This Year On Earth

by Mary Hrovat In 2018, Earth picked up about 40,000 metric tons of interplanetary material, mostly dust, much of it from comets. Earth lost around 96,250 metric tons of hydrogen and helium, the lightest elements, which escaped to outer space. Roughly 505,000 cubic kilometers of water fell on Earth’s surface as rain, snow, or other…

Earth Is (Still) A Clock

by Mary Hrovat Before the second was defined in terms of the characteristics of the cesium atom, before leap seconds or leap days or Julian dates or the Gregorian calendar, before clocks, even before the sundial and the hourglass, there were sunrise, sunset, and shadows. I’ve been thinking about timekeeping using shadows because a tulip…