There are two types of physical body which can hit the Earth, namely, comets and asteroids. In the past ancient people had seen and recorded comets; the bright gaseous plume which is illuminated by the sun was often described as a bow, or sword, or arm in the sky. There are no obvious records of asteroids, small dark bodies which are effectively invisible without a telescope, and not that easy to spot even with large telescopes. Astronomers have devoted quite a lot of time to asteroids because, from a hazard point of view, the most interesting ones are locked into orbits in the inner solar system. But perhaps the interest is actually stimulated by the fact that most of the early ones were discovered by accident and some are in Earth-crossing orbits. [...]
It is now known that the comets we see originate from what is effectively a shell of comets called the Oort Cloud which sits far out on the fringes of the solar system. From time to time gravitational effects from passing stars, or changes in our sun's position relative to the galactic plane, displace comets from the Oort Cloud into the solar system; some of these comets penetrate the inner solar system where we reside.
As already noted, objects moving inside the inner solar system represent a definite hazard to inhabitants of this planet. Looked at simplistically, we are trapped in the middle of a target, orbiting close to the bullseye (the Sun) and from time to time objects are fired towards the centre of the target.
Then, just to make the game more interesting, there is a deflector (in this case the giant planet Jupiter) whose gravitational field is sufficiently strong that it mops up most of the incoming missiles and either captures them or fires most of them back, away from the target. Unfortunately, the deflector is not 100 per cent successful and it actually encourages some material towards the target: worse still, it sometimes breaks the missile up and fires a scatter of debris inwards to the target. Though the reality is much more complicated than this simple model, the model is sufficient to get the feel of the problem.[...]
{Special note: notice that Baillie has reported that Jupiter is a "comet attractor." Consider that in light of all the recent discoveries of "new moons" of Jupiter, the numbers going higher almost daily!}
Comets are loosely compacted, but deeply frozen, hard, masses of rock and ice and organic materials, debris left over from the formation of the solar system. The common term 'dirty snowball' only half does them justice. [...] A snowball is typically thrown at a velocity of around ten metres per second; a comet is typically travelling at 20 to 50 km per second! [72,000 mph] So do not think of dirty snowballs; think of psychopathic iceballs. [...] {NOTE: Many of them with rock cores as is presently being learned}
While the asteroid population in the inner solar system is relatively stable, and as lumps of rock or nickel-iron the asteroids themselves are pretty stable, comets are a bit more diverse. Normally a few kilometer or miles across, they can be captured into fairly stable orbits which can be or long or short periods - a few years or thousands of years. These long-return types will normally appear out of the blue and are not much different from a completely new comet [...]
Then there are giant comets up to hundreds of kilometers across. [...] If left orbiting long enough, all the comet's volatiles will eventually burn off and only the rocky core will be left, effectively indistinguishable from an asteroid. {Not necessarily, according to McCanney's Plasma Comet Theory.} So there are at least two broad classes of hazard from comets: interaction between a live comet and the Earth and interaction between a dead comet and the Earth, with the latter being indistinguishable from the asteroid hazard. [...]
We need to think a little bit more about this idea of being hit - what does it mean in reality.
Well, there are hits and there are near-misses. We can imagine the simple case. A boulder whizzes in and hits the Earth directly at high velocity. Depending on the size of the boulder and the velocity, there is an explosion ranging from the equivalent of a few kilotons to hundreds of millions of megatons. It is clear that nothing in the latter class has occurred in even the last few million years - though we did witness those impacts on Jupiter in July 1994. In this direct hit scenario it is immaterial whether the object was an asteroid or a dead or live comet; size and velocity are all that matter. However, near-misses are a different thing altogether.
A near-miss with an asteroid is just that: 'whoosh - that was lucky', and as mentioned, we have had several of those in recent times.
A near-miss with a comet, whether it is dead or alive, may be very different. Because cometary nuclei are 'loosely packed' there is a tendency for them to be torn apart by the gravitational fields of the Sun or the planets in any close situations. {NOTE: Here he is unaware of the electrical nature of the Cosmos and Comets in particular, but he has noted that Comets seem to be very different!}
So we can be pretty sure that cometary nuclei are not travelling alone; there is likely to be a whole hierarchy of fragments. This could happen in a single pass or it could happen over a number of orbits. Such activity might lead to loading of the Earth's atmosphere with dust and maybe even volatiles and, as Clube and Napier, and Bailey and Steel, and Vershuur and others would argue, with the possibility of multiple Tunguska-class impacts - the 'cosmic swarm.' Simple mathematics indicate that for every comet that would hit us, about 4,000 pass closer to us than one Earth-Moon distance.
{And clearly, according to the Electric Universe theory, any body in the solar system can have electromagnetic effects. Smaller objects can have greater effects if they pass very close, and larger objects can have stronger effects even if they are far away. The question at the moment is: are the effects that Earth is presently experiencing due to Elenin as a LARGE body that is having strong effects even far away? Or is it due to an even larger body not yet seen/identified, such as a companion star? Or, are smaller, unseen, bodies that are closer producing stronger effects? Obviously, science has painted itself into the non-electric universe corner and is generally helpless to sort these questions out.}
This introduction to cometary hazards tells us that the real problem on the timescale of civilization is the debris associated with a 'close pass' comet, irrespective of whether the comet was dead or alive. As we will see, the comet would fairly certainly blow your mind. [...]
What, I asked myself, would actually happen in a close approach? I sought out Gerry McCormac, a colleague who had trained and worked as an atmospheric physicist. [...] When asked what he thought would happen if a comet approached very close to the earth, his reply was startling:
If it came within the earth's magnetosphere it would probably be spectacular ... the sky would go purple or green, particles from the comet would spiral down the lines of force and it is likely that you would have amazing auroral displays and coloured streamers...
Suddenly a new series of possibilities had opened up. One had to try to imagine a cometary body, or associated debris, passing within the Earth's magnetosphere and possibly producing a fabulous, moving, coloured display. So I asked if there would be any other associated phenomena - noise maybe? He replied: "Well, the Eskimos say that at the time of aurora they sometimes hear a hissing noise ... but! ...scientists who took up sensitive listening equipment did not manage to record anything.' [...]
{Back in 1989 when Aurora's were seen in Florida, there was, indeed, this hissing sound witnessed by myself and my children. There was also a cinnamon smell in the air. }
There is a whole literature on auroral sounds and, indeed, sounds heard directly from bolides, even comets. Colin Keay has written extensively on these phenomena. [...]
People have claimed that they have heard an incoming fireball and in fact heard it and turned around to see it. There is the contradiction: the flash of light from the fireball is travelling much faster than any related sound.
{Remember the flash of light in the one video???}
Traditional wisdom holds that we cannot actually hear fireballs coming in, we may hear the rumble and explosion only some time later, usually after we have seen them. Keay has accumulated information showing that some people genuinely do hear fireballs as they come in and before they see them: how? The plasma trail from a large fireball may generate Extra Low or Very Low Frequency radio emissions; if an observer happens to be standing beside a suitable object (or perhaps if he is wearing a suitable object like glasses or headgear, that object can act as a transducer for the electromagnetic signal - thus the observer actually 'hears' the incoming fireball as it enters the atmosphere, before seeing it.
The technical name for this phenomenon is 'geophysical electrophonics.' {Baillie, Exodus to Arthur, Batsford; London, 1999}
