What actually makes ice slippery enough to skate on: pressure melting, friction heating, or an intrinsically liquid-like surface layer?
#condensed-matter
Post a problemIs it true that centuries-old stained-glass windows are thicker at the bottom because glass is secretly a slowly flowing liquid?
Why do snow crystals always grow with six-fold symmetry, and why is no two snowflakes exactly alike?
Why does a cold squash ball barely bounce, while the same ball bounces energetically once warmed up by play?
Why does a drying layer of mud or paint crack into a network of roughly polygonal (often near-hexagonal) plates?
How do rod- or disk-shaped molecules self-organize into the partially ordered liquid-crystal phases, and what microscopic physics produces ferroelectric materials with a switchable spontaneous electric polarization?
Can carbon atoms self-assemble into closed cage molecules (fullerenes) and rolled-up cylindrical sheets (nanotubes), and can these exotic carbon forms be produced, understood, and put to practical use?
When you bend a dry piece of spaghetti until it snaps, why does it almost always shatter into three or more pieces instead of cleanly breaking in half?
Why does a pile of dry sand (or any granular material) poured from a point always come to rest at roughly the same characteristic slope, the 'angle of repose,' regardless of how much sand is poured?
Von Neumann's law generalized to 3D foam coarsening
Research level
The 1952 law for how 2D bubbles in a foam grow or shrink based only on their number of sides was long unmatched in 3D -- does an analogous simple law exist for real three-dimensional foams and grain structures?
Does deeply supercooled water actually separate into two distinct liquid phases (a long-hypothesized liquid-liquid critical point), rather than remaining just a single metastable liquid?
Non-Abelian anyons at quantum Hall filling 5/2
Research level
Does the fractional quantum Hall state observed at filling factor 5/2 host exotic quasiparticles (non-Abelian anyons) whose braiding statistics could form the basis of topological quantum computers, and can this be conclusively demonstrated?
Why do electrons confined to two dimensions in a strong magnetic field condense into exotic liquid states carrying fractionally charged, sometimes non-abelian, quasiparticles?
Why do certain desert sand dunes emit a loud, sustained booming or humming sound (sometimes audible for miles) when sand cascades down their slope, while most sand dunes and beaches stay completely silent when disturbed?