Critical Questions Against Alien Civilazations in Our Galaxy..
March 9, 2010 2 Comments
So here’s a list of some critical questions and answers that might provide us additional insight into the fate of higher lifeforms on other worlds– based upon our own experiences:
Q: How long have complex lifeforms (which would be vulnerable to these sorts of things) been present on Earth?
A: If we don’t count things like algae, maybe around 600 million years. Present evidence indicates around 570 million years– future finds may extend the number deeper into time.
Q: What’s been the average frequency of gamma ray bursters in our galaxy over the past 600 million years or so? What about the frequency of other cosmic radiation events which might have affected climate and/or life on Earth over this time?
A: Over the last 600 million years the most suspect periods for gamma burster episodes appear to be the mass extinctions of the Ordovician (439,000,000 BC), and Permian-Triassic (360,000,000 BC- 250,000,000 BC)– though there’s also evidence of a major asteroid or comet strike relating to the Permian-Triassic too. The cosmic impact may have merely been coincidental, mattering little in the wake of a gamma burster, or complemented the burster’s effect, thereby adding to the death toll, or extended the period of extinctions for much longer than they might have otherwise lasted. Or, the burster itself could have played second fiddle to the impact, in a similar fashion.
It appears the bursters lasted long enough in both instances to fry at least 60-75% of the Earth’s surface life before they faded.
There’s the possibility that more than one burster occured during the Permian-Triassic event– this could help account for the very lengthy period of die offs found by researchers.
If gamma bursters were involved in both these events then the bursts were separated by somewhere between 79 million and 189 million years. And the latest one may have occured sometime between 360 million and 250 million years ago– which appears to make us overdue for another anytime now (if the frequency holds). YIKES! We’re overdue to become just another statistic, folks.
But gamma bursters aren’t the only showers of extra radiation from space periodically suffered by Earth. Much less dangerous radiation showers also occur– sometimes leaving climate changes and less substantial extinction events in their wake. Some of the approximate dates for such events include 5,000,000 BC, 1,006 AD, 1,054 AD, 1,181 AD, 1,320 AD, 1,572 AD, and 1,604 AD. Note that in recent times the average time between such radiation showers has been around 120 years. So we’re perhaps overdue for another by some 276 years.
Q: What’s been the average frequency of large comet and/or asteroid impacts on Earth over the past 600 million years or so?
A: This is a toughie, since our information on these points is very spotty, and the frequency has hopefully been lowering over time, similar to how gamma burster frequency is said to have done. Events like Tunguska in 1,908 AD also seem to show that some comet impacts may not leave craters at all, but still possibly affect climate over large regions, or even globally. Some scientists believe some global climate changes in the past came from Earth merely passing through the dust wake of a comet tail.
Fortunately, we do have some noteworthy impacts and related numbers to draw upon. 590 million BC, 370 million BC, 364 million BC, 150 million BC, 65 million BC, 35 million BC, 35.5 million BC, and 2.3 million BC all seem to have marked such impact or related events. Note that the average time between events appears to be some 84 million years– which means we might not see another until around 82 million AD (if the average holds).
Q: What’s been the average frequency of catastrophic geological upheaval on Earth over the past 600 million years or so?
A: 534 million BC, 200 million BC, 84 million+ BC, 65 million BC, 55.5 million BC, and 69,000 BC represent notable instances of massive geological upheaval which possibly had big effects on climate. The average frequency of these events seems to have been once every 107 million years. If the average also gives us a rough estimate of when to expect the next one, we may have around 107 million years to wait.
Q: What’s been the average frequency of notable extinction events on Earth over the past 600 million years or so?
A: A list of such extinction events would include the following dates: 439 million BC, 367 million BC- 245 million BC, 220 million BC- 208 million BC, 65 million BC, 13 million BC, 5 million BC, and 3 million BC- 2 million BC. The average time between events seems to be some 73 million years (For my calculations I used a number near the median of the values which represented ranges rather than specific dates). Thus, in terms of naturally inspired notable extinction events, we might be about 71 million years away.
Unfortunately, humanity has over the past 50,000 years or so initiated its own unnatural global extinction event– which shows signs of possibly expanding to include us as well, within the next 200 years or so. But that’s a topic to be dealt with elsewhere.
Q: What’s been the average frequency of major tsunamis or global flooding events on Earth over the past 600 million years or so, which were possibly NOT directly related to any of the above events?
A: Again, our records here are spotty– but we do know about such events around 998,000 BC, 98,000 BC, and 15,000 BC to 3,000 BC.
Here our sample is terribly small– so I’m unsure what good an average from the numbers would be. Plus, the 15,000 BC- 3,000 BC event represents the flooding due to the end of the last glaciation of the current Ice Age– a spike which likely belongs in its own wholly owned category along with other Ice Age related sea changes over the past 2 million years and during other icey epochs. But I don’t have the info for that.
So how about this? We’ll assume that all land-based civilizations of a given one million year star farer generation has suffered or will suffer at minimum three catastrophic tsunamis and/or global sea level changes during their span.
Q: What’s been the average frequency of worldwide ecological catastrophe on Earth over the past 600 million years or so, for which a specific cause has yet to be determined?
A: Everything I have in this category is extremely recent. Tree growth rings and rare historical accounts of the times point to worldwide ecological catastrophe occuring around 2,354 BC, 1,628 BC, 1,159 BC, 208 BC, and 536 AD- 541 AD.
The causes may have been asteroid/comet impacts (or near-misses dusting the atmosphere), large volcanic eruptions, or perhaps even the passing of the Earth through a great cloud of cosmic dust in space.
The average time between these events has been approximately 723 years. This implies that we may be overdue for another by around 739 years (YIKES!).
Q: So how fast could life recover evolution-wise from such calamities?
A: It appears Earth on average requires about 10 million years to recover from a fairly wide scale of global extinction events, ranging from massive species extinctions to considerably smaller events. The inability of evolution to recover more quickly than this seems to be due to entire ecosystems collapsing when critical species within them die. Therefore, a bootstrapping process involving both replacement species and replacement ecosystems to support them, must take place.