Astronomers have long struggled to pin down how long a day lasts on Venus, but new research suggests the difficulty stems not from flawed measurements but from real variations in the planet's spin.In a new study, scientists used a massive radar system to bounce lightwaves off our neighboring planet over the course of more than a decade. As a result, the researchers were able to measure how tilted Venus' axis is, how big its core is, and how long it takes the planet to complete one full rotation...Between 2006 and 2020, the team used this radar system to bounce a...