Why dogs can't eat chocolates?

Chocolates and other cocoa products contain a toxic product called theobromine. The darker the chocolates, the theobromine content is more. Our body quickly metabolizes theobromine. Hence, it is not harmful for us. However, the dog's body process theobromine very slowly. Thus, it stays in their body long time and cause vomiting, diarrhoea and other lethal complications. If it eat more chocolates, it increases the heartbeat of the dogs and increasing their blood flow and hence it is harmful to dogs.

Why do animals eye glow in the dark?

Normally our eyes consists of a organ called retina where the photoreceptor cells are present in it. When the light enters into our eyes, it will reach the photoreceptors and the photoreceptors makes us possible to see. However, the lights doesn't hit the photoreceptors remains undetected. Now, nocturnal animals like owl and cats need to see better at night. Hence, their eyes consists of another layer below the retina called tapetum lucidum. Now, when the light doesn't hit the photoreceptors, it reaches the tapetum lucidum. This layer acts like a mirror. It reflects light back to the photoreceptors. Thus, giving them a second chance to detect light. Some of this reflected light also comes out of the animal's eyes. Thus, making it seem that their eyes are glowing.

Why do knuckles pop?

A knuckle is a joint in a finger where two bones come together or connect. This joint is filled with a fluid called synovial fluid. Synovial fluid is a viscous fluid consists of dissolved gases like oxygen and carbon dioxide. When bones move, the synovial fluid prevents them from grinding against each other. On the other hand, when we stretch or bend our finger, the space between the two bones increases. This causes synovial fluid to stretch and thus creating low pressure in it. Now, as gases are less soluble at low pressure, the dissolved gases in the synovial fluid remains undissolve, resulting in the formation of bubble. Thus we hear as the pop sound.

Why nuclear fusion is not used to generate electricity?

Normally we use nuclear fission process to generate electricity in the nuclear power plant by using nuclear power reactors. The process of breaking of a nucleus into several neutrons which releases large amount of energy is called nuclear fission. The neutrons released again and hit another nucleus and in turn several neutrons and energy are prduced. Thus, the chain reaction takes place in the nuclear power plants. This reaction is effected in a very controlled manner in the nuclear reactors. The control rods are placed in the reactors to cool the nuclear reactor frequently. The energy released in the water converts the water into steam and this steam runs the turbines and in turn electricity is generated by using nuclear fission. This energy is called nuclear energy.
                                               Till now, we generate electricity by using nuclear fission process but not using fusion process. When the two lighter nuclei combines to form a heavier nuclei which releases a large amount of energy is called nuclear fusion. This nuclear fusion process takes place in sun. In sun, two hydrogen combine to form a helium nuclei. To create a nuclear fusion process in the earth, it needs a large amount of temperature as well as pressure. Hence, it is impossible to generate such high pressure and temperature. Even if we carried out the process by generating high pressure and temperature, we don't know how the effect will be and what will be the result. The question remains unanswered.

How do migratory birds find their way?

Every year migratory birds fly thousands of kilometers to find food. But, researchers do not know how these birds find their way and travel to the same location year after year. Some researchers suggests that the migratory birds travel along with the earth magnetic lines that emerge from the south pole and merge at the north pole. Also, the migratory birds travel long distance by creating the mental map of their route by remembering mountains, rivers etc.,Besides this, it is also believed that the migratory birds use the location of sun and stars to find their way and reach the same location.

Why ices are clear?

Normally, we use tap water at the room temperature to make ice at homes. This water may consists of dissolved minerals which are invisible to our naked eyes. If we place the water in the freezer, the water starts freezing from outer side to the inner side and hence much of the minerals are trapped inside the inner layer of the water and the water freezes into ice. This makes ice looks like a cloudy appearance. 
            To make clear ice, some specialized ice makers make water to continuously flow over the surface of a cool container. Thus, water begins to freeze from the bottom of the container, layer by layer. Thus, giving the time for minerals and gases to escape from the top, making the ice clear.

Pic 1 - cloudy ice            Pic 2 - clear ice

How do airbags work?

The airbags in our cars work by decomposition reaction. Weird? Right... When our car hits a lamp post or some other things, it took 50 milliseconds for our head to hit the steering. Thus, by using this calculation, they designed air bags to open in 30 - 40 milli seconds and thus it helps our head and it saves us from injuries. When there is a collision, the sensors called accelerometers detect it and send electric signals to the ignitor. This ignitor ignites a chemical called Sodium azide which decomposes and produce sodium and large volume of nitrogen gas. This gas instantly inflates the airbag. This whole process take about just 30 to 40 milli seconds to happen. Thus, air bags helps to save our lives in cars. There is no invention still developed to save our lives from motor cycle. So kindly use helmets to prevent serious injuries while riding two wheelers.

Why do we have different skin colors?

People have different skin colors because of melanin and Ultra violet radiation. Millions of years ago, people live in  equator region receives more sunlight and hence they receive more UV radiation. Their skin absorbs these UV radiations to produce Vitamin D. But excess radiation can cause damage to the body. Hence, in order to prevent their body from the over exposure of UV radiation, their body secretes melanin pigment. Thus, these people and their succeeding generations adapted more melanin in their skin and hence their skin looks black in color. In case of polar regions like Artic and Antartic, people receive lesser UV radiation as compared to equator. Hence, in order to absorb more UV radiation to produce vitamin D, these people and their following generations adapted to have a lower level of melanin. Thus, making their skin lighter.

Why honey doesn't spoil?

Honey does not spoil over years because of  reverse osmosis. Reverse Osmosis is the movement of water from the region of higher water potential to the lower water potential through the semi permeable membrane. The water content present in the bacteria are more than that of honey. Hence, much of the water gets transferred to the honey and eventually the bacteria will die. It may also noted that the bees produce antibiotics to keep them free from bacteria etc., Hence, bees insert the part of antibiotics into the honey while secreting them. This makes the honey free from micro organisms for many years.

Why do heavier objects fall faster?

It may be noted that all objects fall at the same rate. All objects accelerate at same rate on the earth at 9.8 per second squared, whether it is light or heavy. But, this happens only when there is vacuum. Robert Boyle, a scientist, placed a coin and feather in a glass jar. He removed all the air from it. Then, he inverted the jar and observe that both the feather and coin fell to the bottom at same time. In earth, the speed of the fall of the object depends upon the surface area and air resistance. The feather has more surface area as compared to the coin. Hence, more air pushes above the feather than the coin and offering resistance. And hence, feather fall slowly than the coin.

Why vultures don't get food poisoning?

Vultures are generally scavengers. They eat decaying and rotting flesh and dead animals. But, any decaying matter has many harmful microbes which upon consume, can cause food poisoning in animals and humans. However, vultures have strong acid in their stomach that protects them from the harmful microbes. The acids present in the vultures are much stronger than the acids present in the humans's stomach. They can even corrode certain metals like iron. Thus, when the vulture eats decaying or rotting flesh, the strong acid present in their stomach destroys most of the microbes that can cause food poisoning and other health problems and keep the vultures safe.

The science behind Capsaicin

As soon as we take our first bite of spicy food,we feel as our mouth is on fire. This is due to a compound present in the hot peppers called capsaicin. Capsaicin binds with specific heat receptors in our mouth known as vanilloid receptor 1. These are the same receptor that tell our brain when we on fire. Since these receptors cannot able to differentiate capsaicin and heat and can be activated by both. This made our brain to believe that we literally on fire and thus causes burning sensation on our mouth when we eat spicy foods. Hot peppers increase our core body temperature in a process called thermogenesis. To lower the body temperature, our brain tells the body to release the extra heat and thus causes sweating. And also our blood vessel send more blood to the skin as the heat easily radiates, hence our face or hands are red when we eat more spicy foods. The saliva are produces more than the normal, because our mouth releases more salivas to remove the capsaicin present on our mouth. It may also cause intestinal problems, as the capsaicin also binds with the pain receptors present on our stomach. Hence our stomach contracts forcefully to remove capsaicin. Hence, these contractions can cause pain.