My Science School

The pupil is the opening in the center of the iris (the structure that gives our eyes their color). The function of the pupil is to allow light to enter the eye so it can be focused on the retina to begin the process of sight.

Together, the iris and pupil control how much light enters the eye. Using the analogy of a camera, the pupil is the aperture of the eye and the iris is the diaphragm that controls the size of the aperture.

The size of the pupil is controlled by muscles within the iris — one muscle constricts the pupil opening (makes it smaller), and another iris muscle dilates the pupil (makes it larger). This dynamic process of muscle action within the iris controls how much light enters the eye through the pupil.

In low-light conditions, the pupil dilates so more light can reach the retina to improve night vision. In bright conditions, the pupil constricts to limit how much light enters the eye (too much light can cause glare and discomfort, and it may even damage the lens and retina).

 

Picture Credit : Google

Myopia, otherwise known as short-sightedness, is a common eye condition that causes objects in the distance to appear blurred while close objects are often seen clearly.

Myopia occurs when the eye has too much focusing power, either due to the eye being too long or the cornea being more curved than usual making the eye too strong. As a result, when someone with short-sightedness tries to look at distant objects, the rays of light are focused in front of the retina, rather than directly onto it, causing the appearance of those objects to become blurred.

Nearsightedness is the most common vision problem. Currently, about 1.5 billion people worldwide (nearly a quarter of the global population) are nearsighted. Myopia is especially prevalent in East Asia, where 70 to 80 percent of the residents of some countries are affected.

And the rate of myopia worldwide is increasing rapidly. It's estimated that by the year 2050, roughly half of the world population will be nearsighted.

Researchers aren't sure why myopia is becoming so common, but many eye doctors attribute it to eye fatigue from close-up work including reading, studying, using computers and portable electronic devices (including tablets and smartphones) and reduced time spent outdoors.

 

Picture Credit : Google

The retina is the back part of the eye that contains the cells that respond to light. These specialized cells are called photoreceptors. There are 2 types of photoreceptors in the retina: rods and cones.

The rods are most sensitive to light and dark changes, shape and movement and contain only one type of light-sensitive pigment. Rods are not good for color vision. In a dim room, however, we use mainly our rods, but we are "color blind." Rods are more numerous than cones in the periphery of the retina. Next time you want to see a dim star at night, try to look at it with your peripheral vision and use your ROD VISION to see the dim star. There are about 120 million rods in the human retina.

The cones are not as sensitive to light as the rods. However, cones are most sensitive to one of three different colors (green, red or blue). Signals from the cones are sent to the brain which then translates these messages into the perception of color. Cones, however, work only in bright light. That's why you cannot see color very well in dark places. So, the cones are used for color vision and are better suited for detecting fine details. There are about 6 million cones in the human retina. Some people cannot tell some colors from others - these people are "color blind." Someone who is color blind does not have a particular type of cone in the retina or one type of cone may be weak. In the general population, about 8% of all males are color blind and about 0.5% of all females are color blind.

 

Picture Credit : Google

A cataract is a cloudy area in the lens of your eye. Cataracts are very common as you get older. In fact, more than half of all Americans age 80 or older either have cataracts or have had surgery to get rid of cataracts. 

Most cataracts are age-related — they happen because of normal changes in your eyes as you get older. But you can get cataracts for other reasons — for example, after an eye injury or after surgery for another eye problem (like glaucoma).

No matter what type of cataract you have, the treatment is always surgery.

Most cataracts are caused by normal changes in your eyes as you get older.

When you’re young, the lens in your eye is clear. Around age 40, the proteins in the lens of your eye start to break down and clump together. This clump makes a cloudy area on your lens — or a cataract. Over time, the cataract gets more severe and clouds more of the lens.

 

Picture Credit : Google

Flowers get their scent from a mixture of volatile organic compounds (VOCs) produced by the plant. The fragrance is often strongest in the petals.

Different flowering plant species encompass a diversity of VOCs and no two fragrances are the same. The purpose of scent is to attract pollinators and repel herbivores. Flowers also use colour and shape to attract pollinators. The scent is strongest when a flower is ready for pollination - a full bloom's smell is powerful than a bud's.

Maximal emissions also coincide with the active phase of visiting pollinators. Plants pollinated by moths usually emit the most fragrance in the evening or night (when moths are active), while plants pollinated by bees produce the most scent during the day (when bees are active).

 

Picture Credit : Google

Similar to ischemic brain strokes, silent strokes occur when a portion of your brain suddenly stops receiving blood. It stops oxygen supply to the brain, causing considerable damage to the brain cells. However, a silent stroke is hard to understand because it breaks the blood supply to that part of your brain that has nothing to do with any of your visible functions, such as with ambulation, seeing, or speaking. Therefore, it goes unnoticed.

So, what about Silent Stroke Diagnosis? In most cases, people get to find out about their stroke only when they undergo a CT scan or an MRI of the brain for any other health condition. That is when a doctor can identify that a small portion(s) of your brain has sustained some amount of damage.

Also, if a person has had several episodes of silent stroke, they may notice the onset of several neurological symptoms, including difficulty concentrating and loss of memory.

As per the American Stroke Association, silent or asymptomatic stroke puts you at the risk of having symptomatic brain strokes later on in your life. Recent studies confirm that if you have had multiple episodes of silent strokes, you are at a higher risk for vascular dementia (multi-infarct dementia). The symptoms include:

? Problems with remembering things or loss of memory.

? Losing control over bladder and bowel movements.

? Difficulty in decision-making.

? Emotional outbursts like crying or laughing inappropriately.

? Not identifying previously visited places.

 

Credit : Quora

Picture Credit : Google

Thus, when they see an open safari vehicle, full of people, all they see is one single thing: a large beast with some appendices on top (heads). As a large, and potentially powerful, beast does not interest them, as well as other large animals such as adult rhinos and elephants: they know the hunting effort is not worthy. Not because they fear humans.

However, all attention is necessary, as apex predators such as lions or even leopards are relatively intelligent and curious animals. If somebody stands up and detaches himself from the rest of the “beast mass”, the predator may be curious and in doubt if that is a part of the large beast or is something else separate: it may then investigate or attack. In case of an attack, we all can imagine what happens. If it starts to investigate too close, many tourists may lose their nerve, stand up and even run… which will be the worst mistake, as the predator will then be sure that it is a prey and will start chasing (hunting reflex), and they run much faster than any of us.

Considering that, the local guides normally orient passengers to stay seated, quiet, only observing when close to animals. They teach you to never stand up, shake arms or worst, get out of the safari vehicle. In this last case, the animal will be sure you are not part of the large beast and will notice you are actually the perfect size for a prey…

However, some private game reserves do not disclose the fact that, in order to maintain the “savage aspect” of the tour, especially those where an open safari vehicle is used, they “prepare” the animals to get used to human presence. Before opening a new game reserve or when new animals are bought (yes, they do buy animals from other places to populate or replace losses, so there is plenty to be seen by tourists), they get the animals used to the safari vehicle and people, by running close to them on a frequent basis, until the animal is used to the vehicle and people and do not show aggressiveness anymore. They do it until the “large beast” is already a part of the landscape. That is why they really do not attack.

Nevertheless, if a pack of lions insist on being aggressive to humans, which makes the reserve lose money, they resell or even shoot down the rebels. Sad, no? No publicity on this, bad for business.

 

Credit : Quora

Picture Credit : Google

1. During pregnancy, the baby in womb can help repair a mother’s organ damage by giving its stem cells. In Biology, it’s a form of chimerism called the Fetomaternal microchimerism (FMc). Alternatively, this is a survival mechanism by which the fetus ensures maternal fitness in order to enhance its own chances of survival.

2. Some humans have a total of 207 bones instead of 206. The Fabella is a tiny sesamoid bone in the knee that has been making a come back in recent years. At present, around 39% of the population have the extra fabella bone, which is three times more in 100 years, compared to only 11% of world population having it in 1918. Scientists theorize, this emergence is due to increased nutrition and humans getting taller and heavier.

3. A newborn baby has only one cup (0.2 liters) of blood in the whole body, whereas, the healthy adult has about 1.3 to 1.6 gallons or 4.0 to 5.0 litres of blood circulating inside their body.

4. Lungs are the only organ in the human body that can float on water. In fact, medical examiners use the “lung float test” during autopsies to determine if a baby was stillborn (died in the womb). If the lungs float, the baby was born alive; if the lungs don’t float, the baby was stillborn.

5. Speaking about lungs, did you know that you can live with just one lung? Patients with lung cancer, can still live healthily even after a lung is removed, retaining at least 70% of their previous respiratory function. Surprisingly, the remaining lung will expand to fill the empty space of the other lung in the chest.

6. If you pulled out the blood vessels from an an average child and laid out in one single line, it would stretch to over 60,000 miles. The entire circumference of the earth at it’s largest is 24,900 miles.

7. Your eyes blink over ten million times a year!

8. The entire surface of your skin is replaced every month, which put another way means you have about 1,000 different skins in your life.

9. Next time you’re wounded, and can’t find a bandage, just ask the friendly spider next wall. Spiderwebs/cobwebs have natural antiseptic and anti-fungal properties, and were used in ancient Greece and Rome by physicians to make bandages. They’re also thought to be rich in Vitamin K. 

10. While you’re sleeping, your ears continue to function. They will pick up sounds, but your brain acts as a filter and blocks out the unimportant ones.

11. More humans are evolving to have three arteries in their arms. The Median artery which is present during the early human embryonic stage is later replaced by the ulnar and radial artery during developmental changes. However new research shows that median artery is now prevalent in about 35% of the population and researchers predict that people born 80 years from now might all carry a median artery. This is an example of Micro-evolutionary changes that are occurring in the human body.

 

Credit : Quora

Picture Credit : Google

Mosquitoes shouldn’t be able to fly in the rain, but they still do!

Despite being roughly the same size, a single raindrop can weigh up to 50 times more than an average mosquito. So, a mosquito flying in the rain is like a person wandering about when it’s raining buses! Common sense says mosquitoes shouldn’t survive the rain, but they are a stubborn bunch.

So how do they survive the rain?

Well firstly, they do not get wet. The glassy wings and the tiny hairs on their bodies are designed to repel water. So, when a raindrop bounces off of a mosquito, one of the two scenarios may occur:

Raindrop hits wings or legs [very probable]

Raindrop hits the core body or head [unlikely]

In the first scenario, the mosquito rotates around the raindrop due to its hydrophobic body and regains normal flight with minimal effort. In other terms, the mosquitoes just shake it off

In the second scenario, the mosquito gets hit hard and drops in altitude. But it still manages to survive by taking on only a fraction of the full momentum [2–17% depending on the mosquito] of the raindrop upon impact. It does this by making the collision inelastic. The secret to this is to go with the flow

Besides, the drastic difference in mass between the mosquito and the raindrop actually becomes an advantage when we analyse the system by applying the law of conservation of momentum.

And that is how the pesky little mosquitoes fly in the rain.

 

Credit : Quora

Picture Credit : Google

Luckily for us, we don't even have to imagine: we have examples of this happening in the real world, and right here, in the Americas, very close to us.

Can you imagine entire civilizations developing without the help of horses?

Pre-Columbian civilizations not only did not know horses, but had no other means of riding. The reason is quite obvious, in fact: whether in the Amazon rainforest or in the Andes, the terrain was anything but friendly to riding animals.

Even so, our indigenous ancestors managed to domesticate llamas. More precisely, the Inca people. The animal was, without a doubt, one of the most important elements for the development of this people. In addition to pack animals, they served as a source of food, wool and leather. The curious thing is that, unlike their relatives, camels, neither llamas, nor their close cousins, alpacas, are useful as mounts.

They are also not very useful for combat.

Well, except, of course, as pack animals. Although with a much smaller capacity than that of the old world horses and cattle, llamas and alpacas do very well in the steep and rocky terrains of the Andes.

But okay. The question is animals truly used in combat. In this case, the best, biggest and most incredible alternative to horses, you already guessed it...

In India, elephants have been used extensively in combat for ages. At some point, it was said that Indian ruler, Porus, had over 100,000 war elephants in his army.

They’ve been used in Europe, too. One of the greatest achievements of Hannibal, general of Carthage, was to lead an army of 80,000 soldiers along with his troop of elephants, on a march through the Alps. Although many men and animals perished on the crossing, the conclusion of this journey is still considered to be one of the greatest military achievements in history. Hannibal's attack with his elephants was, to some extent, a great success.

Over the next 15 years, Hannibal won significant battles and occupied the south of Italy, once with reinforcements shipped directly from Africa, although no elephants were included. In the 209 B.C. battle of Canusium with the Roman consul Marcellus, Hannibal’s war elephants created havoc until the Romans managed to wound one, touching off a cascade of panic among the pachyderms.

You see, war elephants were a growing problem at some point in history. Because of this, to counter them, another animal, other than the horse, was used with great success…

During the siege of Megara, among the Macedonian troops, were the feared war elephants. To break the siege, it was necessary to eliminate the imposing animals. For this, Mégara's generals devised a plan that was both creative and extremely cruel: oiling pigs and set the poor animals on fire.

When the burning pigs were released, grunting in pain and despair, towards the Macedonian elephants, the pachyderms, seeing the mass of fire coming their way, with their shrill and deafening screeches, panicked. The elephants fled in terror, trampling (and killing) many Macedonian soldiers in the rout.

Probably man has tried and tested every animal he could for war and cargo transportation. I think the best alternative would undoubtedly be the elephants, already tested and approved in the field.

 

Credit : Quora

Picture Credit : Google

The most common myth concerning ostriches is that these birds bury their heads under the sand whenever danger is on the prowl. In reality, this isn’t true, because ostriches do not bury their heads underground when threatened; instead, they will readily defend themselves and protect their chicks.

Sure enough, the world’s biggest and fastest bird can become aggressive if threatened. For that matter, it has long, dagger-like claws at the end of its long feet – as such, one kick can inflict a serious amount of damage. This is why it’s always advisable never to try provoking an ostrich.

However, the myth does come from a true fact: when nesting, a female ostrich will dig shallow holes in the ground, so as to use them as nests for her eggs. In the process, she uses her beak to turn her eggs several times each day.

In fact, from a distance, an ostrich leaning into a hole could easily look like it’s burying its head in the sand! And that is what probably led to the common myth.

But still, despite their comical appearance, ostriches are not cowards; they are dangerous birds that will never relent towards anything that threatens their lives or that of their young. It’s always wise never to mess with ostriches.

 

Credit : Quora

Picture Credit : Google