Impact
Prediction: Comet, asteroid, Nibiru
The scientific truth: Nibiru is the supposed planet discovered by Sumerians circa 2500 BCE that orbits the Sun every 3600 years and is due to hit Earth in December 2012. Also known as Planet X, it supposedly has a very eccentric orbit.
1AU (astronomical unit) is 90 million miles or 150 million kilometers. The long direction of Nibiru's orbit is said to be 470 AU. It must come within 1 AU to the Sun in order to potentially collide with Earth. The above ellipse is grossly inflated. It's actually much flatter than it is represented there, essentially going backwards and forward along the same path. Unfortunately for the Sumerians, the path it takes faces directly towards the galactic core. People used to identify planets as they moved across a starfield, but not only did the Sumerians have to identify it as it came towards them without changing position of brightness, but they also had to identify it against the vast background of stars at the galactic centre.
Today Nibiru would be 7.5 AU away, between the orbits of Saturn and Jupiter. It was it's furthest away in 200 AD and the closest in 1588BCE. However, there have been no sightings or records of disturbances by any of NASAs equipment, and many amateur astronomers would have sighted this planet by now if it did indeed exist. In 2500 BCE, at the time when the Sumerians claim to have observed it, Nibiru was 400 AU away (10x the distance of Pluto), yet they had no telescopes to observe it and we can not see Pluto with the naked eye.
Planets are like big dirty mirrors reflecting sunlight and do not produce their own light. In order for Nibiru to be visible to the Sumerians at 400 AU away it must be 150x the brightness of the Sun and 3.3 million masses of the Sun. Such planets are physically impossible to exist, and such stars do not even exist.
Could it possibly be a small star – a brown dwarf? A brown dwarf is basically a star that has failed to ignite. At around 400 AU a brown dwarf would look bright like any other of the planets to us. However, a brown dwarf at 7.5 AY, Nibiru's supposed position today, would be as bright as the full moon and easily visible in daylight.
Conclusion: Nibiru is fiction. It is also the only 2012 prediction that seems to be purely fiction. All of the other theories have a seed of science beneath it, which has simply been misunderstood and abused.
As for the possibility of an asteroid collision, this is never entirely ruled out. An asteroid is left over from planet formation and most of them lie in the asteroid (or Kuiper) belt between Mars and Jupiter. Some are nudged by gravity into orbits that crass Earth's orbit. An asteroid can cross our orbit with no collision, but there is some probability of a collision.
Small asteroids hit the earth's atmosphere frequently, creating a meteor or a fireball. A lot land in the ocean or countryside.
This is the Barringer crater, or meteor crater, in Arizona. It was created by a 50 meter sized object. There are one of these every 1000 years. This crater is 1 km across and is much older than 1000 years.
Once every 50 – 100 million years a body over 1 km in size hits Earth. 65 million years ago the Chicxulub crater was formed. This is possibly the impact that could have caused the extinction of the dinosaurs.
It would have kicked a phenomenal amount of dust into the atmosphere. That, combined with the subsequent tsunami, would have been devastating. The Lord Byron poem, Darkness, was written in the Summer of 1816, also known as the year without Summer, and is an interesting take on how people behave when they think the world is ending. Isaac Asimov's Nightfall is another interesting perspective on people's reactions to darkness.
In actual fact, in 1816 a volcano in the Philippines had erupted. That large eruption combined with smaller eruptions to push enough ash and dust into the atmosphere to cause serious problems. It will effect warmth, agriculture, and prevent people from traveling by air.
We are due for the next large impact, and this is a serious problem. We have the Near Earth Object monitoring program. One of the telescopes on the program is the Pan Starrs telescope based in Hawaii. It looks for objects 200 m wide and coming within 4.5 million miles of the Earth (20x the Moon's distance). 1000s of objects are currently being watched by this program.
How NASA would move an asteroid would be to paint it's solar side white so the asteroid will move. A robot could also be launched to erect a solar sail on it. The sunlight bouncing off of the sail will push the asteroid aside by the same principle. A shock wave from a nearby exploding rocket could move it, but the movies are horribly exaggerated when they direct a rocket straight at it, which in reality would result in the disastrous situation of breaking the asteroid up into many large chunks.
By now, we would have seen an asteroid lethal enough to wipe out Earth approaching. The next big one if expected in March 2880, so we can set our watches for that instead.
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