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Why do animals have different pupil shapes?Pupil shapes vary widely across the animal kingdom, from the W-shaped pupils of cuttlefish to the bar-like pupils of goats. But why are animal pupils shaped so differently?
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Why don't you usually see your nose?Our nose is right in front of us. So why don't we normally notice it?
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What's the fastest a human can grow?Humans grow tall in spurts, but what's our fastest period of growth?
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Why can pumpkins grow so large, but blueberries can't?Most fruit is pretty small, so why do pumpkins grow to such enormous sizes?
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Could we ever build a transatlantic tunnel?Will we ever have an underwater tunnel between New York and London?
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Why do kangaroos have 3 vaginas?Female kangaroos have one tail, two feet and three vaginas when they're giving birth.
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Do sperm really race to the egg?It's commonly thought that sperm "race" to the egg, with the winner fertilizing it. But is this really the case?
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Are there any planets in the universe that aren't round?Earth is round, but are there any planets in the universe that aren't?
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Why can't you suffocate by holding your breath?The human body has a number of mechanisms that prevent you from holding your breath until you suffocate.
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Why is everything in space always moving?From the moment of the Big Bang, everything in the universe has kept moving, but why is that?
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When did humans start cooking food?When did humans first roast food over a fire? Archaeology and biology can shed light on this mystery.
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How many galaxies are in the universe?If we can see at most 3% of the universe, how can we estimate the total number of galaxies in it?
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Should you floss before or after you brush your teeth?You've probably had a dentist remind you to floss — but when's the best time to do so?
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Why do dogs look like their owners?When a dog looks strikingly like its owner, is that a coincidence or is there more to the story?
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What would happen if a black hole wandered into our solar system?Black holes aren't "cosmic vacuum cleaners," but what would happen if one wandered into our solar system?
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When did humans start wearing clothes?Clothes don't survive the way artifacts made of stone, bone and other hard materials do, so scientists have to get creative to answer this question.
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Why do babies rub their eyes when they're tired?Babies usually rub their eyes when they're tired, but why?
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Do we have taste receptors in other parts of our body?Taste receptors have been found far beyond the tongue, but do they help perceive taste or work like the ones in our mouths?
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Why don't we feel Earth spinning?Earth moves around the sun at 67,000 mph and makes a full rotation once every 24 hours. So why can't we feel the Earth's rotation?
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Do any animals keep pets like humans do?Humans have all kinds of pets, but do any other animals have them too?
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Why do cats throw up so much?What you think is cat vomit may actually be something else, like a fur ball or regurgitation.
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Why does the moon sometimes have a 'halo'?The moon's halo is always 22 degrees wide in the night sky when it appears. So what causes it?
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What is the third law of thermodynamics?Reference According to the third law of thermodynamics, the entropy of a perfect crystal is zero when the temperature of the crystal is equal to absolute zero (0 kelvin).
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Do trees exist (scientifically speaking)?Trees don't fit into a species, family or even an order. So do they really exist, scientifically speaking?
