Science Riddles

I shine brightest in the dark. I have burned for billions of years yet you can cover me with your thumb. I am enormously far away yet I guide sailors home. What am I?

I grow full then thin then disappear then return again. I light the night but I make no light of my own. I pull the ocean but I cannot touch it. What am I?

Everyone sees me every day but nobody can look directly at me. I rise every morning and die every night yet I never truly disappear. What am I?

I measure how hot and cold the world is but I never feel it myself. I rise when others suffer and fall when they are relieved. What am I?

I attract some things and repel others. I am strongest at my ends. I have an invisible force yet I am made of metal. What am I?

I weigh everything without opinion. I am the symbol of justice and the tool of the trader. I have two sides but I always seek balance. What am I?

I make the far seem near and the invisible seem real. I brought humans to the stars without leaving the ground. What am I?

I make the invisible visible. I revealed a world hiding beneath your feet, in your water, and on your skin. What am I?

I store power but I am powerless on my own. I make devices come alive. Leave me unused for too long and I slowly die. What am I?

I show you a version of yourself from a tiny fraction of a second in the past. The image you see is never truly you right now. What am I?

I guided explorers across unknown oceans without a single star to follow. I am ancient yet still used today. I have no engine but I have pointed the way to every continent. What am I?

I cover more than seventy percent of the earth yet most of me has never been seen by human eyes. I am more unexplored than the surface of the moon. What am I?

I am the sea breathing in and out twice a day. I am controlled by something a quarter of a million miles away. Sailors fear me and fishermen live by me. What am I?

I am the sky dancing with colour near the poles. I am caused by particles from the sun colliding with the atmosphere. I have inspired myths in every Arctic culture. What am I?

I hold planets in orbit and keep you on the ground. I am invisible but I am the most powerful force over long distances. I cannot be switched off. What am I?

I am the smallest building block of all ordinary matter. I am mostly empty space yet I feel solid. Split me and you release enormous energy. What am I?

I am the most extreme object in the universe. Nothing that enters me ever returns. Not even light escapes my grasp. I am invisible yet I bend space around me. What am I?

I am the blueprint for every living thing on earth. I am twisted like a ladder. I am found inside almost every cell of your body. I contain the instructions that make you, you. What am I?

I am an invisible river that flows through metal. I power everything in your home yet you cannot see me. Touch me incorrectly and I can kill. What am I?

I have two poles that can never be the same. Pull two of me apart and I become two complete versions of myself. I can attract or repel without touching. What am I?

I am a vibration that becomes meaning. I travel through air, water, and stone but not through space. I can shatter glass and soothe a child. What am I?

I am invisible yet without me nothing burns and nothing lives. I make up a fifth of the air around you. Too much of me is toxic, too little and you die. What am I?

I am the basis of all life on Earth. I can be as soft as pencil lead or as hard as the hardest substance known. I am in every living thing and every dead thing. What am I?

I split white light into seven colours. I reveal what was always there but hidden. I am a triangle that shows the secret of sunlight. What am I?

I teach your body to fight an enemy it has never met. I am made from the thing that could harm you. I have saved more lives than any other medical intervention in history. What am I?

I am sound that has gone on a journey and returned. Bats use me to hunt. Ships use me to find the bottom of the ocean. I am the voice of the mountain answering back. What am I?

I was once alive but now I am stone. I am millions of years old yet I tell us about creatures that lived long before humans. What am I?

I catch light that left its source before the Earth existed. I look outward but I also look backward through time. The bigger I am, the further back I can see. What am I?

I am your home galaxy yet you will never see all of me. I contain over two hundred billion stars. You can see a slice of me on a clear dark night as a band of light. What am I?

I am a dirty snowball with a tail of fire. I visit the inner solar system occasionally and depart for thousands of years. Ancient people thought I was an omen. What am I?

You call me a shooting star but I am no star. I am a rock burning up in the atmosphere. I make wishes come true — or so people say. What am I?

I orbit a star, I have cleared my neighbourhood, and I am nearly round. I am something specific — not a moon, not a star, not an asteroid. What am I?

I am a planet wearing a crown of ice and rock. I am the lightest planet relative to my size — I would float in water if there were an ocean large enough. What am I?

I sound like a measurement of time but I measure distance. I am the distance light travels in a full year. The nearest star to our sun is four of me away. What am I?

I happen when one world stands between another and its light. For a few minutes day becomes night. Animals are confused and humans fall silent. What am I?

I am the death of a star so violent that I briefly outshine an entire galaxy. I scatter the atoms that make up planets and people across the cosmos. What am I?

I am a cloud in space where stars are born. I am made of gas and dust. I glow with colour that takes a telescope to reveal. What am I?

I am neither plant nor animal. I am the fruiting body of an organism that lives mostly underground. I can save lives as medicine or take them as poison. What am I?

I weigh about three pounds yet I contain your entire universe. I can imagine things that do not exist. I am the only organ that named itself. What am I?

I am your largest organ and you wear me every day. I am waterproof, self-healing, and sensitive. I am the only organ visible to other people. What am I?

I am a bag of acid that dissolves what you eat. I expand to hold a full meal and shrink when empty. I growl when I want attention. What am I?

I am your body's chemist, detoxifying everything that enters your blood. I have over 500 functions. I can regenerate even if most of me is removed. What am I?

I carry messages faster than thought from every corner of your body to your brain. I am thinner than a hair yet I can be over a metre long. What am I?

I am an invisible army that fights for you every moment of every day. I remember every enemy I have ever defeated. I can be defeated by things too small to see. What am I?

I am hiding in every circle ever drawn. I begin 3.14159 and never end and never repeat. I am irrational yet I am everywhere in nature. What am I?

I am a number with exactly two factors. I am divisible only by one and myself. There are infinitely many of me, but I become rarer as numbers grow larger. What am I?

I am a sequence where each number is the sum of the two before it. I appear in flower petals, shell spirals, and pine cones. I start 1, 1, 2, 3, 5, 8... What am I?

I am a window to the past disguised as a tool for the future. Everything I show you has already happened. The further I look, the further back in time I see. What am I?

An apple fell and changed the course of physics. I pull everything toward everything else. I am the weakest of the fundamental forces yet I hold galaxies together. What am I?

I have shown you your face every day of your life. Yet you have never seen your face as others see it. What am I?

I make the world flat. I am always wrong but always useful. The bigger I am the more accurate I am but the less portable. What am I?

The oldest of me alive today were saplings before Christ was born. I clean your air, cool your city, and hold the soil together. I am the tallest living thing on Earth. What am I?

I contain an entire tree yet I fit in a pocket. I need darkness to begin my journey and light to complete it. I am the ultimate example of potential. What am I?

I am the part of the tree you never see. I can be larger than the tree above ground. I speak to other trees through underground networks. What am I?

I am one of nature's most sophisticated structures. I am almost weightless yet I can support flight. Each of me contains thousands of interlocking hooks. What am I?

I am a piece of ocean left behind by the tide. I am a whole ecosystem in a rocky puddle. I am destroyed by one careless foot. What am I?

I am your identity written on every surface you touch. No two of me are alike in the entire world. I have been used to catch criminals and identify the dead. What am I?

I am what keeps the Moon from flying away. I am what keeps you from floating off into space. I am the weakest force in the universe over short distances but I rule over long ones. What am I?