I remember a book I owned when I was, oh, maybe 7 or 8. I think its name was "The Solar System". It was very short, of course, with many pictures and it was my first book of astronomy. In the last pages of the book there was a picture of a very large asteroid focused on crashing into New York city. The prose is rather difficult to remember except that it mentioned that some asteroids are the size of the Manhattan and an asteroid could easily destroy a city - actually, we now know, it could destroy nearly all life or most life on a planet if it was that size because very large asteroids and comets have collided with the earth in the distant and have changed everything in a very short time.
Needless to say, perhaps, is the fact I have a particular fascination with big stones spinning in space, since. I have seen some meteors plummeting downward, but as you must have already known, seeing one of the those is like seeing a firefly. You shake your head and wonder if you just saw what you think you just saw.
the usual, useful Wikipedia article. I have seen several comets over the years, including Kohoutek in the early 1970's. I thought it was quite dramatic when I saw it, it was quite large and its tail spanned the western horizon - it was definitely best comet show I ever saw. Comets are believed to be conglomerations of ice and stone - though mostly ice, that have very elongated orbits around the sun - their natural home is on the outer reaches of the system - past the orbits of Neptune in the Oort cloud.
A general explanation of the Oort cloud. I never saw a Bolide or fireball, which is a large (not immense!) meteor, usually of rock, which explodes during its fiery entry into earth's atmosphere, though the word can be used to mean the moment of collusion with the earth, also and I found a page using the word in that sense.
A wonderful picture of an airborne bolide! A new gem of a site to explore concerning meteors. A decent telescope and a lot of time is needed to track Asteroids. We now know that asteroid's natural home seems to be between Mars and Jupiter - and there are many theories of why this is so, including a Krypton like explosion early in our system's history! Sadly, I have never consciously seen one. I would love to have a telescope large enough to try. But the most recent news on asteroids is they do not confine themselves in that nice, safe zone between Mars & Jupiter. Many have orbits that cross Earth's orbit and a few come dangerously close to our planet.
An general article concerning asteroids. Well, there are our monsters, our dangerous and threatening space aliens that could destroy everything if one of them decided to come for a visit.
Now lets get to the meat. I have kept up on what ever news I could find on these monsters and of course, now, on the net there is a literal explosion of news and information available. (Why I call them monsters will become obvious when I explain the heart of my essay.) As noted above, they believe they have found the crater at the center of Tunguska event. This is very important. It has always been believed that the Tunguska event (1908, Russia) was the explosion of a comet or stony meteor
above the forests which leveled miles and killed at least one man and several flocks of reindeer - and leveled many miles of forest.
An absolutely fascinating site with paintings, quotes from survivors. The life of Eugine Shoemaker needs to be mentioned. He was a geologist who became an astronaut, who became an astronomer, who became an advocate/ expert for the search of Near earth objects - that is, those comets and large rocks & asteroids that could collide with the earth. ) He is actually one of my science heroes. Sadly, he died in a traffic accident in Australia but not before he saw the spectacular show of Shoemaker -Levy comet collide with Jupiter in July, 1994. Any claim that it was an extremely rare event that should not concern us was dismissed as we watched what happened to Jupiter.
NASA's near-earth-objects website. A good site that offers lots of links. Asteroids & comets do crash into planets and with terrible results. Tunguska is the small change of universe - the comet and asteroid collisions have and could change everything very suddenly - a truly large one could not only end our civilization but our species. Armageddon, indeed !
There have been extinction events throughout the history of the earth. People are panicking about climate change - but it has changed before, many times - and many things have happened to change the earth, its climate and natural history - some of them have not been of the earth.
Extinction events have happened many times. This page with help you research this history. One of the problems in understanding all this is that most of this science is relatively new. Also, the evidence was long in being accepted because of the old battle between science and religion. Religion believed in Catastrophes - the great flood is the best example. Darwin and modern science (geology & paleontology) up to the late 1960's believed in gradualism, that is the slow sure processes of evolution and environmental planetary change. Now, we know better. There are catastrophes, massive, horrible events that kill up to 3/4 of all life on the earth - (some extinction events are gradual) but others come in from the outer reaches of the solar system and with the power of hundreds of nuclear weapons, changing the planet's environment in seconds. The best example of this kind of extinction event is the event 65 million years ago when the very successful dinosaurs and hundreds of other species were wiped off the earth in a very short time. (and, yes, this is still debated among experts but it's pretty much accepted by the mainstream.)
So comets, asteroids, large and small rocks do hit the earth - these vary in size and composition but we are in a sort of cosmic shooting gallery and we are the bullseye.
There are some good videos on these subjects. I suggest looking at your local library, both NOVA - the science TV show -and the National Geographic video collection has done a good job handling these subjects - the National Geo show called "Asteroids" did a great job for its time though it is a bit dated, now.
Now - for some news. What about historical times - or early historical times ? Have comets, asteroids and bolides descended from the skies and threaten our survival ? Our mythologies speak of great dragons descending to earth and searing our planet. There is the legend of Phaeton, the son of Helios, the sun, who burned the earth when he lost control of father's chariot. We should not be arrogant when it comes to our ancestors- they were good observers but they did not have science to interpret what they were observing, they only had religion.
And what about human prehistory when we lived in caves is there any evidence of the early humans feeling threatened by the sky ? I refer you to the Crater in Arizona.
If these events have threatened life on earth before, could it happen again? The answer is yes. Some scientists suggest it has happened numerous times. I refer you all to several books I am mightily impressed with, the first is
"Exodus to Arthur" by Mike Baillie. The second is another book by the same author.
"New Light on the Black Death" that I found on the library, recently and I am reading this week. These books are not light reading and they are real science.
