What is a scientific theory?

[jbachmurski]

<p>The internet is full of so called &ldquo;new theories&rdquo; how does someone tell the good from the bad?</p><p>In modern physics, what constitutes a scientific theory? Could someone list the most necessary and the not so necessary elements needed for a valid scientific theory?</p><p>What would someone need to do in order turn a revolutionary new idea into a new theory? </p>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The internet is full of so called &ldquo;new theories&rdquo; how does someone tell the good from the bad?In modern physics, what constitutes a scientific theory? Could someone list the most necessary and the not so necessary elements needed for a valid scientific theory?What would someone need to do in order turn a revolutionary new idea into a new theory? <br /> Posted by jbachmurski</DIV></p><p>I think the two most important aspects of a theory is that is should be both falsifyable and it should make predictions that are observable and/or testable with repetition.&nbsp; On a lesser level, though not irrelevant, is the scope of your theory... It should really have some use.&nbsp; It may also help if your theory has relevance or implications to existing theories. </p><p>You start with an observation of some natural phenomena and make a hypothesis about what you observed.&nbsp; Test your hypothesis.&nbsp; If, through testing, your hypothesis appears to be consistent, subject your hypothesis to the peer review process.&nbsp; If it is still found to be consistent after peer review verification and acceptance, you have yourself a theory.&nbsp; Now you, and everyone else on the planet, should be able to go about testing your predictions and/or falsifying it through experimentation and/or observation. </p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The internet is full of so called &ldquo;new theories&rdquo; how does someone tell the good from the bad?In modern physics, what constitutes a scientific theory? Could someone list the most necessary and the not so necessary elements needed for a valid scientific theory?What would someone need to do in order turn a revolutionary new idea into a new theory? <br />Posted by jbachmurski</DIV></p><p>This is really a very good question.&nbsp; The more so because the concept of a physical theory is commonly distorted badly in popular useage.&nbsp; So let me try to address your question by describing both what a theory is and what a theory is not.</p><p>A theory is a model, usually expressed in mathematical terms, that describes natural phenomena.&nbsp; It does so by clearly defining the parameters that govern the phenomena and provides a means whereby the outcome of a physical&nbsp;process &nbsp;can be predicted accurately from the knowledge of those parameters at the start of the&nbsp;process together with a knowledge of the external inputs to the process.&nbsp; Further, the ability of the theory to make such predictions will have been verified by a&nbsp;large body of carefully controlled experiments or careful observations of nature itself.&nbsp; In classical physics the quintessential theories are Newtonian mechanics, Newton's theory of gravitation, and Maxwell's theory of electromagnetism.&nbsp; In modern physics the major theories are general relativity (the theory of gravity), quantum chromodynamics (the theory of the strong force), and quantum electrodynamics unified with the theory of the weak force (the electroweak theory).&nbsp; Directly related to classical mechanics are the somewhat lesser theories of thermodynamics and statistical mechanics and the theories of fluid mechanics.&nbsp; And sub-tier to these theories are a host of mathematical models and theories that run the gamut from plasma physics and solid state physics to cosmological theories like the big bang.&nbsp;&nbsp; These lower tier theories often involve approximations to the complete, but unwieldy and unsolvable models that come from the major theories but do provide significant predictive power when applied properly.</p><p>Now, we need to talk about what a theory is not.&nbsp; Most importantly a theory is neither a conjecture nor a hypothesis.&nbsp; Common useage confuses these terms.&nbsp; There is a place for a conjectcure, a hypothesis or just a plain guess.&nbsp; They are absolutely necessary to scientific progress.&nbsp; But only when a guess has been shown to be correct through controlled experiments or precise observations and clearly related to established theories can it be taken to be valid.&nbsp; The inflationary model of the early universe is a hypothesis.&nbsp; It is a very promisiing hypothesis, since it can be melded with real theories without apparent contradictions and since the available body of data is supportive of the predictions that can be made if one assumes the hypothesis to be true.&nbsp; But there is not yet enought evidence to elevate inflation to the level of an accepted theory.&nbsp;&nbsp; It does have the strudture and predictive power for a theory, just not yet sufficient experimental confirmation.</p><p>If you take away but one thing form this discussion I hope that it is enough to recognize that the statement that "Such and such is just a theory" is an incredibly ignorant assertion.&nbsp; </p><p>&nbsp;</p> <div class="Discussion_UserSignature"> </div>

 

[jbachmurski]

<p>Next question. What happens if two vary different theories can be made from the same empirical data and observations, and in testing produce the same outcome? Can both be the truth? If not, how does one figure out which is right and wrong? </p>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Next question. What happens if two vary different theories can be made from the same empirical data and observations, and in testing produce the same outcome? Can both be the truth? If not, how does one figure out which is right and wrong? <br />Posted by jbachmurski</DIV></p><p>If two theories produce the same verifiable predictions and if those predictions are actually confirmed by experiment then they are actually just one theory.&nbsp; Theories can appear to be different but in reality be the same.&nbsp; For instance basic quantum mechanics can be described by Schrodinger's wave mechanics or by Heisenberg's matrix mechanics.&nbsp; The two theories appear different but are the same.&nbsp; Similarly Langrangian mechanics, based on a variationala principle produces the same results as ordinary Newtonian mechanics based on determination of forces.</p> <div class="Discussion_UserSignature"> </div>

 

[jbachmurski]

Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>If two theories produce the same verifiable predictions and if those predictions are actually confirmed by experiment then they are actually just one theory.&nbsp; Theories can appear to be different but in reality be the same.&nbsp; For instance basic quantum mechanics can be described by Schrodinger's wave mechanics or by Heisenberg's matrix mechanics.&nbsp; The two theories appear different but are the same.&nbsp; Similarly Langrangian mechanics, based on a variationala principle produces the same results as ordinary Newtonian mechanics based on determination of forces. <br />Posted by DrRocket</DIV><br /><br /><p>DR, I understand what you are saying, but its not what I have in mind. </p><p>You write well, and you write fast, &hellip;that&rsquo;s not a skill that I will ever possess. Its hard for me to adequately put my thoughts into words.</p><p>&nbsp;</p><p>What I&rsquo;m trying to say is&hellip; two vary different theories, same predictions and outcomes, but for entirely different reasons? </p>

 

[nimbus]

You wouldn't know they were for entirely different reasons so long as they had the same predictions and outcomes.. <div class="Discussion_UserSignature"> </div>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>DR, I understand what you are saying, but its not what I have in mind. You write well, and you write fast, &hellip;that&rsquo;s not a skill that I will ever possess. Its hard for me to adequately put my thoughts into words.&nbsp;What I&rsquo;m trying to say is&hellip; two vary different theories, same predictions and outcomes, but for entirely different reasons? <br />Posted by jbachmurski</DIV><br />&nbsp;</p><p>It doesn't matter.&nbsp; If the theories always produce the same predictions given the same set of circumstances, then they are the same theory.&nbsp; They would be indistinguishable to an outside observer who cares nothing for philosoophy or "reasons".</p><p>Perhaps if you gave an example we could address it and make this a bit more concrete.</p> <div class="Discussion_UserSignature"> </div>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>DR, I understand what you are saying, but its not what I have in mind. You write well, and you write fast, &hellip;that&rsquo;s not a skill that I will ever possess. Its hard for me to adequately put my thoughts into words.&nbsp;What I&rsquo;m trying to say is&hellip; two vary different theories, same predictions and outcomes, but for entirely different reasons? <br /> Posted by jbachmurski</DIV></p><p>Are you thinking about something similar to the wave-particle duality of light or Einstein's Equivalence Principle ?</p><p>I think the Equivalence principle might be closer to what you are thinking about.&nbsp;</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Are you thinking about something similar to the wave-particle duality of light or Einstein's Equivalence Principle ?I think the Equivalence principle might be closer to what you are thinking about.&nbsp; <br />Posted by derekmcd</DIV></p><p>I hope we don't get into either topic very far.</p><p>Wave-particle duality is at best confusing and really is misleading.&nbsp; Those little buggers are particles, not waves, they just are'nt little marbles and&nbsp; you need to be a bit sophisticated to describe their behavior.</p><p>Here are some pictures and an article from Wikipedia that illustrate what I mean -- the double slit interference patterm emerging one particle at a time.</p><p>&nbsp;http://en.wikipedia.org/wiki/Imageouble-slit_experiment_results_Tanamura_2.jpg</p><p><img src="http://upload.wikimedia.org/wikipedia/commons/thumb/7/7e/Double-slit_experiment_results_Tanamura_2.jpg/206px-Double-slit_experiment_results_Tanamura_2.jpg" border="0" alt="Imageouble-slit experiment results Tanamura 2.jpg" width="206" height="597" /></p><p>The equivalence principle simply postulates that the mass that drives gravity is the same mass that describes inertia.&nbsp; </p><p>I think perhaps the correspondence principle is closer to the spirit of the&nbsp;original question -- new theories must reduce to older theories in the limit for phenomena in which the older theories are known to provide accurate predictions.&nbsp;&nbsp; So general relativity reduces to Newton's theory of universal gravitation for modest gravitational fields and long periods of time.&nbsp;&nbsp;And quantum mechanics reduces to classical mechanics for macroscopic bodies.&nbsp; </p> <div class="Discussion_UserSignature"> </div>

 

[dockeen]

<p>There are many problems in physics that can be addressed in more than one way, be it conservation of different parameters, or different mathematical approaches and operations.</p><p>To an outside observer, these different descriptions and methods of approach may in fact look like different "theories", but the endpoint - the problem solution is the same.</p><p>Wayne</p>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>There are many problems in physics that can be addressed in more than one way, be it conservation of different parameters, or different mathematical approaches and operations.To an outside observer, these different descriptions and methods of approach may in fact look like different "theories", but the endpoint - the problem solution is the same.Wayne <br /> Posted by dockeen</DIV></p><p>You posting incognito?&nbsp;</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[silylene old]

<p>What is a 'theory' is an excellent question, and so misunderstood by the common person.&nbsp; The meaning is also incorrectly taught in schools, by teachers who usually don't understand either.</p><p>In order of increasing data, logical support and absence of contravening information:</p><p>1. Lies</p><p>2. Fallacy and Misinformation</p><p>3. Bullsh!t</p><p>4. Speculations</p><p>5. Hypothesis</p><p>6. Theory</p><p>7. Laws and Principles</p><p>Thoeries have substantial data and logic supporting the concept or hypothesis.&nbsp; There is an absence of contravening data or results or substantiated logic.&nbsp; A&nbsp;large majority of the trained professional community who are experts in this area have reviewed the data, concepts and hypothesis and supports the validity of the information and concepts.</p><p>On this scale, "Intelligent Design" is a '2'.&nbsp; Evolution is a '6.5'.</p><p>&nbsp;</p> <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>What is a 'theory' is an excellent question, and so misunderstood by the common person.&nbsp; The meaning is also incorrectly taught in schools, by teachers who usually don't understand either.In order of increasing data, logical support and absence of contravening information:1. Lies2. Fallacy and Misinformation3. Bullsh!t4. Speculations5. Hypothesis6. Theory7. Laws and PrinciplesThoeries have substantial data and logic supporting the concept or hypothesis.&nbsp; There is an absence of contravening data or results or substantiated logic.&nbsp; A&nbsp;large majority of the trained professional community who are experts in this area have reviewed the data, concepts and hypothesis and supports the validity of the information and concepts.On this scale, "Intelligent Design" is a '2'.&nbsp; Evolution is a '6.5'.&nbsp; <br />Posted by silylene</DIV></p><p>I would disagree with your ranking.&nbsp; Intelligent Design is closer to a 1 since it is promulgated despite an overwhelming and well-known case for the opposition and complete contravention by the facts.&nbsp; Given the damage that has been done in the name of intelligent design, and the complete disconnection from real science, I would rate it lower, but your scale seems to not admit either 0 or negative integers.</p><p>On the other hand evolution is&nbsp;no higher than a 6&nbsp;since it has no quantitative predictive power, and is supported only by historical data (quite strong historical data).&nbsp; I certainly do not dispute the basic premise of evolution, but it requires quite a bit of refinement and quantification before it can be placed higher on the scale.&nbsp; One problem with evolution is that it is sufficiently non-quantifiable that it is not really falsifiable&nbsp;in principle, nor is it directly supportable&nbsp;either (in the sense that one cannot construct an unbroken line demonstrating the continuous evolution of one species into another).&nbsp; Perhaps as molecular biology progresses the capability to make a quantitative model for evolution may arise and it can be elevated in status on your scale.&nbsp; But at the moment biology is not sufficiently quantitative.</p><p>&nbsp;</p><p>&nbsp;</p> <div class="Discussion_UserSignature"> </div>

 

[silylene old]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I would disagree with your ranking.&nbsp; Intelligent Design is closer to a 1 since it is promulgated despite an overwhelming and well-known case for the opposition and complete contravention by the facts.&nbsp; Given the damage that has been done in the name of intelligent design, and the complete disconnection from real science, I would rate it lower, but your scale seems to not admit either 0 or negative integers.On the other hand evolution is&nbsp;no higher than a 6&nbsp;since it has no quantitative predictive power, and is supported only by historical data (quite strong historical data).&nbsp; I certainly do not dispute the basic premise of evolution, but it requires quite a bit of refinement and quantification before it can be placed higher on the scale.&nbsp; One problem with evolution is that it is sufficiently non-quantifiable that it is not really falsifiable&nbsp;in principle, nor is it directly supportable&nbsp;either (in the sense that one cannot construct an unbroken line demonstrating the continuous evolution of one species into another).&nbsp; Perhaps as molecular biology progresses the capability to make a quantitative model for evolution may arise and it can be elevated in status on your scale.&nbsp; But at the moment biology is not sufficiently quantitative.&nbsp;&nbsp; <br />Posted by DrRocket</DIV></p><p>Evolutionary mechanism do have quite a strong mathematical theory underlying them.&nbsp; It is quite interesting.&nbsp; And genetics is increasingly supporting evolutionary concepots by giving testable mechanisms.&nbsp; That's why I elevatyed the number greater than 6.&nbsp; But I am not disagreeing with you, I think we are much closer in thinking than not.</p><p>ID for most believers I think falls under 'misinformation'.&nbsp; Only those few ID-ites who are smart enough with some scientific background actually are outright lying and deceiving.&nbsp; But if you want to rank it as a '1', I won't disagree.</p><p>I do think that astrology is closer to a '2' and should have a higher ranking than Intelligent Design.&nbsp; Same with numerology, it too should have a higher ranking than ID.&nbsp; Acupuncture is about a '3'.</p> <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[jbachmurski]

Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;It doesn't matter.&nbsp; If the theories always produce the same predictions given the same set of circumstances, then they are the same theory.&nbsp; They would be indistinguishable to an outside observer who cares nothing for philosoophy or "reasons".Perhaps if you gave an example we could address it and make this a bit more concrete. <br />Posted by DrRocket</DIV><br /><br /><p>I guess, when you get down to it, what I&rsquo;m asking is, has the Equivalence Principle ever been proven? Does it always apply? And does it apply to theories themselves? </p>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I guess, when you get down to it, what I&rsquo;m asking is, has the Equivalence Principle ever been proven? Does it always apply? And does it apply to theories themselves? <br />Posted by jbachmurski</DIV><br />&nbsp;</p><p>The Equivalence Principle has been addressed with the experiments that support general relativity, and they support it very strongly.&nbsp; Also there have been experiments that show that the mass that occurs in F=ma is the same mass that occurs in Newton's law of universal gravitation.&nbsp; These experiments provide extremely strong evidence for the equivalence principle.&nbsp; http://en.wikipedia.org/wiki/Equivalence_principle#The_weak_equivalence_principle</p><p>I don't understand your last two questions.&nbsp; </p> <div class="Discussion_UserSignature"> </div>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>What is a 'theory' is an excellent question, and so misunderstood by the common person.&nbsp; The meaning is also incorrectly taught in schools, by teachers who usually don't understand either.In order of increasing data, logical support and absence of contravening information:1. Lies2. Fallacy and Misinformation3. Bullsh!t4. Speculations5. Hypothesis6. Theory7. Laws and PrinciplesThoeries have substantial data and logic supporting the concept or hypothesis.&nbsp; There is an absence of contravening data or results or substantiated logic.&nbsp; A&nbsp;large majority of the trained professional community who are experts in this area have reviewed the data, concepts and hypothesis and supports the validity of the information and concepts.On this scale, "Intelligent Design" is a '2'.&nbsp; Evolution is a '6.5'.&nbsp; <br /> Posted by silylene</DIV></p><p>I like your scale, but how do you distinguish between 1, 2 and 3?&nbsp;&nbsp; They all seem like they can be connected in ways.</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Evolutionary mechanism do have quite a strong mathematical theory underlying them.&nbsp; It is quite interesting.&nbsp; And genetics is increasingly supporting evolutionary concepots by giving testable mechanisms.&nbsp; That's why I elevatyed the number greater than 6.&nbsp; But I am not disagreeing with you, I think we are much closer in thinking than not.ID for most believers I think falls under 'misinformation'.&nbsp; Only those few ID-ites who are smart enough with some scientific background actually are outright lying and deceiving.&nbsp; But if you want to rank it as a '1', I won't disagree.I do think that astrology is closer to a '2' and should have a higher ranking than Intelligent Design.&nbsp; Same with numerology, it too should have a higher ranking than ID.&nbsp; Acupuncture is about a '3'. <br />Posted by silylene</DIV></p><p>I would like to see the mathematical theory of evolution.&nbsp; That would be interesting.&nbsp; But be forewarned, I have somewhat high standards for mathematical theories and can and have dissected a few, to the discomfort of some of the proponents.&nbsp; I am particularly sensitive to misapplications of statistics and confusion between correlation and causation.&nbsp; </p><p>I think I basically agree with everything but acupuncture.&nbsp; I would have agreed on that one, since my initial thought was that beneficial effects were basically placebo effects.&nbsp; However, I have a very rational friend who has had acupuncture treatments applied to his Great Dane.&nbsp; They have helped the dog, and I think it is pretty difficult to con a dog (much harder than conning a person).&nbsp; So I think perhaps I would have to give acupuncture, at least veterinary acupuncture a 3+.&nbsp; </p> <div class="Discussion_UserSignature"> </div>

 

[jbachmurski]

Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I like your scale, but how do you distinguish between 1, 2 and 3?&nbsp;&nbsp; They all seem like they can be connected in ways. <br />Posted by derekmcd</DIV><br /><br />I agree,&nbsp;I believe its called politics.&nbsp;

 

[jbachmurski]

Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;The Equivalence Principle has been addressed with the experiments that support general relativity, and they support it very strongly.&nbsp; Also there have been experiments that show that the mass that occurs in F=ma is the same mass that occurs in Newton's law of universal gravitation.&nbsp; These experiments provide extremely strong evidence for the equivalence principle.&nbsp; http://en.wikipedia.org/wiki/Equivalence_principle#The_weak_equivalence_principle&nbsp; <br />Posted by DrRocket</DIV><br /><br /><p>If that&rsquo;s true then wouldn&rsquo;t the Equivalence Principle also suggest that refraction and the gravitational bending of light are equal?</p>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>If that&rsquo;s true then wouldn&rsquo;t the Equivalence Principle also suggest that refraction and the gravitational bending of light are equal? <br />Posted by jbachmurski</DIV></p><p>No, why would it.&nbsp; Perhaps you ought to state the Equivalence Principle as you understand it.</p><p>Do you mean refraction as in the action of a lens or refraction with respect to&nbsp;light propagation across a sharp edge ?&nbsp; In either case the result is explained&nbsp;by Maxwell's equations for electromagnetic waves and interaction with materials.&nbsp; Gravitational bending is the result of curvature of space by mass.&nbsp; Just because two phenomena can&nbsp;affect the path of light, does not mean that they are equivalent, or even related.</p><p>Some people get fatter with time.&nbsp; And some get fatter with ice cream.&nbsp; But no one suggests that ice cream and time are&nbsp;equal.&nbsp;&nbsp;<br /></p> <div class="Discussion_UserSignature"> </div>

 

[MeteorWayne]

Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Some people get fatter with time.&nbsp; And some get fatter with ice cream.&nbsp; But no one suggests that ice cream and time are&nbsp;equal.&nbsp;&nbsp; <br />Posted by DrRocket</DIV><br /><br />Whattttt? I thought IC=dT. rats a whole new paradigm need to be constructed. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[jbachmurski]

Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>No, why would it.&nbsp; Perhaps you ought to state the Equivalence Principle as you understand it.Do you mean refraction as in the action of a lens or refraction with respect to&nbsp;light propagation across a sharp edge ?&nbsp; In either case the result is explained&nbsp;by Maxwell's equations for electromagnetic waves and interaction with materials.&nbsp; Gravitational bending is the result of curvature of space by mass.&nbsp; Just because two phenomena can&nbsp;affect the path of light, does not mean that they are equivalent, or even related.Some people get fatter with time.&nbsp; And some get fatter with ice cream.&nbsp; But no one suggests that ice cream and time are&nbsp;equal.&nbsp;&nbsp; <br />Posted by DrRocket</DIV><br /><br /><p>What I would like to know here is how do the experts differentiate between the two? The sun has an atmosphere as do most if not all large gravitational objects. So when a large body like the sun bends the light from other stars, how do the experts differentiate between refraction and the gravitational bending of light?</p>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>What I would like to know here is how do the experts differentiate between the two? The sun has an atmosphere as do most if not all large gravitational objects. So when a large body like the sun bends the light from other stars, how do the experts differentiate between refraction and the gravitational bending of light? <br />Posted by jbachmurski</DIV></p><p>Take a look at the last paragraph in this the document at this link http://www.mathpages.com/rr/s6-03/6-03.htm</p><p>Basically you can calculate the effect of both refraction (with some assumptions about the composition of the "atmosphere" of the sun and you can calculate the bending due to general relativistic effectds.&nbsp; Those two combined effects can then be compared with experimental data.&nbsp; </p> <div class="Discussion_UserSignature"> </div>