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# 2008 Science Corner Archive

QUESTION:   Two boats are heading upstream and water is flowing downstream, past them.  The two boats will eventually move closer and closer together.  Why?

When the water moves between the boats, its velocity increases and its pressure drops.  The pressure on the outside of the boats stays the same, so it is comparatively stronger, and pushes the boats together.

QUESTION: When you blow bubbles, they are always round.  Why can't they be sausage shaped?

ANSWER:        Bubbles are round because of surface tension.  The uniform pressure of the bubble skin forces pressure inwards, as it tries to occupy the least amount of space possible. Spheres happen to have the smallest possible surface area.

QUESTION:   If you hold a peice of green glass up to an incandescent lightbulb, the light will shine through as green.  If you hold up several peices of green glass, the light will look white, and if you look through five peices of green glass, the light will look red.  Why is that?

ANSWER:        The color of the light will seem to change because of how the glass reflects and absorbs the light. : When you shine the light through one peice of glass, all colors but green are absorbed.  With several peices of glass, all the colors are absorbed so it looks white.  With 5 peices of green glass, the green color becomes neutral, and the  red in the light becomes dominant

QUESTION:    Twinkle twinkle little star - A four part question!
1)Why do stars twinkle?
2) Do they twinkle more in the summer than the winter?
3) why don't the moon and planets twinkle?
4) If you were in outer space, would you see the twinkling?

ANSWER:       Stars twinkle because turbulence in the atmosphere causes variations in the refraction of the light.  It happens more in summer because that is when there is the most turbulence.  The moon and stars do, in fact, twinkle; it's just not that noticeable.  There is no twinkling in outer space becasue there's no atmosphere to distort the light.

QUESTION:   Under certain conditions, lightening can create a trench in the ground.  Why is that?

The lightening travels along the ground, and heats up the water that is in the soil.  When the water is heated, it expands into gas (steam) and that expansion acts like an explosion, blowing the soil away and creating a trench.

QUESTION: If you are driving at night, without streetlights, the lines between the lanes seem to disappear when it rains.  Why is that?

The thin layer of water on the road acts like a mirror, so the light from the headlights bounces off instead of being absorbed.  Also, the small amount of light that does reach the surface then has to travel back through a layer before it bounces back to you.

QUESTION:    If you have a glass of liquid, and want to pour out exactly half, how would you measure it?

If the glass is perfectly cylindrical, you can pour the water out slowly.  When the diagonal line on the surface of the water touches the upper rim where the bottom of the glass hits the side, you are at the 1/2 way point.

QUESTION:   Why do you beat egg whites to stiffen them for meringue, and is it possible to beat them too much.

ANSWER:       When you beat eggwhites, it adds air and changes the molecular structure and allows them to reform and hold the air.  If you overbeat them, the molecular structure will get too stiff, and burst when you put it in the oven.

QUESTION: Dirt roads often become corrugated with use, with hills and valleys in the rocks.  The same happens with ski hills.  What causes it?

ANSWER:      The road becomes corrugated because of washboarding.  When the tires pass over any irregularity in the road, the wheels go up, and then down, and their momentum makes a small indentation in the durt.  The next car hits that indentation, and increases it, and so on.

QUESTION: When male longhorn sheep battle during mating season, they smash their heads together - why doesn't that do more damage to their brains?

ANSWER:      Longhorn sheep are protected in three ways: 1)  the horns are somewhat flexible so the moment of impact is extended slightly, so it is not so sudden 2) their skulls have two layers and 3) some of the impact is passed along a tenden from the head to the neck to the shoulders

QUESTION: Ducks need to stay dry so they don't lost too much body heat. Yet, feathers are porous. How do ducks stay dry?

ANSWER:     A ducks feather composition is hydrophobic -- they repel water. The surface tension of the water prevents it from seeping up into the birds' pores.

QUESTION: Why does a paintbrush fill up with paint, when you dip it into a paint can?

ANSWER:     A paintbrush fills with paint because capillary action pulls the paint molecuse up the bristles.  When the bristles are splayed, the capillary action is stopped and the paint no longer adheres.

QUESTION:   Why do most colourful materials (such as red glass) lose their colour when they're ground up into powder?

ANSWER:      Colour is about selective absorption. When colour is ground up into a powder, the light can not penetrate the surface, and the colour is lost.

QUESTION: Why do football players put black on their cheeks?

ANSWER:       It decreases reflection off their cheeks, therefore, improving vision.

QUESTION:     Why would yellow lenses in ski goggles improve visibility?

LAST WEEK'S ANSWER:      On hazy days, it helps you to see bumps in the snow. When you wear   yellow, it enhances visibility, when you are looking into shadows.

QUESTION :  If water were thicker, could swimmers go faster?

An experiment done with a swimmer in water that was thickened to twice its viscosity shows that his speed would not change.  The thicker water allows better push and pull but it also places more drag on the swimmer, so the effects cancel each other out.

QUESTION:  Can rain falling on a rough ocean actually calm down the waves?

Rain can calm the waves, if the wind is low and the rain is brief.  When raindrops hit the oceans surface, they create a vortex and spiral into the water.  This causes the surface of the water to oscillate and create turbulance, which disrupts and diminishes the waves forming.

QUESTION:  Why do tennis balls have fuzzy coverings?

The fuzzy covering allows more friction between the ball and the air, which slows it down enough to play the game.  It also limits the bounce and allows the players more control.

QUESTION:    Why don't birds fall off a branch or wire when they fall asleep?

ANSWER:    Birds don't fall off because they have special tendons in their feet.  When the bird perches, its weight forces the tendon to tighten, so the bird is locked in position; the tendon loosens when the bird rises up.

QUESTION:   A dinghy is in a pool of water, jam packed with people.  If the people jump overboard, what happens to the water level?

ANSWER:    The water level does not change; items that float will displace the same amount of water whether they're floating, or sitting in the water.

QUESTION:  Two iron bars are on the table in front of you; one is magnetized, and one is not.  Using only your hands (no devices) how do you determine which is which?

ANSWER:      Leave one bar on the table, and pick up the other.  Hold the bar perpendicular to the table and move it toward the center of the other bar.  If it picks up the other bar, it's the magnet.  If it doesn't, the magnet is on the table. (Magnets have a north and south pole, and a neutral zone in the middle).

QUESTION:    An experiment involving moving sidewalks:  Walk from one end of a moving sidewalk to the other, and then turn around and walk back.  Have a friend walk BESIDE the moving sidewalk, and back again.  Which one of you will return to the starting point first?
ANSWER:        Your friends will arrive well ahead of you if he is walking at the same speed.  In fact, he can walk at half your speed and still arrive ahead.  That's because the person on the moving sidewalk has to compensate for the speed of the conveyor belt which is trying to take him in the opposite direction.

QUESTION:    Body armour is usually made of a fabric such as kevlar.  Why can it stop a bullet, but not a knife?
ANSWER:      A bullet is blunt, so when it hits the kevlar fibers, the fabric is able to absorb the energy and disperce it through the vest.  A knife is sharp, so it slides between the fabric fibers and cuts them, and so penetrates the vest.

QUESTION: Why does inhaling helium make your voice go funny?
ANSWER:    The sound of your voice is produced when vocal chords vibrate and create a sound that resonates in the throat and mouth.  When you add helium - which is 3 times lighter than air - the sound resonates much more quickly and so the pitch is raised.

QUESTION:    If you calibrate your rifle to shoot a certain distance, and then move to a shooting range where the target is at the same distance, but on a slope, will you hit the target?

LAST WEEK'S ANSWER:      You will always aim too high.  A firearm is sighted based on the distance between the barrell and the ground. If you shoot up or down, you are changing that reference point, so

QUESTION:     If you chill beer or pop so that it is very cold, but not frozen, a fog will form when you open it.  What causes that?

LAST WEEK'S ANSWER:    When the drink is opened, some carbon dioxide is released and when it leaves the bottle, it expands.  That expansion require energy, which comes from the gas, which cools it down and cuases it to condense.  The condensation is what creates the fog.

QUESTION:     When a bee pollenates flowers, the pollen "jumps" onto its feet and body, and then "jumps" off, onto the second flower.   What is happening there?

ANSWER:   When bees fly, they bbuild up an electrostatic charge.  When they enter a flower, which is grouded, the pollen jumps because of electrostatic forces.

QUESTION:     Fresh snow is white, but when you dig a hole, it sometimes looks blue or green.  Why?
ANSWER:    Sunlight is white light, and it reflects fully off the snow.  but when it passes through the hole, some of the reds are absorbed and the blues are reflected back.

QUESTION:   When you put a conch shell to your ear, you hear a sound like waves.  What causes that?
ANSWER:   What you are hearing in the conch shell is the virbration of air inside the shell, which resonates around the shell and is amplified to make the sound of waves.

QUESTION:   Why would firefighters choose a fine spray of water, instead of a heavy flow?

ANSWER:  Firefights use a spray because it provides many little droplets instead of one flow, and that increases the amount of surface area that the water will cover.  As the droplets move theorught the area, they absorb heat and evaporate.

QUESTION:   If you put two candles  - one taller than the other - under a glass lid, the taller one will go out first.  Why ?

ANSWER:   As the candles burn, they heat up the gases within the jar, so the wast byproduct gases will rise to the top, over the cooler, unburned oxygen.  So, the shorter candle will still have oxygen to keep it alight after the taller candle is smothered.

QUESTION:   When is a can of pop, sitting on a table, more stable - when it's full, or when it's empty?  Why?

ANSWER:   The pop can is more stable when it is full because it has the greatest resistance.  However, the can would be most stable when the height of the liquid is slightly greater than the radius.

QUESTION:   IIn Asia, people carry a heavy load by dividing it into two parts, at each end of a long stick, which bounces as they walk.  Why does that make it easier to carry the load
ANSWER:  The long pole keeps the weight from bouncing on the shoulder. When the carrier starts walking, the long pole oscillates; and the weights at either end keep the load on the shoulder constant.

QUESTION:   If there were a cold snap coming, and you had no antifreeze, could you protect your radiator by putting the car in a garage with a bucked of water?

ANSWER:    You could protect your radiator briefly, because as the bucket of water cools, it will release heat.

QUESTION:   Explain how a one-way mirror works?

A one way mirror has no backing; instead it has a reflective layer that does reflect some light, but the bright light in the room overwhelms that light.

QUESTION:    Why does a squeaky door squeak?

A stick and slip effect, two surfaces move past each other and stretch a little bit and release causing a viration that sends a sound wave in your general direction.

QUESTION:    A woven plastic fruit basket will float, even though it has holes in it.  Why?

A plastic fruit basked will float because of the chemical composition of the plastic:  It is hydrophobic, which means it repels water and allows surface tension to develop.  That surface tension pulls the water away from the holes, and allows the basked to float.

QUESTION:   If Superman really had x-ray vision, could he see criminals behind walls?

Superman may not be able to see the criminal .  X-rays would hit the criminal, some would be transmitted and some would be reflected. But rays would also be reflected back from the wall and everything else, so Superman's brain may not be able to sort it all out.

QUESTION: You can freeze a tray of water at night, even if the temperature is slightly above freezing.  How?

ANSWER: If the bowl is insulated from the ground, and if it is a clear night, more infared radiation will leave the bowl and go into the sky and that will reduce the water temperature enough to freeze it.

QUESTION: Power lines hum or sing in the wind.  Why does that happen, and why is the tone more shrill when it's cold out?

ANSWER:  The sound is caused by te wind passing over the wires, which are elongated cylinders.  The airflow creates vortices, which oscillate to produce an aeolian tone.  On cold days, the wires contract and the  sound is transmitted to the poles, which raises the tone.

QUESTION:
Why do the veins in a pale caucasian appear blue even though the blood is red?
ANSWER: Veins look blue because light penetrates the skin and is absorbed and reflected back - the red color is absorbed and the blue is reflected back.

QUESTION:
When Mount Saint Helen's erupted, no one within 100 miles could hear the noise of the explosion. Why?
The initial explosion of the volcano causes compression waves in the air which changes the frequency of the sound to lower than can be registered by the human ear.

Question: When Mount Saint Helen's erupted, no one within 100 miles could hear the noise of the explosion. Why?

Answer: The initial explosion of the volcano causes compression waves in the air which changes the frequency of the sound to lower than can be registered by the human ear.

Question: If you want to keep your coffee as hot as possible, should you stir it?  Which would be better, a plastic spoon or a metal one?

Answer: To keep your coffee hot, don't stir it (that disperses the heat) and don't put a spoon in it (the spoon conducts the heat up and out of the beverage).

Question: If you store left overs in the fridge, in a stainless steel container and the foil touches both the food and the container, it is possible that the foil will dissolve into the food. Why?

Answer: The foil will dissolve because of a galvanic reaction.  When two metals (stainless steel and aluminium) come in contact with an electrolyte (the tomato sauce), an electric current is produced, which moves the ions from one metal to the other, and causes corrosion.

Question: If you were in an elevator that was plummeting to the bottom, what would be the wisest thing to do:  stay standing, lie down, or jump just as the elevator was about to hit?

Answer: You're best off lying down; if you stand up, you might break your ankles, and it would be impossible to judge the jump.

Question: Aristotle argued that you could see stars in the daytime, if you looked at the sky through a long shaft, which would block out the glare in the sky. Was he right?

Answer: Aristotle was wrong. Even if you look through a shaft, the sky around the stars would be just as bright. The glare would not be reduced, so it would not be easier to see the stars.

Question:It is commonly believed that white clothing reflects the sun and is therefor cooler than dark or black clothing. Why then do Bedoiuns, and desert dwellers, wear black clothing in desert conditions?

Answer:The darker clothes may absorb more heat, but that doesn't mean the person feels more heat. The warm air trapped inside the robe creates a chimney effect; cooler air comes up from the bottom and moves over the body, creating a cooling action.

Question: Why does plastic wrap stick to itself when you take it off food? (if it is electrically charged, you would think the electrons would repel each other)

Answer: In the manufacturing process, there are patches of electrons creating negative charge and patches of no electrons, making a positive charge. Those charges cling to each other. There is a misconception that the entire plastic wrap surface is uniformally negatively charged.

Question: If you stretch a rubber band, it feels warm; when it contracts, it cools. Why?

Answer: The rubber is made up of long chain molecules. When you stretch it, the molecules warm up because of thermal motion.  Conversely, it takes energy for the molecules to contract and so they consume the heat to power their contraction.

Question: Spring seems to come earlier to the city; why is Halifax a "heat island" compared to the surrounding area?

Answer:The city is a heat island for a variety of reasons: the buildings block the wind and so slow the cooling of the air, the proximity to the harbour moderates the weather and heat radiates from the buildings.

Question: When you pour water into a glass, why does the frequency of the sound increase as the glass fills?

Answer:The space between the water and the top of the glass is the tube in which the sound resonates. As more water is added, the tube gets smaller and the frequency of the sound increases.

Question: A study was done in which 132 cats accidentally fell between 2 and 32 stories, mostly onto concrete. 90% survuved, and 60 % escaped major injuries. The number of deaths and injuries INCREASED as the distance DECREASED.  Why would that be?

Answer: The cats who fell the greater distance were less frequently injured because (A) they had time to re-orient themselves and splay their legs to absorb the impact and (b) after a certain distance, the cat stops accelerating and relaxes a bit.  When that happens, it splays its legs even further, and slows itself down.

Question: Why would fog lights be yellow?
Answer: Scientists used to presume that water droplets in fog were bigger than usual.  If they were, yellow light would pass through them best.  But now, they know that droplets are not a uniform size, so white light is just as effective.

Question: Why does it take time for plastic shopping bags to stretch and tear when you carry heavy goods in them?

Answer: Plastic bags are made of polymers, which are bound together like a bunch of spaghetti.  As pressure is applied, the polymers unwind, and lengthen, and that is why the plastic stretches.

Question: Why are birds not electrocuted when perched high on electric wires?

Answer: Birds are sometimes electrocuted on wires, but small bird are usually not because (a) they are not grounded and (b) the resistance of the bird means that it is easier for the current to keep running through the wire.

Question: Why would some people beleive that you can stand a raw egg on its end on the first day of spring?

Answer: It's a myth built around the idea of the day of equal length of day and of night, meaning the sun is directly opposite the equator. Some believe the gravitational pull on that day is enough to stand an egg on its end. However, you'd have to do this experiment on every other day of the year to test that theory.

Question: What makes the sound when a brook babbles.

Answer: The sound in a babbling brook is made by water hitting water, and bubbles bursting.

Question: Sometimes when you turn on a faucet, you will hear a deep rumbling in the pipes. What causes that?

Answer: This is caused by turbulence in the water, which is a result of the turns and fittings of the pipes creating a vortex of gaseous cavatations, or air pockets working through the pipes.

Question: Why is glass transparent but crushed glass is not?

Answer: Glass is transparent because light passes through it. Crushed glass has so many surfaces that it reflects a great deal of light.  Some light does pass through, but it is distorted.

Question: What is the smallest object that an astronaut, orbiting in space, could see in daylight with the naked eye?

Answer: Assuming the astronaut was about 1800 km away, the smallest thing he or she  could see would be a kilometer squared, because of how defraction affects human vision.

Question: How does a megaphone increase the volume of a voice?

Answer: When we speak, our voice goes in all directions, and so the sound is dispersed; a megaphone fouccses the sound in one direction and concentrates the volume.

Question: When space capsules are shot into space, NASA will send them past planets so that the gravity draws them in, and then they can shoot out into space (slingshot effect) Why doesnt the gravity also slow them down as they leave?

Answer: The gravity of the planet coming in and going out do cancel each other out; the added velocity comes from the capsule being caught up in the orbit of the planet, and gaining energy from that velocity.

Question: When you blow bubbles, what holds them together, and why do you need soap?

Answer: Surface tension holds the bubbles together; the detergent decreases the surface tension in the water to allow the bubbles to form.

Question: If you are paddling a boat through a narrow, shallow canal, will the water at the bow be higher or lower than the water at the back of the boat?

Answer: Because of the "draw down" effect, the water at the bow will be lower than at the stern. This is also known as the canal effect.

Question: Why does ketchup come out of the bottle faster after you shake it?

Answer: Ketchup is viscous because there are long chain molecules that hold it all together. When you shake it, you break up the bond in those molecules and the sharing effect causes the ketchup to flow smoothly.

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