Why hasn't the earth been hit by a huge asteroid or somefink yet?

Question

You hear about all these near misses (usually a few billion kms away?) but Earth still manages to dodge em. Who really believes that one huge rock will slam into the planet in the next 50 years causing mass damage. Call me morbid, but I sometimes wonder if it wouldn't be such a bad thing what with all the wars/pollution/evil peeps in the world.

Answer 1

cos your thick heads in the way

Answer 2

Somefink (bad spelling by the way) large did hit the earth. Around 4 billion years ago as the Earth was forming a large Mars-sized planetesimal hit the Earth a glancing blow and the debris through out became the moon (according to some theorists).
Between the time the earth originally started forming and about 3 billion years ago, scientists believe the Earth was struck by large asteroids repeatedly (the odds were just too good back then, with the huge amount of debris still existing in the planetary orbits).
Some scientists (and there is a lot of evidence to support this) believe a large asteroid struck the Earth 65 million years ago and caused the Great Dying of the dinosaurs and thousands of other species.
10,000 years ago a relatively small asteroid crashed into Arizona, creating the Barringer Meteor Crater (its over a mile across).
More recently, some scientists believe the Tunguska Event in Siberia in 1908 was the result of an explosion above the surface of a comet.
Almost-circular lakes and depressions around the world have been investigated and many show all the signs of being created by a meteor impact.
And meteors as small as pebbles and as large as cars are hitting Earth all the time - most burn up in the atmosphere but many reach the ground.

Humans have been recording history for less than 10,000 years, so just because we don't have a record of a huge strike doesn't mean it didn't happen. And that doesn't mean it couldn't happen in the future.
In 1994, pieces of Comet P/Shoemaker-Levy 9 collided with Jupiter. So its happening today in the solar system, which means its simply a matter of statistics and time before something large hits Earth.
And if it does, the damage caused will depend on the size, composition, and impact point of the asteroid. It could do very little damage to the earth and still kill all life.

Answer 3

Meteors hit the earth all the time. Small ones are called metorites when the enter the atmosphere - really small ones are called micrometeorites. These are usually found littering the ice in Antartica (the only place that preserves them). There are really big meteor craters found all around the world. We don't see ALL the meteors that hit the earth because we have a very active environment that errodes most of them.

You see a lot of metorites on Mars and the Moon because there is no significant weathering processes on these planets to erradicate them... So when you look at the moon, you see a large collection of meteorites over billions of years...

Check out the Brent crater in Ontario, Canada to see what I mean:
http://www.unb.ca/passc/ImpactDatabase/images/brent.htm

There is a really cool site on meteor craters here:
http://geology.com/meteor-impact-craters.shtml

Big meteors that leave a dent big enough on the planet to be seen from space do not happen all that often. Though the moon is absolutely pocked with craters, the last visible impact possibly occurred around the time of Mohammed (1400 years ago). There was also an event seen by Canterbury monks in 1178 that some scientists discount (though I disagree with them). But there has been nothing since.

Doomsday Comet Storm... Paleontologists had recently found that mass extinction (a la end of dinosaurs) occurrs around every 26 to 30 million years like clockwork... Astronomers are working on the possibility that the sun has a dark companion orbiting at the end of our solar system... A "brown dwarf" or star that is not big enough to support it's own fusion... The star orbits about every 26 million years and collides with the Oort cloud on on it's closest approach, sending comets comets flying toward the sun and earth with it's collision... A comet (a ball of frozen methane gas) impacting the earths surface would explain a mass extiction of global proportions without leaving a crater. Much like the Tunguska Event in Western Siberia which many theorize to have been caused by a 20 meter wide comet that flattened everything in a 830 square miles and yet left no crater... It was compared to a 20 megaton nuclear bomb.

Answer 4

I do not seriously believe any dangerously large asteroid or comet will hit Earth in the next 50 years. The last big(ish) one to hit was 1908. See the 1st source. It caused a massive explosion that could have destroyed a city, but luckily it hit a sparsely populated area in Siberia. However, that object was quite small compared to some of the near Earth asteroids the we are tracking now. It was probably about 20 meters wide, say about 65 feet.

Asteroid Apophis, that has gotten so much press about its expected close pass in 2036, is about 250 meters, say about 820 feet. If that hit it could take out a small country and cause a giant tidal wave if it hit in the ocean. See the 2nd source.

The object that hit 50,000 years ago to make the crater in the 3rd source was about 50 meters, or about 162 feet.

No 100+ mile size asteroid has any chance at all of hitting Earth. The biggest one that might some day hit is on the order of 10 miles wide. But even that would cause massive local damage and probably disrupt the atmosphere enough to trigger an ice age, possibly threatening civilization or even the extinction of humanity.

Answer 5

The odds may be small, but the time allowed is enormous. Sure, winning the lottery is a very unlikely thing. But if you played every day for a billion years, the probability of winning at *some* time is significant.
We are being bombarded by space debris constantly. Thousands of tons of meteoric dust fall on the earth every day. Every few years a fairly large piece makes it to the ground, maybe causing some damage. Every few centuries a big rock hits us, causing major damage. When you start counting into the billions of years you will be talking about some devastating collisions. We recently saw one on Jupiter. We know of at least two in the earth's history which altered life dramatically.
Like "the Big One" earthquake in California, it's not a matter of if. It's a matter of when. The same *may* be true concerning catastrophic collisions. One could happen during our lifetimes. Or we may be spared for hundreds of millions of years. The latter is probably closer to what will really happen.

Answer 6

An asteroid large enough to destroy huge amounts of life will collide with Earth, it's guaranteed. It has happened before.

The reason why they are uncommon is because of Jupiter. The majority of asteroids that leave the belt are attracted by Jupiter's immense gravity. It acts like the Solar System's vacuum cleaner.

Despite this though, the biggest threat to Earth are NEOs (Near Earth Objects). The largest NEOs are being tracked, but there are several thousand smaller objects that are not, and are capable of hitting Earth at any time, causing considerable damage.

When an asteroid does hit Earth capable of destroying human civilisation, it will probably be a Near Earth Object. NASA and other space agencies claim that these pose no threat to Earth at the present time. So on this basis I do not believe that an asteroid capable of destroying civilisation will hit Earth within 50 years.

Meteorites are very common, but because they are tiny they vapourise in the atmosphere, causing 'shooting stars'. We get thousands of these every day, especially when our planet passes through a meteor shower.

In recent history there have been reports of asteroid collisions, but these have been too small to cause major problems. Occasionally there have been asteroids that have collided with Earth large enough to destroy major cities, but by a stroke of luck they have landed in places with little human habitation (such as Antarctica and Siberia).

The Moon's gravity is too weak to prevent a very large asteroid from colliding with Earth. The only reason the Moon has many visible craters is because it does not have a weather system to erode them away. The majority of them are ancient.

If Earth had no weather systems to erode its craters away, it would look like the Moon.

Answer 7

One of the main factors is probability. Firstly there aren't that many big asteroids out there to hit us. Very tiny ones shoot through our atmosphere, you see them as shooting stars. They are so small they burn compeltely up due to the friction they experience when they reach our atmosphere, and never make it to earth. Sometimes a big one will explode in the sky, which may or may not cause damage on the earth depending on the size of the explosion and height of explosion:

http://en.wikipedia.org/wiki/Tunguska_event

Some big ones have hit the earth, and these create very large craters some of which are still visible today:

http://en.wikipedia.org/wiki/Meteor_Crater

This probably created one almighty explosion and would have destroyed much of the surrounding area, and possibly raised enough dust to blot out the sun for a while. This is just one of the few impact sites still visible today. The earth has wind, rain and tectonic action to wear away any impact craters. The moon does not, so it appears as though the moon gets hit a lot more than the earth because the craters never fade, in reality this isn't true, roughly the same amount of space material hits the earth [more often its atmosphere] as the moon, saying this it is true that the moon does take some of our hits, since it orbits the earth it is fairly likely to get hit first.

However the moon does improve our chances, as does the other planets of the solar system. The comet Shoemaker-Levy 9 could have headed straight for earth but instead it was sidetracked by Jupiter, we have much to thank for Jovian gravity providing cover for earth:

http://en.wikipedia.org/wiki/Comet_Shoemaker-Levy_9

So the chances of a large asteroid big enough to deal considerable damage to the earth actually getting here is quite unlikely. However it does sometimes happen, and it what wiped out the dinosaurs:

http://en.wikipedia.org/wiki/Chicxulub_Crater

The size of that impact is easily enough to destroy all life on earth. It will happen again eventually, unfortunately asteroids are extremely hard to detect early on, and methods of deflecting them would take considerable time.

Answer 8

The Earth has been hit many thousands of times by large asteroids, but it was so long ago (3 to 4 billion years ago) that the scars are mostly obliterated by subsequent geological events. Even so, there are 57 known meteor impact craters known in North America alone. The Moon was similarly bombarded but hasn't an atmosphere to erode the evidence, hence the craters are still visible, muchj as when they forst formed billions of years ago.

Answer 9

Of course we've been hit a bunch of times by even very large asteroids, but most of the earth's history takes place before humans, so we have very little to go by. Still, they say that should we be hit by a big asteroid, we'll be lucky if we see it about a day ahead of when it hits... but even that will hard. Mostly it will just hit and you will instantly die, or die in the next couple of weeks because of the population from ash that will spread around the entire earth (if it's as big as some others). Good luck!

Answer 10

It did happen once. The gulf of Mexico is the footprint of the one that got the earth into a glacial era which caused the dinosaurs to get extinct some million years ago.

On the other hand, most asteroids aren't large enough to survive going through earth's atmosphere in one piece and so they become just "meteorites".

So... it's a matter of chance. Statistically speaking, it "will" happen sooner or later, but nobody can say when.

Answer 11

We need to remember that even though we have war and so called evil people in the world there are still more good people than bad. Try not to wish for the end of the world too soon.