Synopsis
A piece of metal that defines the mass of a kilogramme has, over time, lost the equivalent of the weight of an eyelash. What are the consequences for how we measure our world?
Similar broadcast resources

1: Life From Light | How to Grow a Planet
How plants have driven the greatest changes to the Earth. Prof Iain Stewart shows how they first harnessed light from the sun and created our life-giving atmosphere.

3: Brave New World | Pandemic 2020
From the Amazon to churches in the US and the slums of Delhi, reason and science battle conspiracy and denial.