A distorted view

With the United Nations encouraging wider use of the Equal Earth map, a projection designed to better represent the true size of Earth's landmasses, the Unexpected Elements team have been thinking about distortion and the surprising new ways we can see the world and beyond.

We discover that every city's subway system has its own unique microbial fingerprint, so distinctive that researchers can identify a location from a simple swab. Then we meet the black-capped chickadee, a tiny bird whose remarkable memory-map helps it keep track of thousands of hidden food stores.

Astrophysicist Miguel Zumalacárregui joins us to explain gravitational lensing, the phenomenon that bends and distorts light as it travels through the Universe. We hear how these cosmic distortions help astronomers study distant galaxies, dark matter and even black holes.

We also learn why Europe's mountain summits are becoming greener while still losing rare plants, ask why many continents seem to point downwards, and explore the story behind the online maps in our pockets.

All that, plus many more Unexpected Elements.

Presenter: Marnie Chesterton, with Andrada Fiscutean and Paul Adepoju Producers: Alice Lipscombe Southwell, with Ella Hubber and Debbie Kilbride