This Is the Way the World Ends 394
Dave Knott writes "The CBC's weekly science radio show Quirks and Quarks this week features a countdown of the top ten planetary doomsday scenarios. Nine science professors and one science fiction author are asked to give (mostly) realistic hypotheses of the ways in which the planet Earth and its inhabitants can be destroyed. These possibilities for mankind's extinction include super-volcanoes, massive gamma ray bursts, and everybody's favorite, the killer asteroid. Perhaps the most terrifying prediction is the reversal of the Earth's magnetic field (combined with untimely solar activity), a periodic event which is currently 1/4 million years overdue."
Exit Mundi (Score:4, Informative)
Exit Mundi [exitmundi.nl]
Re:Overdue? (Score:3, Informative)
Think of it as being past the 50th percentile on the probability distribution, not past the 100th percentile.
Soon? Probable ones? (Score:3, Informative)
Sometimes a chain of events is more possible than a single event, specially if those single events counts on rogue black holes getting very close to us. Global warming (something with a bit higher probabilities to happen) maybe wont end us alone, but it could trigger more things (mass emigration, spreading of diseases, extintions of some key species, war, etc) that eventually could finish the work.
Re:I already know how the world end. (Score:5, Informative)
Re:Magnetic field reversal is the new 2k bug. (Score:5, Informative)
Do you happen to know which data points we have?
Anyway I think it will just be another year 2000 fiasco, lots of worries and then nothing happens.
Sure it may fuck up all satellites and some communication but so what? It's not the end of the world.
Actually we have data points going back millions of years. They show flips of the magnetic field happening more frequently, and the current state we are in (with north at the north pole) has been this way longer than most of the other flips lasted.
And no, it won't end the world at all. The world has been through millions of these flips and lasted just fine.
It's ironic how a lot of people confuse 'the end of the world' and 'the end of us'
But as a further point, it's not believed a pole reversal would just kill all humans.
When a flip happens, there are many poles, IE there could be 8 or 10 of each a north and south pole.
Each pole should roughly have a magnetic strength that totals our current one, thus each 'pole' is weaker.
Only people living under these roaming spots need worry, and even then its only expected to give another 10000 cases of cancer a year (give or take an order of magnitude, going from poor memory here)
Defiantly sucks, but not the end of anything.
Sadly, the same is true for a lot of things on the articles list. Only life is screwed (maybe), but the planet will be fine.
Re:Magnetic field reversal is the new 2k bug. (Score:3, Informative)
Sorry for the double reply.
If you can find this show, it is a really interesting watch
http://www.pbs.org/wgbh/nova/magnetic/reversals.html [pbs.org]
They do show how the data points are collected, how they are relevant, and even has some of those funny number things i couldn't recall myself:
You could perhaps take comfort in the knowledge that these reversals happen infrequently--on average every 250,000 years--but maybe not when you consider that it's been over 700,000 years since the last reversal, and the next one may be currently underway.
Also pretty graphs showing the length of periods between reversals, and some more of those funny numbers, at our best friend:
http://en.wikipedia.org/wiki/Geomagnetic_reversal [wikipedia.org]
and more buried in a longer article if you wanna pick through it at:
http://en.wikipedia.org/wiki/Earth's_magnetic_field [wikipedia.org]
72 million years worth of data points back from now.
The rate of reversals in the Earth's magnetic field has varied widely over time. 72 million years ago (Ma), the field reversed 5 times in a million years. In a 4-million-year period centered on 54 Ma, there were 10 reversals; at around 42 Ma, 17 reversals took place in the span of 3 million years. In a period of 3 million years centering on 24 Ma, 13 reversals occurred. No less than 51 reversals occurred in a 12-million-year period, centering on 15 million years ago. These eras of frequent reversals have been counterbalanced by a few "superchrons" -- long periods when no reversals took place, as described below.[5]
It had generally been assumed that the frequency of geomagnetic reversals is random, and it was shown in 2006 that the known reversals conform to a Lévy distribution.
Hopefully those will be interesting, and at least point you in the right direction.
Re:Magnetic field reversal is the new 2k bug. (Score:3, Informative)
Yup. We have a whole ocean's floor worth of data points.
Re:Ummm, probalby not so much (Score:3, Informative)
As for Sagan himself on the issue, his research seems more speculative rather than concrete. Remember he also predicted that the first Iraq war would lead to global cooling because of the particulate matter generated from the oil fires Saddam threatened to set. Well indeed Saddam did set those fires as he threatened and it had no measurable impact on our climate.
I believe part of the problem there lay in the speed at which the allies and the oil companies put those fires out. ie they didn't burn for as long as they were expected to.
Re:Get your facts straight (Score:5, Informative)
Also from the most recent material I have read the threat of a "nuclear winter" was a gross beat up. We have had multiple volcanic events that discharged more particles into the atmosphere than would happen with optimal usage of warheads to cause a "nuclear winter"
In a serious nuclear war you can get a lot more material into the air than that. Here [rutgers.edu] is some very recent analysis on the subject, using one of the latest climate models. (Try this paper [rutgers.edu] and this one [rutgers.edu].) This research group also does work on volcanic events, which the model's response has been tested on. They find that even a regional Indian-Pakistan exchange, each country using 50 Hiroshima-sized bombs, can have pretty significant global climate impacts (almost 1.5 C cooling). They do assume an "optimal" scenario, where the bombs are aimed at the highest population centers, causing maximum burning and thus particulate emission. The "winter" only hangs around for a decade or two, but it's worse for a "full scale" MAD scenario.
For the full "global thermonuclear war" scenario, they see cooling of up to 30 C (~ 60 F) over some regions! The global temperature drops by 8 C, which is colder than an ice age. It doesn't last long enough to form continental ice sheets, of course. But sticking around for a decade or two is Very Bad for plant life and the animals which depend on it. (And this is just the temperature effect, not counting the reduced sunlight for photosynthesis, any burned vegetation outside cities, effects of fallout, etc.)
A full nuclear exchange during the Cold War would have involved up to 10 gigatons of explosives. Even very large volcanic eruptions like Thera were only 0.5-1 gigatons (and I suspect that burning cities would emit more particulate matter). World War III wouldn't have been a Dinosaur Killer, and it wouldn't have sterilized the planet, but it would have had damn large effects on the biosphere.
Re:Ummm, probalby not so much (Score:4, Informative)
At the risk of adding something substantive to the conversation, Physics Today just covered this topic: Environmental consequences of nuclear war [aip.org].
They seem to think nuclear winter isn't that far fetched. The link is to an HTML summary at Physics Today, but there's also a link there to the PDF of the paper.
Close, but... (Score:3, Informative)
The model code is PU-36.
http://www.tvacres.com/weapons_ammunition_uranium.htm [tvacres.com]
Re:Ummm, probalby not so much (Score:5, Informative)
Thus far, there has been no good proof that there's any sort of reality in it.
Pretty much all the studies in your link conclude that there is reality to "nuclear winter", if by that you mean "significant cooling as a result of a large nuclear exchange". What's contested is mostly how much smoke there would actually be. Compared to that, the climatic effects of particulate matter in the atmosphere are relatively well understood. A few people criticized the early models which assumed that the atmospheric doesn't respond dynamically (note your link was published 20 years ago). Modern models which have dynamical circulation bear out the same results (e.g., here [rutgers.edu]). The weak link remains assumptions about what gets injected into the air, not the models themselves. You can get very large variations in particulate emissions if you tweak your assumptions about how the war plays out.
Don't confuse scientists speculating on things with real empiricism. There's lots of interesting ideas and theories, something with mathematical or computer models to back them up. That doesn't mean any of it has a thing to do with reality.
Large climatic effects from particulate emissions are pretty much undeniable. You don't need a fancy theory or model to know that. Particles of that size reflect sunlight. And lo, we see it happen from volcanoes. We even know how much particulate matter the volcanoes emit. The models reproduce the observed volcanic climate effects.
The main uncertainty, as I said, is in how much burning will take place.
String theory would be a good example.
Sigh.
String theory is not a good analogy. While there may be uncertainty about nuclear winter, there is still vastly more experimental evidence underlying our understanding of particulate emissions and atmospheric circulation models than there is about string theory. Comparing the former to the most theoretical of all theoretical physics is grossly exaggerating for effect. The two levels of uncertainty are not comparable.
It is, in fact, not a theory. It makes no testable prediction.
Both those statements are false.
People always try to compare string theory to a model of particle physics like the Standard Model. That's not the right comparison. String theory is a theoretical framework. The correct comparison is to quantum field theory in general.
"Quantum field theory" makes very few testable predictions, because it makes no assumptions about what particles exist or how they interact. To make predictions, you have to construct a specific model within QFT, such as the Standard Model. That is, you have to say that quarks and leptons exist, there are three forces whose interactions take a particular form, etc.
String theory is a theory in the same sense quantum field theory is: they are both frameworks in which you can write down predictive models. String theory by itself doesn't say much other than particles are made of strings. To make predictions, you have to write down a specific model. And you can write down something like the Standard Model (or one of its GUT generalizations) in string theory. It will make the same predictions as the SM in low energy regimes.
The problem with string theory is not that it doesn't make testable predictions. It's just as predictive as QFT is; in fact, QFT is just a limiting case of string theory, so any prediction you make in low energy QFT, you can make in string theory. And its predictions are certainly testable, because you can write down string models that are demonstrably false (the same is true of QFT models, such as all models before the Standard Model). It's hard to think of an experiment that could falsify all possible string models, but the same is true of one that could falsify all possible quantum field theories.
The
Re:Much simpler. We will eat the world to death (Score:5, Informative)
No, it's not. It's not even growing linearly. (Do you know what those terms mean?)
See Wikipedia's World Population [wikipedia.org] page for an article about the subject. According to the article, the world population growth rate peaked at 2.2%/year in 1963, and has been dropping since then. In real terms, the peak was 86 million new people in 1987. In 2007, there were 77 million new people.
The article shows that the growth rate is decreasing, and it is predicted to hit zero then become negative, causing the population to crest, probably around 9-10 billion people sometime around 2050. Various unpredictable events could alter this, both in a positive way (enhanced methods of food production, including my favorite idea, large-scale hydroponic farms) and in a negative way (plague, war, climate change.) However, under the current conditions, population growth is slowing down and approaching a peak, not growing at an exponential rate.
World Ending events well documented. (Score:3, Informative)
For the world to truly end, as in no more planet Earth, scenario 4 is most probable in the near term and scenario 1 inescapable in the long run. If you are defining âoeend of the worldâ as in a major extinction event, with Homo sapiens in a staring roll, then there are a bunch of options. The ones suspected of causing or contributing to major extinction events in the past are outlined in chapter six of my book, The Resilient Earth [amazon.com] (shameless plug). Here are the main ones from the book.
Our planet's past is filled with extinctions,some large, some small, some solitary. All the ages in the fossil record chronicle the departure of species from this Earth. The sweep of geologic time, comprising more than 90 recognized time periods, is partitioned by changes in the fossil record. What is most amazing is how gigantic an event has to be to be recorded in the strata. Visit theresilientearth.com [theresilientearth.com]for more information including pdfs of the book chapters and a link to Amazon for purchase of the paperback version.
Re:Ummm, probalby not so much (Score:3, Informative)
Sagan did make that prediction [wikipedia.org]. He died in 1996, after the war.
Photosynthetic humans (Score:3, Informative)
Actually that reminds me of the book Beggars Ride [wikipedia.org], by Nancy Kress. Disappointing compared to the previous in the series, but interesting.
Sub-linear growth (Score:3, Informative)
No it isn't. [census.gov]
The rate of growth has been slowing for decades. It's not only sub-exponential, it's been sub-linear for 20 years - the world's population was growing at 83M/yr in the 80s, and will end this decade with an average growth of less than 80M/yr, despite a larger population.
Why do you believe that's the most likely outcome? Entire nations have behaved in exactly the opposite manner as you suggest they would; for example, Germany's energy consumption hasn't changed in 20 years [doe.gov], despite a strong economy and substantial population growth. Now that the population of the country is shrinking, its overall energy consumption will most likely also fall.
It is an enormous and fallacious oversimplification to suggest that humans are the same as yeast, for both theoretical reasons (we're able to reason about our situation) and evidential ones (e.g., Germany).
Magnetic field reversal (Score:3, Informative)
Geomagnetic field reversals are perhaps "periodic" in the sense that they happen repeatedly over time, but they aren't particularly regular; they have been known to be erratic since the 1960s. The last reversal was ~780Kya, so the contention here seems based on the assumption of a regular ~500Ky pattern. There is no reasonable basis for this assumption, as the past history of reversals has been nowhere near a regular pattern with a 500,000 year cycle.