You can churn butter on a 6-mile trail run
Libby Cope and her boyfriend, Jacob Arnold, filled zip-top bags with heavy cream and salt, stuffed them into their trail-running vests, and headed out for a six-mile run in Oregon. By the time they got back, the constant jostling had churned the cream into butter.
Cream is fat droplets suspended in liquid, and if you shake it l…
