Well, the world is still here. It didn’t end on May 21 as predicted by Harold Camping and it also didn’t end on the date of his revised prophecy – October 21. For those who were sober enough to notice, the world also failed to end at the dawn of the new millennium, just as it failed to end in 1994 (predicted by the Watchtower Society), and all of the 46 other times (according to the Ontario organization Religious Tolerance) that have been predicted in the last 1981 years. No matter how convincingly the argument is made it seems that the world is determined to end at some unpredictable time in the future. The predicted reasons for the end of the world tend to fall into three categories:
- Divine reasons (e.g. biblical predictions, the wrath of God, the return of a holy figure, etc.)
- “Scientific” reasons (e.g. an alignment of planets, and alignment of stars, etc.)
- Human reasons (e.g. nuclear war, runaway global warming, etc.)
This posting will not try to determine what might (or might not) be on the mind of a deity so the first of these categories will not be discussed, but the other two categories are certainly worth thinking about.
“Scientific” reasons As one example, in 1919 the meteorologist Albert Porta predicted that a rare planetary alignment would cause the Sun to explode. Porta’s prediction obviously didn’t pan out, leaving an opening for John Gribbon to write The Jupiter Effect, predicting the end of the world from a rare planetary alignment – with all of the planets more or less lined up from the Sun outward Gribbon anticipated that the sum of the gravitational forces would cause the Earth to tip over on its side or to trigger earthquakes, or something similar. The latest version of the “alignment” hypotheses is the 2012 prediction – that when the Solar System passes through the exact centerline of the Milky Way galaxy the gravitational forces (or possibly other more esoteric forces) will cause the world to end.
What all of these predictions have in common is the Earth will be stressed to the breaking point by the forces caused by some rare (from a human perspective) celestial alignment. What is interesting is that the most potentially stressful planetary alignments – with every planet lined up precisely so that, looking from the Sun, they would all overlap in the sky – happen so rarely that they are unlikely to ever occur. East Tennessee State University astronomer Donald Lutermoser figures that the most precise alignments happen only about once every 1046 years – hugely longer than the Solar System’s scanty four and a half billion year age. Chances are that such an alignment will never occur. Other alignments are far less rare, happening on the order of every few centuries to every tens of millions of years.
Consider, for example, the passage of the Solar System through the plane of the Milky Way. The Sun bobs up and down through the plane of the galaxy like a cosmic yo-yo with a periodicity of tens of millions of years. This is a huge length of time and it’s easy to think that something that happens so infrequently might well cause the end of the world. On the other hand, the Earth is ancient and it has survived hundreds of such crossings without yet being destroyed. Odds are good that we’ll survive the next such alignment. And the same goes for the other such alignments – even something that happens only once every billion years has been survived four or five times over the history of our planet and chances are that the Earth will live through the next occurrence as well. In other words, astronomical alignments are either too rare or too common to be seriously considered as a way to end the world.
To add to that the putative mechanism doesn’t hold water either – Lutermoser also points out that the gravitational and tidal forces exerted on the Earth from anything other than the Moon and the Sun are minuscule. Tidal forces can, indeed, rip a planet apart – this is likely the mechanism responsible for the rings around Saturn and the other gas giants in our Solar System – and space science journalist Charles Choi reports a recent paper published in Nature suggesting that astronomers might soon see the Milky Way’s central black hole “feeding” on a gas cloud (and maybe even a planet or two) in the next few years. But barring a close passage close to a massive object tidal forces simply cannot muster enough force to rip the Earth asunder – were this possible the Solar System today would be filled with rubble and not planets. The bottom line is that ”science” based speculation about the end of the world – even those supposedly tied to the Mayan calendar – simply don’t hold water. Even the real events we have records of, such as the impact responsible for the demise of the dinosaurs, were (shall we say) unfortunate for a great many species but the Earth survived. The Earth will certainly end come to an end at some point, but right now the best bet is that this will be several billion years from now.
Human causes Of course we have more worries than simple planetary alignments – people have been predicting that humanity will destroy the world for some time. Even the biblical Noah’s Flood and the destruction of Sodom and Gomorrah can be seen in this light – that humanity’s wickedness brought catastrophe (albeit divine). More recently end-of-the-world predictions have centered on our scientific and technical prowess – nuclear war, global warming, biological weapons, and more.
Undoubtedly, we can do some serious harm to the Earth’s biosphere if we put our mind to it. Even with the recent dramatic reductions in nuclear arsenals, for example, there are still more than enough weapons in the world (more than 20,000 as of 2011 with a cumulative yield of as much as 5,000 Mt) to destroy our civilization and, possibly, to destroy much of the life on Earth. But the asteroid impact responsible for killing the dinosaurs released about 10,000 times this amount of energy. A bummer for the dinosaurs (and for about 75% of all the Earth’s species of life), but the Earth is still here and life – obviously – made it through the cataclysm.
Radiation is something that probably was not released after a major impact, but even here there is precedent. A number of astronomers (John Scalo and Craig Wheeler at the University of Texas in Austin, the University of Illinois’ Brian Fields, and others) have concluded that radiation from nearby supernovae and gamma ray bursts has likely been high enough to have an impact on terrestrial life several times since life first appeared. Fields, in particular, predicted that we might even find evidence of supernova-produced radioactivity on Earth, a prediction that was confirmed in the early years of this century by German astronomer K. Knie with the discovery of “live” 60Fe in deep-sea sediments (with a half-life of “only” 2.6 million years, this nuclide would have decayed away long ago were it not replenished somehow). The bottom line is that the radiation and radioactivity from a nuclear war are higher than what is considered normal, but they are not necessarily unprecedented over the Earth’s history.
Nuclear war – even one that destroyed humanity – would be a major blow for life on Earth, but it is unlikely to sterilize the planet. Life might be set back millions or even tens of millions of years, but it would recover just as surely as it recovered after the five major mass extinctions and every other catastrophe that has afflicted our planet.
Global warming also falls into this category – for most of the Earth’s history the Earth’s poles were bereft of ice and temperatures were much higher than what we have today. Even high carbon dioxide levels are not unique to our time – Yale University professors Robert Berner and Zavareth Kothavala have estimated that atmospheric concentrations of this greenhouse gas have been as much as 25 times those we see today (about 500 million years ago) and, with the exception of the Carboniferous period (about 315-270 million years ago) our atmosphere has almost never contained less carbon dioxide than we have today. This is not to say that we can relax our efforts to stave off global warming – more to point out that the Earth has survived far worse than we can apparently dish out. Global warming would be a tragedy without parallel in human history, causing death, disease, extinction, and so forth – but it would almost certainly not be the end of humanity, let alone the end of the world.
So is the end of the world nigh? Barring divine intervention (which is beyond the scope of ScienceWonk) it doesn’t seem likely – at least not within the next several billion years. This is not to say that we can’t do damage – we can do considerable harm if we set our minds to it, or even through sheer negligence – but after over four billion years and countless natural disasters the Earth and the life it holds has made it through quite a bit. At the least, I’m making plans for 2013 and beyond.
Dr Y is a certified health physicist, trained in nuclear power plant design and operations, with experience in nuclear power, environmental science, and planning for radiological and nuclear emergencies. He has 30 years of experience in the areas of nuclear and radiation safety.