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Do they want us to know?

2007-07-27 12:44:58 · 12 answers · asked by tuthutop 2 in Science & Mathematics Astronomy & Space

12 answers

Meteorites are hitting the Earth every day, though usually they are small and cause no damage. I suspect that you are actually asking whether there are any known asteroids (much larger bodies) which are predicted to hit the Earth. Currently, none are known. Every year or two, an asteroid on a potential collision course with Earth is discovered, but so far, more accurate determinations of their orbits have shown that they will miss us.

The trouble is that "Asteroid To Hit Earth" makes big headlines on the front page, but the follow up article "Asteroid To Miss Earth" gets buried on page 27.

2007-07-27 13:18:30 · answer #1 · answered by GeoffG 7 · 3 1

Meteorites fall on earth all the time.
But I presume you probably meant the next meteorite that could be really dangerous, city obliterating impact big.

To this, the answer is no one knows. There are no known meteorites that could potentially be dangerous that are on a high probability of impact orbit. But orbit fluctuate due to influence of everything, even the light pressure from the sun, so long term orbits are very hard to figure out (and the exact position of any meteorite is not known to a precision that is high enough to remove the uncertainty).
There is an effort to detect and track potentially dangerous meteorites, but the space agencies have to make it with relatively small budgets, and the disbelief of some people--some religious fundamentalists--who would insist that earth will be protect by god, or conversely, would maintain that a meteor impact, if it was to occur, would be the will of god that we should not oppose.

2007-07-27 20:06:01 · answer #2 · answered by Vincent G 7 · 2 0

Quite frankly the most likely meteorite strike will occur during the period August 10 - August 15, 2007. We have forecasts of a large meteor shower during that period listed on the Internet right now. So, plan to go out at night when the skies are clear and check out the display in the sky.

If by any chance one lands near you, be sure to let it cool off completely before making an attempt to pick it up and take it home with you. Serious burns might result.

2007-07-27 19:52:30 · answer #3 · answered by zahbudar 6 · 0 0

Someone should give you some links. I've included the JPL NEO Risk Page below and the NEODys page.

Jim is incorrect in naming April 13, 2029 as an impact. That is the date that (99942) Apophis will come as close as 38,000 km. It will not hit on that day but there is a small chance that its orbit could be altered in just the right way to impact the Earth in 2036. Odds of that are presently put at 1 in 45,000.

The reference to the report by Morrison and others indicating around 2,100 Near Earth Asteroids about 1km in diameter or larger is to the earlier Spaceguard reports of 1992 and 1994. Current estimates put the number at around 1,100. Depending on how you draw the boundaries we currently know of about 700 to 800 Near Earth Asteroids larger than 1km (and about 4700 of all sizes). Most of these have been discovered since 1998 by surveys funded by NASA and also by the US military, such as LINEAR, LONEOS, NEAT, Spacewatch, Catalina, Mt Lemmon and Siding Spring.

Many amateurs have also contributed follow-up observations of objects to pin down their orbits. The Minor Planet Center is the clearing-house for such data.

2007-07-28 07:23:22 · answer #4 · answered by Peter T 6 · 0 0

Unlike the users above have stated, there is a known metoer on a collision course with Earth. The next metoeroid will supposedly hit earth on Friday, April 13, 2029. A show about it was premiered on the Discovery channel. However, the US government is currently speculating ways to divert it. The current theory is to send out a satellite to the meteoroid and use it's gravity to direct the object away from our planet.

2007-07-27 20:26:22 · answer #5 · answered by Jim ((C.A.B.)) 6 · 0 4

The Earth's atmosphere protects us from the multitude of small debris, the size of grains of sand or pebbles, thousands of which pelt our planet every day. The meteors in our night sky are visible evidence of this small debris burning up high in the atmosphere. In fact, up to a diameter of about 10-meters (33 feet), most stony meteoroids are destroyed in the atmosphere in thermal explosions. Obviously some fragments do reach the ground, because we have stony meteorites in our museums. Such falls are known to cause property damage from time to time. On October 9, 1992, a fire ball was seen streaking across the sky all the way from Kentucky to New York. A 27-pound stony meteorite (chondrite) from the fireball fell in Peekskill, New York, punching a hole in the rear end of an automobile parked in a driveway and coming to rest in a shallow depression beneath it. Falls into a Connecticut dining room and an Alabama bedroom are well documented incursions in this century. A 10-meter body typically has the kinetic energy of about five nuclear warheads of the size dropped on Hiroshima, however, and the shock wave it creates can do considerable damage even if nothing but comparatively small fragments survive to reach the ground. Many fragments of a 10-meter iron meteoroid will reach the ground. The only well-studied example of such a fall in recent times took place in the Sikhote-Alin Mountains of eastern Siberia on February 12, 1947. About 150 US tons of fragments reached the ground, the largest intact fragment weighing 3,839 pounds. The fragments covered an area of about 1 x 2 kilometers (0.6 x 1.2 miles), within which there were 102 craters greater than 1 meter in diameter, the largest of them 26.5 meters (87 feet), and about 100 more smaller craters. If this small iron meteoroid had landed in a city, it obviously would have created quite a stir. The effect of the larger pieces would be comparable to having a car suddenly drop in at supersonic speeds! Such an event occurs about once per decade somewhere on Earth, but most of them are never recorded, occurring at sea or in some remote region such as Antarctica. It is a fact that there is no record in modern times of any person being killed by a meteorite. It is the falls larger than 10 meters that start to become really worrisome. The 1908 Tunguska event was a stony meteorite in the 100-meter class. The famous meteor crater in northern Arizona, some 1219 meters (4,000 feet) in diameter and 183 meters (600 feet) deep, was created 50,000 years ago by a nickel-iron meteorite perhaps 60 meters in diameter. It probably survived nearly intact until impact, at which time it was pulverized and largely vaporized as its 6-7 x 1016 joules* of kinetic energy were rapidly dissipated in an explosion equivalent to some 15 million tons of TNT! Falls of this class occur once or twice every 1000 years.

There are now over 100 ring-like structures on Earth recognized as definite impact craters. Most of them are not obviously craters, their identity masked by heavy erosion over the centuries, but the minerals and shocked rocks present make it clear that impact was their cause. The Ries Crater in Bavaria is a lush green basin some 25 kilometers (15 miles) in diameter with the city of Nordlingen in the middle. Fifteen million years ago a 1500-meter (5000 feet) asteroid or comet hit there, excavating more than a trillion tons of material and scattering it all over Europe. This sort of thing happens about once every million years or so. Another step upward in size take us to Chicxulub, an event that occurs once in 50-100 million years. Chicxulub is the largest crater known which seems definitely to have an impact origin, but there are a few ring-like structures that are 2-3 times larger yet about which geologists are uncertain. There are now more than 150 asteroids known that come nearer to the Sun than the outermost point of Earth's orbit. These range in diameter from a few meters up to about 8 kilometers. A working group chaired by Dr. David Morrison, NASA Ames Research Center, estimates that there are some 2,100 such asteroids larger than 1 kilometer and perhaps 320,000 larger than 100 meters, the size that caused the Tunguska event and the Arizona Meteor Crater. An impact by one of these larger meteors in the wrong place would be a catastrophe, but it would not threaten civilization. However, the working group concluded that an impact by an asteroid larger than 1-2 kilometers could degrade the global climate, leading to widespread crop failure and loss of life. Such global environmental catastrophes, which place the entire population of the Earth at risk, are estimated to take place several times per million years on average. A still larger impact by an object larger than about 5 kilometers is damaging enough to cause mass extinctions. In addition there are many comets in the 1-10 kilometer class, 15 of them in short-period orbits that pass inside the Earth's orbit, and an unknown number of long-period comets. Virtually any short-period comet among the 100 or so not currently coming near the Earth could become dangerous after a close passage by Jupiter.

2007-07-27 20:59:49 · answer #6 · answered by Anonymous · 1 0

Who's they?

2007-07-27 21:47:37 · answer #7 · answered by stork5100 4 · 1 0

Any minute, now, government conspiracy nut.

Shhhhhh, it's a secret.

No prior research? Off-the-wall answer to off-the-wall question.

2007-07-28 01:29:25 · answer #8 · answered by Anonymous · 0 1

Fu...in WOW dude. Derrrrrrrrrr

2007-07-27 22:36:41 · answer #9 · answered by comethunter 3 · 0 2

don't listen to geoff .. he thinks he knows but .. nope.
He's jelous of people who know more than him. So he tries to out do them.

He doesn't have me fooled

2007-07-28 01:47:01 · answer #10 · answered by Anonymous · 0 1

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