Category Science

Why do cheetahs have a tear line?

Cheetahs have two tear lines that run from the inside corners of their eyes down to the outside edges of their mouth. These marks help reflect the sun’s glare whenever the cats are off hunting during the sunniest of days – in that way, cheetahs don’t get blinded by direct sunlight like we do, even in midday.

The tear lines work in a similar way to the black marks worn by rugby players. They’re also helpful features for the cheetah in order to stay focused on its prey.

There is a Zulu folklore tale about how the cheetah got its tear lines: once, a hunter was too lazy to be about his business, wishing that someone could get the meat for him. Soon, he saw a female cheetah making a successful kill and feeding it to her cubs, and all of a sudden decided to steal all these cubs in order to train them for hunting.

Soon, when the mother cheetah was away, the wicked hunter accomplished his terrible deed, kidnapping all the cubs without leaving a single one. Once the mother found her babies gone, she became heartbroken, searched for them far and wide, and kept calling and crying all day and night, so long and so hard, until her tears made dark stains down her cheeks.

Soon, the elders got wind of the event and went to punish the lazy hunter, who had also broken the tribe’s most sacred traditions – in Zulu culture, it’s tradition that a hunter must use only his own strength and skill, otherwise dishonor comes. But even when the wicked man was eventually forced to bring the cubs back to their mother, nevertheless her long weeping stained her face forever – and those tears are worn by her children (modern-day cheetahs) to this day.

According to the locals, this tale carries a moral: a cheetah wearing the tear stains on its face is a reminder for hunters that it is not honorable to hunt in a non-traditional, inconvenient way.

 

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If fire needs oxygen, where does the sun get oxygen if there’s no oxygen in space?

Indeed, this was a scientific problem for hundreds of years: if Sun consisted of oxygen, it would run out of fuel in a few hundred years. So what’s the deal?

But wait, nowadays we know more. What other objects glow like the Sun, even without oxygen?

This example of a lamp bulb shows that not all objects that shed light need oxygen to do so. Of course, for light bulb that gas is typically some inert gas (see e.g. Which gas is typically used in light bulb?).

In fact, the light bulb doesn’t use up the gas. Instead, it uses an electric wire, i.e. a resistor, heated up by the electricity flowing through it. The wire heats up, in turn heating up the gas.

The Sun is a bit similar to a light bulb. From early spectroscopic studies in the 1800s, we know that it consists of gas, mostly hydrogen and helium. The latter was actually first discovered on Sun giving the element its name from Helios, Greek name for Sun.

Nowadays we also know that this gas is heated up not by directly burning its chemical constituents, but by a special phenomenon that is the reverse of what’s happening in nuclear power plants: nuclear fusion.

While in nuclear power plants uranium splits up and by doing so releases energy (nuclear fission), in nuclear fusion the hydrogen atoms combine to form helium or even more massive particles. In case of light particles like hydrogen this again releases large amounts of energy.

The energy released speeds up the particles in the Sun’s core and in turn these super-heated particles slowly bounce around and raise to Sun’s surface. There, the temperature of the hydrogen-helium gas is 5500 degrees Celsius or near 10 000 degrees Fahrenheit.

A gas this hot will glow literally like the Sun, finally releasing the heated energy to the universe and, consequentially, to us.

Sun continually loses a tiny portion of its mass to keep shining, combining hydrogen to helium in its fusion forge, its core. From observing other stars like it, we know it has enough nuclear fuel to shine for another few billions of years.

 

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What is analemma?

This is what the sun looks like when you take a picture a week, for a year, always at the same time of the day, and in the same place.

Due to the 23.5° inclination of earth’s axis and the ellipticity of its orbit, the height of the sun is not the same every day, and the combined effects is what the image shows.

The height of the points corresponds to the declination of the sun on that date, while the horizontal coordinate indicates the deviation of the solar position with respect to the average time (shown by clocks).

The inclination of the figure depends on the latitude in which it is observed and on the time.

If earth’s orbit were a perfect circle and its axis were perpendicular to the orbit, the sun would be in the same spot every day and the analemma would be a point. With a circular orbit but an inclined axis, the two parts of the analemma would be symmetrical. If the axis were not inclined but the orbit were elliptical, the analemma would instead be a segment.

On other planets the analemma has a different shape, on Mars for example, it looks like a drop.

 

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Can mosquitoes fly when it rains?

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.

 

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Which animal is believed to be dangerous but is actually altogether harmless?

While many animals in the world look dangerous and live up to their frightening appearances, there are many others which pose little to no threat to us humans.

Here’s my list of 7 scary looking animals that are practically harmless.

1. Gharial

Many people would be right to fear a gharial if they’ve heard stories about how other crocodilians kill hundreds of humans each year, but is this slim snouted creature really as dangerous as its cousins?

In truth, gharials only hunt small prey like fish and frogs as their jaws are too slim and weak to take down larger quarry. As a result gharials are unable to attack large prey, namely humans.

2. Milk snake

While, the milk snake may bear a striking resemblance to the venomous coral snake they are completely harmless. They have no venom and are actually quite docile in nature which makes them pretty good pets for reptile lovers.

3. Sand tiger shark

Most people know that sharks in general don’t deserve their fearsome reputation as an eating monsters but very few of them are completely harmless. While, the great white, tiger and bull shark have all been known to kill people, the sand tiger shark is actually completely harmless.

This shark’s barbed jaws may look threatening but these scary looking teeth are exactly what keep this fish from being even a slight danger towards us. The shark’s mouth is too small to cause a human fatality so only squid and fish fall victim to this shark’s jaws. While this shark is very docile there have been a few attacks when it’s been provoked…

4. Goliath bird eater

Goliath bird eating spiders may have venom. They may take down small birds and they may be freaking massive but are they really a danger towards humans?

In truth this tarantula’s venom is harmless and is quite similar to how a wasp’s sting would feel. Main difference is that these spiders only bite in self defense, so I’m pretty sure you won’t be bothered by this giant.

5. Manta rays

Manta rays are very large and if you have ever heard of sting rays, you might be frightened by this aquatic creature. Manta rays are actually gentle giants and are only filter feeders, meaning they eat really small prey. To make things better, they don’t have stingers so divers have nothing to fear!

6. Thorny devil

These lizards may be small but I’m pretty sure most of us would be scared if this spiky reptile came charging. Luckily this animal only feeds on insects and when it does feel threatened it squirts blood from its eyes…which may seem gross but wouldn’t really harm a human being. To make things even better, these scary looking lizards run at the first sight of a human being!

7. Basking shark

The second-largest shark species is pretty harmless despite its frightening set of jaws. Like many of the ocean’s largest predators, this creature is a filter feeder and that means humans aren’t on the menu!

 

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If horses did not exist, what animal would we use for combat?

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

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