# Thread: The Doomsday argument : 95% chance of extinction within 9,120 years

1. ## The Doomsday argument : 95% chance of extinction within 9,120 years

The Doomsday argument (DA) is a probabilistic argument that claims to predict the number of future members of the human species given only an estimate of the total number of humans born so far. Simply put, it says that supposing the humans alive today are in a random place in the whole human history timeline, chances are we are about halfway through it.

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Simplification: two possible total number of humans

Assume for simplicity that the total number of humans who will ever be born is 60 billion (N1), or 6,000 billion (N2).

If there is no prior knowledge of the position that a currently living individual, X, has in the history of humanity, we may instead compute how many humans were born before X, and arrive at (say) 59,854,795,447, which would roughly place X amongst the first 60 billion humans who have ever lived. Now, if we assume that the number of humans who will ever be born equals N1, the probability that X is amongst the first 60 billion humans who have ever lived is of course 100%.

However, if the number of humans who will ever be born equals N2, then the probability that X is amongst the first 60 billion humans who have ever lived is only 1%. Since X is in fact amongst the first 60 billion humans who have ever lived, this means that the total number of humans who will ever be born is more likely to be much closer to 60 billion than to 6,000 billion.

In essence the DA therefore suggests that human extinction is more likely to occur sooner rather than later.

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Mathematics-free explanation by analogy :

Assume the human species is a car driver. The driver has encountered some bumps but no catastrophes, and the car (Earth) is still road-worthy. However, insurance is required.

The cosmic insurer has not dealt with humanity before, and needs some basis on which to calculate the premium. According to the Doomsday Argument, the insurer merely need ask how long the car and driver have been on the road—currently at least 40,000 years without an "accident"—and use the response to calculate insurance based on a 50% chance that a fatal "accident" will occur inside that time period.

Consider a hypothetical insurance company that tries to attract drivers with long accident-free histories not because they necessarily drive more safely than newly qualified drivers, but for statistical reasons: the hypothetical insurer estimates that each driver looks for insurance quotes every year, so that the time since the last accident is an evenly distributed random sample between accidents.

The chance of being more than halfway through an evenly distributed random sample is one-half, and (ignoring old-age effects) if the driver is more than half way between accidents then they are closer to their next accident than their previous one.

A driver who was accident-free for 10 years would be quoted a very low premium for this reason, but someone should not expect cheap insurance if they only passed their test two hours ago (equivalent to the accident-free record of the human species in relation to 40,000 years of geological time.)

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What the argument is not

The Doomsday argument (DA) does not say that humanity cannot or will not exist indefinitely. It does not put any upper limit on the number of humans that will ever exist, nor provide a date for when humanity will become extinct.

An abbreviated form of the argument does make these claims, by confusing probability with certainty. However, the actual DA's conclusion is:

There is a 95% chance of extinction within 9,120 years.

The DA gives a 5% chance that some humans will still be alive at the end of that period. The DA does not predict the extinction of all intelligent life on Earth, only the extinction of humans.

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This argument has generated a lively philosophical debate, and no consensus has yet emerged on its solution.

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(source: wikipedia.org/Doomsday_argument)

2. ## Re: The Doomsday argument : 95% chance of extinction within 9,120 years

Earth has had six extinctions , we are on the verge of repeating history for we have eyes to see but do not see, ears to hear but do not hear ... We have been involved in War my entire life ... killing thousands every year ... and still we kill ... it changes nothing , peace will change everything ...we won't be wiped out , this time we will live a golden age , remembering who we really are , it all leads up to this age , the final pope , the final prophet , the final battle , the fight for the right for earth to exsist without interference from ET's ... the way to mountaintop is thru the valley ...

3. ## The Following 4 Users Say Thank You to ghostrider For This Post:

Atlas (18th September 2013), Hazelfern (18th September 2013), marlowe (18th September 2013), Wind (18th September 2013)

4. ## Re: The Doomsday argument : 95% chance of extinction within 9,120 years

Posted by ghostrider (here)
... the way to mountaintop is thru the valley ...
Exciting!!!!!!

5. ## The Following User Says Thank You to Bubu For This Post:

Atlas (20th September 2013)

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