rhinoceros
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My point is ...
  
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Life extinction circles in galaxies
« on: 2005-04-11 11:09:28 » |
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The theory of periodic life extinctions is not new. This article which appeared today in the Guardian (noticed by Lucifer in #virus IRC) is related.
Sea life 'killed by exploding star'
http://www.guardian.co.uk/uk_news/story/0,3604,1456594,00.html
A huge blast of radiation from an exploding star might have been behind one of the Earth's worst mass extinctions, some 450m years ago.
In the latest issue of the Astrophysical Journal Letters, scientists argue that a gamma ray burst, the most powerful explosion that occurs in the universe, was responsible for the Ordovican mass extinction in which 60% of all marine invertebrates died.
<snip>
For around 10 seconds, intense pulses of energy are fired off, which can be detected right across the universe. All the bursts recorded by astronomers so far have come from distant galaxies and are therefore harmless to the Earth.
But if a burst occurred in our own galaxy, the effect would be devastating.
Dr Adrian Melott, of the University of Kansas and an author of the latest paper, said: "A gamma ray burst originating within 6,000 light years from Earth would have a devastating effect on life.
"We don't know exactly when one came, but we're rather sure it did come - and left its mark."
Such a burst would strip the Earth of its protective ozone layer, allowing deadly ultraviolet radiation to pour down from the sun.
Computer models showed that up to half the ozone layer could be destroyed within weeks. Five years later, at least 10% would still be missing.
Using computer models, the researchers calculated that plankton and other life in the first few feet of the oceans would have been destroyed.
The knock-on effect would have been huge: plankton are at the bottom of the marine food chain providing for animals which are then preyed upon by larger species.
Previously, scientists thought that an ice age caused the Ordovican extinction. A gamma ray burst would have had a similar effect, causing a fast die-off early on and triggering a significant drop in surface temperature.
<snip>
Because the bursts happen suddenly and are so short, scientists have been lucky to detect one a month with instruments on Earth.
[rhinoceros]
What is scary compared to other extinction theories is that a gamma ray burst is something from which it is rather hard to run away. When you detect its light it's already over.
Gamma ray bursts and their afterglow as a periodic cause of life extinction has often been discussed as an answer to the Fermi Paradox: "If aliens exist, why haven't we ever seen any trace of them?"
http://en.wikipedia.org/wiki/Fermi_paradox
Here is how the reasoning goes:
http://www.kurzweilai.net/mindx/frame.html?main=/mindx/show_thread.php?rootID%3D26621
Gamma Ray Burst Theory:
<snip>
By observing a large number of galaxies at different distances, hence different times in history (due to the time it takes their light to reach Earth), astronomers have been able to determine the average period for such supernovae. The startling fact that has emerged is that the period has been slowing down. There are more supernovae bursts in more distant galaxies, hence younger galaxies, than in closer, hence older, galaxies.
As the number of supernovae bursts decreases with the age of a galaxy, there comes a zone of time where the interval between bursts exceeds the amount of time it would take a biosphere to develop life, even technological civilization. Thus the Universe may be in a phase transition. We may be going from an era where life was being constantly wiped out by gamma radiation to an era were life has enough time to develop. If this is true, then all the life in our galaxy got wiped out when the last supernovae happened, BUT all the life in our galaxy started over at exactly the same time. Thus "we," if any, are all the same age. This might explain why none of us have communicated with each other, thus explaining the Fermi Paradox.
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