Every year, companies and space agencies launch hundreds of rockets into space^[1] – and that number is set to grow dramatically with ambitious missions to the Moon, Mars and beyond. But these dreams hinge on one critical challenge: propulsion – the methods used to push rockets and spacecraft forward.

To make interplanetary travel faster,...

Curious Kids^[1] is a series for children of all ages. If you have a question you’d like an expert to answer, send it to This email address is being protected from spambots. You need JavaScript enabled to view it.^[2]. How will the universe end? – Iez M., age 9, Rochester, New York Whether the universe will “end” at all is not certain, but all evidence suggests it will continue being

Pecans have a storied history in the United States. Today, American trees produce hundreds of million of pounds^[1] of pecans – 80% of the world’s pecan crop^[2]. Most of that crop stays here. Pecans are used to produce pecan milk, butter and oil, but many of the nuts end up in pecan pies.

Throughout history, pecans have been...