In this episode of Ask, if the universe is expanding, what's it expanding into? What's the relationship between descended testes and the chance of having children? Why does more urine come out when I stand rather than sit on the loo? How do surgeons join the cut ends of a colon together? At what age is it suitable to start taking creatine supplements? Why do I wake up in the middle of the night? Like this podcast? Please help us by supporting the Naked Scientists

On Ask! the Naked Scientist this week: What led to the 'leopard spots' found on Mars? What is the purpose of finger and toe nails? How do bone conduction headphones work? Why do non-magnetic metals sometimes interact with magnetic objects? What role did our teeth play in our evolution? What's the cause of my unintended weight loss? Could astronauts create an environment for life on Mars? What's wrong with a pear shape? Like this podcast? Please help us by supporting the Naked Scientists

Is it dangerous to have floaters in your eye? Can you power a lamp with your mouth? Are nations in the global north more innovative than nations in the global south? How can you control your phobias? How do leap years come about? Dr Chris Smith and Relebogile Mabotja have all the answers... Like this podcast? Please help us by supporting the Naked Scientists

Is the flipping of Earth's magnetic field a concern? Why might half-filled ice cube trays freeze faster? Why does sex make you sleepy? Why might you get an 'electric shock' from moving your head? Is nicotine addictive? Why does scratching an itch feel so good? Why do we have different blood groups? What are statins? Could we ever see the dark side of the moon? Dr Chris Smith and Clarence Ford have all the answers... Like this podcast? Please help us by supporting the Naked Scientists

Dr Chris answers listener questions including: do men and women have an equal chance of getting sports injuries? What health benefits can a sugar free diet bring? Why does my sock shift around my foot at night? How should we navigate testosterone levels in women's sport? How can we treat hypertrophic cardiomyopathy? Is 'biowater' a marketing gimmick? Like this podcast? Please help us by supporting the Naked Scientists

Dr Chris is back to answer listener questions. Why do cat's eyes reflect bright colours? What are the short, high pitched ringing noises that can sometimes be heard? What causes Bell's palsy? Will botox help keep my eyelid up? Like this podcast? Please help us by supporting the Naked Scientists

Do animals feel fear the same way that we do? Do diet supplements boost your immune systems? Can using phones and headphones change the shape of your body? Why don't birds get electrocuted on pylons? Is the northern hemisphere more 'innovative' than the south? Dr Chris Smith and Relebogile Mabotja have all the answers... Like this podcast? Please help us by supporting the Naked Scientists

Dr Chris takes on more listener questions. Including: is Chinese medicine separate from Western medicine? Why do we sometimes cry in response to feelings of sadness and joy? Why do I have a blotch in my vision after looking directly at a light source? Why do kids cry when they get injured, but adults less so? What happens if I scratch a mosquito bite? What is the relationship between science and religion. Like this podcast? Please help us by supporting the Naked Scientists

The questions keep coming for Dr Chris. This week they include: have scientists got their hands on the oldest ice ever studied? Does putting the air conditioning on too high or low make you ill? What factors contribute to chronic mental illness? How do you reduce puffiness under the eyes? Can cold weather make healed operation sites sore again? Like this podcast? Please help us by supporting the Naked Scientists

In this episode of Ask! Dr Chris is asked: what is ivermectin? Are sodium ion batteries a rival to lithium? Is the Earth spinning slightly faster? Why do we warn against using phones around petrol stations? Like this podcast? Please help us by supporting the Naked Scientists