What is a Non-Newtonian Fluid

A non-Newtonian fluid is a fluid whose viscosity is variable based on applied stress. The most commonly known non-Newtonian fluid is cornstarch dissolved in water. Contrast with Newtonian fluids like water, whose behavior can be described exclusively by temperature and pressure, not the forces acting on it from second to second. Non-Newtonian fluids are fascinating substances that can be used to help us understand physics in more detail, in an exciting, hands-on way.

If you punch a bucket full of a shear thickening non-Newtonian fluid, the stress introduced by the incoming force causes the atoms in the fluid to rearrange such that it behaves like a solid. Your hand will not go through. If you shove your hand into the fluid slowly, however, it will penetrate successfully. If you pull your hand out abruptly, it will again behave like a solid, and you can literally pull a bucket of the fluid out of its container in this way. 

A shear thinning non-Newtonian fluid behaves in the opposite way. In this type, the fluid becomes thinner, rather than thicker, when stress is applied. Also called pseudoplastic, examples of this type of non-Newtonian fluid include ketchup, toothpaste, and paint. The effect doesn't usually last for long in either type, continuing only as long as the stress is applied.

Non-Newtonian fluids help us understand the wide variety of fluids that exist in the physical world. Plastic solids, power-law fluids, viscoelastic fluids, and time-dependent viscosity fluids are others that exhibit complex and counterintuitive relationships between shear stress and viscosity/elasticity. However, non-Newtonian fluid is probably the most exciting to play with. 

A search for non-Newtonian fluid on YouTube brings up some interesting results. On several game shows, hosts or contestants run across big vats of shear thickening non-Newtonian fluid, able to traverse them unless they stop - in which case they sink immediately. When combined with a oscillating plate, non-Newtonian fluids demonstrate other unusual properties, like protruding "fingers" and holes that persist after creating them. An oscillating plate applies stress on a periodic basis, rapidly changing the viscosity of the fluid and putting it in an odd middle ground between a liquid and a solid.

A practical application for shear thickening non-Newtonian fluids may be in body armor of the future. Since such fluids are usually flexible, they would allow soldiers to move freely when not under attack. But if confronted with a speeding bullet, they would quickly harder, performing like traditional armor. More research is necessary to see if non-Newtonian fluids are suitable for the military, but until then, it's sure fun to play with.

What is Thermal Energy

Thermal energy is generated and measured by heat of any kind. It is caused by the increased activity or velocity of molecules in a substance, which in turn causes temperature to rise accordingly. There are many natural sources of thermal energy on Earth, making it an important component of alternative energy.

The laws of thermodynamics explain that energy in the form of heat can be exchanged from one physical object to another. For instance, putting fire under a pot of water will cause the water to heat up as a result of the increased molecular movement. In that way, the heat, or thermal energy, of the fire, is partially transmitted to the water.

Understanding the principles of thermodynamics has allowed human beings to harness natural sources of heat to create thermal energy out of a variety of sources. The sun, ocean, and geothermal sources such as geysers and volcanoes, can all be sources of thermal energy. As humans attempt to turn to sustainable forms of alternative energy instead as fossil fuel resources become depleted, much attention has been focused on improving methods of harnessing thermal energy to power human activity.

Solar thermal power is one of the most commonly used forms of thermal energy. Although gathering solar power is only available when the sun is visible in the sky, scientists have developed many different ways of storing and utilizing the power absorbed by solar devices. On a small level, a person can heat his or her pool by placing low-temperature collecting systems in or around the water. By absorbing sunlight and distributing it to the water, the temperature is increased throughout the day and even after the sun has set. Solar panels, evaporation pools, and other advanced systems can perform this function on a much more wide-spread level, creating enough stored power to run a factory or even city on solar thermal power.

The Earth is constructed around a molten core of incredible heat that lessens considerably as it reaches the surface or crust level. Yet by harnessing some of the heat generated below the surface of the planet, humans can extract enormous amounts of energy. The simplest way to do this is through geothermal energy sources such as geysers, or at the boundaries of tectonic plates. Geothermal wells pump out energy in the form of hot water or steam that can be converted into usable energy, or simply used directly. 

Thermal energy is an awesome force that is just beginning to be fully understood. By creating new devices and methods to concentrate, store, and transport naturally-created thermal energy, human beings can reduce dependence on non-sustainable forms of energy. Thanks to the power of heat, hot baths, boiled water, and thermally-powered cities are all possible.

Why Does Bread get Moldy

Bread gets moldy because it provides a good source of food for some types of fungus. The air is usually full of tiny mold spores, and under the right conditions, they can settle on nearly any organic substance and start to digest it. In bread, these enzymes break down the cell walls of the organic material making up the loaf, releasing easily digestible, molecularly simple compounds. This is how bread gets moldy.

Mold, found on old or unrefrigerated bread, comes from fungi, one of the most ubiquitous and successful forms of life on the planet. There are dozens of thousands of species, which can be found practically everywhere. Scientists who study fungi, called mycologists, tell say that approximately one out of every 20 living species is a form of fungus.

Fungi cannot receive energy directly from the sun because they do not have chlorophyll, and must therefore live off other plants and animals. Some fungi are parasites, actively attacking a host for nutrients. Most, however, are scavengers, turning organic matter into soil. Without fungi, many plants would die, because they require rich soil to thrive.

Most fungi tend to be flexible about their food choices. They feed on a wide variety of organic molecules, and their flexibility is largely responsible for their ubiquity. Fungi produce dozens of digestive enzymes and acids, which they secrete into a material as they grow over it. 

Unlike humans, mold digests first, then eats, rather than vice versa. Under the right conditions, there exist forms of fungi that eat practically anything but metal. Special fungi produced through selective breeding are sometimes used as agents to target specific compounds for cleanup. 

Fungi reproduce exponentially until all available nutrients are exhausted. Some forms of mold can double their mass every hour. They reproduce by means of spores, tiny vectors which are produced by the fungus en masse. Spores are extremely small and numerous — there are probably millions of fungal spores in any room at one time. 

Luckily, these spores can be destroyed by cooking, which is why bread doesn't immediately get infected with mold. Over time, however, airborne spores find their way onto the nutrient-rich surface of bread and start multiplying — even under the cold conditions of a refrigerator. At freezing point, fungi become dormant. If they are exposed to heat again, they can revive and continue to grow.

What are Hypnagogic Hallucinations

Hypnagogic hallucinations are hallucinations which occur at the boundary between sleeping and waking. They can occur when people are falling asleep, or when they are starting to wake up, and they tend to be extremely vivid, feeling like a Technicolor Oz after the black and white Kansas of every day life. Many people experience hypnagogic hallucinations at some point during their lives, but recurrent intense hallucinations can be a sign of an underlying medical condition which may require treatment.

Visual, auditory, tactile, and kinetic sensations can all be experienced during hypnagogic hallucinations, and everyone experiences slightly different forms. Some people, for example, may feel like they are falling, and jerk themselves awake to avoid hitting the ground. Others may hear voices as they are trying to drift off to sleep, or experience a vivid sensation that someone or something is in the room. Sensory experiences such as feeling like one is submerged in a pool of water are also not uncommon.

In some cases, hypnagogic hallucinations can be frightening for the people who experience them. They may include vivid and frightening images, including images which are out of scale, which can make the hallucinations seem even more unsettling; people may see giant spiders on the walls, for example, or feel like they have shrunk down to a tiny size in the bed. The vivid experiences may also be brought to mind over the course of the day, causing inexplicable images or sensations to filter through someone's consciousness at an unexpected moment.

The cause of hypnagogic hallucinations is not fully understood. These hallucinations tend to be more common in people with sleep disorders, especially narcolepsy, but they can also appear as a side effect related to prescription drugs, and drug abusers often experience them as well. Hypnagogic hallucinations tend to be more common in young people, especially children, which may be because their minds are still developing and forming pathways, which can occasionally lead to some crossed wires.

If someone experiences numerous hypnagogic hallucinations, repetitive or not, it is a good idea to see a doctor to check for health problems which could be related to the experiences. If no cause is evident, a psychologist or similar mental health professional might be able to explore the subconscious causes and help the patient deal with the hallucinations. Consulting a psychologist can also yield useful tips for people who are shaken or upset by hypnagogic hallucinations, even if the hallucinations continue to occur.

What is Benedict's Reagent

Benedict's reagent is a chemical compound made up of copper sulfate, which can detect the presence of glucose or fructose. A reagent is a chemical that is applied to another substance in order to produce a chemical reaction that can give valuable information regarding the substance. Benedict's reagent is most commonly used to calculate ways of reducing glucose or fructose in foods. In the past, it was the way diabetes was detected through the testing of urine.

In food tests, a small amount of the food is added to Benedict's reagent and boiled for several minutes to test the amount of sugar present. The results will show precipitates, or solid formations within the tested substance. The amount to which a precipitate is present can show the exact glucose or fructose present in the substance. 

Since the precipitates are likely to be very small, Benedict's reagent also shows color changes that can gauge the amounts of the sugars glucose and fructose. For example, a substance treated with Benedict's reagent that is green shows very little or possibly no glucose or fructose present. On the other hand a red color indicates a high quantity of these sugars.

In people who are suspected of having diabetes, analysis of urine is one of the main diagnostic method. Pregnant women used to undergo an analysis of urine that was treated with Benedict's reagent to check for gestational diabetes. Today, other tests may be used because they are more precise in measuring sugar levels. 

Pregnant women may resent these frequent urine tests but they are in fact very important to rule out diabetic conditions during a pregnancy. Benedict’s reagent only works so far in diabetic testing however, since presence of fructose in the urine does not suggest a diabetic condition.

Thus, urine must be further tested, if it shows positive when mixed with Benedict's reagent to evaluate for the presence of glucose. For some, this may mean no further testing with Benedict's reagent, but drinking a glucose solution that most find quite distasteful. However, untreated diabetes should not go unchecked. Thus, diagnosis is extremely valuable and may help begin early treatment, which can significantly change later outcome.

What is a Wind Farm

A wind farm is a collection of windmills or turbines which are used to generate electrical power through their mechanical motions as they are pushed by the wind. Both Europe and the United States have large numbers of wind farms, and the technology is also found on other continents. In Asia, India especially has devoted a great deal of funding to establishing wind farms. The energy generated by a wind farm can be fed directly into the general energy grid after passing through transformers.

As a potentially large source of renewable energy, wind farms are particularly popular in nations which are focusing on alternative energy. Other types of renewable energy include wave power and solar arrays. All of these technologies take advantage of already existing energy, converting it into a usable form. Since a wind farm does not actively deplete resources as it generates power, it is considered a form of “green” energy.

Naturally, some resources must be expended to create a wind farm. The turbines, transformers, and grid system on a wind farm are often made from less than ideal substances, such as metals mined in an unclean way. However, once installed, a wind farm requires no additional energy output other than that required for basic maintenance. This is a marked contrast to a power plant which relies on coal or petroleum products. Consumers who want to support wind farms can buy energy credits which go to developers of wind farms.

Naturally, the best place for a wind farm is a windy location. In some instances, a windy location may also be generally unusable or uninhabitable. In other instances, a wind farm may take up useful real estate which could be used for farming. This has led to some criticism of wind farms, since they take up a great deal more space than a comparable non-renewable energy generating facility. In addition, wind farms pose a severe threat to migratory birds, as has been clearly documented by several scientific organizations.

These issues aside, the technology is generally believed to be environmentally sound and fiscally viable. Especially if wind farms are combined with other renewable energy sources, green energy could make up a bulk of the power grid. This could have a huge impact on the environment and on society in general. Especially at the end of the twentieth century, when a growing number of citizens began to call for energy reforms, wind farms held a great deal of promise.

What Is a BTU

BTU, short for British Thermal Unit, is a basic measure of thermal (heat) energy. One BTU is the amount of energy needed to heat one pound of water one degree Fahrenheit, measured at its heaviest point. In other words, if you placed 16 ounces of water at 59°F into a stovetop pan and turned on the gas burner, it would take one BTU to raise the temperature of the water to 60°F. As more BTUs continue to flow from the gas flame, the water will eventually reach the boiling point of 212°F. 

A BTU is also the equivalent of 252 heat calories, not to be confused with the kilo-calories of food, and of approximately a third of a watt-hour. When speaking of cooling power, the BTU also works in reverse. The air-cooling power of an air conditioning system refers to the amount of thermal energy removed from an area. Hence a 65,000 BTU heater and a 65,000 BTU air conditioner are of roughly the same capacity and size. The higher the BTU output, the more powerful the heating or cooling system.

Strangely enough, the British Thermal Unit is rarely used in Great Britain anymore, where it is considered a non-metric measurement. Even in countries which use the BTU as a standard measurement, there is some disagreement over the formula used to derive it. The thermal energy needed to raise water one degree Fahrenheit can depend on the original temperature and the method used for heating. Therefore, it is possible to get several different definitions of a BTU from different sources. This rarely has a palpable effect on consumer product information, however.

Most heating and cooling systems produce thousands of BTUs, almost rendering the measurement of one BTU pointless. One is more likely to encounter smaller BTU figures during scientific experiments, where the slightest change in thermal energy may need to be calculated in terms of calories. When dealing with central air conditioning units and commercial pizza ovens, however, the BTU numbers can easily reach the hundreds of thousands. A unit of measure called the MMBTU is the equivalent of a million BTUs. Few man-made objects can generate this level of thermal energy, however.

When shopping for heating or cooling systems, keep in mind that even the smallest window-mounted air conditioner or space heater can produce thousands of BTUs. The BTU numbers should primarily be used as a comparison between systems. Larger and more expensive systems should provide significantly higher BTUs than smaller ones. When deciding between similarly priced units, compare the BTUs for a better gauge of performance.