Fashion 101 : Do Whatever with Your Skirt ;)

Since i've been so geeky in my previous posts..LOL..now i want to share something more fun..
I grabbed some styles from other websites... :p Just check it ..=)

Angel

Isaac Newton : Theory of Gravity

11:13 am
I'm working now at my office and get bored.. and I remember about one of the world famous scientist..Isaac Newton. He was born on Christmas day 1642.. He was an English Physicist, mathematician, astronomer, natural philosopher, alchemist and theologian.. I admire him because he dedicated his life for science.. Now,enjoy reading guys.. ;)

Gravity

Newtonian Relationships

by Nathaniel Page Stites, M.A./M.S.

What causes objects to fall toward the earth? Why do the planets orbit the sun? What holds galaxies together? If you traveled to another planet, why would your weight change? All of these questions relate to one aspect of physics: gravity. For all of its influence on our daily lives, for all of its control over the cosmos, and for all of our ability to describe and model its effects, we do not understand the actual mechanisms of gravitational force. Of the four fundamental forces identified by physicists – strong nuclear, electroweak, electrostatic, and gravitational – the gravitational force is the least understood. Physicists today strive toward a "Grand Unified Theory," wherein all four of these forces are united into one physical model that describes the behavior of everything in the universe. At this point in time, the gravitational force is the troublesome one, the force that resists unification.
In spite of the mystery behind the mechanisms of gravity, physicists have been able to describe the behavior of objects under the influence of gravity quite thoroughly. Isaac Newton, a seventeenth into eighteenth century English scientist and mathematician (among other things), was the first person to propose a mathematical model to describe the gravitational attraction between objects. Albert Einstein built upon this model in the twentieth century and devised a more complete description of gravity in his theory of general relativity. In this module, we will explore Newton’s description of gravity and some of the experimental confirmations of his theory that came many years after he proposed his original idea.

The Apple

©Corel Corporation

Whether or not Isaac Newton actually sat under an apple tree while pondering the nature of gravity, the fact that objects fall toward the surface of the earth was well understood long before Newton’s time. Everyone has experience with gravity and its effects near the surface of the earth, and our intuitive view of the world includes an understanding that what goes up must come down. Galileo Galilei (1564 – 1642) demonstrated that all objects fall to the surface of the earth with the same acceleration, and that this acceleration was independent of the mass of the falling object. Isaac Newton was no doubt familiar with this concept, and he would eventually formulate a broad and far-reaching theory of gravitation. Newton’s theory would encompass not only the behavior of an apple near the surface of the earth, but also the motions of much larger bodies quite far away from the earth.






Leaning Tower of Pisa Experiment

Concept simulation - Reenacts Galileo's experiment of two different objects falling at the same rate.

(Flash required)

The Planets

Early conceptions of the universe were "geocentric" – they placed the earth at the center of the universe and had the planets and stars move around the earth. The Ptolemaic Model of the universe dominated scientific thought for many centuries, until the work of such careful astronomers as Tycho Brahe, Nicolaus Copernicus, Galileo Galilei, and Johannes Kepler supplanted this view of the cosmos. The “Copernican Revolution” placed the sun at the center of the solar system and the planets, including earth, in orbit around the sun. This major shift in perception laid the foundation for Isaac Newton to begin thinking about gravitation as it related to the motions of the planets.

Figure 1: The Solar System

An early unification theory

Just as physicists today are searching for ways to unify the fundamental forces, Isaac Newton also sought to unify two seemingly disparate phenomena: the motion of objects falling toward the earth and the motion of the planets orbiting the sun. Isaac Newton’s breakthrough was not that apples fall to the earth because of gravity; it was that the planets are constantly falling toward the sun for exactly the same reason: gravity! Newton built upon the work of early astronomers, in particular Johannes Kepler, who in 1596 and 1619 published his laws of planetary motion. One of Kepler's central observations was that the planets move in elliptical orbits around the sun. Newton expanded Kepler’s description of planetary motion into a theory of gravitation.

Newton’s Law of Universal Gravitation

The essential feature of Newton’s Law of Universal Gravitation is that the force of gravity between two objects is inversely proportional to the square of the distance between them. Such a connection is known as an “inverse square” relationship. Newton derived this relationship from Kepler’s assertion that the planets follow elliptical orbits. To understand this, consider the light radiating from the surface of the sun. The light has some intensity at the surface of the sun. As the light travels away from the sun, its intensity diminishes. The intensity of the light at any distance away from the sun equals the strength of the source divided by the surface area of a sphere surrounding the sun at that radius.
As the distance away from the sun (r) doubles, the area of the sphere surrounding the sun quadruples. Thus, the intensity of the sun’s light depends inversely on the square of the distance away from the sun. Newton envisioned the gravitational force as radiating equally in all directions from a central body, just as sunlight in the previous example. Newton recognized that his gravitational model must take the form of an inverse square relationship. Such a model predicts that the orbits of objects around a central body will be conic sections, and years of astronomical observations have borne this out. Although this idea is most commonly attributed to Isaac Newton, the English mathematician Robert Hooke claimed that he originated the idea of the inverse square relationship. Nonetheless, Newton eventually published his theory of gravitation and became famous as a result.
The relationship that Newton came up with looks like this:

Figure 2: Newton's Law of Universal Gravitation

where F is the force of gravity (in units now referred to as newtons), m₁ and m₂ are the masses of the two objects (in kilograms), r is the distance separating the centers of mass of the objects and G is the "gravitational constant." This relationship has come to be known as Newton's Law of Universal Gravitation. It is "universal" because all objects in the universe are attracted to all other objects in the universe according to this relationship. Two people sitting across a room from each other are actually attracted gravitationally. As we know from everyday experience, human-sized objects don't crash into each other as a result of this force, but it does exist even if it is very small. Although Newton correctly identified this relationship between force, mass, and distance, he was able only to estimate the value of the gravitational constant between these quantities. The world would have to wait more than a century for an experimental measurement of the constant of proportionality: G.

Measuring the Mass of the Earth: The Cavendish Experiment

In 1797 and 1798 Henry Cavendish set out to confirm Newton's theory and to determine the constant of proportionality in Newton's Law of Universal Gravitation. His ingenious experiment, based on the work of John Michell, was successful on both fronts. To accomplish this, Cavendish created a "torsion balance," which consisted of two masses at either end of a bar that was suspended from the ceiling by a thin wire (see Figure 3).

Figure 3: The Torsion Balance, devised by Michell and Cavendish to determine the constant of proportionality in Newton's Law of Universal Gravitation.

Attached to the wire was a mirror, off of which a beam of light was reflected. Cavendish brought a third mass close to one of the masses on the torsion balance. As the third mass attracted one of the ends of the torsion balance, the entire apparatus, including the mirror, rotated slightly and the beam of light was deflected. Through careful measurement of the angular deflection of the beam of light, Cavendish was able to determine the extent to which the known mass was attracted to the introduced mass. Not only did Cavendish confirm Newton's theory, but also he determined the value of the gravitational constant to an accuracy of about 1 percent.

Figure 4: Gravitational Constant

Cavendish cleverly referred to his research as “Measuring the Mass of Earth.” Since he had determined the value of G, he could do some simple calculations to determine the mass of the earth. By Newton’s Second Law, the force between an object and the earth equals the product of the acceleration (g) and the mass of the object (m):






F = ma Galileo had determined the acceleration of all objects near the surface of the earth in the early 1600s as g = 9.8 m/s².
Therefore, setting this equation equal to Newton’s Law of Universal Gravitation described above, Cavendish found:

Figure 5: Newton's Law of Universal Gravitation as used by Cavendish to determine the mass of the Earth.

where m is the mass of the object, m_E is the mass of the earth, and r_E is the radius of the earth. Solving for the mass of the earth yields the following result:

Figure 6: Results of Cavendish's calculation for the mass of the Earth.

Cavendish had determined the mass of the earth with great accuracy.
We can also use this relationship to calculate the force of attraction between two people across a room. To do this, we simply need to use Newton’s Law of Universal Gravitation with Cavendish’s gravitational constant. Assume the two people have masses of 75 and 100 kilograms, respectively, and that they are 5 meters apart. The force of gravitation between them is:

Figure 7: Gravitational attraction between two people.

Although it is small, there is still a force!

Conclusion

Newton’s Law of Universal Gravitation grew in importance as scientists realized its utility in predicting the orbits of the planets and other bodies in space. In 1705, Sir Edmund Halley, after studying comets in great detail, predicted correctly that the famous comet of 1682 would return 76 years later, in December of 1758. Halley had used Newton’s Law to predict the behavior of the comet orbiting the sun. With the advent of Cavendish’s accurate value for the gravitational constant, scientists were able to use Newton’s law for even more purposes. In 1845, John Couch Adams and Urbain Le Verrier predicted the existence of a new, yet unseen, planet based on small discrepancies between predictions for and observations of the position of Uranus. In 1846, the German astronomer Johann Galle confirmed their predictions and officially discovered the new planet, Neptune.
While Newton’s Law of Universal Gravitation remains very useful today, Albert Einstein demonstrated in 1915 that the law was only approximately correct, and that it fails to work when gravitation becomes extremely strong. Nonetheless, Newton’s gravitational constant plays an important role in Einstein’s alternative to Newton’s Law, the Theory of General Relativity. The value of G has been the subject of great debate even in recent years, and scientists are still struggling to determine a very accurate value for this most elusive of fundamental physical constants.

source : http://www.visionlearning.com/library/module_viewer.php?mid=118

The Formation of Petroleum

Step 1: Diagenesis forms Kerogen
Diagenesis is a process of compaction under mild conditions of temperature and pressure. When organic aquatic sediments (proteins, lipids, carbohydrates) are deposited, they are very saturated with water and rich in minerals. Through chemical reaction, compaction, and microbial action during burial, water is forced out and proteins and carbohydrates break down to form new structures that comprise a waxy material known as “kerogen” and a black tar like substance called “bitumen”.  All of this occurs within the first several hundred meters of burial.
The bitumen comprises the heaviest components of petroleum, but the kerogen will undergo further change to make hydrocarbons and, yes, more bitumen…

Step 2: Catagenesis (or “cracking”) turns kerogen into petroleum and natural gas
As temperatures and pressures increase (deeper burial) the process of catagenesis begins, which is the thermal degradation of kerogen to form hydrocarbon chains. Importantly, the process of catagenesis is catalyzed by the minerals that are deposited and persist through marine diagenesis. The conditions of catagenesis determine the product, such that higher temperature and pressure lead to more complete “cracking” of the kerogen and progressively lighter and smaller hydrocarbons. Petroleum formation, then, requires a specific window of conditions; too hot and the product will favor natural gas (small hydrocarbons), but too cold and the plankton will remain trapped as kerogen.
This behavior is contrary to what is associated with coal formation. In the case of terrestrial burial, the organic sediment is dominated by cellulose and lignin and the fraction of minerals is much smaller. Here, decomposition of the organic matter is restricted in a different way. The organic matter is condensed to form peat and, if enough temperature (geothermal energy) and pressure is supplied, it will condense and undergo catagenesis to form coal. Higher temperatures and pressures, in general, lead to higher ranks of coal.


Source : http://www.ems.psu.edu/~pisupati/ACSOutreach/Petroleum_2.html

Petroleum formation occurs over millions of years

Petroleum formation occurs over millions of years

Petroleum formation occurs by various hydrocarbons combining with certain minerals such as sulphur under extreme pressure. Modern day scientists have proven that most if not all petroleum fields were created by the remains of small animal and plant life being compressed on the sea bed by billions of tons of silt and sand several million years ago.

When small sea plants and animals die they will sink, they will then lie on the sea bed where they will decompose and mix with sand and silt. During the decomposition process tiny bacteria will clean the remains of certain chemicals such as phosphorus, nitrogen and oxygen.

This leaves the remains consisting of mainly carbon and hydrogen. At the bottom of the ocean there is insufficient oxygen for the corpse to decompose entirely. What we are left with is the raw materials for the formation of petroleum.

The partially decomposed remains will form a large, gelatinous mass, which will then slowly become covered by multiple layers of sand, silt and mud. This burying process takes millions of years, with layers piling up one atop another.

As the depth of the sediment build up increases the weight of the sand and silt pressing down on the mass will compress it into a layer which is much thinner than the original.

Finally, when the depth of the buried decomposing layer reaches somewhere around 10,000 feet the natural heat of the earth and the intense pressure will combine to act upon the mass. The end result, over time, is the formation of petroleum.

 With petroleum formation the actual temperature applied to the original organic mass is critical in determining the overall properties of the resulting petroleum. Typically lower temperatures during petroleum formation

will result in thicker, darker raw petroleum deposits, the most solid of which being a bitumen substance.

If the heat applied during the formation of petroleum process fluctuates too much then gas will be produced, often separating from the petroleum, sometimes remaining mixed with the raw oil. If temperatures are too high, in the somewhere over 450 degrees Fahrenheit then the original biomass will be destroyed and no gas or petroleum is formed.

As the mud and silt above the deposit become heavier and the forces placed upon the silt and mud begin to change the bottom layers of the compressing layer above the petroleum then it will turn into shale.

As the shale forms the oil will be forced out of its original area of formation. The raw petroleum then moves to a new rock formation, usually termed a reservoir rock, and lays trapped until it is accessed in some way.

As we can see, the formation of naturally occurring raw petroleum takes millions of years, certainly far longer than can be deemed renewable, yet mankind has managed to almost complete deplete the world supply in little more than a century.

source : http://www.petroleum.co.uk/formation/