Word: planet
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...under the other), the reverse dip-slip (in which they pull apart) and the strike-slip (a sideways grinding of the plates). Haiti's quake was a strike-slip, but all three varieties are preceded by years or centuries of accumulated stress, in which the slowly drifting slabs of planet try to shift their position but remain hung up on one another. The quake occurs when that rock lock is broken. Seismometers can detect the years of stirrings that lead up to that moment, providing some help to geologists. (See pictures of Haitian protests over rising food and fuel prices...
...best the USGS and other organizations can do is use the global web of seismometers and other instruments that are already in place and always being improved to build the best map possible of the planet's interior and at least narrow the predictive window of when quakes are likely to happen. They can also use these data to anticipate how severe the next tremor, whenever it comes, is likely to be. This can help drive policy decisions like improving building codes, reinforcing infrastructure and zoning some areas as unsuitable for development. That's hardly the same as precise predicting...
...those early models didn't take into account the fact that compressed gas heats up, which limits how dense it can become, and in turn limits how hard its gravity can pull on the proto-planets. Beyond that, the planets' own gravity would fling gas around - the same sort of phenomenon NASA counts on, say, when a spacecraft en route to Saturn gets a slingshot velocity boost from Jupiter on the way. By adding in both effects, Mac Low's collaborator Sijme-Jan Paardekooper, now at Cambridge, found that there are places where the net force pushes a planet inward...
...History. Or, rather, it was a problem - but Mac Low and his collaborators may have solved it. In a paper recently submitted to the Astrophysical Journal, they say that the old, Earth-destroying theory was generally accurate but lacked some key details - ones that both reshape theories about how planets form and, oh yes, allow the planet we know best to exist. (See an illustrated history of Earth...
...theory is one that has deep appeal to planet geeks but perhaps not as much to folks who don't ordinarily contemplate these things. But consider this: if the theory weren't right, it's possible that none of us would be here to contemplate anything...