In the Beginning: Compelling Evidence for Creation and the Flood - Theories Attempting to Explain the Origin of Comets

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[ The Fountains of the Great Deep > The Origin of Comets > Theories Attempting to Explain the Origin of Comets ]

Theories Attempting to Explain the Origin of Comets

Seven modern theories have been proposed to explain the origin of comets. Each theory will be described as an advocate would. Later, we will test each theory with the characteristics of comets, listed above, that require an explanation.

Questions Precede Advances

Scientific advances require recognizing anomalies—observations that contradict current understanding and show a need for deeper insight. Unless anomalies are recognized, scientists lose focus, researchers become complacent, and future discoveries are delayed. Although comet experts will acknowledge many anomalies, textbooks seldom mention them, so teachers rarely hear about them. Consequently, students (and our next generation of teachers) are deprived of much of the excitement of science. Critical thinking skills are not fully developed.

Some important conclusions about comets involved several scientists and were gradually accepted. However, for simplicity and to show the flow of progress, only one scientist and date are listed in each row below.

Current anomalies are italicized. While each major discovery removes some earlier anomalies and false ideas, each discovery raises new questions. Notice how the major questions preceding 1868 have been answered, and the hydroplate theory answers the italicized question remaining since 1868. Pointing out anomalies in science may draw the wrath of some scientists, but it advances knowledge and can increase the interest and excitement of students.

Table 16. Progress and Problems in Understanding Comets
Date	Conclusions and Questions	Scientist	Reference
340 B.C.	Comets are not planets, because comets change appearance quickly and do not travel in the narrow planetary path across the sky.	Aristotle	Lee⁹⁸
A.D. 63	Many comet characteristics show that they are not stars, planets, fires, or atmospheric phenomena. [Falsified existing theories.]	Seneca	Corcoran⁹⁹
635	Comet tails generally point away from the Sun. [Implies that comets have some relationship to the Sun.]	Li Chung-feng	Y, 46–47
1577	Comets do not travel inside Earth’s atmosphere, but beyond the moon and into “the realm of the planets.”¹⁰⁰	Brahe	B;¹⁰¹ PLB¹⁰²
1665	Specific comets reappear. [This idea is usually credited, incorrectly, to Edmond Halley. When Robert Hooke made his proposal, Halley was 9 years old.]	Hooke	Pepys¹⁰³; SD, 48
1680	Comets do not travel in straight lines. Their paths are [almost] parabolas.	Dörffel	Y, 99; PLB, 70
1687	Because comets are usually seen near the Sun, comets orbit the Sun. Vapor surrounding the nucleus brightens when near the Sun. Comets obey Newton’s law of gravity. [Because they obey fixed, natural laws, they do not portend human disasters.]	Newton	Newton¹⁰⁴
1698	Six numbers, called orbital elements, describe a comet’s movement if planetary perturbations and non-gravitational effects can be neglected. Orbital elements help identify returning comets seen earlier.	Halley	W, 37–40
1705	No incoming comets are on obviously hyperbolic orbits. [No known comets come from outside the solar system.]	Halley	PLB, 124
1759	With great computational effort to adjust for planetary perturbations, comet positions can be calculated (with fair accuracy) about a thousand years forward or backward.	Clairaut	W, 43
1805	Comets have low densities and are largely made of water-ice.	Laplace	Whipple¹⁰⁵
1812	Comets’ elongated and widely inclined orbits are best explained by an explosion in the solar system.	Lagrange	Y, 304–305
1819	Comets shine by reflected light, not by their own light.	Arago	PLB, 167
1864	Spectral analyses of a comet’s light reveal some of its chemical composition.	Donati	Y, 214; W, 106
1866	Meteor streams are associated with comets.	Schiaparelli	W, 97
1868	Why do comets contain organic molecules? What was the source of the carbon?	Huggins	SD, 146–155
1884	How could so many fragile comets with short life spans be forced into Jupiter’s family?	Proctor	Proctor¹⁰⁶
1925	How could comets survive for billions of years?	Russell	B, 67
1948	Why are there so many short-period, prograde comets and so many long-period, retrograde comets?	van Woerkom	van Woerkom³³
1950	Near-parabolic comets fall toward the Sun with large, but remarkably similar, energies.	Oort	Oort⁸⁶
1973	Comets cannot form far from the Sun.	Öpik	Öpik¹⁰⁷
1986	About once every 3 seconds, a small comet hits the Earth’s upper atmosphere and vaporizes.	Frank	Frank⁶⁴
1986	Why didn’t small comets form more lunar craters and put more water on Earth, Venus, and Mars?	Donahue	Donahue¹⁰⁸
1998	Comets are unusually rich in heavy hydrogen. Where did comets get it?	Meier	Meier⁶²
Abbreviations in the right column are B=Bailey et al., PLB=Peter Lancaster Brown, SD=Sagan and Druyan, W=Whipple (Mystery of Comets), Y=Yeomans. Page numbers usually follow each abbreviation. See endnotes for complete citations.

Hydroplate Theory. Comets are literally out of this world. As the flood began, the extreme pressure in the interconnected subterranean chambers and the power of supercritical water exploding into the vacuum of space launched material that later merged to become about 50,000 comets, containing less than 1% of the water in the chambers. (These estimates will be derived later.) The chapter on “The Origin of Earth’s Radioactivity,” beginning on page 387, will explain the source of most of this launch energy and the great abundance of heavy hydrogen in comets.

As subterranean water escaped, the chambers’ pillars were crushed. Also, the 60-mile-high walls along the rupture were unstable, because granitic rock is not strong enough to support a cliff greater than 5 miles high.⁸² The bottom portions of the walls were crushed into large blocks which were swept up and launched by the fountains of the great deep. Carried up with the water were eroded dirt particles, minerals that form only in scalding-hot, high-pressure, liquid water, pulverized organic matter (especially cellulose from preflood forests), and even bacteria.

As explained in "Rocket Science" on pages 598–599, droplets in this muddy mixture froze quickly in outer space. The expanding spheres of influence of the larger rocks captured more and more smaller rocks and ice, which later merged gravitationally to form comets. Five days later, comets and rocks began hitting the Moon and formed large basins. [See pages 603–609.] Those impacts produced lava flows and debris, which then caused secondary impacts. Water vapor condensed in the permanently shadowed, very cold craters near the poles of Mercury and the Moon.

Hyperbolic comets never returned to the solar system. Near-parabolic comets now being detected are returning to the inner solar system for the first time. Comets with slower velocities received most of their orbital velocity from Earth’s orbital motion around the Sun. They are short-period comets with elliptical, prograde orbits lying near the Earth’s orbital plane. Since the flood, many short-period comets have been pulled gravitationally into Jupiter’s family. Small comets are composed of material that escaped Earth with the least velocity. [Pages 113–149 give a more detailed description of the hydroplate theory.]

Exploded Planet Theory.⁸³ Consistent with Bode’s “law,”⁸⁴ a tenth planet once existed 2.8 AU from the Sun, between the orbits of Mars and Jupiter. It exploded about 3,200,000 years ago, spewing out comets and asteroids. Many fragments collided with other planets and moons, explaining why some planets and moons are cratered primarily on one side. The fragments visible today are those that avoided the disturbing influence of planets: those launched on nearly circular orbits (asteroids) and those launched on elongated ellipses (comets). This theory also explains the origin of asteroids and some similarities between comets and asteroids.

Volcanic Eruption Theory.⁸⁵ The large number of short-period comets, as compared with intermediate-period comets, requires their recent formation near the center of the solar system. Volcanic eruptions, probably from the giant planets (Jupiter, Saturn, Uranus, and Neptune) or their moons, periodically launch comets. Jupiter’s large, recently-acquired family suggests that Jupiter was the most recent planet to erupt. The giant planets are huge reservoirs of hydrogen, a major constituent of comets. New eruptions replenish comets that are rapidly lost through collisions with planets or moons, evaporation when passing near the Sun, and ejection from the solar system.

Oort Cloud Theory.⁸⁶ As the solar system formed 4.5-billion years ago, a cloud of about 10¹² comets also formed approximately 50,000 AU from the Sun⁸⁷—more than a thousand times farther away than Pluto and about one-fifth the distance to the nearest star. Stars passing near the solar system perturbed parts of this Oort cloud, sending randomly oriented comets on trajectories that pass near the Sun. This is why calculations show so many long-period comets falling into the inner solar system from about 50,000 AU away. As a comet enters the planetary region (0–30 AU from the Sun), the gravity of planets, especially Jupiter, either adds energy to or removes energy from the comet. If energy is added, the comet is usually thrown from the solar system on a hyperbolic orbit. If energy is removed, the comet’s orbital period is shortened. With so many comets in the initial cloud (10¹²), some survived many passes through the inner solar system and are now short-period comets.

Revised Oort Cloud Theory.⁸⁸ As the solar system began 4.5-billion years ago, all comets formed in a comet nursery near or just beyond the outer giant planets. Because these comets were relatively near the Sun, passing stars and the massive galactic clouds (molecular clouds) could not eject them from the solar system. As with planets, these early comets all had prograde orbits near the plane of the ecliptic. Perturbations by the giant planets gave some comets short periods with prograde orbits near the ecliptic plane. Other perturbations ejected other comets out to form and resupply an Oort cloud, 50,000 AU from the Sun. Over millions of years, passing stars have circularized these latter orbits. Then, other passing stars perturbed some Oort cloud comets back into the planetary region, as described by the original Oort cloud theory. Therefore, large numbers of near-parabolic comets are still available to fall into the inner solar system from about 50,000 AU away. An unreasonably large number of comets did not have to begin in the Oort cloud 4.5-billion years ago (where, after a few billion years, passing stars, galactic clouds, and the galaxy itself would easily strip them from the cloud). Short-period comets cannot come from the Oort cloud.

Meteor Stream Theory.⁸⁹ When particles orbiting the Sun collide, they exchange some energy and momentum. If the particles are sufficiently absorbent (squishy), their orbits become more similar.⁹⁰ After millions of years, these particles form meteor streams. Water vapor condenses on the particles in the meteor streams as they pass through the cold, outer solar system. Thus, icy comets form continually. This is why so many meteor streams have cometlike orbits, and why more short-period comets exist than an Oort cloud could provide.

Interstellar Capture Theory.⁹¹ Comets form when the Sun occasionally passes through interstellar gas and dust clouds. As seen from the Sun, gas and dust stream past the Sun. The Sun’s gravity deflects and focuses these particles around and behind the Sun. There, they collide with each other, lose velocity, enter orbits around the Sun, and merge into distinct swarms of particles held together by their mutual gravity. These swarms become comets with long and short periods, depending on how far the collisions were from the Sun.