Sunlight looks white but is a mixture of colours. When it passes through air, the tiny gas molecules scatter blue light much more than red light. Blue light reaches our eyes from every direction, so the sky looks blue.

Why is the sunset red?

At sunset, sunlight travels through much more air to reach us. Most blue light is scattered away on the long journey, and the red and orange light that is left comes through to our eyes.

Why does the moon change shape?

The moon does not make its own light. We see the half that faces the sun. As the moon goes around the Earth in about a month, we see more or less of that lit half, and that is why we see phases.

Why do we have day and night?

The Earth spins like a top, once in about 24 hours. The side facing the sun has day, and the side turned away has night. The sun does not move around us; the Earth turns.

Why do we have seasons?

The Earth is tilted as it goes around the sun. When our part leans towards the sun, days are longer and sunlight is stronger, so it is summer. When it leans away, it is winter. Distance from the sun is not the main reason.

Why do stars twinkle?

Starlight passes through moving layers of air before it reaches our eyes. The air bends the light a little in different directions, so the star seems to flicker. Planets look steadier because they are much closer and appear as tiny discs.

Why can we not feel the Earth moving?

The Earth moves very smoothly, at a steady speed, and everything on it, including air and us, moves along with it. We feel a push only when speed or direction changes quickly, like when a bus brakes.

The sun warms water in rivers, seas and puddles, and it rises as invisible vapour. High up it cools and becomes tiny water drops that form clouds. When the drops grow heavy, they fall as rain.

What makes a rainbow?

A rainbow forms when sunlight passes into raindrops, bends, bounces inside and comes out, splitting into its colours. You see it when the sun is behind you and rain is in front of you.

Why is thunder heard after lightning is seen?

Light travels extremely fast and reaches us almost at once. Sound travels much slower, so the rumble of thunder arrives later. The longer the gap, the farther away the lightning is.

Why is the sea salty?

Rivers carry tiny amounts of salts from rocks into the sea. When sea water evaporates, the salt stays behind. Over a very long time, the sea has become salty.

Why does ice float on water?

When water freezes, its molecules arrange in a way that takes more space, so ice is lighter than the same volume of liquid water. Because it is lighter, it floats.

Why do we see our breath in winter?

Our breath is warm and holds water vapour. In cold air, the vapour cools quickly and forms tiny drops of water, which we see as a white mist.

Why does a wet cloth dry faster in the sun?

Heat gives water molecules energy, so they escape into the air faster as vapour. Wind also helps by carrying the vapour away, so a breezy, sunny day dries clothes quickest.

Sleep gives the body time to rest and repair, and it helps the brain sort and store what we learned. Children need more sleep than adults because their bodies and brains are growing.

Why do we feel hungry?

Our body uses food as fuel. When the stomach is empty and energy runs low, the body and brain send signals that make us feel hungry, reminding us to eat.

Why do we get hiccups?

A hiccup happens when the muscle below the lungs, the diaphragm, suddenly jerks, and the voice box snaps shut with a short sound. Eating quickly or laughing while eating can start it. It usually stops by itself.

Sweat is mostly water. When it dries on the skin, it takes heat away, and this cools the body. That is how our body keeps its temperature steady in hot weather and during exercise.

Why do we get goosebumps?

When we feel cold or scared, tiny muscles at the base of our body hairs tighten and make the hairs stand up, which raises small bumps on the skin. In animals with thick fur this helps keep warm.

Scientists are not completely sure. A yawn may help us take in more air and wake up when we are tired or bored. Yawning is also catching: seeing someone yawn often makes us yawn.

Why do we need to wash our hands?

Our hands touch many things, and germs that cannot be seen can stay on them. Washing with soap and water for about twenty seconds removes most germs and helps prevent illnesses from spreading.

Why do we have to eat vegetables and fruit?

They give vitamins, minerals and fibre that help the body fight infection, keep the eyes and skin healthy and help digestion. A balanced plate has grains, pulses, vegetables, fruit and some milk products.

Why do we get a fever?

A fever is the body raising its temperature, often when it is fighting an infection. It is a sign that something is happening, and a child with a fever should rest, drink fluids and see a doctor if it continues or is high.

Why are leaves green?

Leaves contain a green substance called chlorophyll. It captures sunlight so that the plant can make its food by photosynthesis. Chlorophyll reflects green light, which is why we see leaves as green.

Why do leaves change colour and fall in autumn?

In some trees, shorter, cooler days make the green chlorophyll break down, and yellow and red colours show. The tree then drops its leaves to save water and energy in the dry or cold season.

Why do plants need sunlight and water?

Plants use sunlight, water and carbon dioxide to make their own food, and they release oxygen. Water also carries minerals from the soil and keeps the plant firm.

Why do birds fly and we cannot?

Birds have light bones, strong chest muscles and wings shaped to push air downward and lift them up. Humans are too heavy and our arms are not shaped or strong enough to lift our body.

Why do fish not drown in water?

Fish have gills that take oxygen dissolved in the water. We have lungs that take oxygen from the air. A fish out of water cannot get enough oxygen and a person in water cannot breathe air.

Why do cats see in the dark?

Cats have large pupils that let in more light, and a layer at the back of the eye that reflects light for a second chance to be seen. They do not see in total darkness, but they see well in dim light.

Why do bees make honey?

Bees collect nectar from flowers and turn it into honey as food for the hive, especially when flowers are few. Bees also carry pollen between flowers, which helps plants make seeds and fruits.

Why do some animals sleep through winter?

In very cold months, food is scarce. Some animals slow down their body and sleep for a long time, which saves energy until warm weather returns. This is called hibernation.

Why do things fall down?

The Earth pulls everything towards its centre with a force called gravity. That is why a dropped ball falls to the ground and why we stay on the Earth.

A plane's wings are shaped so that moving air pushes them upward, which is called lift. Engines push the plane forward so that air flows fast over the wings. When lift is greater than the weight, the plane rises.

A ship is shaped to push aside a large amount of water. The water pushes back up with a force equal to the weight of the water pushed aside. If that force equals the ship's weight, the ship floats.

Why do we feel pushed back when a bus starts?

Our body wants to stay where it is until a force changes that, which is called inertia. When the bus moves forward, our body tends to stay at rest, so we feel pushed back.

Why do magnets stick to some things and not others?

Magnets attract iron, steel, nickel and cobalt. Materials such as wood, plastic, glass and most coins are not attracted. A magnet has a north pole and a south pole, and opposite poles attract each other.

Why does a ball stop rolling?

Friction between the ball and the ground, and air resistance, slow it down. If there were no friction, a rolling ball would keep going at a steady speed.

Why do we hear an echo?

Sound bounces off hard, flat surfaces like walls and hills. If the surface is far enough away, we hear the sound again after a short gap. That repeated sound is an echo.

Why do we see our face in a mirror?

A smooth mirror reflects light in a regular way. Light from your face hits the mirror and bounces to your eyes, so you see an image that looks as far behind the mirror as you are in front.

Why do shadows change in length during the day?

When the sun is low in the morning and evening, shadows are long. When it is high at noon, shadows are short. The shadow lies on the side opposite the sun.

How does a bulb light up?

In a simple electric bulb, current flows through a thin wire called the filament. The wire gets hot and glows. In an LED, light comes out when current passes through a special material, and it uses much less energy.

Why must a circuit be closed for a bulb to glow?

Electric current flows only in a complete loop from one end of the cell around to the other. If there is a gap, like an open switch, the current stops and the bulb goes off.

Why is a metal spoon hot when left in hot tea?

Metals are good conductors of heat. Heat travels quickly from the hot tea along the spoon to your hand. Wood and plastic are poor conductors, so they do not heat up as fast.

Why does a pressure cooker cook food faster?

The lid is sealed, so steam cannot escape and the pressure rises. At higher pressure water boils at a higher temperature than usual, so the food cooks faster.

One end of a soap molecule sticks to water and the other end sticks to oil and grease. Soap lifts dirt and oil off the skin or cloth so that water can wash them away.

Why do onions make us cry?

Cutting an onion releases a gas that reaches our eyes and mixes with the moisture there, forming a mild irritant. Our eyes make tears to wash it away.

Iron slowly reacts with oxygen and water to form a reddish brown substance called rust. Painting, oiling or galvanising iron keeps air and water away and prevents rusting.

How does the internet work?

Computers and phones around the world are connected by cables, radio waves and satellites. A message is broken into small packets that travel through many connected computers and are put back together at the other end.

How does a phone know where I am?

Many phones use signals from satellites of a navigation system, along with signals from mobile towers and Wi-Fi, to estimate their position. The app then shows this on a map.

Why does a phone battery run down?

A battery stores energy from charging. Everything the phone does, such as the screen, apps and signals, uses a little energy. When the stored energy is used up, the phone must be charged again.

For curious children

Questions kids ask

Fifty short, correct answers to why and how questions, in plain words. Read one aloud at dinner, in the first five minutes of a class, or on a long bus ride, and then ask your child what they think.

Sky and space

Why is the sky blue?: Sunlight looks white but is a mixture of colours. When it passes through air, the tiny gas molecules scatter blue light much more than red light. Blue light reaches our eyes from every direction, so the sky looks blue.
Why is the sunset red?: At sunset, sunlight travels through much more air to reach us. Most blue light is scattered away on the long journey, and the red and orange light that is left comes through to our eyes.
Why does the moon change shape?: The moon does not make its own light. We see the half that faces the sun. As the moon goes around the Earth in about a month, we see more or less of that lit half, and that is why we see phases.
Why do we have day and night?: The Earth spins like a top, once in about 24 hours. The side facing the sun has day, and the side turned away has night. The sun does not move around us; the Earth turns.
Why do we have seasons?: The Earth is tilted as it goes around the sun. When our part leans towards the sun, days are longer and sunlight is stronger, so it is summer. When it leans away, it is winter. Distance from the sun is not the main reason.
Why do stars twinkle?: Starlight passes through moving layers of air before it reaches our eyes. The air bends the light a little in different directions, so the star seems to flicker. Planets look steadier because they are much closer and appear as tiny discs.
Why can we not feel the Earth moving?: The Earth moves very smoothly, at a steady speed, and everything on it, including air and us, moves along with it. We feel a push only when speed or direction changes quickly, like when a bus brakes.

Weather and water

Why does it rain?: The sun warms water in rivers, seas and puddles, and it rises as invisible vapour. High up it cools and becomes tiny water drops that form clouds. When the drops grow heavy, they fall as rain.
What makes a rainbow?: A rainbow forms when sunlight passes into raindrops, bends, bounces inside and comes out, splitting into its colours. You see it when the sun is behind you and rain is in front of you.
Why is thunder heard after lightning is seen?: Light travels extremely fast and reaches us almost at once. Sound travels much slower, so the rumble of thunder arrives later. The longer the gap, the farther away the lightning is.
Why is the sea salty?: Rivers carry tiny amounts of salts from rocks into the sea. When sea water evaporates, the salt stays behind. Over a very long time, the sea has become salty.
Why does ice float on water?: When water freezes, its molecules arrange in a way that takes more space, so ice is lighter than the same volume of liquid water. Because it is lighter, it floats.
Why do we see our breath in winter?: Our breath is warm and holds water vapour. In cold air, the vapour cools quickly and forms tiny drops of water, which we see as a white mist.
Why does a wet cloth dry faster in the sun?: Heat gives water molecules energy, so they escape into the air faster as vapour. Wind also helps by carrying the vapour away, so a breezy, sunny day dries clothes quickest.

Our body

Why do we sleep?: Sleep gives the body time to rest and repair, and it helps the brain sort and store what we learned. Children need more sleep than adults because their bodies and brains are growing.
Why do we feel hungry?: Our body uses food as fuel. When the stomach is empty and energy runs low, the body and brain send signals that make us feel hungry, reminding us to eat.
Why do we get hiccups?: A hiccup happens when the muscle below the lungs, the diaphragm, suddenly jerks, and the voice box snaps shut with a short sound. Eating quickly or laughing while eating can start it. It usually stops by itself.
Why do we sweat?: Sweat is mostly water. When it dries on the skin, it takes heat away, and this cools the body. That is how our body keeps its temperature steady in hot weather and during exercise.
Why do we get goosebumps?: When we feel cold or scared, tiny muscles at the base of our body hairs tighten and make the hairs stand up, which raises small bumps on the skin. In animals with thick fur this helps keep warm.
Why do we yawn?: Scientists are not completely sure. A yawn may help us take in more air and wake up when we are tired or bored. Yawning is also catching: seeing someone yawn often makes us yawn.
Why do we need to wash our hands?: Our hands touch many things, and germs that cannot be seen can stay on them. Washing with soap and water for about twenty seconds removes most germs and helps prevent illnesses from spreading.
Why do we have to eat vegetables and fruit?: They give vitamins, minerals and fibre that help the body fight infection, keep the eyes and skin healthy and help digestion. A balanced plate has grains, pulses, vegetables, fruit and some milk products.
Why do we get a fever?: A fever is the body raising its temperature, often when it is fighting an infection. It is a sign that something is happening, and a child with a fever should rest, drink fluids and see a doctor if it continues or is high.

Plants and animals

Why are leaves green?: Leaves contain a green substance called chlorophyll. It captures sunlight so that the plant can make its food by photosynthesis. Chlorophyll reflects green light, which is why we see leaves as green.
Why do leaves change colour and fall in autumn?: In some trees, shorter, cooler days make the green chlorophyll break down, and yellow and red colours show. The tree then drops its leaves to save water and energy in the dry or cold season.
Why do plants need sunlight and water?: Plants use sunlight, water and carbon dioxide to make their own food, and they release oxygen. Water also carries minerals from the soil and keeps the plant firm.
Why do birds fly and we cannot?: Birds have light bones, strong chest muscles and wings shaped to push air downward and lift them up. Humans are too heavy and our arms are not shaped or strong enough to lift our body.
Why do fish not drown in water?: Fish have gills that take oxygen dissolved in the water. We have lungs that take oxygen from the air. A fish out of water cannot get enough oxygen and a person in water cannot breathe air.
Why do cats see in the dark?: Cats have large pupils that let in more light, and a layer at the back of the eye that reflects light for a second chance to be seen. They do not see in total darkness, but they see well in dim light.
Why do bees make honey?: Bees collect nectar from flowers and turn it into honey as food for the hive, especially when flowers are few. Bees also carry pollen between flowers, which helps plants make seeds and fruits.
Why do some animals sleep through winter?: In very cold months, food is scarce. Some animals slow down their body and sleep for a long time, which saves energy until warm weather returns. This is called hibernation.

Forces and energy

Why do things fall down?: The Earth pulls everything towards its centre with a force called gravity. That is why a dropped ball falls to the ground and why we stay on the Earth.
How do planes fly?: A plane's wings are shaped so that moving air pushes them upward, which is called lift. Engines push the plane forward so that air flows fast over the wings. When lift is greater than the weight, the plane rises.
How do ships float?: A ship is shaped to push aside a large amount of water. The water pushes back up with a force equal to the weight of the water pushed aside. If that force equals the ship's weight, the ship floats.
Why do we feel pushed back when a bus starts?: Our body wants to stay where it is until a force changes that, which is called inertia. When the bus moves forward, our body tends to stay at rest, so we feel pushed back.
Why do magnets stick to some things and not others?: Magnets attract iron, steel, nickel and cobalt. Materials such as wood, plastic, glass and most coins are not attracted. A magnet has a north pole and a south pole, and opposite poles attract each other.
Why does a ball stop rolling?: Friction between the ball and the ground, and air resistance, slow it down. If there were no friction, a rolling ball would keep going at a steady speed.
Why do we hear an echo?: Sound bounces off hard, flat surfaces like walls and hills. If the surface is far enough away, we hear the sound again after a short gap. That repeated sound is an echo.

Light and electricity

Why do we see our face in a mirror?: A smooth mirror reflects light in a regular way. Light from your face hits the mirror and bounces to your eyes, so you see an image that looks as far behind the mirror as you are in front.
Why do shadows change in length during the day?: When the sun is low in the morning and evening, shadows are long. When it is high at noon, shadows are short. The shadow lies on the side opposite the sun.
How does a bulb light up?: In a simple electric bulb, current flows through a thin wire called the filament. The wire gets hot and glows. In an LED, light comes out when current passes through a special material, and it uses much less energy.
Why must a circuit be closed for a bulb to glow?: Electric current flows only in a complete loop from one end of the cell around to the other. If there is a gap, like an open switch, the current stops and the bulb goes off.
Why is a metal spoon hot when left in hot tea?: Metals are good conductors of heat. Heat travels quickly from the hot tea along the spoon to your hand. Wood and plastic are poor conductors, so they do not heat up as fast.

Everyday things

Why does a pressure cooker cook food faster?: The lid is sealed, so steam cannot escape and the pressure rises. At higher pressure water boils at a higher temperature than usual, so the food cooks faster.
Why does soap clean?: One end of a soap molecule sticks to water and the other end sticks to oil and grease. Soap lifts dirt and oil off the skin or cloth so that water can wash them away.
Why do onions make us cry?: Cutting an onion releases a gas that reaches our eyes and mixes with the moisture there, forming a mild irritant. Our eyes make tears to wash it away.
Why does iron rust?: Iron slowly reacts with oxygen and water to form a reddish brown substance called rust. Painting, oiling or galvanising iron keeps air and water away and prevents rusting.

Technology

How does the internet work?: Computers and phones around the world are connected by cables, radio waves and satellites. A message is broken into small packets that travel through many connected computers and are put back together at the other end.
How does a phone know where I am?: Many phones use signals from satellites of a navigation system, along with signals from mobile towers and Wi-Fi, to estimate their position. The app then shows this on a map.
Why does a phone battery run down?: A battery stores energy from charging. Everything the phone does, such as the screen, apps and signals, uses a little energy. When the stored energy is used up, the phone must be charged again.

Not sure about an answer, or want to go deeper? Look it up together in the NCERT textbook, ask the teacher, or turn it into a small experiment. Our article on raising a curious child shows how.

Questions? We are happy to help.

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