[meteorite-list] Doomsday Recalculation Gives Humanity Greater Chance of Long-Term Survival

[Ron Baalke]

http://www.technologyreview.com/view/512771/doomsday-recalculation-gives-humanity-greater-chance-of-long-term-survival/

Doomsday Recalculation Gives Humanity Greater Chance of Long-Term Survival
MIT Technology Review
March 21, 2013

And the odds would improve further, say physicists, were we to make serious 
efforts to counter existential threats such as asteroid strikes.

The Doomsday Argument is the idea that we can estimate the total number of 
humans that will ever exist, given the number that have lived so far. This 
in turn tells us how likely it is that human civilisation will survive far 
into the future.

The numbers are not optimistic. Anthropologists think some 70 billion humans 
have so far lived on Earth.  If we assume that we have no special status in 
 human history, then simple probabilistic arguments suggest that there 
is a 95 per cent chance that we are among the last 95 per cent of humans 
that will ever be born. And this means there is a 95 per cent chance that 
the total number of humans that will ever exist will be less than 20 x 
70 billion or 1.4 trillion. 

Now suppose that the world population stabilises at 10 billion and our life 
expectancy is 80 years, then the remaining humans will be born in the next 
10,000 years. That's not a long future for humanity. Today, Austin Gerig at 
the University of Oxford and a couple of pals put forward a new argument with 
a (slightly) happier ending.  

These guys look at the scenario in which many civilisations have evolved 
throughout the universe, the so-called "universal doomsday" argument. "In that 
case, we should consider ourselves to be randomly chosen from all individuals 
in that universe or multiverse," they say.

In the past, these universal arguments have been no more optimistic than the 
ordinary ones. They generally state that long-lived civilizations must be rare 
because if they were not, we would be living in one. What's more, because 
long-lived civilizations are rare, the prospects for our civilisation 
ever becoming long-lived are poor.

One problem with these conclusions is that they are based on very general 
arguments. So the new work that Gerig and co have done is to develop a more 
detailed analysis that takes into account factors such as the number of 
existential threats that civilisations will face - things like nuclear wars, 
asteroid impacts and global pandemics, not to mention the many threats we have 
not yet thought of.

This new approach approach allows Gerig and co to take a more fine-grained look 
at the odds that humanity will survive for much longer in future than 
it has existed in the past.

The results are complex but their main conclusion gives some reason for hope. "If 
[the number of existential threats] is not too large, the probability of 
long-term survival is about a few percent," they say.

Although this can hardly be called optimistic, it is nowhere near as gloomy as 
previous calculations.

Gerig and co say their calculations suggest some obvious actions humanity could 
take to significantly improve its chances of long term survival. 'If there is a 
message here for our own civilization, it is that it would be wise to devote 
considerable resources (i) for developing methods of diverting known existential 
threats and (ii) for space exploration and colonization," say Gerig and buddies. 
"Civilizations that adopt this policy are more likely to be among the lucky few 
that beat the odds."

Scientists have only recently has begun to study existential risk in a systematic 
way but this work is only beginiing to feed through into the public arena in the 
form, for example, of an increased focus on Earth-crossing asteroids. Perhaps 
it's time to take existential threats much more seriously.

Ref: arxiv.org/abs/1303.4676 : Universal Doomsday: Analyzing Our Prospects for 
Survival