New Ferguson's Paradox large orrery
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“This machine is so much of an ORRERY, as is sufficient to shew [sic] the different lengths of days and nights, the vicissitudes of the seasons, the retrograde motion of the nodes of the Moon’s orbit, the direct motion of the apogeal point of her orbit, and the months in which the Sun and Moon must be eclipsed.”
-James Ferguson, 1764
This orrery is a special type of planetarium based on the
“Paradox orrery” model of James Ferguson
It can be used to aid to explain several facts about the Sun - Earth - Moon system:
Seasons of the year:
The seasons result from the Earth's axis of rotation being tilted with respect to its orbital plane by an angle of approximately 23.5 degrees. This causes that one part of the planet is more directly exposed to the rays of the Sun than the other.
If you rotate the mechanism holding the knob next to the pointer you can see that the Earth maintains its orientation as it orbits around the Sun.
If you set the mechanism approx. on 21 of June, the tilt directs to the Sun, so it is summer in the northern hemisphere and winter in the southern hemisphere. If you continue rotating counterclockwise direction you will see how the miniature Earthglobe maintains its orientation according to the seasons and month printed in the dial.
An eclipse season is one of only two periods during a year when eclipses can occur, due to the orbital inclination of the Moon. In this planetarium the Moon orbit is represented with a ring that have engraved both the ascending (north) node and
the descending (south) node.
When the nodes are aligned in the same line of the Earth and the Sun, eclipses can occur if in this period the Moon is in new moon (solar eclipse) or in full moon (lunar eclipse).
You can see how this possibility occurs by turning the pointer.
This ring rotates in the correct ratio of 18,6 years turn. The direction of the movement is retrograde respect of the Moon- Earth movement around the Sun.
The advance of the Lunar Apogee:
The lower base with the bronze pointer demonstrates the eccentricity of the Moon orbit.
The pointer displays the point of the apogee and it is easy to see its movement in the zodiac ring (ecliptic plane) that surrounds the Earth.
When the pointer is aligned between the Earth and the Sun and a node determines the possibility of an annular eclipse but if it is in the other side, the eclipses will be total.
When the pointer is opposite to the Sun it is possible to occur a supermoon in a full moon.
This pointer moves in practically the correct ratio. It rotates in advance one turn in approx. 8,85 years.
The different duration of the days troughout the year:
The earth terminator divides the daylit side and the dark night side of the earth.
Due to the tilt of the earth axis, this varies throughout the year.
It fits anywhere by its exceptional size and it is an authentic eyecatching.
If a special collector item is what you are after, this is a must.
The mechanism is made of solid brass. Sun is in solid brass. All the gears are made in a manual vertical milling machine with a manual indexing head. It is designed to last without practically any mechanical maintenance.
The brass is polished without any coat. Over time it acquires a museum like look.
The Earth globe is 12 mm in diameter. It is made of wood and covered with handpainted paper gores in the traditional style with our own cartography without text due to its miniature size. It is protected with some coats of varnish.
The dial is a high quality print with our original design that depicts the months, the seasons of the year and the zodiac. It is protected with several coats of varnish too.
The base is in solid beech wood stained in mahogany tone. It is available in sapelly wood stained in mahogany tone with the same dial.
For more information please contact.