Part 15 (1/2)

If the Earth turns in twenty-four hours upon itself, a point upon the equator would simply travel at a rate of 465 meters (1,525 feet) per second This speed, while considerable in comparison with the move compared with the fantastic rapidity at which the Sun and stars would have to lobe

Thus we have to choose between these two hypotheses: either to make the entire Heavens turn round us in twenty-four hours, or to suppose our globe to be animated by a motion of rotation upon itself For us, the impression is the same, and as we are insensible to the motion of the Earth, its immobility would seem almost natural to us So that, in last resort, here as in many other instances, the decision o ress of Astronomy has confirmed the rotary movement of the Earth in twenty-four hours, and its movement of revolution round the Sun in a year; while at the sareat nu planet

The learned philosophers of antiquity divined the double ht it o, and the ancient authors quote a others Nicetas of Syracuse, and Aristarchus of Sa the first to promote the doctrine of the Earth's movement But at that remote period no one had any idea of the real distances of the stars, and the argument did not see discussion of the diurnalas his principal reason that if the Earth turned, the objects that were not fixed to its surface would appear to move in a contrary direction, and that a body shot into the air would fall back to the West of its starting-point, the Earth having turned ht, because the Earth controls not only all the objects fixed to the soil, but also the atht veil, and all that exists upon its surface The ats and beings, all are adherent to it andin its movement, as sometimes happens to ourselves in the compartment of a train, or the car of an aerostat When, for instance, we drop an object out of such a car, this object, animated with the acquired velocity, does not fall to a point below the aerostat, but follows the balloon, as though it were gliding along a thread The author has made this experiment more than once in aerial journeys

Thus, the hypothesis of the Earth's , direct proof is not wanting

1 The spheroidal shape of the Earth, slightly flattened at the poles and swollen at the equator, has been produced by the rotary enders

2 In virtue of this centrifugal force, which is at its ht in proportion as they are farther real force is alal force, the length of the pendulum in seconds is shorter at the equator than in Paris, and the difference is one of 3froht, should follow the vertical if the Earth were ht deviation to the East, of the plumb-line that marks the vertical Wethe recent experinificent experiment of Foucault at the Pantheon, just renewed under the auspices of the Astronomical Society of France, demonstrates the rotary motion of the Earth to all beholders A sufficiently heavy ball (28 kilograms, about 60 pounds) is suspended from the dome of the edifice by an excessively fine steel thread When the pendulum is in motion, a point attached to the bottoe upon two little heaps of sand arranged some yards away from the center

At each oscillation this point cuts the sand, and the furrow gets gradually longer to the right hand of an observer placed at the center of the pendulum The plane of the oscillations remains fixed, but the Earth revolves beneath, from West to East The fundamental principle of this experiment is that the plane in which any pendulum is made to oscillate remains invariable even when the point of suspension is turned This demonstration enables us in so under our feet

The annual displaceain confir the course of the year, the stars that are least remote from our solar province appear to describe minute ellipses, in perspective, in the Heavens These small apparent variations in the position of the nearest stars reproduce the annual rotation of the Earth round the Sun, in perspective

We could adduce further observations in favor of this double iven are sufficiently convincing to leave no doubt in the mind of the reader

Nor are these two the only lobe is rocked in space To its diurnal rotation and its annual rotation we may add another series of _tenthe constantly renewed It is, however, ies to enter into the detail reserved for et that our present aie as simply as possible, and to offer our readers only the ”best of the picking”

The two principal ive us the measure of time, the day of twenty-four hours, and the year of 365-1/4 days

The Earth turning upon itself in twenty-four hours from West to East, presents all its parts in succession to the Sun fixed in space

Illuminated countries have the day, those opposite, in the shadow of the Earth, are plunged into night The countries carried by the Earth toward the Sun haveThose which receive the rays of the day-star directly have noon; those which are just opposite have ives us the measure of time; it has been divided arbitrarily into twenty-four periods called hours; each hour into sixty minutes; each minute into sixty seconds

In consequence, each country turns in twenty-four hours round the axis of the Earth The difference in hours between the different regions of the globe is therefore regulated by the difference of geographical position The countries situated to the West are behind us; the Sun only gets there after it has shone upon our meridian When it is midday in Paris, it is only 1151 AM in London; 1136 AM in Madrid; 1114 AM

at Lisbon; 1112 AM at Mogador; 706 AM at Quebec; 655 AM at New York; 514 AM in Mexico; and so on The countries situated to the East are, on the contrary, ahead of us When it is noon in Paris, it is already 56 minutes after midday at Vienna; 125 PM at Athens; 221 PM at Moscow; 316 PM at Teheran; 442 PM at Bo of real times, and not of the conventional times

[Illustration: FIG 60--Motion of the Earth round the Sun]

If we couldatith the Sun, we should have hi round the world froains by one day; in taking the opposite direction, from East to West, one loses a day

In reality, the exact duration of the Earth's diurnal rotation is twenty-three hours, fifty-six minutes, four seconds That is the sidereal day But, while turning upon itself, the Earth circulates upon itsobt, and at the end of a diurnal rotation it is still obliged to turn during three minutes, fifty-six seconds in order to present exactly the same meridian to the fixed Sun which, in consequence of the rotary period of our planet, is a little behind The solar day is thus one of twenty-four hours There are 366 rotations in the year

And now let us come back to the consequences of the Earth's motion In the first place our planet does not turn vertically nor on its side, but is tipped or inclined a certain quantity: 23 27'

Now, throughout its annual journey round the Sun, the inclination remains the same That is what produces the seasons and clier circle to travel over in the heer days, those which have a smaller circle, shorter days At the equator there is constantly, and all through the year, a twelve-hour day, and a night of twelve hours