Category Science

WHAT IS A COLOUR WHEEL?

Garden and interior designers sometimes make use of a colour wheel. This helps them to choose colours that are in harmony with each other when that is appropriate. When a more striking effect is required, colours that contrast can be chosen. One half of the wheel has colours that give a warm feeling, while the other half has cooler hues.

A color wheel or color circle is an abstract illustrative organization of color hues around a circle, which shows the relationships between primary colors, secondary colors, tertiary colors etc.

Some sources use the terms color wheel and color circle interchangeably; however, one term or the other may be more prevalent in certain fields or certain versions as mentioned above. For instance, some reserve the term color wheel for mechanical rotating devices, such as color tops, filter wheels or Newton disc. Others classify various color wheels as color disc, color chart, and color scale varieties.

As an illustrative model, artists typically use red, yellow, and blue primaries (RYB color model) arranged at three equally spaced points around their color wheel. Printers and others who use modern subtractive color methods and terminology use magenta, yellow, and cyan as subtractive primaries, Intermediate and interior points of color wheels and circles represent color mixtures. In a paint or subtractive color wheel, the “center of gravity” is usually (but not always) black, representing all colors of light being absorbed; in a color circle, on the other hand, the center is white or gray, indicating a mixture of different wavelengths of light (all wavelengths, or two complementary colors, for example).

The original color circle of Isaac Newton showed only the spectral hues and was provided to illustrate a rule for the color of mixtures of lights, that these could be approximately predicted from the center of gravity of the numbers of “rays” of each spectral color present. The divisions of Newton’s circle are of unequal size, being based on the intervals of a Dorian musical scale. Later color circles include the purples, however, between red and violet, and have equal-sized hue divisions. Color scientists and psychologists often use the additive primaries, red, green and blue; and often refer to their arrangement around a circle as a color circle as opposed to a color wheel.

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DOES LIGHT ALWAYS TRAVEL IN A STRAIGHT LINE?

Beams of light do travel in straight lines, but those lines can be deflected. Light travels at different speeds in different substances. When the light passes from one substance to another its beam bends. This is called refraction.

Once light has been produced, it will keep travelling in a straight line until it hits something else. Shadows are evidence of light travelling in straight lines. An object blocks light so that it can’t reach the surface where we see the shadow. Light fills up all of the space before it hits the object, but the whole region between the object and the surface is in shadow. Shadows don’t appear totally dark because there is still some light reaching the surface that has been reflected off other objects.

Once light has hit another surface or particles, it is then absorbed, reflected (bounces off), scattered (bounces off in all directions), refracted (direction and speed changes) or transmitted (passes straight through).

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WHAT IS ELECTROMAGNETIC ENERGY?

Light is not the only kind of energy to travel at the speed of light! In fact, every kind of energy in what is called the electromagnetic spectrum travels at that speed. Electromagnetic energy travels in waves. Only a small part of the electromagnetic spectrum is visible to us — the part that makes up the colours of the rainbow — but all of it has proved to be useful to us.

Electromagnetic energy travels in waves and spans a broad spectrum from very long radio waves to very short gamma rays. The human eye can only detect only a small portion of this spectrum called visible light. A radio detects a different portion of the spectrum, and an x-ray machine uses yet another portion. NASA’s scientific instruments use the full range of the electromagnetic spectrum to study the Earth, the solar system, and the universe beyond.

When you tune your radio, watch TV, send a text message, or pop popcorn in a microwave oven, you are using electromagnetic energy. You depend on this energy every hour of every day. Without it, the world you know could not exist.

Our Sun is a source of energy across the full spectrum, and its electromagnetic radiation bombards our atmosphere constantly. However, the Earth’s atmosphere protects us from exposure to a range of higher energy waves that can be harmful to life. Gamma rays, x-rays, and some ultraviolet waves are “ionizing,” meaning these waves have such a high energy that they can knock electrons out of atoms. Exposure to these high-energy waves can alter atoms and molecules and cause damage to cells in organic matter. These changes to cells can sometimes be helpful, as when radiation is used to kill cancer cells, and other times not, as when we get sunburned.

Electromagnetic radiation is reflected or absorbed mainly by several gases in the Earth’s atmosphere, among the most important being water vapor, carbon dioxide, and ozone. Some radiation, such as visible light, largely passes (is transmitted) through the atmosphere. These regions of the spectrum with wavelengths that can pass through the atmosphere are referred to as “atmospheric windows.” Some microwaves can even pass through clouds, which make them the best wavelength for transmitting satellite communication signals.

While our atmosphere is essential to protecting life on Earth and keeping the planet habitable, it is not very helpful when it comes to studying sources of high-energy radiation in space. Instruments have to be positioned above Earth’s energy-absorbing atmosphere to “see” higher energy and even some lower energy light sources such as quasars.

Electromagnetic energy is a form of energy that is reflected or emitted from objects in the form of electrical and magnetic waves that can travel through space. Examples are radio waves, microwaves, infrared radiation, visible light – (all colors of the spectrum that we see), ultraviolet light,
X-rays and gamma radiation.

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WHAT TRAVELS FASTEST IN THE UNIVERSE?

Nothing that has a physical existence travels faster than light. In a vacuum it travels at 300,000km (186,000 miles) per second. We tend to think that we are seeing things as they are, but that is not quite true. We are seeing them as they were at the moment that the light left them to travel to us. Of course, for most purposes, as light travels so quickly, this makes no difference at all. It is only when we are looking at the stars, which are unimaginably huge distances away that we really are seeing the distant past. Light from our Sun takes about eight minutes to reach the Earth, but it takes less than a tenth of a second to travel across the Atlantic.

When Albert Einstein first predicted that light travels the same speed everywhere in our Universe, he essentially stamped a speed limit on it: 300,000 kilometres per second (186,000 miles per second) – fast enough to circle the entire Earth eight times every second.

But that’s not the whole story. In fact, it’s just the beginning. Before Einstein, mass – the atoms that make up you, me, and everything we see – and energy were treated as separate entities. But in 1905, Einstein forever changed the way physicists view the Universe. Einstein’s special theory of relativity permanently tied mass and energy together in the simple yet fundamental equation E = mc2.

This little equation predicts that nothing with mass can move as fast as light, or faster. The closest humankind has ever come to reaching the speed of light is inside of powerful particle accelerators like the Large Hadron Collider and the Tevatron.

These colossal machines accelerate subatomic particles to more than 99.99 percent the speed of light, but as Physics Nobel laureate David Gross explains, these particles will never reach the cosmic speed limit. To do so would require an infinite amount of energy and, in the process, the object’s mass would become infinite, which is impossible. (The reason particles of light, called photons, travel at light speeds is because they have no mass.)

Since Einstein, physicists have found that certain entities can reach superluminal (that means “faster-than-light”) speeds and still follow the cosmic rules laid down by special relativity. While these do not disprove Einstein’s theory, they give us insight into the peculiar behavior of light and the quantum realm.

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WHAT IS HARD WATER?

Water is said to be “hard” when it has certain minerals dissolved in it. The most noticeable effect of hard water is that soap does not lather well in it, instead forming a kind of scum. There are two kinds of water hardness, depending on which chemicals are dissolved in it. Temporary hardness can be removed by boiling the water. The chemicals become a solid, which is the scale that sometimes furs up kettles and shower heads. Permanent hardness can be removed by using a water softener, which exchanges the calcium and magnesium ions that cause the hardness with sodium ions.

Hard water (or water hardness) is a common quality of water which contains dissolved compounds of calcium and magnesium and, sometimes, other divalent and trivalent metallic elements.

The term hardness was originally applied to waters that were hard to wash in, referring to the soap wasting properties of hard water. Hardness prevents soap from lathering by causing the development of an insoluble curdy precipitate in the water; hardness typically causes the buildup of hardness scale (such as seen in cooking pans). Dissolved calcium and magnesium salts are primarily responsible for most scaling in pipes and water heaters and cause numerous problems in laundry, kitchen, and bath. Hardness is usually expressed in grains per gallon (or ppm) as calcium carbonate equivalent.

Oils and fats do not mix with water, so washing greasy clothes or hair in water alone will not clean them. Soap contains ions that are attracted to water at one end and to grease at the other. This end of each ion attaches itself to the grease, while the other end, attracted to the water, pulls the grease away from the fabric or hair. Hard water is a problem because the ions react with the chemicals in the water to form scum.

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WHY IS EVAPORATION USEFUL?

Evaporation is another way of separating water from chemicals dissolved in it. It works in the same way as distillation, except that evaporation is usually used when it is the substances in the water that are needed, not the water itself. The water is usually allowed to drift away as steam. In other words, distillation is used to obtain the solvent, while evaporation is used to obtain the solute.

Evaporation happens when a liquid turns into a gas. It can be easily visualized when rain puddles “disappear” on a hot day or when wet clothes dry in the sun. In these examples, the liquid water is not actually vanishing—it is evaporating into a gas, called water vapor.

Evaporation happens on a global scale. Alongside condensation and precipitation, evaporation is one of the three main steps in the Earth’s water cycle. Evaporation accounts for 90 percent of the moisture in the Earth’s atmosphere; the other 10 percent is due to plant transpiration.

Substances can exist in three main states: solid, liquid, and gas. Evaporation is just one way a substance, like water, can change between these states. Melting and freezing are two other ways. When liquid water reaches a low enough temperature, it freezes and becomes a solid—ice. When solid water is exposed to enough heat, it will melt and return to a liquid. As that liquid water is further heated, it evaporates and becomes a gas—water vapor.

These changes between states (melting, freezing, and evaporating) happen because as the temperature either increases or decreases, the molecules in a substance begin to speed up or slow down. In a solid, the molecules are tightly packed and only vibrate against each other. In a liquid, the molecules move freely, but stay close together. In a gas, they move around wildly and have a great deal of space between them.

In the water cycle, evaporation occurs when sunlight warms the surface of the water. The heat from the sun makes the water molecules move faster and faster, until they move so fast they escape as a gas. Once evaporated, a molecule of water vapor spends about ten days in the air.

As water vapor rises higher in the atmosphere, it begins to cool back down. When it is cool enough, the water vapor condenses and returns to liquid water. These water droplets eventually gather to form clouds and precipitation.

Evaporation from the oceans is vital to the production of fresh water. Because more than 70 percent of the Earth’s surface is covered by oceans, they are the major source of water in the atmosphere. When that water evaporates, the salt is left behind. The fresh-water vapor then condenses into clouds, many of which drift over land. Precipitation from those clouds fills lakes, rivers, and streams with fresh water.

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