Dipole model of the Earth's magnetic field (MLAT), or geomagnetic latitude, formula_10 is measured northwards from the equator (analogous to geographic latitude) and is related to formula_9 by formula_12. In this case, the radial and azimuthal components of the magnetic field (the latter still in the formula_9 direction, measured from the axis of the north pole) are given by formula_14 formula_15 formula_16 where formula_17 in this case has units of Earth radii (formula_18). Invariant latitude is a parameter that describes where a particular magnetic field line touches the surface of the Earth. It is given by formula_19 or formula_20 where formula_21 is the invariant latitude and formula_22
The Last Dog on Earth appeal to teen readers. "The Last Dog on Earth" was included in the "What Ails You?" category, comprising literature "about how diseases, disorders, and other general health related symptoms affect our lives". In a 2005 interview, Daniel Ehrenhaft mentioned that a school in Chicago created an extracurricular activity wherein "kids designed games and gadgets", having been inspired by Logan's hobby of inventing devices. "The Last Dog on Earth" has received mixed reception from critics, who have praised the plot, but criticized the heavy use of coincidences to advance the plot. "Kirkus Reviews" commented that "happenstance plays a large role in