Readers discuss Earth’s hidden electric field, black hole measurements, more

Location, location

Scientists launched a rocket from Svalbard, Norway, that measured Earth’s ambipolar electric field for the first time. The weak field may control the shape and evolution of the upper atmosphere and may contribute to Earth’s habitability, astronomy writer Lisa Grossman reported in “At long last, scientists detect Earth’s hidden electric field.”

Reader Jayant Bhalerao, a college physics instructor, found the story useful in class: “We will share it with our students, so that they can appreciate how things they are learning in the textbook have real-life applications.”