Married at First Sight, Channel 4, 9pm
FINDING your soulmate, somebody you can spend the rest of your life with, can often be a challenging and trying process. Those who took part in the first two series of this reality show adopted a different approach. They were matched on a range of scientific and compatibility criteria by a panel of experts, who looked on as they tie the knot just seconds after meeting. Cameras then followed the couples during the first weeks of their fledgling relationships. Tonight police officer Stephanie is matched with quantity surveyor Benjamin, before estate agent Carrie and insurance broker Wayne get together.

From Ice to Fire: The Incredible Science of Temperature, BBC 4, 9pm
IN this new series, physicist Dr Helen Czerski is exploring the temperature scale – and where better to start than Absolute Zero? She explores how cold has shaped the world around us and why frozen might not mean what you think it does. She also meets the scientists who are discovering a new world of possibilities by pushing temperature to its limits, and finds out why the extraordinary ways in which matter behaves when it approaches Absolute Zero could lead to some major technological advances.

Death in Paradise, BBC 1, 9pm
ANOTHER mystery for Ardal O’Hanlon as Irish detective Jack Mooney working on the Caribbean island of Saint Marie, where the sun shines all day and it seems half the residents are killers-in-waiting. And so it appears this week as someone from JP’s past is caught red-handed at a murder scene, raking up old memories for the young officer. But can the DI unravel the complex mystery to get at the truth?

Children Who Kill, STV, 9pm
JUVENILES found guilty of murder in the US are given life, with no chance of parole – a hardline approach that in 2015 prompted the American Supreme Court to rule such sentences as “unconstitutional”. With the system now under review, Susanna Reid travels to the US and talks to young killers about their crimes and life in jail, including one speaking for the first time since discovering he might have the right to have his sentence reviewed. Susanna also meets the families of victims.