Have you ever wished you could only let half your brain sleep so the other half could finish 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 all heard the phrase “sleep with one eye open.” People say it when they want to suggest that someone could be in danger. It’s not just an expression for dolphins, though; they actually do it.

The two halves of a dolphin’s brain work independently of each other, so one side can go to sleep while the other stays awake. This serves two functions. One, presumably, is so the dolphin can look out for threats from various predators without losing any shut-eye. The other is to make sure the dolphin keeps breathing.

Dolphins move to the surface to get air 2-3 times each minute. If they went into a deep sleep, they wouldn’t do this and would eventually die. Instead, because one side of the brain is always awake, the dolphin always gets enough air.

During each 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. After the sleeping side wakes, the dolphin can either stay completely awake or let the other side gets its rest while the rested side takes over the breathing.

Unlike the 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’re always awake. Makes you a little jealous, doesn’t it?

(Non-) Sleeping Baby Dolphins

It’s hard to imagine a baby not sleeping for long periods of time. That’s what makes baby dolphins so unusual, especially among mammals. 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. Scientists don’t know why this happens, but it makes the adult’s sleep patterns seem a bit less strange.

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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.

A supernova (Image credit: NASA)

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

The Death of a Star

Stars produce energy by nuclear fusion. Each star contains vast reserves of hydrogen, which fuses into helium. Toward the end of its life, a star runs out of hydrogen. Without hydrogen, the star starts fusing helium into heavier elements. The core of the star shrinks, but the outer layers expand to create a red giant star, which often destroys surrounding 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 white dwarf, slowly dies. Larger stars go through violent changes when they run out of helium. The core collapses almost instantly.

Temperature within the collapsing core builds in a matter of seconds to over 100 billion degrees Fahrenheit. The outer layer collapses inwards, and then explodes outwards in a supernova. During the supernova explosion, the dying star produces enough energy to fuse heavy elements, such as uranium and gold. Any planets lucky enough to survive the star’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 is crushed under gravitational forces so strong even light cannot escape.

Star Birth

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

The new star’s gravitation causes more nebulae material to clump up, eventually creating planets and everything on them. Yup, the planet and all of us are made of remanufactured parts. Sagan was right. When you get right down to it, we’re all born from the stars.

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

This is absolutely wrong. Cats have rough tongues in order to use them like miniature sanders to help them rip the flesh off their victims. Cats are killing machines, after all. They’re loaded with natural 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, but once an animal is dead its pelt needs to come off so that the cat can get to the fleshy goodness contained within.

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

How does it work?

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

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Every time you take a long shower, you might feel a pang because you’re wasting water. On a micro scale, shame on you! However, on a macro scale, you’re in the clear.

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

Bear in mind that only 2.5% of the world’s water supply is drinkable. The rest is brackish sludge that will kill you. Even so, the vast majority—an estimated 70%—of potable water is locked up in glaciers. Most of the rest of the fresh water is contained deep underground or in soil, and is virtually inaccessible.

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

How Does Industry Use Water?

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

Excluding farming, it is worth noting how water is used in various industries. Water is used to make cars, electricity, refining oil and everything else. Manufacturing overall uses approximately 20,000,000,000 gallons of water a day. Sounds like a lot? 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. The pharmaceutical industry uses an advanced water purification method. Indeed, the use of pharmaceutical engineering vapor compression machines is integral in the manufacturing process. The upshot is that the technology used in pharmaceutical grade water purification is making its way to purifying water on a macro scale. This use of alternative water sources supplies large populations with a net positive increase in clean drinking water.