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Welcome to Science Decoder where science is made easy. Here you will find a compilation of notes and tutorials covering areas mainly in Physics, Biology and Chemistry. These are aimed at students studying these subjects at the early stages of tertiary level education. If your lucky enough you might even see some of our amazing science pictures and find some unbelievable facts about the universe we are still yet to understand.

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Dolphins: The Insomniac Mammal

Have youever wished you could only let half your brain sleep so the other half couldfinish a long day’s work? Unfortunately, as a human, you don’t have that option.But if you were a dolphin, you’d be doing it every day of your life.

Sleep With One Eye Open -Literally
We’ve allheard the phrase “sleep with one eye open.” People say it when they want tosuggest that someone could be in danger. It’s not just an expression for dolphins,though; they actually do it.

The twohalves of a dolphin’s brain work independently of each other, so one side cango to sleep while the other stays awake. This serves two functions. One,presumably, is so the dolphin can look out for threats from various predatorswithout losing any shut-eye. The other is to make sure the dolphin keepsbreathing.
Dolphinsmove to the surface to get air 2-3 times each minute. If they went into a deepsleep, they wouldn’t do this and would eventually die. Instead, because oneside of the brain is always awake, the dolphin always gets enough air.

Duringeach sleep cycle, one side gets its sleep, typically about eight hours. Meanwhile,the other side is taking care of the usual surfacing and breathing activities. Afterthe sleeping side wakes, the dolphin can either stay completely awake or letthe other side gets its rest while the rested side takes over the breathing.
Unlikethe fish you might see at an El Paso aquarium, which can fall asleep in dark rooms,the dolphins in the water are always resting, and yet at the same time they’realways awake. Makes you a little jealous, doesn’t it?

(Non-) Sleeping Baby Dolphins
It’s hard to imagine a baby not sleeping for longperiods of time. That’s what makes baby dolphins so unusual, especially amongmammals. Where most young need far more sleep than their adult counterparts,baby dolphins don’t get any sleep at all until they’re 4-5 months old. Scientistsdon’t know why this happens, but it makes the adult’s sleep patterns seem a bitless strange.

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Why Do Cats Purr?

Image credit: Clarissa Rossarola

Cats are one of the most common household pets. These adorable creatures are playful, huggable and notoriously independent. They make great companions for adults and playmates for children. What makes them more fascinating is the interesting and well-known sound, the purr that they make. 

Although purring is a common sound from cats, you may have wondered why they make it. It can happen at any time of the day, much like humans when they sigh.

Some theorize that cats purr when threatened, even though they are not guarded against like some animals such as groundhogs, where people use live trap groundhog setups to keep them away from their properties. Cats are usually considered welcoming creatures, but what's causing your furry friend to give off this sound? Let's take a look at some interesting facts about why cats purr.

How Does a Purr Happen?

Purring is caused by a motion coming from the cat's central nervous structure. As the cat inhales and exhales, the vocal muscles in the larynx tremble and produce the sound burst that occurs every 30 to 40 milliseconds. This process produces the purring sound. The frequency of purring also depends on the cat's weight, sex and age. Research has found that cats purr in a range of situations.

Purring for Pleasure

Many are aware that cats purr due to experiencing pleasure like when they are nursing babies or when stroked or petted by a human. Purring can also occur during a cat's sleep or when it is rolling. It can also occur around familiar cats.

Purring for Pain

Cats can also purr while under pressure from stressful times like recovering from an injury or when in pain. Therefore all purring cats are not content with their current situations. When a cat is brought in for treatment at a hospital after a tragedy like being hit by a car, a cat may produce a purr. Interestingly, larger cats such as the leopard, jaguar and lion do not purr.

In general cats can purr in good times and in bad, but it's mainly associated with human interactions or positive cat exchanges.

Supernovas and You

A supernova (Image credit: NASA)

Carl Sagan famously said we are all made ofstardust, and he was right on the money. Everything around us began in thedeath of a star. Supernovas create giant clouds of matter which provide thebuilding blocks for new stars, planets, and the matter that makes up living andinorganic substances.

TheDeath of a Star

Stars produce energy by nuclear fusion. Eachstar contains vast reserves of hydrogen, which fuses into helium. Toward theend of its life, a star runs out of hydrogen. Without hydrogen, the star startsfusing helium into heavier elements. The core of the star shrinks, but theouter layers expand to create a red giant star, which often destroyssurrounding planets.

Eventually the star runs out of helium as well.If it’s a small star, like our sun, fusion ends and the star, now a whitedwarf, slowly dies. Larger stars go through violent changes when they run outof helium. The core collapses almost instantly.

Temperature within the collapsing core buildsin a matter of seconds to over 100 billion degrees Fahrenheit. The outer layercollapses inwards, and then explodes outwards in a supernova. During thesupernova explosion, the dying star produces enough energy to fuse heavyelements, such as uranium and gold. Any planets lucky enough to survive thestar’s expansion into a red giant are obliterated by the supernova.

As for the remains of the collapse star core,if conditions are right it may become a black hole, an area where matter iscrushed under gravitational forces so strong even light cannot escape.


The material expelled during the explosion sometimesforms massive clouds of dust and gas called nebulae that float in theinterstellar void. Gravity causes nebulae material to clump together,eventually giving birth to a protostar. As millions of years pass, theprotostar develops into a fully-formed star.

Thenew star’s gravitation causes more nebulae material to clump up, eventuallycreating planets and everything on them. Yup, the planet and all of us are madeof remanufacturedparts. Sagan was right. When you get right down to it,we’re all born from the stars.

Ever Wondered Why Cats Have Rough Tongues?

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It might be startling to be licked by a felineand find out that their tongues are incredibly rough. Every cat has thisfeature, and many people who have felt it mistakenly think their abrasivetongue developed to help them clean their coat. It makes sense, since catsspend a lot of time grooming themselves with their tiny tongues.

This is absolutely wrong. Cats have roughtongues in order to use them like miniature sanders to help them rip the fleshoff their victims. Cats are killing machines, after all. They’re loaded withnatural weapons, such as their marquee retractable claws on each of their toes.The claws are used to take down their prey in conjunction with a neck bite, butonce an animal is dead its pelt needs to come off so that the cat can get tothe fleshy goodness contained within.

Of course, this isn’t immediately apparent inyour everyday house cat. You’re much more likely to see a lion literally lickthe flesh off a gnu carcass than see a cat messing about with a small kill.

How does it work?

The cattongue is covered in tiny reverse barbs called filiform papillae. These arespecialized taste bud cells that feel hard because of keratin, the substancethat makes your fingernails hard. Surprisingly, only a small percentage ofthese papillae can actually sense taste. Because felines don’t rely on theirsense of taste for making sure foods are edible, they were able to sacrificetaste for this particular adaptation.

How Much Water Are You Wasting?

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Everytime you take a long shower, you might feel a pang because you’re wastingwater. On a micro scale, shame on you! However, on a macro scale, you’re in theclear.

All thisis a drop in the bucket when it comes to industrial use of water. In point offact, industry worldwide makes up approximately 92% of water usage. Only 8% ofthe water supply goes for domestic use.

Bear inmind that only 2.5% of the world’s water supply is drinkable. The rest isbrackish sludge that will kill you. Even so, the vast majority—an estimated70%—of potable water is locked up in glaciers. Most of the rest of the freshwater is contained deep underground or in soil, and is virtually inaccessible.

In factthe fresh water we have access to makes up 0.005% of the world’s total watersupply. This is causing shortages all over the world, leading countries to findalternative means of obtaining fresh water, such as desalination of seawater.

How Does Industry Use Water?

Farmingis the big culprit when you look at it on a global scale, making upapproximately 80% of water usage worldwide. The picture changes inindustrialized nations, and farming pales in comparison to manufacturing, whichmakes up 60% of water usage in developed countries. That is a lot of water.

Excludingfarming, it is worth noting how water is used in various industries. Water isused to make cars, electricity, refining oil and everything else. Manufacturingoverall uses approximately 20,000,000,000 gallons of water a day. Sounds like alot? Nuclear power plants use up 200,000,000,000 gallons of water per day,making up 50% of industrial water use worldwide.

Some industrial water use has led to good. Thepharmaceutical industry uses an advanced water purification method. Indeed, theuse of pharmaceutical engineering vapor compression machines is integral in the manufacturing process. Theupshot is that the technology used in pharmaceutical grade water purificationis making its way to purifying water on a macro scale. This use of alternativewater sources supplies large populations with a net positive increase in cleandrinking water.