Kids invent stuff and the coldest city in the world

Ruth Amos is from the YouTube channel Kids Invent Stuff, and is chatting to Dan all about the cool things they've been inventing, and bringing the inventions to life! 

Plus if you think you're cold in the snow this week, Dangerous Dan is looking at Yatutsk, the coldest city on earth, scientists observe a mark in the sky from the first ever stars and techno mum explains how fingerprint scanners work.