What are the lights on curling stones? Explaining the Winter Olympic sport

The curling has captivated fans at the 2022 Winter Olympics in Beijing.

Great Britain’s curling mixed doubles pair Bruce Mouat and Jen Dodds are on course for a medal if they can defeat Norway in the semi-finals.

A win over the USA 8-4 rounded off their group final with Mouat delighted with the performance.

“It was our best team performance of the week and exactly the way we want to go into the semi-finals,” Mouat said. “We put a lot of stones in good spots to put them under pressure. Our draw weight was on point which is exactly what you need in mixed doubles.”

During games there are lights on top of the stones used, here is what they mean.

The lights are a tracking system to ensure the athletes release the stone before the first hog line - the red line at both ends where both teams must release the stone before passing it.

During Team USA’s second game against Italy, Stefania Constantini was penalised with a hogline violation in the sixth end.

A heat sensor is embedded into the ice and will be triggered if your hand continues to hold onto the handle while breaching the line, meaning each stone has batteries to power these sensors.

Failure to release your hand before the line will turn the lights red and that team will be forced to remove it from play.

It rarely happens at this elite level, but such is the pressure at the Winter Olympics, it can occasionally happen.

The official USA Curling rulebook states that each curling stone cannot be greater than 44 pounds (19.96kg) in weight, and no less than 38 pounds (17.24kg). The handle is included as part of the weight.

The stone’s circumference cannot exceed 36 inches (91.4cm) and cannot exceed 4.5 inches (11.43cm) in height.

The stones are made of a special type of