, and he died at the close of his fifty-ninth year, leaving his wife
and seven children. They were left very poorly off, but they would have been comparatively rich had
the long arrears of their father's pension been paid.
Kepler led a very busy life. He published no less than thirty-three separate works, and left
twenty-two volumes of manuscript. In addition to his astronomical work, he was a pioneer in the
region of Optics. He was a devout Christian, and a serious student of the Holy Scriptures.