Top 10 Tricky Science Questions: Answered
How to Answer Children's Questions
Science is all about asking questions, and some of the most interesting and thought provoking questions come from the imaginations of children. They can be staring out of a window and then drop such bombshells as:
"How much does the sky weigh?"
The media often laments how few parents are equipped to answer these questions. Fortunately we live in the information age, with answers just a few clicks away; the important thing is never to dismiss or dodge these questions. This inquisitive nature passes by all too quickly—if you are unsure of an answer, seek it out with your child! Children crave parental attention and this is a great opportunity for you to spend time together whilst learning something new.
Here are some of the science questions I am asked quite often (particularly by my younger students). Each question has a simple answer, followed by a slightly fuller explanation and, where necessary, a link for more information. Enjoy!
1. Why Is the Sky Blue?
Light arrives on Earth from the sun in every colour (including 'colours' we can't see like UV and infrared). When the sunlight hits the Earth's atmosphere it collides with certain particles that 'shine' blue.
Explanation: What we see as white light is actually a mix of different colours, all with a different wavelength. We see colours when a particular wavelength of light gets reflected into our eyes (the other wavelengths get absorbed or pass through an object). Our atmosphere is around 78% nitrogen; when light collides with our atmosphere, the red and green wavelengths of light pass through unobstructed. The blue wavelength is reflected by the nitrogen in the atmosphere and eventually reaches our eyes. As there is so much nitrogen, you can see the blue light from everywhere—hence the colour of the sky!
2. Why Is the Moon Sometimes out in the Day?
The Moon does not produce its own light—we see it when light coming from the sun is reflected off of the surface of the moon. Whenever the Moon reflects the Sun's rays we can see it —even in the day time. Just like in pool—it all depends on the angle! When the moon and sun are on the same side of Earth, the moon is 'out' in the day; when the moon and sun are on opposite sides of the Earth, the moon is 'out' at night.
Explanation: Just like the stars, the moon is always 'out.' Celestial objects do not go anywhere during the day, they are just outshone by the Sun and any remaining light is scattered by our atmosphere. When the sun, Earth and moon align correctly, enough light is reflected off the moon's surface to be seen from Earth, even during the day. The reason we can see the moon and not the stars is that the light reflected from the moon makes it 100,000 times brighter than the brightest star in the sky—bright enough to be seen during the day.
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3. How Much Does the Earth/Sky Weigh?
A. The Earth weighs around 6,000,000,000,000,000,000,000,000 kg.
Explanation: This is particularly tricky: technically, the Earth weighs nothing, because weight depends on the gravitational field strength of the planet the object is on. The Earth is falling through space around the sun. However, some clever mathematical tricks returns the answer above. Basically, we look at the strength of the gravitational pull from the Earth on nearby objects to calculate this number
B. The sky weighs the same as 570,000,000,000,000 adult Indian elephants (according to the UK's Science and Technology Facilities Council).
Explanation: Air weighs something, but we don't notice it as it presses on us evenly from all directions and we are used to it. Helium balloons float because helium weighs less than air. Air pressing against us is called air pressure. Barometers work because the atmosphere has weight. If you are still struggling with the concept of air having weight, just think of a hurricane: all that is is moving air.
4. How Do Planes Stay Up?
Planes stay in the air because of the shape of their wings. Air moving over the wing gets forced downwards, which pushes the wing up. This 'push' is stronger than gravity and so makes the plane fly.
Explanation: This is a very technical subject that the video deals with very nicely. Planes take advantage of Newton's Third Law: for every action, there is an equal and opposite reaction. As air moving over the wing gets forced down, there is an equal and opposing force generated. This is a combination of the bottom of the wing getting 'pushed' up, and the top of the wing getting 'pulled' up.
5. Why Is Water Wet?
'Wet' is ultimately just a word that applies to water. What we feel as wetness is actually coldness as the water evaporates. Below is an experiment from the Institute of Physics to test the feeling of 'wetness' between two different liquids:
"The feeling of wetness is actually coldness. You can test this by comparing water with another liquid - cooking oil - which doesn't evaporate so freely. Fill two small cups (egg-cups are ideal) - one with water, and the other with cooking oil. (Young children should ask an adult to help.) Let both liquids come to room temperature for a day, or overnight. Dip one index finger in each liquid, lift them out, and then observe for a few minutes."
Explanation: Liquids make surfaces wet (i.e. they stick to many solid surfaces) due to the electrostatic (opposite charges) forces between molecules. Water is polar—it has an uneven spread of electrical charge—which makes one end of the molecule positive and the other end negative. This causes water to be attracted to many surfaces and also explains many other properties of water.
6. What Makes a Rainbow?
When sunlight goes through droplets of water, the beam of light is 'split' into the different colours that make up light. The same effect can be seen if you shine a light through a glass prism.
Explanation: White colour is actually a mix of several different colours. Each constituent colour of a rainbow is caused by a specific wavelength of light. When light hits a medium that forces it to slow down, the light ray bends...but not equally. Each wavelength bends by a certain amount, which causes the different coloured rays of light to exit the raindrop in slightly different directions. This results in the colours 'fanning out.'
7. Why Don't Birds get Electrocuted...
...when they land on electrical wires?
Because the birds are sat on only one wire and do not complete the circuit. Take a look at the video below for extra detail.
Explanation: To be 'electrocuted' you must be part of a complete circuit. You must touch both a positive wire, and a negative or neutral wire. If the bird was touching the ground, the ground would act as a neutral wire and the current would flow through the bird (i.e. electrocuting it). If the bird was sat on the wire and touched the metal of the pylon or another wire, it would also complete a circuit and get electrocuted. Because the bird is only sat on one wire, it is safe.
8. Are There Such Things as Aliens?
Short answer: We actually don't know.
Explanation: Whilst we know there are planets orbiting stars at the right distance for liquid water to exist, we have no idea if there is any form of life outside of our planet.
9. Where Do Birds Go in Winter?
Many birds don't like our cold winters and fly south for the winter—it's like a six month holiday! Other birds like our winters and either stay, or fly here from further north. The reason we don't see many birds during the winter is that most of them have left!
10. Where Do Babies Come From?
This is one question where the scientific content actually comes second to the choice of the parents. Give an answer you feel comfortable with, whether that is the stork, each parent giving special gifts that grow into a baby...anything! The important thing is that you don't dodge this question. You must nurture this inquisitive nature! Have an answer ready—you never know when this question might pop out!
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- BBC - BBC One Programmes - Bang Goes the Theory
Bang is the BBC's guide to popular science. Watch videos and do real experiments at home.
- The Big Question
A Blog set up after the 2008 UK National Science and Engineering Week. Some great headscratchers answered here, including the all-time favourite: Which came first? The Chicken or the Egg
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