STRETCHY materials, such as rubber or melted cheese, get thinner when you
pull them, right? Well, not always. A few substances do the opposite—they
get wider when stretched—and a group of scientists now believes that the
superdense shells of neutron stars have this odd property. This could shed light
on starquakes, in which giant cracks tear through neutron star crusts, they say.
It could also help produce exotic materials here on Earth.
One measure of the way a material responds to stretching is called the
Poisson’s ratio. Everyday materials have a positive Poisson’s ratio. But some
foams and…
