Making Model Earths

first_imgModeling how the earth got here can be fun.  One doesn’t have to be right, just creative.  There are certain accepted paradigms to work within, and certain accepted constraints that are taken as a given.  Beyond that, there is a lot of leeway.  This is illustrated by two teams who published in two different journals who used the same paradigms and constraints but came up with radically different models.    The Niels Bohr Institute’s story was told by PhysOrg and was published in Earth and Planetary Science Letters.  We’ll dub them the NBI team.  The ETH Zurich team’s paper was published in Nature Geoscience, and was also told by PhysOrg.  Here’s what they both assumed: the earth and moon were formed by a collision when a Mars-sized object hit the early earth once upon a time.  When it happened, and how long it took for the melted pieces to accrete and form our earth-moon system, is up for grabs, given a few constraints like how long it took for some assumed radioactive elements to fizzle out.    What’s notable in the articles are the fudge factors, or unknowns, or surprises, that give modelers plenty of wiggle room to either announce their model as a good one, or change it at will for next time.  For instance (labeling NBI or ETH for the team’s article involved):ETH: “just how long it took for the Earth to reach its eventual size and what the accretion of the planet was like, however, is much disputed among the experts.”ETH: “‘The latest models reveal that an accretion period of around 100 million years is the most consistent with the formation of the Moon and the Earth’, says Bernard Bourdon, a professor from the Institute of Geochemistry and Petrology at ETH Zurich, Switzerland.  However, there are also models that clearly suggest the Earth reached 70% of its size in just 10 million years.”ETH: “This distribution depends on the pressure and temperature conditions during the core formation, which probably varied during the accretion.”ETH: “In their study published in Nature Geoscience, Bourdon and his team now demonstrate that there are several models that are compatible with the chemical observations.”ETH: “‘Up to now, it was always assumed that you could only explain the distribution of the elements through equilibrium; we show, however, that the distribution is just as easy to explain in disequilibrium’, says Thorsten Kleine.”ETH: “The observations are also compatible with a state of equilibrium of only about 40 percent; this means the cores of the colliding protoplanets could have reached the Earth’s core directly without a major equilibration with the Earth’s mantle.”ETH: “The age difference had always puzzled the scientists; after all, the termination of the Earth’s accretion should actually coincide with the Moon’s age as it ended due to the impact of a Mars-sized protoplanet that formed the Moon.”NBI: “But new research from the Niels Bohr Institute shows that the Earth and Moon must have formed much later – perhaps up to 150 million years after the formation of the solar system.”NBI: “Until recently it was believed that the rock and iron mixed completely during the planet formation and so the conclusion was that the Moon was formed when the solar system was 30 million years old or approximately 4,537 million years ago.  But new research shows something completely different.”NBI: “The new studies imply that the moon forming collision occurred after all of the hafnium had decayed completely into tungsten.”NBI: “‘Our results show that metal core and rock are unable to emulsify in these collisions between planets that are greater than 10 kilometres in diameter and therefore that most of the Earth’s iron core (80-99%) did not remove tungsten from the rocky material in the mantle during formation’, explains Tais W. Dahl.NBI: “The result of the research means that the Earth and the Moon must have been formed much later than previously thought – that is to say not 30 million years after the formation of the solar system … but perhaps up to 150 million years after the formation of the solar system.”Despite these wild swings in the story, both articles spoke of the collision theory as matters of fact.  “The Earth and Moon were created as the result of a giant collision between two planets the size of Mars and Venus, the NBI article said.  Similarly, “Earth was formed during the creation of our Solar System when Moon and Mars-sized protoplanets collided,” the ETH article stated flatly, as if no one disagrees – but geologist Apollo 17 astronaut Harrison Schmidt disagrees with it (11/04/2002), and it has numerous problems (01/26/2007, 02/19/2007).Here is more job security for storytellers.  They don’t have to be right.  They’re not even trying to tell the truth.  They’re happy if such and such a set of models are consistent with a few observations.  Well, guess what!  An infinite number of theories are consistent with partial observations.  This allows them to play their little computer games and simulators and make things come out partially consistent all the time, and thus keep their jobs comfortably till retirement.  They never have to tell the truth, the whole truth, and nothing but the truth.  They never have to show progress toward the truth.  No one could ever prove them wrong without a time machine.  It’s the perfect scam.  The tweak space is greater than the constraint space.  There is plenty of room for centuries of modelers to play this scam, publish their papers, get paid, and look like experts, without having any accountability.  What a racket.(Visited 10 times, 1 visits today)FacebookTwitterPinterestSave分享0last_img