— Archimedes (287 – 212 BCE), demonstrating that the Greeks knew the world’s shape.
It so happens that
the earth and the universe have the same centre, for the heavy bodies do move also
towards the centre of the earth, yet only incidentally, because it has its centre
at the centre of the universe. As evidence that they move also towards the centre
of the earth, we see that weights moving towards the earth do not move in parallel
lines but always at the same angles to it: therefore they are moving towards the
same centre, namely that of the earth. It is now clear that the earth must be at
the centre and immobile … From these conclusions it is clear that the earth does
not move …
— Aristotle (384 – 322 BCE), showing how you can reach a wrong conclusion from the
right facts.
But this is not found
to be the case; and therefore the alleged cause is not the true one. Let us then
examine into the natural cause. The surface of every liquid body, when at rest,
is spherical and concentric with that of the earth; and, if the liquid be not at
rest, it moves until it attains such a surface. If then we take two vessels and
pour water into each, and, after filling the siphon and closing its extremities
with the fingers, insert one leg into one vessel plunging it beneath the water,
and the other into the other, all the water will be continuous, for each of the
liquids in the vessels communicates with that in the siphon … as soon as the water
is continuous it must inevitably flow into the lower vessel through the channel
of communication, until either all the water in both vessels stands at the same
height, or one of the vessels is emptied.
— Hero of Alexandria (1st century CE), on the siphon.
If the extent of the
Atlantic Ocean were not an obstacle, we might easily pass by sea from Iberia to
India, keeping in the same parallel.
— Eratosthenes (c. 275 – 194 BCE).
These men made a statement
which I myself do not believe, though others may, to the effect that as they sailed
on a westerly course round the southern end of Libya [Africa], they had the sun
on their right — to the northward of them. This is how Libya was first discovered
to be surrounded by sea …
— Herodotus (c. 480 BCE – 425 BCE), The Histories,
Book 4, Penguin Classics, 284.
To be sure, the great
majority of writers agree that the earth is at rest in the centre of the universe,
so that they consider it unbelievable and even ridiculous to suppose to the contrary.
Yet, when one weighs the matter carefully, he will see that this question is not
yet disposed of, and for that reason is by no means to be considered unimportant.
Every change of position which is observed is due either to the motion of the observer,
or of the observed object, or to motions in different directions of both …Now the
earth is the place from which we observe the revolution of the heavens and where
it is displayed to our eyes. Therefore, if the earth should possess any motion,
[it] would be noticeable in everything that is situated outside of it, but in the
opposite direction, just as if everything were travelling past the earth. And of
this nature is, above all, the daily revolution. For this motion seems to embrace
the whole world, in fact, everything that is outside the earth, with the single
exception of the earth itself … This opinion was actually held by the Pythagoreans
Heracleides and Ekphantus and the Syracusean Nicetas (as told by Cicero) in that
they assumed the earth to be rotating in the centre of the universe …
If therefore, one
should maintain that the earth is not in the centre of the universe, but that the
difference between the two is not great enough to be measurable on the sphere of
the fixed stars, but on the other hand noticeable and recognisable on the orbits
of the sun and the planets; and if further he were of the opinion that the motions
of the latter for this reason appear irregular, just as if they [revolved around]
another centre than that of the earth such a person might, perhaps, have assigned
the true reason for such apparently irregular motions. For since the planets appear
now nearer, now more distant from the earth, this betrays necessarily that the earth
is not at the centre of these circular orbits.
— Nicolas Copernicus (1473 – 1543), de Revolutionibus
Orbium Caelestium.
This world is more
wonderful than convenient
— Henry David Thoreau (1817 – 1862), Commencement oration, Harvard, 1837.
Can anyone be so foolish
as to believe that there are men whose feet are higher than their heads, or places
where things may be hanging downwards, trees growing backwards, or rain falling
upwards? Where is the marvel of the hanging gardens of Babylon if we are to allow
of a hanging world of the Antipodes?
— Lucius Caelius Firmianus Lactantius (4th century), quoted by Daniel Boorstin,
The Discoverers.
‘Belief in Antipodes’
became another stock charge against heretics prepared for burning. Some few compromising
spirits tried to accept a spherical earth for geographic reasons, while still denying
the existence of Antipodean inhabitants for theological reasons. But their numbers
did not multiply.
— Daniel Boorstin, The Discoverers, Dent,
1984, 108.
The apparatus is very
simple; it consists of a wooden arm, 6 feet long, made so as to unite great strength
with little weight [it was a truss structure]. This arm is suspended in an horizontal
position, by a slender wire 40 inches long, and to each extremity is hung a leaden
ball, about 2 inches in diameter; and the whole is inclosed in a narrow wooden case,
to defend it from the wind.
As no more force is
required to make this arm turn round on its centre than what is necessary to twist
the suspending wire, it is plain, that if the wire is sufficiently slender, the
most minute force, such as the attraction of a leaden weight a few inches in diameter,
will be sufficient to draw the arm sensibly aside. The weights which Mr. Michell
intended to use were 8 inches in diameter. One of these was to be placed on one
side of the case, opposite to one of the balls, and as near as it could conveniently
be done, and the other on the other side, opposite to the other ball, so that the
attraction of both these weights would conspire in drawing the arm aside; and, when
its position, as affected by the weights, was ascertained, the weights were to be
removed to the other side of the case, so as to draw the arm the contrary way, and
the position of the arm was to be again determined; and, consequently, half the
difference of these positions would show how much the arm was drawn aside by the
attraction of the weights.
In order to determine
from hence the density of the earth, it is necessary to ascertain what force is
required to draw the arm aside through a given space. This Mr. Michell intended
to do, by putting the arm in motion, and observing the time of its vibrations, from
which it may easily be computed.
— Henry Cavendish (1731 – 1810), Scientific
Papers, published 1921.
I have made here [in
San Domingo] a simple pendulum of steel which I have made as invariant as possible.
It has a bob of [12 kilograms], about [12 centimetres] in diameter and [3 centimetres]
deep. To keep it swinging true, I have put on the rod a crossbar of iron to serve
as an axis, at right-angles to the rod. The instrument is mounted on a tempered
steel knife-edge on two steel springs. These two springs are mounted on a copper
plate in which there is a hole for the rod. The plate rests on a stool [1.5 metres]
high, and is levelled by three screws …
— Pierre Bouguer (1698 – 1758), letter from Bouguer to René de Réaumur in 1735.
We used the barometer
that we set up to study the balance between the weight of the mercury and the air
in all the accessible parts of the atmosphere. We saw how many feet we had to rise
or descend to make the mercury change height by one line. It is then necessary to
find the specific weight of air that balances other bodies. In this way, I have
found by comparison with copper that on the top of Pichincha, there is a loss from
unity of 1/11 000. Now it follows that the weight of my simple pendulum also loses
1/11 000 part of its weight. This loss produces a similar reduction in the restoring
force, and naturally, I found the pendulum to be slow by 1/11 000. To correct this
loss, it was necessary to adjust the pendulum’s length by 4/100 of a line …
— Pierre Bouguer (1698 – 1758), ‘Memoirs Sur le Pendule’, Memoire de Physique, IV,
pp. B-33, B-34.
Since the discovery
by Richer of the shortening of the pendulum near the Equator, several observers
have reported results from different places and at different times. It would have
been useless to repeat these measures if we could not improve on the accuracy of
the first observers; but if the accuracy of a set of measures is to be judged, it
seems to me necessary that the methods of operation should be described. I have
never feared to present to the Académie the details of my experiments, showing the
care taken, and the degree of accuracy; I still say that this is the minimum acceptable
in the circumstances to let the reader do the same.
— Charles Marie de La Condamine (1701 – 1774), Memoires de l’Academie Royale des Sciences, 1735, reprinted in Memoires sur le Pendule, no date, 4.
In this country, night
and day were of more even length than in either Greenland or Iceland: on the shortest
day of the year, the sun was already up by 9 a.m., and did not set until after 3
p.m.
— Grænlendinga Saga, chapter 3, Penguin
Classics, 56.
‘My guide … Where
is now the ice?
How standeth he in posture thus revers’d?
And how from eve to morn in space so brief
Hath the sun made his transit?’ He in few
Thus answering spake; ‘Thou deem’st thou art still
On th’ other side of the centre, where I grasp’d
Th’ abhorred worm, that boreth through the world.
This wast on th’ other side, so long as I
Descended; when I turn’d, thou didst o’erpass
That point, to which from ev’ry part is dragg’d
All heavy substance. Thou art now arriv’d
Under the hemisphere oppos’d to that,
Which the great continent doth overspread …
— Dante Alighieri (c. 1265 – 1321), The Divine
Comedy: Hell, canto XXXIV, 95-108, translated by Henry Cary, 1814, and travelling
down through a spherical earth.
It is now evident
that this earth really moves though to us it seems stationary. In fact, it is only
by reference to something fixed that we detect the movement of anything. How would
a person know that a ship was in movement, if, from the ship in the middle of the
river, the banks were invisible to him and he was ignorant of the fact that water
flows? Therein we have the reason why every man, whether he be on the earth, in
the sun or on another planet, always has the impression that all other things are
in movement whilst he himself is in a sort of immovable centre; he will certainly
always choose poles which will vary accordingly as his place of existence is the
sun, the moon, Mars, etc.
— Nicolas Cusanus (Nicholas Krebs of Cusa) (1401 – 1464).
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