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P2H56B Weasel standing upright, Mustela nivalis, Germany

Why do many animals have white underbellies? Part 2

Our readers continue to grapple with this question, taking into account the energy cost of producing dark pigment as well as the need for camouflage

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Male nose close up bottom view - hair in the nostrils; Shutterstock ID 1895123341; purchase_order: -; job: -; client: -; other: -

I see why we have two eyes and two ears – but why two nostrils? Part 2

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Piles of old tyres in a garage. Romania

This week’s new questions

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rainy days rain drops on the window surface ; Shutterstock ID 724215220; purchase_order: -; job: -; client: -; other: -

Why does water never move in straight lines?

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Male nose close up bottom view - hair in the nostrils; Shutterstock ID 1895123341; purchase_order: -; job: -; client: -; other: -

I understand why we have two eyes and two ears – but why two nostrils?

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an australopithecus, one of our ancestors; Shutterstock ID 790742188; purchase_order: -; job: -; client: -; other: -

When did humans first start to sing? Part 2

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JAPAN. Tokyo. Bank near Tokyo Station. 2002.

This week’s new questions

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Battle cruiser approaching light speed in an outer space wormhole, 3d digitally rendered illustration; Shutterstock ID 91289105; purchase_order: -; job: -; client: -; other: -

How long would it take to accelerate to 99 per cent light speed?

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an australopithecus, one of our ancestors; Shutterstock ID 790742188; purchase_order: -; job: -; client: -; other: -

Is it known when humans or our ancestors first started to sing?

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Lola the Cat, behind a window, London

This week’s new questions

What difference would it have made to our species’ technological development if glass wasn’t transparent? And can you reheat food without additionally cooking it? Is there a threshold temperature that begins the re-cooking process?

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Why do many animals have white undersides?

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Why do plastic clothes pegs fade and get brittle in the sun?

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Is it more efficient to cart water in a bottle or my stomach? Part 2

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This week’s new questions

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