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Why are there seven colours in a rainbow?

Seeing seven colours in a rainbow is down to what we expect to see, not reality. In fact, there are many more colours in a rainbow, as our readers explain

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Why do snails sometimes leave dotted trails?

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Side view portrait of two young African-American musicians playing guitar and writing music together while sitting on floor in recording studio, copy space

This week鈥檚 new questions

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B1GCT0 Satellite Image of The Earth from Space

What would Earth be like if life had never existed?

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a metal water barrel stands in the garden; Shutterstock ID 1980910310; purchase_order: -; job: -; client: -; other: -

How does water become stale?

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If sitting cross-legged is unhealthy, why is it so comfortable? Part 2

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Common frog (Rana temporaria) sheltering from rain under toadstool (Macrolepiota procera) the Netherlands

This week鈥檚 new questions

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an explosion of colored particles on a dark background, composition on the theme of science, molecular physics, space and a festive background

How does a photon know to travel at the speed of light?

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KMXN2B Beautiful fun happy smiling African American couple wearing white shirts laying in grass, faces of woman and man next to eachother in opposite

Why do humans show their teeth to signal friendship or mirth?

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2D6CTBM Wedding candy bar with different colored bright cupcakes, macaroons, cakes, jelly and fruits.

This week鈥檚 new questions

What makes a cake a cake and a biscuit a biscuit? And is there an upper limit to temperature, akin to absolute zero?

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Is the sky really clearer early in the morning? If so, why?

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What is the evolutionary reason for superstitious behaviour?

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This week鈥檚 new questions

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What is the smallest whole number with no interesting properties?

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