A hippopotamus is sprayed with water on a hot summer day at Anna National Zoological Park in Chennai, India on April 26, 2017. (Photo by Arun Sankar/AFP Photo)

A man carries food supplies on a donkey to Dhalamlam Mountain in the Jafariya district of the western province of Raymah, Yemen June 2, 2016. In villages perched high on a mountain in Western Yemen, residents are a safe distance from a conflict raging throughout most of the country but have had to turn the clock back on their lifestyles by centuries. (Photo by Abduljabbar Zeyad/Reuters)

Women sell bananas in the street, after traders in markets were prohibited from selling any non-food items in an attempt to halt the spread of the new coronavirus, in Kampala, Uganda Thursday, March 26, 2020. (Photo by Ronald Kabuubi/AP Photo)

Photographer Loes Heerink spent hours waiting on bridges in Hanoi to capture the street vendors who walked underneath. She recently launched a Kickstarter project to publish a book of these images. Here: “In Hanoi there are a lot of street vendors who roam the city with their bicycles trying to sell goods, from vegetables to flowers”. (Photo by Loes Heerink/The Guardian)

Record snowfall in the Sahara Desert near the town of Ain Sefra in Algeria on January 21, 2017. (Photo by Geoff Robinson/Rex Features/Shutterstock)

Margaret Morris dancers exercising on the sands at Saint-Idesbald. (Photo by Fox Photos/Getty Images). August 1929

From footballs to live fish, delivery mopeds piled high with unwieldy, unlikely goods are one of the Vietnamese capital’s most distinctive sights. As the city plans to ban motorbikes altogether, photographer Jon Enoch captured the drivers at work. (Photo by Jon Enoch/The Guardian)

Soap Bubble Structures by Kym Cox. Bubbles optimise space and minimise their surface area for a given volume of air. This phenomenon makes them a useful tool in many areas of research, in particular, materials science and “packing” – how things fit together. Bubble walls drain under gravity, thin at the top, thick at the bottom, which interferes with travelling lightwaves to create bands of colour. Black spots show the wall is too thin for interference colours, indicating the bubble is about to burst. (Photo by Kym Cox/2019 Science Photographer of the Year/RPS)