GRAVITY AND ME: THE FORCE THAT SHAPES OUR LIVES, BBC4, 9pm

GRAVITY is so obvious we rarely think about it, which reminds me of a comical scene from a Tintin story in which a baddie, trying to enrage Captain Haddock, slyly asks him if he sleeps with his beard inside or outside the covers.

The captain had never considered this before and so that night he can’t sleep, and is furiously tossing and turning and trying out how it feels to have his bushy beard in or out.

That’s how I think of gravity: we don’t consider it in daily life, but when this programme compels us to, it’s quite overwhelming.

The cool physics professor Jim Al-Khalili talks us through this force that “sculpts the universe” and shows how it affects our daily lives, with the power to change our weight and height and how quickly we age.

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INSIDE NO 9, BBC2, 10pm

THIS is a repeat but I’m including it here as it’s one of the most powerful things I’ve seen on TV.

It was first broadcast two years ago but I find myself thinking of it often.

Inside No 9 is usually described as a dark (very dark!) comedy anthology, but there is no humour in this episode, only tension, fear and an almost unbearable sadness.

Sheridan Smith plays Christine, a care-free party girl. There’s a party, a one-night stand, which then becomes a relationship, then on into a marriage.

A child is born ... we go racing through Christine’s life at an increasingly fast pace and see her change from the laughing, tipsy girl in the first scene to a stressed and confused single mother who is haunted by strange images of an anxious man in her flat.

She must be going mad, you think. She must be ill.

Then everything becomes clear and you will cry furiously for a week.