In October, members of the General Conference on Weights and Measurements will consider potential changes to the way time is measured on Earth. Currently, an extra second—called a leap second—can be added to atomic clocks to keep them aligned with the Earth's natural rotation, which is based on the position of the sun. However, recent observations suggest that the Earth’s rotation is speeding up slightly, which could complicate the use of leap seconds and the synchronization of global timekeeping systems. To better understand the implications, Tom Whipple, host of BBC Inside Science, visited Setnam Shemar, a principal scientist at the National Physics Laboratory. Shemar explained how scientists manage the delicate balance between atomic time and solar time, ensuring that clocks remain accurate despite natural variations in the Earth’s rotation. These adjustments are crucial for maintaining consistency in global systems like GPS, telecommunications, and financial markets. Associate Professor Claire Nichols from Oxford University highlighted the challenges that changes in Earth’s rotation pose to timekeeping. She emphasized that while the Earth’s rotation has been slowing down over long periods due to tidal forces, recent data suggest a slight acceleration. This shift could require rethinking how leap seconds are used or even the way time is defined in the future. In addition to timekeeping, Professor Kit Yates discussed recent scientific discoveries, including how researchers estimate the body temperature of the Tyrannosaurus rex by analyzing fossilized bones. He also addressed whether the record for the highest temperature that complex life can survive has been broken, offering insights into the resilience of life in extreme conditions. Meanwhile, the Royal Society Trivedi book prize is nearing its announcement. Author Bill Bryson expressed his admiration for the prize, while shortlisted author Lise Barnéoud discussed her book, Hidden Guests, which explores the fascinating science of microchimerism—when cells from another person can live within our bodies, often without us even knowing.