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Date Posted: 06:53:58 06/29/16 Wed
Author: Pahu
Subject: Poynting-Robertson Effect



Poynting-Robertson Effect



Dust particles larger than about a 100,000th of a centimeter in diameter form a large disk-shaped cloud that orbits the Sun between the orbits of Venus and the asteroid belt. This cloud produces zodiacal light (a). Forces acting on these particles should spiral most of them into the Sun in less than 10,000 years. (This is called the Poynting-Robertson effect.) Known forces and sources of replenishment cannot maintain this cloud, so the solar system is probably less than 10,000 years old.


This is how the Poynting-Robertson effect works: Rain falling on a speeding car tends to strike the front of the car and slow it down slightly. Likewise, the Sun’s rays that strike particles orbiting the Sun tend to slow them down, causing them to spiral into the Sun. Thus, the Sun’s radiation and gravity act as a giant vacuum cleaner that pulls in about 100,000 tons of nearby micrometeoroids per day. Disintegrating comets and asteroids add dust at less than half the rate at which it is being destroyed (b).


A disintegrating comet becomes a cluster of particles called a meteor stream. The Poynting-Robertson effect causes smaller particles in a meteor stream to spiral into the Sun more rapidly than larger particles. After about 10,000 years, these orbits should be visibly segregated by particle size. Because this segregation is generally not seen, meteor streams are probably a recent phenomenon (c).


Huge quantities of microscopic dust particles also have been discovered around some stars (d). Yet, according to the theory of stellar evolution, those stars are many millions of years old, so that dust should have been removed by stellar wind and the Poynting-Robertson effect. Until some process is discovered that continually resupplies vast amounts of dust, one should consider whether the “millions of years” are imaginary.


a. “For decades, astronomers have speculated that debris left over from the formation of the solar system or newly formed from colliding asteroids is continuously falling toward the sun and vaporizing. The infrared signal, if it existed, would be so strong at the altitude of Mauna Kea [Hawaii] , above the infrared-absorbing water vapor in the atmosphere, that the light-gathering power of the large infrared telescopes would be overkill. ... In the case of the infrared search for the dust ring, [Donald N. B.] Hall [Director of the University of Hawaii’s Institute for Astronomy] was able to report within days that ‘the data were really superb.’ They don’t tell an entirely welcome story, though. ‘Unfortunately, they don’t seem to show any dust rings at all.’ ”  Charles Petit, “A Mountain Cliffhanger of an Eclipse,” Science, Vol. 253, 26 July 1991, pp. 386–387.


To understand the origin of zodiacal light, see page
319.


b. Steidl, The Earth, the Stars, and the Bible, pp. 60–61.


Harold S. Slusher and Stephen J. Robertson, The Age of the Solar System: A Study of the Poynting-Robertson Effect and Extinction of Interplanetary Dust, ICR Technical Monograph No. 6, revised edition (El Cajon, California: Institute for Creation Research, 1978).


c. Stanley P. Wyatt Jr. and Fred L. Whipple, “The Poynting-Robertson Effect on Meteor Orbits,” The Astrophysical Journal, Vol. 3, January 1950, pp. 134–141.


Ron Cowen, “Meteorites: To Stream or Not to Stream,” Science News, Vol. 142, 1 August 1992, p. 71.


d. David A. Weintraub, “Comets in Collision,” Nature, Vol. 351, 6 June 1991, pp. 440–441.


[From “In the Beginning” by Walt Brown]

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