The Japanese mission to bring back a sample of an asteroid, are changes in Earth's magnetic field linked to climate change, what causes tip-of-the-tongue experiences when you cannot remember a word, why does the Moon look much larger on the horizon, how do farts form and can farts be harnessed to power things? And is a TV screen next to my bed bad for me? Will mobile phone use do me harm? Why flowers and chocolates for Valentine's Day? Join Dr Chris for this week's crop of questions and answers... Like this podcast? Please help us by supporting the Naked Scientists

Does marijuana help with cancer? How can one sibling be smart and another be stupid? Are we alone in the Universe? Can vitamin D kill cancer? Plus, male contraception. Like this podcast? Please help us by supporting the Naked Scientists

Why do we get butterflies in our stomach? Why is singing in tune difficult? What does vitamin K do? Is aluminium foil safe? How do you measure metres above sea level? Can cold water make you wee more? Like this podcast? Please help us by supporting the Naked Scientists

Is the sky actually blue? Does petrol go off? What causes myeloma? Why are chicken eggs different colours? If salt melts ice, why are icebergs frozen? Like this podcast? Please help us by supporting the Naked Scientists

Why does dog poo change colour? What happens to the brain when we're sleeping? Do animals also get jet lag? Is time travel possible? Like this podcast? Please help us by supporting the Naked Scientists

How do you measure time when traveling close to light speed? How do you predict the weather? Why don't zebras look dirty? How do they get the stripes into toothpaste? Why do wheels look like they spin backwards? Why can some people move their ears? Like this podcast? Please help us by supporting the Naked Scientists

Why don't birds get electrocuted on an electric fence? Why do I want to sing along to tunes I know? Does a cut onion soak up toxins from the air? Is Everest really the tallest mountain? Why does chilli make my head itch after I've shaved off my hair? What's the prospect of terraforming Mars? And can women synchronise their periods? Plus, news of the New Horizon's probes fly-by of Kuiper Belt Object (KBO) Ultima Thule, with Chris Smith and Eusebius McKaiser... Like this podcast? Please help us by supporting the Naked Scientists

Why do I appear upside down in a spoon? Is the Universe getting bigger or smaller? What would Earth be like if we had two moons? What's the atomic weight of silver? Why does my bum tingle when I get my hair cut? If water can expand why can't it compact? Why do animals never run in a straight line? Like this podcast? Please help us by supporting the Naked Scientists

Can I catch germs from cockroaches? How does the shape of the ear tell you where something is? If the Universe is expanding, is it being pushed or pulled? Is rain water better for crops than irrigation? What's the difference between macro and micro evolution? Do men enjoy spice more than women? Like this podcast? Please help us by supporting the Naked Scientists

How do we tell where a sound is coming from? Why does wine taste differently after many years? Why can't we manufacture blood? Why was Pluto downgraded? Plus, a new blood test for cancer. Like this podcast? Please help us by supporting the Naked Scientists