How often have you “slept on” a problem and found that the right answer was easily reached afterwards? More and more research is suggesting that sleep is essential not just to recharge our energy, but to help process the day’s events and plan for the future. While scientists often use human subjects in sleep studies, the work that taps directly into brain activity is more often done with rats. But how do you listen in on brain activity in the first place? In this clip from the 2015 World Science Festival program “What is Sleep?” neuroscientist Matthew Wilson explains how it works.

Seven days, lots of science in the news. Here’s our roundup of some of the week’s most notable and quotable items: Researchers unlocked the genetic secrets behind the sweet scent of roses. The New Horizons spacecraft drew ever closer to Pluto, beaming back color images showing enigmatic dark spots 300 miles across along the planet’s equator. In the Amazon, many birds follow roving bands of noisy monkeys around; the primate parade flushes out tasty insects and also scares away predators. New memories, a new study suggests, can be linked to individual neurons in the brain.

Summer is going to stretch on a little bit longer this year thanks to the addition of a leap second. But it’ll be a fleeting add-on. On June 30, 2015, clocks will move from 11:59:59 p.m. to 11:59:60 before continuing normally into midnight on July 1. Why? “Earth’s rotation is gradually slowing down a bit, so leap seconds are a way to account for that,” NASA scientist Daniel MacMillan said in a statement. Adding this leap second will bring the time standard set by precise measurements of Earth’s rotation (UT1) more into line with the time standard set by atomic clocks (UTC). If the two time standards aren’t coordinated, the gap between the two could widen over years until an atomic clock is reading 6 p.m. when the sun is directly overhead.

Seven days, lots of science in the news. Here’s our roundup of some of the week’s most notable and quotable items. The first color movies of Pluto are starting to arrive from the New Horizons spacecraft. Dwarf porcupines can’t jump. Laser beams can be used to control the shape and direction of electrical discharges. Iowa State University researchers created tiny soft robotic tentacles that can handle delicate objects safely. The Neptune-sized planet GJ 436b sports a comet-like tail created by its red dwarf home star blasting 1,000 tons of hydrogen gas off the planet’s atmosphere every second. Yeti crabs have distinctive “hairs” on their bodies that provide a place for its favorite food source, bacteria, to grow. Genetically modified wheat tweaked to emit an insect-warning pheromone to drive away pests failed in field trials with aphids. Climate change is already thinning out California’s wildflowers.

The first roller coaster at Coney Island, which opened in June 1884, would barely rate in the kiddie section of a modern-day amusement park. The “Switchback Railway” trundled along at just six miles per hour over a series of gentle hills. Nowadays, roller coasters can put you through loop-de-loops, send you screaming up 38 stories to momentarily rise up free of gravity, and even hang you from a shoulder harness, limbs a-dangle, shooting through corkscrews and switchbacks and cobra turns, with your life in the hands of engineering. Arguably, no other leisure activity makes physics quite so visceral as the roller coaster. Here’s a quick breakdown of the forces that cause your stomach to drop—and keep you in your seat.