Stockcreations/Shutterstock
Why does a slightly damp sponge absorb water so much better than the same sponge when it is bone dry?
Bert Laan,
Ashurst, Hampshire, UK
Shutterstock/Vadim Sadovski
Why does our planet have an iron core, rather than one made of another abundant element such as silicon?
Greg Tanner,
Melbourne, Australia
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