Posted by Ellen

In the cells of a salivary gland of a mouse, pictured above at left, and deep within the crust of a neutron star, shown at right, are multilevel structures connected by spiraling ramps, an architecture familiar to us all as the parking garage.

In fact, each of the levels in both these structures is connected to the levels above and below by two mirror-image ramps, one spiraling left, the other right, pretty much like separate up and down ramps in a real parking garage.

The parking garages inside living cells–your cells, my cells, even those nasty cells living underneath a rock–consist of flat membranes visible with a scanning electron microscope. These membranes surround the cell nucleus, where biophysicists say they function as the "shop floor of protein synthesis." Knobby little protein-making thingamabobs called ribosomes dot the membranes "like cars populating a densely packed parking structure."

Best of all, if the cell is called on to make more proteins and thus has a need for more spaces in which to park ribosomes, the garage "can add more levels as it gets full."

The parking garages in neutron stars are not directly observable, of course, since the stars are far, far away and millions of degrees hot and very nearly as punishing, gravitywise, as a black hole. Physicists "see" the garage structures when they run computer simulations that mathematically impose on tens of thousands of hypothetical atoms the various forces associated with neutron-star development.

The forces involved are pretty crazy. Neutron stars appear when very large stars–several times as big as our sun–grow old and run out of the nuclear fuel that gives them their twinkle. They explode as supernovae and then collapse into tiny little astronomical bodies, only 10 or so km in diameter, that are so dense that a teaspoonful of neutron-star stuff would weigh about ten billion tons.

The way they get that dense is by smushing atomic particles together till normal atomic structure is obliterated. A proton and an electron mashed together make a neutron, and gazillions of neutrons mashed together make a neutron star. There are believed to be at least 100 million neutron stars in the Milky Way.

The parking garages postulated in neutron-star crust are not well understood, to put it mildly. Perhaps their geometry plays a role in the way the stars cool off or lose magnetic energy over time. Perhaps the sheets and ramps transport protons, making them into superconductors.

Scientists want to know. One of the scientists who wants to know very badly, and who has been modeling neutron-star architecture for many years now, is my own little brother, Charles Horowitz at Indiana University.

 One of the scientists investigating parking garages in cell biology, and the one who stumbled on the parallels between the architecture of living cells and that of neutron stars is Greg Huber at the University of California Santa Barbara. Huber was once a student of my brother's.

Maybe Huber and Horowitz, working together, will finally establish that the parking garage is the fundamental architecture of the universe. Some of us would prefer the tree house or at least the flying buttress, but we only live in this world.