Abstract
For thousands of years, humans on Earth across all cultures knew of seven luminaries: The Sun; the Moon; and five planets, Mercury, Venus, Mars, Jupiter, and Saturn, all of which move relative to the fixed stars. The number seven was therefore considered special and sacred (Chap. 10, Vol. 1) and the possibility that there could be more than five planets had never entered anyone’s mind. After Copernicus proposed the heliocentric model, the Solar System was centered around the Sun, which had six planets (including the Earth) revolving around it. The Earth, therefore, became a part of the cosmic structure. Although the positions of the Solar System objects were re-arranged, the total number of celestial objects remained the same. When Galileo began his telescopic observations, he found that Jupiter has four moons similar to the Earth’s Moon (Chap. 20, Vol. 1). So, the Solar System consisted of a total of 11 objects: The Sun, six planets, and five moons. The special significance given to the number seven was therefore no longer secure.
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Notes
- 1.
In Planetary Hypothesis, Ptolemy listed the minimum and maximum distances to Mercury as 64–166 Earth radii, and to Venus as 166–1079 Earth radii.
- 2.
The Bode’s law can be expressed in a simple arithmetic form: a = 0.4 + 0.3 × 2n, where a is the orbital radius of a planet in units of AU, and n = –∞,0, 1, 2, 3, 4, 5, 6, 7 for Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, and Neptune, respectively.
- 3.
To the laymen, the term “law” suggests “authority”, but in science “law” means an empirical relationship which may or may not be real. Bode’s law is an example of the latter.
- 4.
Pallas was discovered in 1802, Juno in 1804, Vesta in 1807, followed by more smaller objects.
- 5.
The maximum elongation of Mercury is not a constant value because of its elliptical orbit and the inclination of its orbital plane relative to the plane of the ecliptic.
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Kwok, S. (2021). New Members of the Solar System. In: Our Place in the Universe - II. Springer, Cham. https://doi.org/10.1007/978-3-030-80260-8_6
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DOI: https://doi.org/10.1007/978-3-030-80260-8_6
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