Time

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to curiouskidsus@theconversation.com. Why does a leap year have 366 days? Does the Earth move slower every four years? – Aarush, age 8, Milpitas, California You may be used to hearing that it takes the Earth 365 days to make a full lap, but that journey actually lasts about 365 and a quarter days. Leap years help to keep the 12-month calendar matched up with Earth’s movement around the Sun. After four years, those leftover hours add up to a whole day. In a leap year, we add this extra day to the month of February, making it 29 days long instead of the usual 28. The idea of an annual catch-up dates back to ancient Rome, where people had a calendar with 355 days instead of 365 because it was based on cycles and phases of the Moon. They noticed that their calenda...

As a child growing up in the early 1990s, I remember learning in school about the greenhouse effect. Carbon dioxide released by burning fossil fuels traps heat near the Earth’s surface, like the glass of a greenhouse. I imagined myself on the playground, roasting inside a humid hothouse. Fast forward 30 years, and the terms have changed. For a while, “global warming” was the go-to expression for talking about rising global temperatures and the role of human activities, particularly the use of fossil fuels. It had a spike in internet searches in 2007, probably due to former Vice President Al Gore’s documentary “An Inconvenient Truth: A Global Warning,” which hit theaters in 2006. Near the end of the Obama administration, “climate change” became the most common term. It’s now trending in Google searches more than global warming. Both terms make the same point: Rising global temperatures have major consequences on local weather...