1. Glue the aluminum foil inside the bucket. Take care to smoothen out the wrinkles.
2. Cut two holes in the lid—one for the torch, second for the hosepipe.
3. Cut a small hole near the base of the bucket.
4. Place the bucket near the sink.
5. Attach the hosepipe to the water tap.
6. Fill the bucket with water.
7. Simultaneously, shine the torch into it.
8. You will see light streaming out along with the stream of water coming out from the hole near the base.

Compare a primitive sundial with a modern watch. You will need:
• Cardboard sheet
• Scissors
• Ruler
• Marker
• Watch

1. Cut out a 3“ X 3” square from the cardboard sheet.
2. Next, cut out a 1” x 3” bar. Glue it upright on to the square.
3. Set your sundial in the sun.
4. Check the shadow of the vertical bar, then check the time in your watch.
5. Mark the position of the shadow as the current time.
6. Repeat every hour until you get a complete time face on the sundial.

We all know that tides are the cyclic rise and fall in sea level within a day, and that this is caused by the gravitational pull of the moon. Most of us also know that as the earth and moon rotate around each other, each acts like a magnate attracted to the other, constantly pulling the other towards itself. This gives rise to lunar tides.

While the earth’s gravitational pull keeps the moon in orbit, the earth remains largely unaffected by the moon’s gravitational pull. The only visible effect of the lunar gravity is on the great liquids of the oceans and seas, which swell or ebb, as the moon rotates around the earth. The moon’s gravitational forces are stronger on the moon side of the earth, i.e., the side closer to the moon, and less so on the other side of the earth. So, when large water bodies, such as oceans, seas or even large lakes are on the moon side, they experience an increased gravitational pull of the moon. This force causes their waters to swell TOWARDS the moon. This is what we call a high tide.

That brings us to our question –If a particular spot in the ocean faces the moon only once during the day, it should experience only one high tide during a day. Yet there are two. What’s happening?

The answer lies in the wrong assumption that when there’s a high tide on the moon-side of the earth, the other side of the earth is going through a low tide phase. It’s not. On the contrary, it’s experiencing a high tide.

This is because during high tide, there are two forces at play – the gravitational pull of the moon and the centrifugal force of the earth. When the moon exerts its gravity on the earth, the water on the moon-side responds by swelling away from the earth and towards the moon. This is the higher of the two high tides.

At the same time, the earth is also spinning on its own axis. This causes it to exert centrifugal force on the water on the other side. This water is pushed outwards, away from the moon, but also away from the earth. This swell is also a high tide, and the lower of the two.

Which is why, we have two high tides and two low tides in a day.

Brainteaser: If the moon, whose gravitational pull is just ten millionth that of the earth, can displace the ocean waters and cause lunar tides, why is it that we don’t have solar tides?

Answer: The sun’s gravitational pull is almost 180 times stronger than the moon. However, its force on the earth is far lesser than that of the moon because of its distance from the earth. So while the sun’s gravity also produces tides, its visible effect is also far less.

However, when the sun and the moon are in a straight line with the earth, i.e. during the Full Moon or the New Moon, their gravitational forces combine to give us Spring tides. Spring tides have nothing to do with spring. The word Spring tides comes from the Welsh word sprigan or to bulge and indicate very high tides.

Facts: Did you know that the highest tidal waves occur at Bay of Fundy in Canada. Records show that they can rise as high as 16 meters!

What are you most likely to be doing when you are watching TV, or enjoying your favorite movie? My guess is that, just like me, you too would be munching on popcorn - everyone’s favorite snack. Which is why, nothing disappoints me more than finding split seeds in my bag!

But have you ever wondered why is it that some popcorn won’t pop? For that we will have to first know why popcorn pops.

Corn, or maize as the Indians called it, has three main parts – Pericarp, which is the hard outer shell, Germ, or the part that sprouts out of the seed when it is planted, and Endosperm or the starch that pops out when kernels are heated as the soft, fluffy popcorn.

To pop the corn, we heat the kernels. This turns the water contained in the starch, into steam. As the steam expands, it creates pressure within the kernel, and as a result, the pericarp or the skin of the kernel bursts open, and the starch pops out as soft, fluffy popcorn.

That brings us back to where we started, if it’s so easy to pop the corn, why is that sometimes the corn doesn’t pop?

One reason is that not all varieties of corn will pop. For example, field corn that is used to feed cattle, and sweet corn do not contain the hard starch, which is necessary for popping. So choose the right corn variety for your popcorn.

Next, the water contained in the in the endosperm or the starch. For best results, kernels should contain 13-14% of moisture levels. Lower moisture levels mean that there won’t be enough steam to create adequate pressure that will pop the pericarp. On the other hand, very high moisture levels will crack open the seed even before the starch has been cooked, and all you will get is split seeds of corn.

The third factor is how you apply the heat. If you heat the corn slowly, there will be a slow build-up of pressure in the kernel that will soften the pericarp, but will not rupture it. On the other hand, when you apply the heat quickly, there is a fast build-up of pressure in the kernel that will crack the corn with a sharp, pop sound.

But what if you do everything right, and yet the corn doesn’t pop? Then maybe the pericarp of the kernel has been damaged. If there’s a crack in this hard outer shell, the steam will simply escape and not pop the starch. In which case, there’s nothing we can do!

Things to do:

Popcorn facts: Popcorn is approximately three-fourths parts carbohydrate. The rest is protein, fiber, fat, minerals and water.

This has something to do with echoes, which are the reflection of sound.

Sound waves travel in a straight line. When these waves hit an obstruction, they are reflected, absorbed or transmitted through the obstructing material.

When you are singing in the bathroom, the first factor that adds an extra dimension to your voice is the material that covers the reflecting surfaces. If the obstruction is made of solid material like stone or tiles, most of the sound is reflected, as opposed to soft materials like carpets and foam, which absorb sound. In a bathroom covered with porcelain tiles, your voice is rather well reflected giving rise to echoes.

The second factor that imparts a rich feel to your singing is your distance from the reflecting surfaces. When you are far from the reflecting surface, you can distinguish between the original sound and the echo because it takes longer for the reflected sound waves to travel back to you. For example, you can hear echoes in mountains as distinct repetitions of the original sound, as there is a considerable delay between the echo and the original signal. But in a bathroom, you are too close to the reflecting surface. The echo will reach you much sooner. As a result, you are unable to distinguish between the original sound and the echo.

These two factors ensure that what you hear in the bathroom is a rich mlange of the many reflections of your voice that cannot be separated from the original sound. This adds a rich feel to your singing and makes it sound quite different (and often better) as compared to singing in say a studio.

Brainteaser: Is it true that dolphins use echoes to see?

Answer: Well, they don't actually see with echoes. They just have an unusual way of figuring out what is around them in the dark. Marine mammals like dolphins and whales use a technique called echolocation to obtain information about their surroundings. Deep waters and dark nights reduce visibility. Unable to see the environs clearly, marine mammals like whales and dolphins produce high-decibel sounds or sonar clicks to navigate. When these high-frequency sound waves hit an object, they are reflected and reach the dolphin as an echo. The dolphin's brain then interprets these echoes to detect its distance from the obstacle in its path, based on the time an echo takes to return. It can also determine if the object is moving towards it, by sensing the frequency of the echo. The pitch of the echo is higher if the object is moving towards the dolphin, but lower if it is moving away.

Some bats use the same technique while flying in the dark and to find food. Imagine, by processing the echo, it not only finds information such as how far away a moth is, which direction it is flying in, and at what speed, but also how big the moth is. Amazing, eh?

Fast Facts: Did you know that ocean scientists explore the deep sea using equipment based on the principle of echolocation? The equipment used to send and receive the sound, called SONAR (Sound Navigation and Ranging), was first invented in 1915 by a French scientist called Paul Langevine.

To do: Next time you hear an ambulance siren, notice its sound. Can you tell which direction it might be moving in based on the changes in the pitch?

Tricky question!

Although we cannot say for certain, it is believed that most mammals, except primates, have trouble distinguishing between colors. On the contrary, some birds, fish and insects have a developed color vision. That’s a baffling mystery of the evolution process. But one guess is that color vision is better developed in lower order species as a ploy to attract members of the opposite sex. So, if the male or female of a species is brightly colored, then you can presume that the species is probably not colorblind.

What is colorblindness?

Colorblindness is when a person has trouble distinguishing between red and green color. To understand this, lets first find out how we see color. Human retina has two types of vision receptive cells, cones and rods. While rods are sensitive to low light conditions and movement, cones are sensitive to bright light and color.

Humans have three types of cones for the red, green, and blue colors. In colorblind individuals, the green receptor goes missing. Typically, such people will see red as a dark hue and green as a shade of gray. Which is why, a colorblind person has difficulty telling a red traffic light from a green one.

Research on dogs and cats has shown that they have both the vision receptors i.e., cones and rods in their retinas. Dogs have only two types of cones. This affects their ability to distinguish between red and green. Experiments show that they respond better to colors like yellow and blue but have a problem with red and green. As for cats, although they have three types of cones, like humans, scientists believe that they miss rich shades of the colors around them. Most colors appear pastel to them.

Brainteaser: If animals are colorblind, why is it that bulls charge at the red cloth that the matador waves during a bullfight?

Answer: Its got nothing to do with the color red! You could well be waving a blue, green, yellow or a white cloth. If you have seen in a bullfight, you will have noticed that the animal is often intoxicated. And the matador repeatedly stabs it with spears. Numbed by the pain, the bull senses the movement of the cloth, perceives it as danger, and charges towards it.

Check out for yourself:

But how can we know for sure if animals see color or not? After all, they cannot talk.

For one, scientists can find out the type of vision receptors that animals possess by examining the makeup of their eyes. And two, researchers conduct experiments using a reward system for particular colors. For example, if you want to find out if your pet dog is colorblind or not, here’s a small experiment that you can do.

Those sparkling rocks of light and color… gemstones are a mesmerizing work of nature. But do you know how these natural stones get their color? Surprisingly, they owe their color to the mineral from which they are derived. That’s right. Most gemstones are naturally found minerals, and their brilliant hues are a reflection of the chemical composition of the parent mineral.

Some gemstones like the peridot get their color from mineral itself. But others owe their color to certain chemicals found in the mineral from which they are formed. Amazingly, sometimes, the different chemical impurities in a mineral can lead to diametrically different colored gemstones. For example, the same mineral that gives us the blood red ruby, also gives us the cool blue sapphire! Both ruby and sapphire are formed from the mineral, Corundum. In its pure state, Corundum is white in color. But when it contains chromium and iron, it will produce rubies, whereas presence of iron and titanium will give us a blue variant of the corundum, or sapphire. Some other examples of chemical impurities that affect the appearance of gemstones formed from the same mineral are, emerald and aquamarine stones, which are gem forms of beryl. Similarly, if amethyst is purple quartz, yellow quartz is called citrine.

Surprisingly, these dazzlers are not much to look at in their natural state. Just rough, dull chunks of minerals. It takes different processes like cutting, shaping, faceting of angled surfaces, and polishing to bring out their color, clarity and luster. Of course it helps that these luminous crystals have an innate high refractive index. Plus, different patterns of faceting are used for different gems, in order to get the most out of their refractive properties and natural crystalline structure. So that when you get a finished gemstone, it has a shiny appearance, along with a high degree of internal reflections.

Fast Facts: Did you know that diamond is the only gem that is composed of a single element - carbon? That amber, is not a mineral but the fossilized resin of trees? That pearl is produced when an oyster attempts to isolate a foreign particle within its shell?

To do: Now you know that gems are crystals formed from minerals. But did you know that you could grow crystals too? Here’s what you will need:

1 cup sugar, 1 ½ cups of water, a glass jar with a lid, a piece of string, a pencil, a heavy paperweight.

1. Boil the water.
2. Add the sugar to the water.
3. Stir well.
4. Pour the solution into the glass jar.
5. Tie one end of the string to the pencil. To the other end tie the paperweight.
6. Holding the pencil in your hand, immerse the string in the sugar solution.
7. The paperweight will help to keep the string straight in the jar.
8. Now close the lid of the jar tightly, and leave the jar undisturbed.