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The end of the world as we know it
Forget man-made threats – the catalyst for the apocalypse will come from outer space, warns astronomer Chris Impey
The Mayan Indians set the date 21 December 2012.
Crash landing: every 100 million years, a rock the size of a small asteroid slams into the Earth, causing earthquakes, tidal waves, and killing all large land animals.
Apocalyptic thought has a tradition that dates to the Persian prophet Zoroaster in the 14th century BC. Recently, anxiety has grown over the prediction of the end of the world in the Mayan calendar.
It's true that the Mayan odometer will hit zeros on 21 December 2012, as it reaches the end of a 394-year cycle called a baktun. But this baktun is part of a larger 8,000-year cycle called a pictun, and there's no evidence that anything astronomically untoward will happen as the current baktun slides into the next. However, that hasn't stopped the feverish speculating that sells books and cinema tickets.
What kind of catastrophe would it take to end the world? Astronomical intruders provide a potentially serious threat. Impacts can be caused by stray rubble from the Asteroid Belt and the rocky snowballs that travel in highly elliptical orbits in the comet cloud. There are many fewer large bits of debris than small bits, so the interval between large impacts is much longer than the interval between small impacts.
When massive stars exhaust their nuclear fuel, the result is a titanic explosion called a supernova. The dying star brightens to rival an entire galaxy and emits high-energy particles that can destroy the ozone layer of a planet like Earth if it occurs within 30 light years. The demise of large North American mammals 41,000 years ago has been linked to a supernova, and several other mini-extinctions may be tied to the cataclysm of stellar death.
A supernova is a small squib compared to a hypernova. In this dramatic and rare event, the violent collapse of a very massive star ejects jets of gas and high-energy particles at close to the speed of light, and for a few moments the star outshines the entire universe in gamma rays.
Forget man-made threats – the catalyst for the apocalypse will come from outer space, warns astronomer Chris Impey
The Mayan Indians set the date 21 December 2012.
Crash landing: every 100 million years, a rock the size of a small asteroid slams into the Earth, causing earthquakes, tidal waves, and killing all large land animals.
Apocalyptic thought has a tradition that dates to the Persian prophet Zoroaster in the 14th century BC. Recently, anxiety has grown over the prediction of the end of the world in the Mayan calendar.
It's true that the Mayan odometer will hit zeros on 21 December 2012, as it reaches the end of a 394-year cycle called a baktun. But this baktun is part of a larger 8,000-year cycle called a pictun, and there's no evidence that anything astronomically untoward will happen as the current baktun slides into the next. However, that hasn't stopped the feverish speculating that sells books and cinema tickets.
What kind of catastrophe would it take to end the world? Astronomical intruders provide a potentially serious threat. Impacts can be caused by stray rubble from the Asteroid Belt and the rocky snowballs that travel in highly elliptical orbits in the comet cloud. There are many fewer large bits of debris than small bits, so the interval between large impacts is much longer than the interval between small impacts.
When massive stars exhaust their nuclear fuel, the result is a titanic explosion called a supernova. The dying star brightens to rival an entire galaxy and emits high-energy particles that can destroy the ozone layer of a planet like Earth if it occurs within 30 light years. The demise of large North American mammals 41,000 years ago has been linked to a supernova, and several other mini-extinctions may be tied to the cataclysm of stellar death.
A supernova is a small squib compared to a hypernova. In this dramatic and rare event, the violent collapse of a very massive star ejects jets of gas and high-energy particles at close to the speed of light, and for a few moments the star outshines the entire universe in gamma rays.
