Piranhas' reputation vs reality

This Boxing Day and holiday season, our present to you is the science of gifts.

First, we investigate the health benefits of donating blood, and find out about the predator sharing a feast of food in the Arctic.

We’re then joined in the studio by physicist Dr Krishma Singal from Rice University, who unravels the soft-matter physics and brilliant engineering potential of knitting.

Next, we discuss the reputation of piranhas, enquire about the uniqueness of our sneezes, and break down how salting roads makes them safer in the winter.

All that, plus many more Unexpected Elements.

Presenter: Alex Lathbridge, with Camilla Mota and Meral Jamal Producer: Imaan Moin