Irrelevant post game

[DanMan69]

General relativity is a theory of gravitation and to understand the background to the theory we have to look at how theories of gravitation developed. Aristotle's notion of the motion of bodies impeded understanding of gravitation for a long time. He believed that force could only be applied by contact, force at a distance being impossible, and a constant force was required to maintain a body in uniform motion. Copernicus's view of the solar system was important as it allowed sensible consideration of gravitation. Kepler's laws of planetary motion and Galileo's understanding of the motion and falling bodies set the scene for Newton's theory of gravity which was presented in the Principia in 1687. Newton's law of gravitation is expressed by

F = G M1M2/d2
where F is the force between the bodies of masses M1, M2 and d is the distance between them. G is the universal gravitational constant.
After receiving their definitive analytic form from Euler, Newton's axioms of motion were reworked by Lagrange, Hamilton, and Jacobi into very powerful and general methods, which employed new analytic quantities, such as potential, related to force but remote from everyday experience. Newton's universal gravitation was considered proved correct, thanks to the work of Clairaut and Laplace. Laplace looked at the stability of the solar system in Traité du Mécanique Céleste in 1799. In fact the so-called three-body problem was extensively studied in the 19th Century and was not properly understood until much later. The study of the gravitational potential allowed variations in gravitation caused by irregularities in the shape of the earth to be studied both practically and theoretically. Poisson used the gravitational potential approach to give an equation which, unlike Newton's, could be solved under rather general conditions.

Newton's theory of gravitation was highly successful. There was little reason to question it except for one weakness which was to explain how each of the two bodies knew the other was there. Some profound remarks about gravitation were made by Maxwell in 1864. His major work A dynamical theory of the electromagnetic field (1864) was written

... to explain the electromagnetic action between distant bodies without assuming the existence of forces capable of acting directly at sensible distances.
At the end of the work Maxwell comments on gravitation.
After tracing to the action of the surrounding medium both the magnetic and the electric attractions and repulsions, and finding them to depend on the inverse square of the distance, we are naturally led to inquire whether the attraction of gravitation, which follows the same law of the distance, is not also traceable to the action of a surrounding medium.
However Maxwell notes that there is a paradox caused by the attraction of like bodies. The energy of the medium must be decreased by the presence of the bodies and Maxwell said
As I am unable to understand in what way a medium can possess such properties, I cannot go further in this direction in searching for the cause of gravitation.
In 1900 Lorentz conjectured that gravitation could be attributed to actions which propagate with the velocity of light. Poincaré, in a paper in July 1905 (submitted days before Einstein's special relativity paper), suggested that all forces should transform according the Lorentz transformations. In this case he notes that Newton's law of gravitation is not valid and proposed gravitational waves which propagated with the velocity of light.
In 1907, two years after proposing the special theory of relativity, Einstein was preparing a review of special relativity when he suddenly wondered how Newtonian gravitation would have to be modified to fit in with special relativity. At this point there occurred to Einstein, described by him as the happiest thought of my life , namely that an observer who is falling from the roof of a house experiences no gravitational field. He proposed the Equivalence Principle as a consequence:-

... we shall therefore assume the complete physical equivalence of a gravitational field and the corresponding acceleration of the reference frame. This assumption extends the principle of relativity to the case of uniformly accelerated motion of the reference frame.
After the major step of the equivalence principle in 1907, Einstein published nothing further on gravitation until 1911. Then he realised that the bending of light in a gravitational field, which he knew in 1907 was a consequence of the equivalence principle, could be checked with astronomical observations. He had only thought in 1907 in terms of terrestrial observations where there seemed little chance of experimental verification. Also discussed at this time is the gravitational redshift, light leaving a massive body will be shifted towards the red by the energy loss of escaping the gravitational field.
Einstein published further papers on gravitation in 1912. In these he realised that the Lorentz transformations will not apply in this more general setting. Einstein also realised that the gravitational field equations were bound to be non-linear and the equivalence principle appeared to only hold locally.

This work by Einstein prompted others to produce gravitational theories. Work by Nordström, Abraham and Mie was all a consequence of Einstein's, so far failed, attempts to find a satisfactory theory. However Einstein realised his problems.

If all accelerated systems are equivalent, then Euclidean geometry cannot hold in all of them.

Einstein then remembered that he had studied Gauss's theory of surfaces as a student and suddenly realised that the foundations of geometry have physical significance. He consulted his friend Grossmann who was able to tell Einstein of the important developments of Riemann, Ricci (Ricci-Curbastro) and Levi-Civita. Einstein wrote
... in all my life I have not laboured nearly so hard, and I have become imbued with great respect for mathematics, the subtler part of which I had in my simple-mindedness regarded as pure luxury until now.
In 1913 Einstein and Grossmann published a joint paper where the tensor calculus of Ricci and Levi-Civita is employed to make further advances. Grossmann gave Einstein the Riemann-Christoffel tensor which, together with the Ricci tensor which can be derived from it, were to become the major tools in the future theory. Progress was being made in that gravitation was described for the first time by the metric tensor but still the theory was not right. When Planck visited Einstein in 1913 and Einstein told him the present state of his theories Planck said
As an older friend I must advise you against it for in the first place you will not succeed, and even if you succeed no one will believe you.
Planck was wrong, but only just, for when Einstein was to succeed with his theory it was not readily accepted. It was the second half of 1915 that saw Einstein finally put the theory in place. Before that however he had written a paper in October 1914 nearly half of which is a treatise on tensor analysis and differential geometry. This paper led to a correspondence between Einstein and Levi-Civita in which Levi-Civita pointed out technical errors in Einstein's work on tensors. Einstein was delighted to be able to exchange ideas with Levi-Civita whom he found much more sympathetic to his ideas on relativity than his other colleagues.
At the end of June 1915 Einstein spent a week at Göttingen where he lectured for six 2 hour sessions on his (incorrect) October 1914 version of general relativity. Hilbert and Klein attended his lectures and Einstein commented after leaving Göttingen

To my great joy, I succeeded in convincing Hilbert and Klein completely.
The final steps to the theory of general relativity were taken by Einstein and Hilbert at almost the same time. Both had recognised flaws in Einstein's October 1914 work and a correspondence between the two men took place in November 1915. How much they learnt from each other is hard to measure but the fact that they both discovered the same final form of the gravitational field equations within days of each other must indicate that their exchange of ideas was helpful.
On the 18th November he made a discovery about which he wrote For a few days I was beside myself with joyous excitement . The problem involved the advance of the perihelion of the planet Mercury. Le Verrier, in 1859, had noted that the perihelion (the point where the planet is closest to the sun) advanced by 38" per century more than could be accounted for from other causes. Many possible solutions were proposed, Venus was 10% heavier than was thought, there was another planet inside Mercury's orbit, the sun was more oblate than observed, Mercury had a moon and, really the only one not ruled out by experiment, that Newton's inverse square law was incorrect. This last possibility would replace the 1/d2 by 1/dp, where p = 2+ for some very small number . By 1882 the advance was more accurately known, 43'' per century. From 1911 Einstein had realised the importance of astronomical observations to his theories and he had worked with Freundlich to make measurements of Mercury's orbit required to confirm the general theory of relativity. Freundlich confirmed 43" per century in a paper of 1913. Einstein applied his theory of gravitation and discovered that the advance of 43" per century was exactly accounted for without any need to postulate invisible moons or any other special hypothesis. Of course Einstein's 18 November paper still does not have the correct field equations but this did not affect the particular calculation regarding Mercury. Freundlich attempted other tests of general relativity based on gravitational redshift, but they were inconclusive.

Also in the 18 November paper Einstein discovered that the bending of light was out by a factor of 2 in his 1911 work, giving 1.74". In fact after many failed attempts (due to cloud, war, incompetence etc.) to measure the deflection, two British expeditions in 1919 were to confirm Einstein's prediction by obtaining 1.98" 0.30" and 1.61" 0.30".

On 25 November Einstein submitted his paper The field equations of gravitation which give the correct field equations for general relativity. The calculation of bending of light and the advance of Mercury's perihelion remained as he had calculated it one week earlier.

Five days before Einstein submitted his 25 November paper Hilbert had submitted a paper The foundations of physics which also contained the correct field equations for gravitation. Hilbert's paper contains some important contributions to relativity not found in Einstein's work. Hilbert applied the variational principle to gravitation and attributed one of the main theorem's concerning identities that arise to Emmy Noether who was in Göttingen in 1915. No proof of the theorem is given. Hilbert's paper contains the hope that his work will lead to the unification of gravitation and electromagnetism.

In fact Emmy Noether's theorem was published with a proof in 1918 in a paper which she wrote under her own name. This theorem has become a vital tool in theoretical physics. A special case of Emmy Noether's theorem was written down by Weyl in 1917 when he derived from it identities which, it was later realised, had been independently discovered by Ricci in 1889 and by Bianchi (a pupil of Klein) in 1902.

Immediately after Einstein's 1915 paper giving the correct field equations, Karl Schwarzschild found in 1916 a mathematical solution to the equations which corresponds to the gravitational field of a massive compact object. At the time this was purely theoretical work but, of course, work on neutron stars, pulsars and black holes relied entirely on Schwarzschild's solutions and has made this part of the most important work going on in astronomy today.

Einstein had reached the final version of general relativity after a slow road with progress but many errors along the way. In December 1915 he said of himself

That fellow Einstein suits his convenience. Every year he retracts what he wrote the year before.
Most of Einstein's colleagues were at a loss to understand the quick succession of papers, each correcting, modifying and extending what had been done earlier. In December 1915 Ehrenfest wrote to Lorentz referring to the theory of November 25, 1915. Ehrenfest and Lorentz corresponded about the general theory of relativity for two months as they tried to understand it. Eventually Lorentz understood the theory and wrote to Ehrenfest saying I have congratulated Einstein on his brilliant results . Ehrenfest responded
Your remark "I have congratulated Einstein on his brilliant results" has a similar meaning for me as when one Freemason recognises another by a secret sign.
In March 1916 Einstein completed an article explaining general relativity in terms more easily understood. The article was well received and he then wrote another article on relativity which was widely read and went through over 20 printings.
Today relativity plays a role in many areas, cosmology, the big bang theory etc. and now has been checked by experiment to a high degree of accuracy. Now that we have everything in order let’s have a go at solving the equation. We will use a mass of 1kg to keep things simple and I will list all of the workings of the equation. So, with 1kg of mass (around 2.2 pounds) we get:



Note how the units were dealt with and that kg m2 s-2 is the same as joules (a rigorous proof of this is outside the scope of these pages).

So from 1kg of matter, any matter, we can get out 9 ´ 1016 joules of energy. Writing that out fully we get:



That is a lot of energy! For example, if we converted 1 kg of mass into energy and used it all to power a 100 watt light bulb how long could we keep it lit for? The first thing to do is divide the result by watts (remember that 1 watt is 1 joule per second):



How long is that in years? A year (365.25 days) is 31,557,600 seconds, so we get:



That is a very, very long time!

Of course, converting mass into energy is not quite that simple, and apart from with some tiny particles in experimental situations has never been carried out with 100% efficiency. Perhaps that’s just as well!



Conclusion.
We have seen that the equation is very easy to solve as it is and that for even a small amount of mass a huge amount of energy can, at least in theory, be released. Other pages in this series go on to show how the energy can be released in practical ways as well as using the equation in a more mathematical and physical way.

[drummerboy765]

feet

[Anticrombie0909]

[fuck][/fuck]

[DanMan69]

how much wood could a woodchuck chuck if a woodchuck could chuck wood

[drummerboy765]

I like bananas

[aleco]

How much ground could a groundhog hog if a groundhog could hog ground?

[Moogy]

e=mc^2

[Lupin_the_3rd]

no, put it off till tomorrow thomas. The tomato paste can be ironed in a few days

[hydrojakep]

I dont understand this game

[qualy]

Your Digestive System and How It Works
On this page:

Why is digestion important?
How is food digested?
How is the digestive process controlled?
The digestive system is a series of hollow organs joined in a long, twisting tube from the mouth to the anus (see figure). Inside this tube is a lining called the mucosa. In the mouth, stomach, and small intestine, the mucosa contains tiny glands that produce juices to help digest food.

Two solid organs, the liver and the pancreas, produce digestive juices that reach the intestine through small tubes. In addition, parts of other organ systems (for instance, nerves and blood) play a major role in the digestive system.

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Why is digestion important?
When we eat such things as bread, meat, and vegetables, they are not in a form that the body can use as nourishment. Our food and drink must be changed into smaller molecules of nutrients before they can be absorbed into the blood and carried to cells throughout the body. Digestion is the process by which food and drink are broken down into their smallest parts so that the body can use them to build and nourish cells and to provide energy.

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How is food digested?
Digestion involves the mixing of food, its movement through the digestive tract, and chemical breakdown of the large molecules of food into smaller molecules. Digestion begins in the mouth, when we chew and swallow, and is completed in the small intestine. The chemical process varies somewhat for different kinds of food.


Movement of Food Through the System
The large, hollow organs of the digestive system contain muscle that enables their walls to move. The movement of organ walls can propel food and liquid and also can mix the contents within each organ. Typical movement of the esophagus, stomach, and intestine is called peristalsis. The action of peristalsis looks like an ocean wave moving through the muscle. The muscle of the organ produces a narrowing and then propels the narrowed portion slowly down the length of the organ. These waves of narrowing push the food and fluid in front of them through each hollow organ.

The first major muscle movement occurs when food or liquid is swallowed. Although we are able to start swallowing by choice, once the swallow begins, it becomes involuntary and proceeds under the control of the nerves.

The esophagus is the organ into which the swallowed food is pushed. It connects the throat above with the stomach below. At the junction of the esophagus and stomach, there is a ringlike valve closing the passage between the two organs. However, as the food approaches the closed ring, the surrounding muscles relax and allow the food to pass.

The food then enters the stomach, which has three mechanical tasks to do. First, the stomach must store the swallowed food and liquid. This requires the muscle of the upper part of the stomach to relax and accept large volumes of swallowed material. The second job is to mix up the food, liquid, and digestive juice produced by the stomach. The lower part of the stomach mixes these materials by its muscle action. The third task of the stomach is to empty its contents slowly into the small intestine.

Several factors affect emptying of the stomach, including the nature of the food (mainly its fat and protein content) and the degree of muscle action of the emptying stomach and the next organ to receive the contents (the small intestine). As the food is digested in the small intestine and dissolved into the juices from the pancreas, liver, and intestine, the contents of the intestine are mixed and pushed forward to allow further digestion.

Finally, all of the digested nutrients are absorbed through the intestinal walls. The waste products of this process include undigested parts of the food, known as fiber, and older cells that have been shed from the mucosa. These materials are propelled into the colon, where they remain, usually for a day or two, until the feces are expelled by a bowel movement.

Production of Digestive Juices
The glands that act first are in the mouth--the salivary glands. Saliva produced by these glands contains an enzyme that begins to digest the starch from food into smaller molecules.

The next set of digestive glands is in the stomach lining. They produce stomach acid and an enzyme that digests protein. One of the unsolved puzzles of the digestive system is why the acid juice of the stomach does not dissolve the tissue of the stomach itself. In most people, the stomach mucosa is able to resist the juice, although food and other tissues of the body cannot.

After the stomach empties the food and juice mixture into the small intestine, the juices of two other digestive organs mix with the food to continue the process of digestion. One of these organs is the pancreas. It produces a juice that contains a wide array of enzymes to break down the carbohydrate, fat, and protein in food. Other enzymes that are active in the process come from glands in the wall of the intestine or even a part of that wall.

The liver produces yet another digestive juice--bile. The bile is stored between meals in the gallbladder. At mealtime, it is squeezed out of the gallbladder into the bile ducts to reach the intestine and mix with the fat in food. The bile acids dissolve the fat into the watery contents of the intestine, much like detergents that dissolve grease from a frying pan. After the fat is dissolved, it is digested by enzymes from the pancreas and the lining of the intestine.

Absorption and Transport of Nutrients
Digested molecules of food, as well as water and minerals from the diet, are absorbed from the cavity of the upper small intestine. Most absorbed materials cross the mucosa into the blood and are carried off in the bloodstream to other parts of the body for storage or further chemical change. As already noted, this part of the process varies with different types of nutrients.

Carbohydrates. Based on a 2,000-calorie diet, it is recommended that 55 to 60 percent of total daily calories be from carbohydrates. Some of our most common foods contain mostly carbohydrates. Examples are bread, potatoes, legumes, rice, spaghetti, fruits, and vegetables. Many of these foods contain both starch and fiber.

The digestible carbohydrates are broken into simpler molecules by enzymes in the saliva, in juice produced by the pancreas, and in the lining of the small intestine. Starch is digested in two steps: First, an enzyme in the saliva and pancreatic juice breaks the starch into molecules called maltose; then an enzyme in the lining of the small intestine (maltase) splits the maltose into glucose molecules that can be absorbed into the blood. Glucose is carried through the bloodstream to the liver, where it is stored or used to provide energy for the work of the body.

Table sugar is another carbohydrate that must be digested to be useful. An enzyme in the lining of the small intestine digests table sugar into glucose and fructose, each of which can be absorbed from the intestinal cavity into the blood. Milk contains yet another type of sugar, lactose, which is changed into absorbable molecules by an enzyme called lactase, also found in the intestinal lining.

Protein. Foods such as meat, eggs, and beans consist of giant molecules of protein that must be digested by enzymes before they can be used to build and repair body tissues. An enzyme in the juice of the stomach starts the digestion of swallowed protein. Further digestion of the protein is completed in the small intestine. Here, several enzymes from the pancreatic juice and the lining of the intestine carry out the breakdown of huge protein molecules into small molecules called amino acids. These small molecules can be absorbed from the hollow of the small intestine into the blood and then be carried to all parts of the body to build the walls and other parts of cells.

Fats. Fat molecules are a rich source of energy for the body. The first step in digestion of a fat such as butter is to dissolve it into the watery content of the intestinal cavity. The bile acids produced by the liver act as natural detergents to dissolve fat in water and allow the enzymes to break the large fat molecules into smaller molecules, some of which are fatty acids and cholesterol. The bile acids combine with the fatty acids and cholesterol and help these molecules to move into the cells of the mucosa. In these cells the small molecules are formed back into large molecules, most of which pass into vessels (called lymphatics) near the intestine. These small vessels carry the reformed fat to the veins of the chest, and the blood carries the fat to storage depots in different parts of the body.

Vitamins. Another vital part of our food that is absorbed from the small intestine is the class of chemicals called vitamins. The two different types of vitamins are classified by the fluid in which they can be dissolved: water-soluble vitamins (all the B vitamins and vitamin C) and fat-soluble vitamins (vitamins A, D, and K).

Water and salt. Most of the material absorbed from the cavity of the small intestine is water in which salt is dissolved. The salt and water come from the food and liquid we swallow and the juices secreted by the many digestive glands.

[Top]
How is the digestive process controlled?
Hormone Regulators
A fascinating feature of the digestive system is that it contains its own regulators. The major hormones that control the functions of the digestive system are produced and released by cells in the mucosa of the stomach and small intestine. These hormones are released into the blood of the digestive tract, travel back to the heart and through the arteries, and return to the digestive system, where they stimulate digestive juices and cause organ movement.

The hormones that control digestion are gastrin, secretin, and cholecystokinin (CCK):

Gastrin causes the stomach to produce an acid for dissolving and digesting some foods. It is also necessary for the normal growth of the lining of the stomach, small intestine, and colon.


Secretin causes the pancreas to send out a digestive juice that is rich in bicarbonate. It stimulates the stomach to produce pepsin, an enzyme that digests protein, and it also stimulates the liver to produce bile.


CCK causes the pancreas to grow and to produce the enzymes of pancreatic juice, and it causes the gallbladder to empty.


Nerve Regulators
Two types of nerves help to control the action of the digestive system. Extrinsic (outside) nerves come to the digestive organs from the unconscious part of the brain or from the spinal cord. They release a chemical called acetylcholine and another called adrenaline. Acetylcholine causes the muscle of the digestive organs to squeeze with more force and increase the "push" of food and juice through the digestive tract. Acetylcholine also causes the stomach and pancreas to produce more digestive juice. Adrenaline relaxes the muscle of the stomach and intestine and decreases the flow of blood to these organs.

Even more important, though, are the intrinsic (inside) nerves, which make up a very dense network embedded in the walls of the esophagus, stomach, small intestine, and colon. The intrinsic nerves are triggered to act when the walls of the hollow organs are stretched by food. They release many different substances that speed up or delay the movement of food and the production of juices by the digestive organs.

[Top]
--------------------------------------------------------------------------------

National Digestive Diseases Information Clearinghouse
2 Information Way
Bethesda, MD 20892-3570
Email: nddic@info.niddk.nih.gov

The National Digestive Diseases Information Clearinghouse (NDDIC) is a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). The NIDDK is part of the National Institutes of Health under the U.S. Department of Health and Human Services. Established in 1980, the clearinghouse provides information about digestive diseases to people with digestive disorders and to their families, health care professionals, and the public. NDDIC answers inquiries, develops and distributes publications, and works closely with professional and patient organizations and Government agencies to coordinate resources about digestive diseases.

Publications produced by the clearinghouse are carefully reviewed by both NIDDK scientists and outside experts.

This e-text is not copyrighted. The clearinghouse encourages users of this e-pub to duplicate and distribute as many copies as desired.


--------------------------------------------------------------------------------

NIH Publication No. 02-2681
March 2002

[Top]

[aleco]

Man alive, where did you get that from? It looks like a mushroom with antante on it!
What's the world coming to?
*Sigh*

[qualy]

you must not do this, jimmy.

[Tempest513]

meep?

[Brainmaster07]

Ding! 1752 posts.

[Lupin_the_3rd]

Alex trebek will rape vxdx if the flying orangutans don't save the day...

let us hope they don't come...

[TheDancingBoy]

21 things you didn't know about the greatest beauty show on earth


The Sheraton Sanya Resort, where the girls are staying, has to prepare 3,000 kgs of fresh fruit every day to satisfy the girl's requirements.
The girls have between them over 650 suitcases which were all handled within 45 minutes by the staff of The Sheraton Sanya Resort.
The prime table at the final has been sold to a lucky person for $45,000, the proceeds of which go to The China Charity Federation (The CCF).
1 ticket for the event was auctioned for $42,000, again the proceeds go to The CCF.
Hainan Airlines provided 2 Boeing 737's to transport the contestants and the Miss World Organisation around China on their 2 week tour.
100,000 Gold Hearts, specially shipped in by Miss World Executive Chairman Julia Morley, have also gone on sale throughout China to raise money for The CCF.
The Miss World Organisation has raised over £150 million for charity since it was founded.
This year's final will go interactive for the first time. It will also be the world's first World Wide Web vote through www.missworld.tv.
There are 8 birthdays amongst the contestants including Miss Wales' 21st.
There are 106 contestants in this year's final which is an all time record for the event.
Microsoft has just released figures that show that The Miss World website www.missworld.tv is the largest website in the world receiving 100 million hits per day.
The beach beauty and personality pictures both made Yahoo's most viewed slide shows. The beach beauty picture made Yahoo's most emailed. http://story.news.yahoo.com/news?tmpl=index2&cid=702 http://story.news.yahoo.com/news?tmpl=index2&cid=1756
The Presidential suite at The Sheraton Sanya Resort is being auctioned along with a pair of tickets to the final on www.sina.com, China's largest portal.
Over 2 billion people will be tuning in world wide to watch the spectacular on December 6th which makes it the largest annual TV event in the world
23 of this year's contestants saw snow for the first time when the party visited The Great Wall of China.
15 of this year's contestants had never seen the sea before arriving in China.
This year there are 2 doctors and a dentist taking part.
Miss Ireland Rosanna Davison, daughter of Irish singing legend Chris de Burgh, won the first Miss World Beach Beauty title on November 28th.
The Chinese authorities kindly relaxed their controls to allow 10 lucky contestants the chance to stand next to the terracotta army.
In Xian they opened the gates of the city for the first time since President Clinton's state visit to let the contestants walk through. They were all given the keys to the city and invited to return at any time.
The Tsing Ma Bridge in Hong Kong, one of the busiest roads in the city, was closed for the first time in history to allow the girls to parade across.

[aleco]

uber goober

[RobbyZero]

IRRELEVANT POSTING HERE


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[IAMTHEEVILBEAN]

happy birthday

[drummerboy765]