Sand, spanning miles of beaches, carpeting vast oceans and deserts, is a visual metaphor for limitless resources. Yet researchers in this week’s journal Science seize another metaphor – sand in an hourglass, marking time running out.
Sand, spanning miles of beaches, carpeting vast oceans and deserts, is a visual metaphor for limitless resources. Yet researchers in this week’s journal Science seize another metaphor – sand in an hourglass, marking time running out.