However, if this is true, why is it that unusually large meteoroids have a tendency to explode before they hit the ground? The Tanguska event was by all accounts a large meteoroid. The Chelyabinsk event, famously documented by dash-cams on February 15 2013, was also a large meteoroid. In both cases, the meteoroids exploded in the air before impact.
While the large ones explode from internal stress, the smaller ones slow down due to air resistance, discharge its excess charge into the atmosphere, and might not even glow as it falls to Earth.
Large meteoroids do not have increased chances of hitting our planet. Rather, the opposite is the case. The larger a meteoroid is, the less likely it is to hit Earth. They explode before impact.
This is why all so called impact craters on Earth are completely circular. They are caused by a tremendous explosion at low altitude. Had they been due to a kinetic impact, they would not be round but oblong, with an uneven rim, low at the point where the meteoroid entered and high at the end it was moving towards. To verify this, simply toss an iron ball into a sand pit. The mark will only be perfectly round if it was dropped straight from above.
Instead of oblong, impact craters are all circular. They also show sign of electrical activity. There is often a raised center, and irregular scarring in and around the crater.
What happens when a large meteoroid comes into close contact with Earth is that our planet seeks to equalize its charge with that of the meteoroid, and the meteoroid gets completely obliterated in the process. The force of the explosion depends on the size of the meteoroid. Very big meteoroids result in visible craters.
This process of obliterating meteoroids before impact is not unique to Earth. This happens on our Moon as well. However, having no atmosphere in which to burn meteoroids at a far distance from its surface, even the smallest meteoroids get zapped at close range, and so our Moon gets littered with circular craters.
Some lunar craters may not be impact craters, but the result of electrical whirlwinds in which bits of charged dust circle around an exit point before heading out to space. Over time, this process can create circular marks. However, this does not diminish the fact that meteoroids almost always explode before impact. There are no sign of direct impact of large meteoroids on Earth, and very few signs of direct impacts on the Moon.
Interestingly enough, an experiment performed by NASA goes a long way in confirming the electrical explosion theory. On July 4 2005, NASA's Deep Impact spacecraft successfully struck a comet with a copper plated impactor. What is rarely mentioned is that there was a flash detected before the subsequent flash of the impact. The copper plate did not get obliterated, but that is probably entirely due to the fact that it was striking a comet and not a planet or moon.
At some point an object gets so large that it does not get obliterated, so could a comet or a rogue moon or planet strike our planet directly?
As it happens, there is some evidence to suggest that a close encounter between Earth and a very large object has happened in a not too distant past. The result was not an impact crater but a scar.
The Grand Canyon looks like it may have been created from a discharge between our planet and a large object in close proximity. There is even a round exit shape at the bottom right hand corner of the pictures taken from space. This is where the discharge lingered as the large object headed back out into space.
More dramatically and easily recognizable is the famous scar on Mars. Valles Marineris has a round entry shape and a round exit shape at either end, and it is at its broadest in the middle where the distance between Mars and the intruder was at its smallest.
Both the Grand Canyon and Valles Marineris have the irregular markings of electrical discharge. But Valles Marineris is straighter and deeper. The encounter must have been very close.
Valles Marineris and Grand Canyon are example of what happens when very large bodies come in close contact with each other. Instead of a single flash, there is a continuous flash. There is not a single sharp explosion. There is a long continuous explosion. In both cases, there are enormous repelling forces in action, and herein lies the answer to the above question.
Large objects are extremely unlikely to collide. Even if they were to come into close contact, there would be a strong repelling discharge between the two. Additionally, most electrical theories of gravity predict a repelling gravitational force between large objects in close proximity.
Large objects don't collide. They glide past each other, exchanging violent discharges in the process.
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By NASA / USGS (see PIA04304 catalog page) - http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-mars.html http://nssdc.gsfc.nasa.gov/image/planetary/mars/marsglobe1.jpg, Public Domain, Link
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