Four planets out of the eight that make up our Solar System are graced with a permanent set of rings around them. Of them, the Lord of the Rings title is preeminently held by the beautiful and majestic planet Saturn, with no less than seven major ring divisions and numerous gaps interspaced within them.
Fans of science fiction and space will be all too familiar with the wonder and spectacle of what life could be like for the inhabitants living on such a world graced with rings. The planet would be rotating on its spin-axis underneath the rings and, as seen from the surface of such a world, there would be an endless celestial display of "ring rise" and "ring set" each and every single day. It could be likened to how we experience a full moon that rises in the east in the early evening, rides high in the sky at midnight, eventually sinking low down in the west by dawn; with the moon, all the while, leaving behind a trail of silvery light along its path of travel as it goes across the night sky, which mimics a ring.
Such awe-inspiring imaginations of how the sky might appear on "Ring World" raises the question of rings of our own Earth. Could our planet have possessed a set of particulate rings around it at some point in its past history? And with the steady stream of artificial satellites now being sent up by every major country in the world, could it some day again possess an artificial ring system similar to that of Saturn's?
The question dates as far back into antiquity as the Scientific Revolution of the 16th century, and it is essentially one of celestial mechanics.
History of Earth Rings
Ever since the times of Isaac Newton, Joseph-Louis Lagrange, Pierre Simon Laplace, Carl Friedrich Gauss, and other great mathematicians of the Renaissance Era, there has been an inherent belief in the scientific community that the Earth is capable of retaining a stable ring system in orbit around it for millions of years on end.
For instance, in an article published in Nature back in 1980, the ex-NASA astronomer Dr. John A. O'Keefe (who is noted for discovering the Earth's slight pear-shape back in the 1950s) theorized the "O'Keefe Earth ring." He hypothesized it to be a Saturn-like ring of tektites that could explain the Eocene extinctions of 35 million years ago.
That ring was thought to have cut out as much as a third of all sunshine reaching the Earth's surface. It is also thought that it was in existence for between one and several million years. Colder Winters, and the extinction of hundreds of species including horses in Europe and plankton in the Caribbean, marked the end of the geologic Eocene period in Earth's history, occurring approximately 35 million years ago.
In Science Frontiers (Issue #76, Jul-Aug 1991), we read, "In the past, the Earth had a ring system just like Saturn, Uranus and Neptune," according to a Danish astronomer. He has gone so far as to say that our planet boasted rings on 16 separate occasions in the past 2,800 years. As recently as September 2002, Sandia National Laboratories published an article by two University of New Mexico researchers who again reinforced the notion of past "Earth rings."
In that study, the authors supposed the existence of a thin system of rings created by large meteoritic impacts, which caused material to get ejected back out into space and then gather into a debris ring formation along the Earth's equatorial plane. They again suggested that such a ring system, perhaps of similar opacity to Saturn's B-ring, may have caused past climatic changes on the Earth by blotting out sunlight and casting a cooling shadow over the equator for hundreds of thousands of years.
Since then, there have been many proponents in the global space community who advocated that an artificial ring system could help us to cool off a runaway greenhouse effect resulting from current global warming. The article "Earth Rings for Planetary Environment Control," authored by four researchers from the World Space Congress and published in the Smithsonian/NASA ADS system, is most notable in that respect. It argues in favor of many advantages of having a ring around the Earth, such as controlling climate temperature, reducing the intensity of the Van Allen radiation belts, making dangerous near-Earth flying asteroids more useful, providing night-time illumination without power, and creating an artificial ionosphere for radio communications.
New Perspective
Going at a 180 degrees against this flow of opinion is a recent dynamical study by the eminent Muslim astronomer and space science researcher Abdul Ahad. His studies have concluded that such a ring system around the Earth would in fact never hold together. Ahad initially published his findings over the Internet, and his paper was subsequently picked up by the Google Earth community and publicized by other users elsewhere on forums.
In view of its findings, Ahad's paper is now being widely viewed as a landmark study in scientific circles, as it provides the first analytical proof that the Earth has always been — and will most likely always remain — forever ringless. The paper highlights a range of technical scenarios that were evaluated on the basis of proven equations of motion for artificial satellites orbiting about the Earth. Of particular significance are those objects orbiting in the geostationary satellite belt, some 35,786 km above the equator of our planet.
The paper's conclusion is that an Earth-circling ring that is positioned above the equator, will gradually scatter over many years into a random mess around our planet, with its particles oscillating with a mean geocentric latitude of some plus or minus 15 degrees. A polar ring, according to the same study, may prove dynamically more stable, but it will serve absolutely no purpose to humanity for any climatic-control initiatives and, in any event, it too will eventually scatter because of the solar wind particle pressure, in addition to other smaller forces.
"The particles in the ring will likely drift thousands of miles apart and we have no hope of keeping the ring together, even by artificial means of perpetual replenishment or through thruster control of individual particles," Ahad said.
"In the most favorable scenario, you can probably get away with a very loose artificial 'quasi-ring,' but then it will not be dense enough to blot out any solar insolation and it certainly won't be anything like the rings of the outer planets."
I asked Ahad what prompted him to investigate such an Earth ring phenomenon in the first place.
"I was toying with the idea of hollowing out a captured asteroid in orbit around our world to build a potential Earth-circling space station of the future," the celestial luminary from Luton, UK, told.
"I wanted to know if the debris from such a project would be containable within a neat plane, so as to not pose a random collision hazard to spacecraft leaving our home planet and returning safely back from places as far afield as the Moon and Mars. The results of my study told me that that would be simply wishful thinking."
Ahad's simulations showed that ring material will oscillate around something known as the Laplacian Plane of the Earth-Moon system, and the testimonial proof of that can be seen by the way in which geostationary satellites behave in their orbits once they become spent pieces of junk after their rocket fuel has run dry.
The Future
There are three major reasons, Ahad pointed out, as to why the Earth rings will disperse in this way. The first is that the Earth has a rather large Moon close by; the second being that we orbit the Sun in much closer proximity compared to the ringed gas giants like Saturn and Uranus in the outer Solar System. The opposing gravitational tugs from both the Moon and the Sun would be the biggest disturbing function to any potential Earth-ring set up. The third, and lesser cause, would be the shape of the Earth itself, which has a slight polar flattening giving it an equatorial bulge that makes its gravitational force field deviate away from a spherical harmonic. This in turn would pull on ring particles in a non-uniform kind of way, causing the collapse of the ring system. Other smaller disturbing functions would be the solar wind particle and radiation pressures that would impact a thin ring system made up of very small particles. "The Van Allen radiation belts would be an additional hindrance, especially if the ring were built 3,000 km above the equator," the researcher said.
When asked what impact this research will have on the future of spaceflight, Ahad stated, "The way in which we strategically manage our near-Earth space and the manner in which satellites are deployed into various orbits by various nations, will all need radical and responsible rethinking from here on. Knowing that we have virtually no control over the situation will create an even stronger commitment toward action by world governments."
In recognition of his pioneering research efforts such as this, the Bangladesh Astronomical Society (the national space organization of his country of origin) awarded Ahad Honorary Membership in May of 2008. The eponymous "Ahad's Constant" and "Ahad's Sphere of Solar Illuminance" — both of which he mathematically formulated in 2004 to be astrophysical insights that are new to science — have been named in his honor.
Ahad is also an award-winning, British-Bangladeshi novelist, having authored two books in his First Ark to Alpha Centauri science fiction series. He is a member of the British Astronomical Association in the UK and the Planetary Society in America.
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