Conservapedia - User contributions [en]

Carl Sagan

2014-08-29T21:24:05Z

4ArthurDent2:

[[File:Another atheist pothead.JPG|thumbnail|250px|right|Carl Sagan
 
 
(picture obtained from [http://commons.wikimedia.org/wiki/File:Carl_Sagan_Planetary_Society.JPG Wikimedia commons], [http://commons.wikimedia.org/wiki/File:Carl_Sagan_Planetary_Society.JPG Public domain picture])]]
'''Carl Sagan''' (1934-1996) was a [[liberal]] professor of [[astronomy]] at [[Cornell University]] in Ithaca, New York, who became a celebrity on television and a vocal advocate for increased searches for intelligent life in outer space. ''Time'' magazine reported that Carl Sagan "talked with [[Jimmy Carter]] about such esoteric matters as [[black hole]]s and [[exobiology]] (the speculation that [[extraterrestrial life]] exist)."<ref>[http://www.time.com/time/magazine/article/0,9171,951539,00.html Frederic Golden, "The Cosmic Explainer," Time.com 20 Oct. 1980.]</ref> He was instrumental in the development of Search for Extra-Terrestrial Intelligence([[SETI]]).

==Scientific Accomplishments==
Carl Sagan was one of the first and foremost professors of the theory that the surface of Venus is in fact hot, arid and dry. He studied radio emissions from Venus and concluded that the surface temperature had to have been about 900° Farenheit. He was also a contributer to the [[Mariner]] missions to Venus, which confirmed his theories.

Sagan also was an early promoter of the theory that Saturn's moon Titan is covered with oceans of liquid compounds. Sagan also was pivotal in solving the mystery of Titan's reddish glow. Carl Sagan theorized that there must be many organic chemicals constantly raining down on the surface of Titan. He also theorized that Jupiter's moon Europa may have vast subsurface oceans of liquid water. This excited Sagan as there is a great potential for life to inhabit Europa<ref>Detailed information about Sagan's scientific work comes from the primary research articles. Example: Sagan, C., Thompson, W. R., and Khare, B. N. ''[[Titan: A Laboratory for Prebiological Organic Chemistry]]'', Accounts of Chemical Research, volume 25, page 286 (1992). There is commentary on this research article about Titan at [http://www.daviddarling.info/encyclopedia/T/Titanprebiotic.html The Encyclopedia of Astrobiology, Astronomy, and Spaceflight].</ref> . This theory was later confirmed by the Galileo spacecraft.

Sagan also concluded that the variations in color of Mars' surface were not due to seasonal or vegetational affects, but rather were caused by shifts in surface dusts caused by windstorms. This was later confirmed by other scientists and subsequent missions to mars.

He also recieved the 1994 recipient of the Public Welfare Medal, from the National Academy of Sciences for "Distinguished contributions in the application of science to the public welfare<ref>{{Cite web | url=http://www.planetary.org/about/founders/carl_sagan.html | title=Carl Sagan | publisher=The Planetary Society | author=The Planetary Society| accessdate=May 14, 2007}}</ref>. the Public Welfare Medal is the highest honor given by the National Academy of Sciences.

Sagan was a main advocate for the scientific theory of [[evolution]]. In addition, as noted earlier Sagan advocated government funded exobiology research.

==Ideas==
Professor Sagan, like many scientists throughout the 20th century, believed that intelligent life may exist on planets other than Earth. <blockquote>"The significance of a finding that there are other beings who share this universe with us would be absolutely phenomenal, it would be an epochal event in human history," Sagan declared.<ref>[http://www.cnn.com/US/9612/20/sagan/ Norma Quarles, "Carl Sagan Dies at 62," CNN.com 20 Dec. 1996.]</ref></blockquote>

Indeed, Sagan's most popular work of fiction ''Contact'', later made into a movie, was about finding extraterrestrial life.

To Sagan, there was nothing beyond physical reality as can be seen by this quote from his famous documentary series, "The Cosmos":
{{Cquote|The cosmos is all that is, or ever was, or ever will be."<ref>Cosmos series, 1980</ref>}}

Professor Sagan would often advocate for peaceful diplomatic resolution by arguing:
{{Cquote|We have looked close-up at dozens of new worlds. Worlds we never saw before. And unless we are so stupid to destroy ourselves, we are going to be moving out to space in the next century," he said. "And if I'm fortunate enough to have played a part in the first preliminary reconnaissance in the [[solar system]], that's a terrifically exciting thing.<ref>[http://www.cnn.com/US/9612/20/sagan/ Quarles]</ref>}}

He often made his opposition to nuclear weapons clear. An episode of Cosmos, "Who Speaks for Earth," dealt with the possibility of nuclear annihilation explicitly.

From a religious point of view, Sagan was an [[atheist]] or an [[agnostic]] depending upon how it is interpreted. In practice he was an atheist, but as a scientist could never say with certainty that evidence couldn't arise that is currently unknown that would point toward a god force, he is more correctly described as being agnostic.<ref>http://www.nndb.com/people/324/000022258/</ref><ref>http://www.adherents.com/people/ps/Carl_Sagan.html</ref>

Interestingly, the ending of ''Contact'' does imply to some extent the existence of a Universal Creator. The novel concludes {{Cquote|The universe was made on purpose ... In the fabric of space and in the nature of matter, as in a great work of art, there is, written small, the artist's signature ... there is an intelligence that antedates the universe.}}

Some commentators feel that this represents a shift in Sagan's views, much as the protagonist of the novel experiences a similar shift. However, others feel that since this was a work of fiction, it did not necessarily represent what Sagan really thought. For instance, science-fiction author Robert J. Sawyer opines that "Sagan was no more obligated to believe in what he wrote than than George Lucas was to believe in The Force". (In Lucas' movie series ''Star Wars'', "The Force" was the guiding principle behind the fictional [[Jedi]] religion practiced by the characters in the film).

At the height of his popularity, Sagan became something of a media celebrity, occasionally appearing on popular entertainment programs. His speaking style became well known, and one phrase of his was often spoofed and referenced in the media—"'''BILLIONS''' and '''BILLIONS'''"—with the words emphasized and drawn out, though he never actually used it.<ref>http://www.nytimes.com/learning/general/onthisday/bday/1109.html</ref>

Sagan had a notable effect on the space program, being the man who conceived the first written message to go into space, on gold plaques attached to the Pioneer 10 and 11 spacecraft. Later, he would be a part of the team that assembled golden records, containing information on Earth's culture and daily life, that would go out with the Voyager space probes later.

==Kuwait Oil Crisis==

<blockquote>
"Though Dr. Sagan is one of the most frequently cited experts on atmospheric issues by the media, his predictions are often wrong. For example, at the outset of the Persian Gulf War, Sagan warned that if Saddam Hussein delivered on his threat to set fire to Kuwait's oil wells, so much black soot would be sent into the stratosphere that sunlight would be blocked and a variation of the "[[nuclear winter]]" scenario would occur. Hussein followed through on his threat and by the close of the war over 600 wells were on fire. But the fires had little environmental or climatic effect beyond the Gulf region and virtually no ill effects globally."<ref>http://www.nationalcenter.org/dos7124.htm</ref></blockquote>

[[Fred Singer]] famously rebutted Sagan's prediction on national TV and was vindicated a few days later, when Sagan's nuclear winter scenario failed to materialize.<ref>"Retired atmospheric physicist Fred Singer dismissed Sagan's prediction as nonsense, predicting ['''correctly'''] that the smoke would dissipate in a matter of days." [http://www.crystalinks.com/sagan.html] </ref>
Later, Sagan would admit he was wrong, noting: "it was pitch black at noon and temperatures dropped 4°–6°C over the Persian Gulf, but not much smoke reached stratospheric altitudes and Asia was spared."<ref>Sagan, Carl (1996). The demon-haunted world: science as a candle in the dark. New York: Random House. p. 257. ISBN 0-394-53512-X.</ref>

== See also ==
*[[Essay: Another agnostic pothead|Another agnostic pothead]] - [[satire]]
*[[Theory of evolution and liberalism]]

== References ==

<references/>

{{DEFAULTSORT:Sagan, Carl}}
[[Category:Astronomers]]
[[Category:Authors]]
[[Category:Agnostics]]
[[Category:Evolutionists]]
[[Category:American Jews]]

General theory of relativity

2014-08-29T21:22:43Z

4ArthurDent2:

''See [[Theory of Relativity]]'' for a comprehensive treatment of this topic.''

The '''General Theory of Relativity''' is an extension of [[Special theory of relativity|special relativity]], dealing with curved coordinate systems, accelerating frames of reference, curvilinear motion, and curvature of spacetime itself. It could be said that general relativity is to special relativity as vector calculus is to vector algebra. General relativity is best known for its formulation of gravity as a [[fictitious force]] arising from the curvature of spacetime. In fact, "general relativity" and "Einstein's formulation of gravity" are nearly synonymous in many people's minds. That's because they are.

The general theory of relativity was first published by Marcel Grossman in 1913 and [[David Hilbert]] and [[Albert Einstein]] in 1916.
However, "even though General Relativity has passed many tests, most physicists don’t believe it is ultimately correct because it conflicts with [[quantum mechanics]]." [http://newsdesk.org/2010/08/conservapedia-calls-theory-of-relativity-a-liberal-conspiracy/] Hopefully, within the next few years, a 'theory of everything' will be found, that will combine general relativity and quantum mechanics into one, thus ending the conflict.

General relativity, like [[quantum mechanics]] (the other of the two theories comprising "modern physics") both have reputations for being notoriously complicated and difficult to understand. In fact, in the early decades of the 20th century, general relativity was praised, and was one of the key moments in Einstein's rise to fame as the greatest scientist of his time. General relativity and quantum mechanics are both advanced college-level and postgraduate level topics. Hence this article can't possibly give a comprehensive explation of general relativity at the expert level, because it is written by conservapedia. But we will attempt to give a rough outline, for lay people, of the general relativistic formulation of gravity.

In the [[weak field approximation]], where velocities of moving objects are low and gravitational fields are not very severe, the theory of general relativity is said to ''reduce to'' the law of universal gravitation. That is to say, under those circumstances the equations of general relativity are mathematically equivalent to the equations of Newtonian gravitation.

Modern science does not say that Newtonian (classical) gravity is wrong. It is obviously very very very very very very very very very very very very very very very very nearly correct. In the weak field approximation, such as one finds in our solar system, the differences between general relativity and Newtonian gravity are miniscule. It takes very sensitive tests to show the difference. The history of those tests is a fascinating subject, and will be covered near the end of this article. But in all tests conducted so far, where there are discrepancies between the predictions of general relativity and Newtonian gravity (or other competing theories for that matter), experimental results have shown general relativity to be a better description.

Outside of the solar system, one can find stronger gravitational fields, and other phenomena, such as quasars and neutron stars, that permit even more definitive tests. General relativity appears to pass those tests as well.

This is not to say, by any means, that general relativity is the ultimate, perfect theory. It has never been unified with modern formulations of quantum mechanics, and it is therefore known to be incorrect at extremely small scales. Just as Newtonian gravity is very nearly correct, and completely correct for its time, general relativity is believed to be very nearly correct, but not completely so. Contemporary speculation on the next step involves extremely esoteric notions such as string theory, gravitons, and "quantum loop gravity".

The theory is sometimes explained with a thought experiment developed by Einstein involving two elevators. The first elevator is stationary on the Earth, while the other is being pulled through space at a constant acceleration of g. Einstein realized that under Newtonian mechanics, any physical experiment carried out in the elevators would give the same result. This realization is known as the [[equivalence principle]] and it states that accelerating frames of reference and gravitational fields are indistinguishable. General relativity is the theory of gravity that incorporates special relativity and the equivalence principle.

The general theory of relativity is a ''metric theory,'' sometimes also called a ''geometric theory.'' Metric theories describe physical phenomena in terms of [[differential geometry]]. This stands in contrast to Isaac Newton's [[Law of Universal Gravitation]], which described gravity in terms of a [[vector field]]. In the case of general relativity, the theory relates ''stress-energy'' — an extension of the concept of [[mass]] — and the [[curvature]] of [[spacetime]]. In the words of physicist John Wheeler, "Space tells matter how to move, matter tells space how to curve."<ref>Misner, Thorne & Wheeler. ''Gravitation.'' (1973)</ref>

==Coordinate Systems and Spacetime Diagrams==

Figure 1 shows a "spacetime diagram", with my house, my neighbor's house, and my neighbor walking from his house to mine.

:This is the same kind of diagram that is used in explanations of special relativity. The "spacetime" is sometimes called "Minkowski space". Spacetime is actually four-dimensional, but we can only show two dimensions, so we leave out y and z. The single x spatial coordinate is good enough for our purposes, so the diagram has x going from left to right, and t (time) going upward. For the purposes of this explanation, don't worry about the considerations of special relativity such as the speed of light, the Lorentz transform, or light cones. None of that is important just now.

The diagram shows the calibration, in space (that is, x) and time. These measurements are made with respect to my (stationary) frame of reference. My house is at x=0, and my neighbor's house is at x=1250 (feet). My neighbor walks at 250 feet per minute.

The diagram shows some "events"—my house, now; my house, 5 minutes from now; and my neighbor's house now and 5 minutes from now. The diagonal line depicts my neighbor walking from his house to mine, arriving 5 minutes from now. That line is called his ''world line''. The line going straight up in my house is my own world line (I'm sitting at home.)

A car is driving down the street, from left to right. Figure 2 shows the@� $e four events and two world lines, but with different calibration—the car's own coordinate system. The car is driving 500 feet per minute, but in the opposite direction. The event of my neighbor's arrival at my house is now at x=-2500. It's way behind the car, though the car was directly in front of my house at t=0.

Because the car's frame of reference is in motion, the calibration lines in figure 2 are not perpendicular. The formerly vertical lines are now slanted. But there is something very important to notice about the two coordinate systems: They are ''flat''<ref>The words "flat" and "curved" used in this article are the same terms used by differential topology experts.</ref>. The flatness comes from the fact that the calibration lines are straight and parallel. The boxes created by the lines are parallelograms. But note that the lines don't have to be perpendicular, and the boxes don't have to be rectangles. Straight parallel lines and parallelograms are all that is required.

These two flat coordinate systems have a very important physical property: Neither I, sitting at home, nor a passenger in the car, experiences any "[[fictitious force]]s". That is, people in the car don't feel any recoil from acceleration, or centrifugal force, or Coriolis force. These frames of reference are said to be ''inertial''. This leads to an important principle of geometrical physics:

::*''Inertial frames of reference have flat coordinate systems. Flat coordinate systems lead to an absence of fictitious forces.''

Now consider figure 3. The coordinate system is once again that of the car, but the car is accelerating, starting at a standstill in front of my house at t=0. Its world line is curved. Once again, it crosses paths with my neighbor. This case is very different from the other two. The calibration lines are curved, and the boxes that they create are not parallelograms. This coordinate system is ''curved''. Another thing to notice is that people in the car will feel a fictitious force—a "recoil" force agains the back of the seat. This frame of reference is not inertial.

::*''Accelerating frames of reference have curved coordinate systems. Curved coordinate systems lead to fictitious forces.''

::::: .... !!!! We need these three diagrams, of course. I'll do them, but they will take a lot of work. If anyone else has the tools and expertise to do this, and more skill than I, feel free to make them, or to communicate with me (PatrickD).

... In progress ...

==Qualitative Introduction to General Relativity==

The relationship between the curvature of spacetime and the motions of freely falling bodies is often explained by an easily imagined analogy: bowling balls and golf balls on a trampoline.

Imagine that we place a golf ball on an ordinary backyard trampoline. If we give the golf ball a slight push, it will roll along in a straight line until friction brings it to a halt. But if we imagine that friction doesn't exist, then the golf ball will roll in a straight line at a constant speed forever — or at least until it reaches the edge of the trampoline and falls off.

Now imagine a bowling ball sitting in the middle of a trampoline. The trampoline isn't a rigid surface, so it deforms where the weight of the bowling ball pushes it down. This causes the surface to be curved downward, toward the ground.

If we place a golf ball near the edge of the trampoline, it will begin to roll toward the bowling ball, because the trampoline is sloped downward in that direction. The golf ball will start off moving very slowly, then pick up speed as it approaches the bowling ball, until finally it collides with the bowling ball and comes to rest.

But if we give the golf ball a slight push in a direction perpendicular to the direction of the bowling ball, then it will move in a curved path. If we only push it a little bit, the golf ball will curve slightly, but still collide with the bowling ball. If we push the golf ball somewhat harder, it will curve toward the bowling ball, pass by it on one side and climb back out of the depression until it reaches the edge and falls off.

But if we're ''very'' careful, and give the golf ball ''just the right'' push, it will curve completely around the bowling ball and return to our hand.

This is, in a nutshell, how spacetime and matter interact under the theory of general relativity. Massive objects — represented in our analogy by the bowling ball — curve spacetime. Less-massive objects also curve spacetime, but to a lesser extent. If the object is small enough, like our golf ball, the amount of curvature is so slight that we can't even measure it.

The way the golf ball moved in the three scenarios we imagined correspond to ''conic-section orbits,'' or ''Kepler orbits.'' When we just placed the golf ball and it rolled straight toward the bowling ball, that was a ''degenerate'' orbit: a straight line. When we gave it a push and it curved around the bowling ball and off the edge of the trampoline, that was a ''hyperbolic'' orbit. And when we gave it just the right push so that it curved around the bowling ball and back to our hand, that was an ''elliptical'' orbit.

These are the same orbits that are predicted by Isaac Newton's [[Law of Universal Gravitation|law of universal gravitation]]. But in Newton's equations, objects move in conic-section orbits because of a force that accelerates them toward the central mass. In general relativity, objects move in conic-section orbits because spacetime itself is curved, just like our imaginary trampoline was curved by the bowling ball.

Of course, our analogy is far from perfect. Our imaginary trampoline curved ''downward,'' toward the ground, pushed down by the weight of the bowling ball. That's not how spacetime behaves in general relativity. It curves, but not ''toward'' anything, not in any ''direction.'' Spacetime in general relativity is instead said to have ''intrinsic curvature,'' which is mathematically quite simple but very difficult to visualize.

And of course there are many, many other aspects of general relativity that our imaginary trampoline didn't model. But the analogy captures the essential nature of the theory: the bowling ball caused the trampoline to be curved, and the curvature of the trampoline caused the golf ball to move in a different way than if the trampoline had been flat. This is the essence of general relativity: matter tells space how to curve, and space tells matter how to move.

==Quantitative Introduction to General Relativity==
* ''See [[Quantitative Introduction to General Relativity]]''

==Consequences and Tests of General Relativity==

===Orbits===
General relativity provides one explanation for the precession of Mercury's perihelion, which was moving at a different speed than that predicted by a simple application of Newton's law of universal gravitation. (Previous scientists had attempted to explain it by the gravitational pull of a hypothetical planet inside Mercury's orbit, which they called [[Vulcan]]. This could also be explained by altering the precise inverse-square relation of Newtonian gravity to distance, but that was disfavored by mathematicians due to its inelegance in integrating.)

===Gravitational Lensing===
''Main article:'' [[Gravitational lensing]]

General relativity predicts that the path of light will be distorted when it passes near a massive object. In 1919, Sir [[Arthur Eddington]], an esteemed English astronomer, used this to test general relativity by observing the bending of starlight around the sun during a total [[solar eclipse]].<ref>Paul Johnson, British historian</ref>. (A smaller degree of bending could also be consistent with Newton's theory, if one hypothesized light to consist of particles. However, that [[particle theory of light]] had gone out of favor previously.) Eddington detected a bending of light, but his range of error overlapped both Einstein's and Newton's predictions. Upon his return to England, Eddington declared that his observations proven the theory of relativity. His experiment was later confirmed by more rigorous experiments, such as those performed by the [[Hubble Space Telescope]] <ref>[http://www.spaceimages.com/gravlen.html Hubble Gravitational Lens Photo]</ref><ref> [http://csep10.phys.utk.edu/astr162/lect/galaxies/lensing.html Gravitational Lensing] </ref><ref>[http://www.iam.ubc.ca/~newbury/lenses/glgallery.html]</ref>. Lorentz has this to say on the discrepancies between the empirical eclipse data and Einstein's predictions.

::''It indeed seems that the discrepancies may be ascribed to faults in observations, which supposition is supported by the fact that the observations at Prince's Island, which, it is true, did not turn out quite as well as those mentioned above, gave the result, of 1.64, somewhat lower than Einstein's figure.''<ref>Lorentz, H.A. [http://ia331314.us.archive.org/2/items/theeinsteintheor11335gut/11335-h/11335-h.htm The Einstein Theory of Relativity]</ref>

Modern-day astronomers suspect they also see such "gravitational lensing" going on between galaxies, where one galactic cluster distorts the paths of the light passing around it.

==Relation to Special Relativity==

[[Special relativity]] is the limiting case of general relativity where all gravitational fields are weak. Alternatively, special relativity is the limiting case of general relativity when all reference frames are inertial (non-accelerating and without gravity).

{{Relativity}}

==External Links==
*Einstein, Albert (1916), [http://www.alberteinstein.info/gallery/pdf/CP6Doc30_English_pp146-200.pdf "The Foundation of the General Theory of Relativity"] (PDF), Annalen der Physik 49
*[http://www.rareuniverse.org/general_science/general_relativity.html A simple explanation of General Relativity]

==References==
{{reflist}}

[[Category:Physics]]

General theory of relativity

2014-08-29T21:21:31Z

4ArthurDent2:

''See [[Theory of Relativity]]'' for a comprehensive treatment of this topic.''

The '''General Theory of Relativity''' is an extension of [[Special theory of relativity|special relativity]], dealing with curved coordinate systems, accelerating frames of reference, curvilinear motion, and curvature of spacetime itself. It could be said that general relativity is to special relativity as vector calculus is to vector algebra. General relativity is best known for its formulation of gravity as a [[fictitious force]] arising from the curvature of spacetime. In fact, "general relativity" and "Einstein's formulation of gravity" are nearly synonymous in many people's minds. That's because they are.

The general theory of relativity was first published by Marcel Grossman in 1913 and [[David Hilbert]] and [[Albert Einstein]] in 1916.
However, "even though General Relativity has passed many tests, most physicists don’t believe it is ultimately correct because it conflicts with [[quantum mechanics]]." [http://newsdesk.org/2010/08/conservapedia-calls-theory-of-relativity-a-liberal-conspiracy/] Hopefully, within the next few years, a 'theory of everything' will be found, that will combine general relativity and quantum mechanics into one, thus ending the conflict.

General relativity, like [[quantum mechanics]] (the other of the two theories comprising "modern physics") both have reputations for being notoriously complicated and difficult to understand. In fact, in the early decades of the 20th century, general relativity had a sort of cult status in this regard. General relativity and quantum mechanics are both advanced college-level and postgraduate level topics. Hence this article can't possibly give a comprehensive explation of general relativity at the expert level, because it is written by conservapedia. But we will attempt to give a rough outline, for lay people, of the general relativistic formulation of gravity.

In the [[weak field approximation]], where velocities of moving objects are low and gravitational fields are not very severe, the theory of general relativity is said to ''reduce to'' the law of universal gravitation. That is to say, under those circumstances the equations of general relativity are mathematically equivalent to the equations of Newtonian gravitation.

Modern science does not say that Newtonian (classical) gravity is wrong. It is obviously very very very very very very very very very very very very very very very very nearly correct. In the weak field approximation, such as one finds in our solar system, the differences between general relativity and Newtonian gravity are miniscule. It takes very sensitive tests to show the difference. The history of those tests is a fascinating subject, and will be covered near the end of this article. But in all tests conducted so far, where there are discrepancies between the predictions of general relativity and Newtonian gravity (or other competing theories for that matter), experimental results have shown general relativity to be a better description.

Outside of the solar system, one can find stronger gravitational fields, and other phenomena, such as quasars and neutron stars, that permit even more definitive tests. General relativity appears to pass those tests as well.

This is not to say, by any means, that general relativity is the ultimate, perfect theory. It has never been unified with modern formulations of quantum mechanics, and it is therefore known to be incorrect at extremely small scales. Just as Newtonian gravity is very nearly correct, and completely correct for its time, general relativity is believed to be very nearly correct, but not completely so. Contemporary speculation on the next step involves extremely esoteric notions such as string theory, gravitons, and "quantum loop gravity".

The theory is sometimes explained with a thought experiment developed by Einstein involving two elevators. The first elevator is stationary on the Earth, while the other is being pulled through space at a constant acceleration of g. Einstein realized that under Newtonian mechanics, any physical experiment carried out in the elevators would give the same result. This realization is known as the [[equivalence principle]] and it states that accelerating frames of reference and gravitational fields are indistinguishable. General relativity is the theory of gravity that incorporates special relativity and the equivalence principle.

The general theory of relativity is a ''metric theory,'' sometimes also called a ''geometric theory.'' Metric theories describe physical phenomena in terms of [[differential geometry]]. This stands in contrast to Isaac Newton's [[Law of Universal Gravitation]], which described gravity in terms of a [[vector field]]. In the case of general relativity, the theory relates ''stress-energy'' — an extension of the concept of [[mass]] — and the [[curvature]] of [[spacetime]]. In the words of physicist John Wheeler, "Space tells matter how to move, matter tells space how to curve."<ref>Misner, Thorne & Wheeler. ''Gravitation.'' (1973)</ref>

==Coordinate Systems and Spacetime Diagrams==

Figure 1 shows a "spacetime diagram", with my house, my neighbor's house, and my neighbor walking from his house to mine.

:This is the same kind of diagram that is used in explanations of special relativity. The "spacetime" is sometimes called "Minkowski space". Spacetime is actually four-dimensional, but we can only show two dimensions, so we leave out y and z. The single x spatial coordinate is good enough for our purposes, so the diagram has x going from left to right, and t (time) going upward. For the purposes of this explanation, don't worry about the considerations of special relativity such as the speed of light, the Lorentz transform, or light cones. None of that is important just now.

The diagram shows the calibration, in space (that is, x) and time. These measurements are made with respect to my (stationary) frame of reference. My house is at x=0, and my neighbor's house is at x=1250 (feet). My neighbor walks at 250 feet per minute.

The diagram shows some "events"—my house, now; my house, 5 minutes from now; and my neighbor's house now and 5 minutes from now. The diagonal line depicts my neighbor walking from his house to mine, arriving 5 minutes from now. That line is called his ''world line''. The line going straight up in my house is my own world line (I'm sitting at home.)

A car is driving down the street, from left to right. Figure 2 shows the@� $e four events and two world lines, but with different calibration—the car's own coordinate system. The car is driving 500 feet per minute, but in the opposite direction. The event of my neighbor's arrival at my house is now at x=-2500. It's way behind the car, though the car was directly in front of my house at t=0.

Because the car's frame of reference is in motion, the calibration lines in figure 2 are not perpendicular. The formerly vertical lines are now slanted. But there is something very important to notice about the two coordinate systems: They are ''flat''<ref>The words "flat" and "curved" used in this article are the same terms used by differential topology experts.</ref>. The flatness comes from the fact that the calibration lines are straight and parallel. The boxes created by the lines are parallelograms. But note that the lines don't have to be perpendicular, and the boxes don't have to be rectangles. Straight parallel lines and parallelograms are all that is required.

These two flat coordinate systems have a very important physical property: Neither I, sitting at home, nor a passenger in the car, experiences any "[[fictitious force]]s". That is, people in the car don't feel any recoil from acceleration, or centrifugal force, or Coriolis force. These frames of reference are said to be ''inertial''. This leads to an important principle of geometrical physics:

::*''Inertial frames of reference have flat coordinate systems. Flat coordinate systems lead to an absence of fictitious forces.''

Now consider figure 3. The coordinate system is once again that of the car, but the car is accelerating, starting at a standstill in front of my house at t=0. Its world line is curved. Once again, it crosses paths with my neighbor. This case is very different from the other two. The calibration lines are curved, and the boxes that they create are not parallelograms. This coordinate system is ''curved''. Another thing to notice is that people in the car will feel a fictitious force—a "recoil" force agains the back of the seat. This frame of reference is not inertial.

::*''Accelerating frames of reference have curved coordinate systems. Curved coordinate systems lead to fictitious forces.''

::::: .... !!!! We need these three diagrams, of course. I'll do them, but they will take a lot of work. If anyone else has the tools and expertise to do this, and more skill than I, feel free to make them, or to communicate with me (PatrickD).

... In progress ...

==Qualitative Introduction to General Relativity==

The relationship between the curvature of spacetime and the motions of freely falling bodies is often explained by an easily imagined analogy: bowling balls and golf balls on a trampoline.

Imagine that we place a golf ball on an ordinary backyard trampoline. If we give the golf ball a slight push, it will roll along in a straight line until friction brings it to a halt. But if we imagine that friction doesn't exist, then the golf ball will roll in a straight line at a constant speed forever — or at least until it reaches the edge of the trampoline and falls off.

Now imagine a bowling ball sitting in the middle of a trampoline. The trampoline isn't a rigid surface, so it deforms where the weight of the bowling ball pushes it down. This causes the surface to be curved downward, toward the ground.

If we place a golf ball near the edge of the trampoline, it will begin to roll toward the bowling ball, because the trampoline is sloped downward in that direction. The golf ball will start off moving very slowly, then pick up speed as it approaches the bowling ball, until finally it collides with the bowling ball and comes to rest.

But if we give the golf ball a slight push in a direction perpendicular to the direction of the bowling ball, then it will move in a curved path. If we only push it a little bit, the golf ball will curve slightly, but still collide with the bowling ball. If we push the golf ball somewhat harder, it will curve toward the bowling ball, pass by it on one side and climb back out of the depression until it reaches the edge and falls off.

But if we're ''very'' careful, and give the golf ball ''just the right'' push, it will curve completely around the bowling ball and return to our hand.

This is, in a nutshell, how spacetime and matter interact under the theory of general relativity. Massive objects — represented in our analogy by the bowling ball — curve spacetime. Less-massive objects also curve spacetime, but to a lesser extent. If the object is small enough, like our golf ball, the amount of curvature is so slight that we can't even measure it.

The way the golf ball moved in the three scenarios we imagined correspond to ''conic-section orbits,'' or ''Kepler orbits.'' When we just placed the golf ball and it rolled straight toward the bowling ball, that was a ''degenerate'' orbit: a straight line. When we gave it a push and it curved around the bowling ball and off the edge of the trampoline, that was a ''hyperbolic'' orbit. And when we gave it just the right push so that it curved around the bowling ball and back to our hand, that was an ''elliptical'' orbit.

These are the same orbits that are predicted by Isaac Newton's [[Law of Universal Gravitation|law of universal gravitation]]. But in Newton's equations, objects move in conic-section orbits because of a force that accelerates them toward the central mass. In general relativity, objects move in conic-section orbits because spacetime itself is curved, just like our imaginary trampoline was curved by the bowling ball.

Of course, our analogy is far from perfect. Our imaginary trampoline curved ''downward,'' toward the ground, pushed down by the weight of the bowling ball. That's not how spacetime behaves in general relativity. It curves, but not ''toward'' anything, not in any ''direction.'' Spacetime in general relativity is instead said to have ''intrinsic curvature,'' which is mathematically quite simple but very difficult to visualize.

And of course there are many, many other aspects of general relativity that our imaginary trampoline didn't model. But the analogy captures the essential nature of the theory: the bowling ball caused the trampoline to be curved, and the curvature of the trampoline caused the golf ball to move in a different way than if the trampoline had been flat. This is the essence of general relativity: matter tells space how to curve, and space tells matter how to move.

==Quantitative Introduction to General Relativity==
* ''See [[Quantitative Introduction to General Relativity]]''

==Consequences and Tests of General Relativity==

===Orbits===
General relativity provides one explanation for the precession of Mercury's perihelion, which was moving at a different speed than that predicted by a simple application of Newton's law of universal gravitation. (Previous scientists had attempted to explain it by the gravitational pull of a hypothetical planet inside Mercury's orbit, which they called [[Vulcan]]. This could also be explained by altering the precise inverse-square relation of Newtonian gravity to distance, but that was disfavored by mathematicians due to its inelegance in integrating.)

===Gravitational Lensing===
''Main article:'' [[Gravitational lensing]]

General relativity predicts that the path of light will be distorted when it passes near a massive object. In 1919, Sir [[Arthur Eddington]], an esteemed English astronomer, used this to test general relativity by observing the bending of starlight around the sun during a total [[solar eclipse]].<ref>Paul Johnson, British historian</ref>. (A smaller degree of bending could also be consistent with Newton's theory, if one hypothesized light to consist of particles. However, that [[particle theory of light]] had gone out of favor previously.) Eddington detected a bending of light, but his range of error overlapped both Einstein's and Newton's predictions. Upon his return to England, Eddington declared that his observations proven the theory of relativity. His experiment was later confirmed by more rigorous experiments, such as those performed by the [[Hubble Space Telescope]] <ref>[http://www.spaceimages.com/gravlen.html Hubble Gravitational Lens Photo]</ref><ref> [http://csep10.phys.utk.edu/astr162/lect/galaxies/lensing.html Gravitational Lensing] </ref><ref>[http://www.iam.ubc.ca/~newbury/lenses/glgallery.html]</ref>. Lorentz has this to say on the discrepancies between the empirical eclipse data and Einstein's predictions.

::''It indeed seems that the discrepancies may be ascribed to faults in observations, which supposition is supported by the fact that the observations at Prince's Island, which, it is true, did not turn out quite as well as those mentioned above, gave the result, of 1.64, somewhat lower than Einstein's figure.''<ref>Lorentz, H.A. [http://ia331314.us.archive.org/2/items/theeinsteintheor11335gut/11335-h/11335-h.htm The Einstein Theory of Relativity]</ref>

Modern-day astronomers suspect they also see such "gravitational lensing" going on between galaxies, where one galactic cluster distorts the paths of the light passing around it.

==Relation to Special Relativity==

[[Special relativity]] is the limiting case of general relativity where all gravitational fields are weak. Alternatively, special relativity is the limiting case of general relativity when all reference frames are inertial (non-accelerating and without gravity).

{{Relativity}}

==External Links==
*Einstein, Albert (1916), [http://www.alberteinstein.info/gallery/pdf/CP6Doc30_English_pp146-200.pdf "The Foundation of the General Theory of Relativity"] (PDF), Annalen der Physik 49
*[http://www.rareuniverse.org/general_science/general_relativity.html A simple explanation of General Relativity]

==References==
{{reflist}}

[[Category:Physics]]

Liberal bigotry

2014-08-29T21:17:28Z

4ArthurDent2: Undo revision 1101891 by Karajou (talk)

'''Bigotry''' is the expression of [[hatred]] or [[aggression]] towards those who are different. Examples of bigotry include [[racism]] and [[religious intolerance]].

Bigotry is common among [[elitism|elitists]], [[racists]], and religious extremists (i.e. [[Westboro Baptist Church]], [[Ku Klux Klan]], [[Al Qaeda]], etc.) towards critics of their ideologies. Liberals uphold equality of all viewpoints and free speech. It is typical to see liberals refer to their opponents as "[[racism|racists]]", "[[Fascism|fascists]]", "[[Nazis]]", "[[redneck|rednecks]]", "[[fanaticism|fanatics]]", or any number of more profane slurs that are true to the situation. Bigotry can also be evidently seen when people refer to others who disagree with them as "bigots" or "intolerant", and this is a severe form of [[hypocrisy]] because it excuses their accountability by blaming someone else.

== Examples ==
* The infamous [[Hamilton Square Baptist Church Riot]], in which gays maliciously attacked a church, terrorized its congregation, assaulted some of the parishioners and threatened young children present at the church.
* Liberal and pro-abortion attacks on Pregnancy Centers. <ref>http://www.cbn.com/cbnnews/458992.aspx</ref>
* Students threaten and verbally abuse a student wearing a McCain T-shirt. <ref>http://www.chicagotribune.com/news/columnists/chi-kass-13-nov13,0,2881384.column?page=1</ref>
* [[Gay rights]] supporters protested outside of Los Angeles' largest Mormon temple because members of the Mormon church gave millions of dollars to the campaigning for [[Proposition 8]], which banned homosexual marriage in [[California]].<ref>http://www.independent.co.uk/news/world/americas/mormon-stars-face-backlash-after-gay-marriage-ban-1003967.html</ref> 
* Gay rights protesters at a pro-Proposition 8 rally tore a cross out of an elderly woman's hands and stomped on it. They then proceeded to verbally accost the woman for at least 10 minutes, some of which was shown on live TV.<ref>http://www.worldnetdaily.com/index.php?fa=PAGE.view&pageId=80711</ref>
* An ad for the campaign against Proposition 8 depicts Mormons as a type of religious "[[gestapo]]".<ref>http://www.worldnetdaily.com/index.php?fa=PAGE.view&pageId=80047</ref>
* Radical homosexual anarchists shouted profanities and blasphemies in a Michigan church, before engaging in malicious mischief such as unfurling a banner, throwing glitter at the parishioners and pulling a fire alarm.<ref>http://newsbusters.org/blogs/tom-blumer/2008/11/12/national-press-ignores-mi-media-whitewash-lansing-church-homosexual-anar</ref>
* Someone hacked the website of the Mormon church and replaced the front page with a video of gay porn. <ref>http://www.ldsmag.com/ideas/081110hate.html</ref>
* [[Bill Maher]]'s movie ''[[Religulous]]'' uses lies and distortions to mock most major religions.<ref>http://www.worldnetdaily.com/index.php?fa=PAGE.view&pageId=76123</ref>
* The [[ACLU]] attempted to stop a Christian band from playing at a city festival.<ref>http://www.worldnetdaily.com/index.php?fa=PAGE.view&pageId=80649</ref>
* ''[[New York Times]]'' correspondent Dan Mitchell allegedly sent a harassing [[Facebook]] email to a conservative correspondent for [[World Net Daily]]<ref>http://newsbusters.org/blogs/seton-motley/2008/11/03/ny-times-reporters-iat-again-facebook-miller-says-nb-contributor-vadum</ref> 
* [[Hate speech]] laws might be able to be used to ban the Bible.<ref>http://www.worldnetdaily.com/index.php?fa=PAGE.view&pageId=78339</ref>
* Colorado law SB200 bans discriminatory references to homosexuals, which might include the Bible. <ref>http://www.wnd.com/index.php?fa=PAGE.view&pageId=77383</ref>
* Liberal [[Paul Krugman]] calls [[Republican Party]] a "haven for racists". <ref>http://newsbusters.org/blogs/mark-finkelstein/2008/11/03/krugman-gop-haven-racists-reactionaries</ref>
* Liberal Charles Karel Bouley calls for the death of [[Joe the Plumber]]. <ref>http://newsbusters.org/blogs/kerry-picket/2008/11/02/lib-radio-host-karel-calls-joe-wurzelbachers-death-air-obscenity-laced</ref> 
* [[Al Franken]] mocks Christians.<ref>http://newsbusters.org/blogs/tim-graham/2008/10/22/media-skipping-over-al-frankens-acidulous-mockery-christians</ref>
* [[Democrat]] [[John Murtha]] called his constituents "rednecks".
* [[Barack Obama]] accuses the public of clinging to guns and religion.
* [[Muslims]] in India rioted when an author critcized Islam. <ref>http://www.times.com/books/99/04/18/specials/rushdie-riot.html</ref>
* The [[Ku Klux Klan]]'s often violent activities against African Americans, Jews, homosexuals and Catholics.
* The [[Holocaust]]; an attempted extermination of the entire European Jewish population by the [[Nazis]].
* Liberals on the Huffington Post website attacked one of their own, a liberal Brown University student who enrolled at Liberty University to investigate the school and write a book about his experiences, when his findings conflicted with their bigoted beliefs about conservative Christian evangelicals. They also predictably attacked Christian beliefs.<ref>http://www.newsbusters.org/blogs/p-j-gladnick/2009/04/22/liberal-student-infiltrates-liberty-university-write-expos-discovers-i</ref><ref>http://www.huffingtonpost.com/2009/04/22/kevin-roose-infiltrates-l_n_190124.html</ref>

==References==
{{reflist|2}}
{{liberalism}}
[[category: Psychology]]
[[Category:Bigotry]]
[[Category:Liberal Traits]]
[[Category: Anti-American]]