**!The sky is Falling!**
--- In FairfieldLife@yahoogroups.com, "salyavin808" wrote: > > > I can say with a high degree of confidence that this is how the world > ends, maybe not with this particular asteroid, this particular time but > someday. For a start, it's happened before - a good many times and with > a great deal of mass extinction. Sure, every time a big one hits there's > one less big one *to* hit but just in my life there have been several > instances of previously unknown asteroids crossing between the Earth and > Moon. In 1989 one that, had it been travelling one millionth of a mile > an hour slower, would have hit in the middle of the atlantic and set off > every volcano and earthquake faultline on earth, not to mention swamping > Europe, Africa and the America's with the resulting tsunami. > Hardly a rare occurrence then but something to loose sleep over? Not for > me but just think, there were three in the last century that struck > land, one in Siberia, one in Arabia and one in south America. No known > casualties but there was massive destruction in each case. Millions of > felled trees in Tunguska, a desert melted into glass in Arabia. I often > wonder what would have happened at the height of the cold war if, say, > New York or Moscow had been suddenly vapourised by an incoming comet. > Would the powers that be been able to stop themselves retaliating > against the mistaken foe? Most of these things are unknown before they > flash by close enough to part our hair, cosmically speaking, without us > being aware of their existence - except this one. Anyway, it's all just > something to help keep life in perspective.... > > > Apophis a 'potentially hazardous' asteroid flies by Earth on > Wednesday > Asteroid Apophis arrives this week for a close pass of Earth. This isn't > the end of the world but a new beginning for research into potentially > hazardous asteroids > > [A computer generated image of a near Earth asteroid] A > computer-generated image of a near-Earth asteroid. Astronomers will get > a close-up view of Apophis on Wednesday. Photograph: Planetary > Resources/EPA > Apophis hit the headlines in December 2004. Six months after its > discovery, astronomers had accrued enough images to calculate a > reasonable orbit for the 300-metre chunk of space > rock. What they saw was > shocking. > > There was a roughly 1 in 300 chance of the asteroid hitting Earth during > April 2029. Nasa issued a press release > spurring astronomers around > the world to take more observations in order to refine the orbit. Far > from dropping, however, the chances of an impact on (you've guessed it) > Friday 13 April 2029 actually rose. > > By Christmas Day 2004, the chance of the 2029 impact was 1 in 45 and > things were looking serious. Then, on 27 December astronomers had a > stroke of luck. > > Looking back through previous images, they found one from March on which > the asteroid had been captured but had gone unnoticed. This > significantly improved the orbital calculation and the chances of the > 2029 impact dropped to essentially zero. However, the small chance of an > impact in 2036 opened up and remains open today > > . > > While there is no cause for alarm, similarly there is no room for > complacency either. Apophis remains on the list of Potentially Hazardous > Asteroids compiled by the International Astronomical Union's Minor > Planet Center. > > Although most asteroids are found in the belt of space between Mars and > Jupiter, not all of them reside there. Apophis belongs to a group known > as theAten family . These > do not belong to the asteroid belt and spend most of their time inside > the orbit of the Earth, placing them between our planet and the sun. > > That makes them particularly dangerous because they spend the majority > of their orbit close to the sun, whose overwhelming glare obscures them > to telescopes on Earth rather like a second world war fighter ace > approaching out of the sun. > > Having crossed outside Earth's orbit, Apophis will appear briefly in the > night-time sky. Wednesday 9 January will afford astronomers the rare > opportunity to bring a battery of telescopes to bear: from optical > telescopes to radio telescopes to the European Space Agency's Infrared > Space Observatory Herschel. Two of the biggest unknowns that remain to > be established are the asteroid's mass and the way it is spinning. Both > of these affect the asteroid's orbit and without them, precise > calculations cannot be made. > > Another unknown is the way sunlight affects the asteroid's orbit, either > through heating the asteroid or the pressure of sunlight itself > . > Russia has announced tentative plans to land a tracking beacon on > Apophis sometime after 2020 > , so that its > orbit can be much more precisely followed from Earth. > > Wednesday's pass is only really close by astronomical standards, taking > place at around 14.5 million kilometres above Earth's surface. The > moon's orbit is 385,000 km. The 2029 close pass is another matter > entirely, however. > > On Friday 13 April 2029, Apophis will slip past the Earth just 30,000km > above our heads less that one-tenth the distance of the moon and > closer even than the communication satellites that encircle the Earth at > 36,000km. It will appear as a moderate bright moving object, visible > from the mid-Atlantic . Depending > upon its composition, astronomers could watch the Earth's gravity pull > the asteroid out of shape, offering an unprecedented insight into its > composition. > > So, although Apophis poses no immediate danger, we are almost certain to > hear a lot more about it over the coming years and decades. Apart from > all the science we can learn, its orbit's proximity to Earth's makes it > a potential target for future robotic and even manned missions > > . > > Stuart Clark is the author of Voyager: > 101 Wonders Between Earth and the Edge of the Cosmos > 848875432> (Atlantic). >
