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PaulK Member Posts: 17822 Joined: Member Rating: 2.2 |
Classical physics is not the same as Newtonian physics. Relativity is a Classical theory and it has subsumed and replaced Newtonian mechanics. Newtonian mechanics is still used only because it is simpler and a good enough approximation under many conditions.
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Monk Member (Idle past 3924 days) Posts: 782 From: Kansas, USA Joined: |
Classical physics is not the same as Newtonian physics. This is not entirely true. Our disagreement seems to be purely semantics. The term classical or traditional physics has often been used to describe Newtonian physics with Einstein's Relativity being treated as separate. Here are a few examples:
Classical physics was basically a British enterprise. It started with Isaac Newton at Cambridge in the 17th century with his invention of the infinitesimal calculus and his formulation of the idea of a vector force as mass multiplied by acceleration. Source Classical physics includes the traditional branches and topics that were recognized and fairly well developed before the beginning of the 20th cent. mechanics , sound , light , heat , and electricity and magnetism . Mechanics is concerned with bodies acted on by forces and bodies in motion and may be divided into statics (study of the forces on a body or bodies at rest), kinematics (study of motion without regard to its causes), and dynamics (study of motion and the forces that affect it); mechanics may also be divided into solid mechanics and fluid mechanics, the latter including such branches as hydrostatics, hydrodynamics, aerodynamics, and pneumatics. Acoustics , the study of sound, is often considered a branch of mechanics because sound is due to the motions of the particles of air or other medium through which sound waves can travel and thus can be explained in terms of the laws of mechanics. Among the important modern branches of acoustics is ultrasonics , the study of sound waves of very high frequency, beyond the range of human hearing. Optics, the study of light, is concerned not only with visible light but also with infrared and ultraviolet radiation, which exhibit all of the phenomena of visible light except visibility, e.g., reflection , refraction , interference , diffraction , dispersion (see spectrum ), and polarization of light . Heat is a form of energy, the internal energy possessed by the particles of which a substance is composed; thermodynamics deals with the relationships between heat and other forms of energy. Electricity and magnetism have been studied as a single branch of physics since the intimate connection between them was discovered in the early 19th cent.; an electric current gives rise to a magnetic field and a changing magnetic field induces an electric current. Electrostatics deals with electric charges at rest, electrodynamics with moving charges, and magnetostatics with magnetic poles at rest. Source When I took physics in college, my text book included Newtonian mechanics which was described as classical. The text also included chapters on relativity, special relativity, and quantum mechanics, but these were treated as wholly separate topics. In this wiki article on Physics , the term classical is used in conjuction with classical mechanics as a broad theory with major subtopics including Newtonian physics, Newton's laws of motion, Lagrangian mechanics, Hamiltonian mechanics, Chaos theory, Fluid dynamics, Continuum mechanics. The theory of Relativity is defined separately whose major subtopics include special and general relativity.
Relativity is a Classical theory and it has subsumed and replaced Newtonian mechanics. Newtonian mechanics is still used only because it is simpler and a good enough approximation under many conditions. These statements are also not entirely correct. Your problem is using absolute statements such as relativity has replaced Newtonian mechanics without further clarification. This is simply not true in the vast majority of cases. It is an understatement to say Newtonian mechanics is used in many conditions. It is used in the overwhelming and vast majority of conditions. Relativity has replaced Newtonian mechanics only in very special situations where Newtonian mechanics breaks down. These are cases where the motion of matter approaches the speed of light or where great distances are involved. If relativity has replaced Newtonian mechanics, then the vast majority of the world would be using relativistic equivalents to the basic physics of Statics, Kinematics, Dynamics, Hydrostatics, Hydrodynamics, Aerodynamics, Pneumatics, Acoustics, Optics, Thermodynamics, Electricity, Magnetism, Electrostatics, Electrodynamics, Magnetostatics to name a few. But the vast majority of the world does not modify or replace the mathematics or physical laws used in these areas of physics with equivalent mathematics or laws from Einstein’s relativity. Why? Because the vast majority of the time, we are dealing with a single frame of reference, at much slower speeds than the speed of light and at much smaller distances than at planetary distances. In these instances, Newtonian physics provides correct and acceptable solutions. That is not to say that the areas of physics listed above are not addressed using Relativity because they are when conditions warrant it. Relativity has its place to be sure and Einstein’s contribution was significant. But it should be kept in perspective. It is also a misnomer to say Newtonian mechanics is used "only" because it is simpler and gives a good enough approximation. There is another rather significant reason. Newtonian mechanics is imbedded everywhere in our world. From manufacturing to construction to research and development to nearly all commercial and institutional endeavors. Extracating Newtonian mechanics in order to replace it with a "more accurate" relatavistic based physics would cause worldwide disruption, confusion, and would be completely unnecessary. The US can't even convert to the metric system, let alone uproot Newtonian mechanics.
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PaulK Member Posts: 17822 Joined: Member Rating: 2.2 |
You'll find sites taking the opposite view, too.
http://www.absoluteastronomy.com/...cl/classical_physics.htm
Classical physics is physics based on principles developed before the rise of quantum theory. It includes special theory of relativity as well.
University of Birmingham - A leading global university
This course is a first step to the summit of classical physics, the Theory of Relativity
[quote]
qsRelativity is a Classical theory and it has subsumed and replaced Newtonian mechanics. Newtonian mechanics is still used only because it is simpler and a good enough approximation under many conditions.[/qs] These statements are also not entirely correct. Your problem is using absolute statements such as relativity has replaced Newtonian mechanics without further clarification. This is simply not true in the vast majority of cases.
[/qs] That further clarification is provided by the second sentence.
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Monk Member (Idle past 3924 days) Posts: 782 From: Kansas, USA Joined: |
Newtonian physics is, in fact, false. It is wrong. It is not correct. Scientific truth is a continual scale, it’s a matter of degree where truth is measured not in the simple true or false, but in the amount of truth it contains compared to alternative theories. Theories in science are true, but one theory may be more true than another. I believe it is more accurate to say Newtonian physics is true, but Einsteinian physics is more true under certain conditions. Einsteinian physics didn't prove that newtonian physics was wrong, but that newtonian physics contained some amount of falsehood under certain conditions. That’s why I take issue with blanket statements such as Newtonian physics is wrong, incorrect. This implies that it should no longer be used and that another theory should be used under all conditions as a valid replacement. I believe we are in agreement, and you have qualified your absolute statement about Newtonian mechanics. I simply have reservations about describing anything scientific in absolute terms.
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Monk Member (Idle past 3924 days) Posts: 782 From: Kansas, USA Joined: |
Then you acknowledge that the term Classical physics has both included and excluded relativity as part of the definition depending on the source. As such, a blanket statement Classical != Newtonian does not hold in all circumstances.
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PaulK Member Posts: 17822 Joined: Member Rating: 2.2 |
And you acknowledge that the term Classical Physics is sometimes used to include Relativity. Thus the two terms are not semantically identical and it is better not to use "Classical" if "Newtonian" is meant.
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Monk Member (Idle past 3924 days) Posts: 782 From: Kansas, USA Joined: |
Consider it acknowledged.
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Wounded King Member Posts: 4149 From: Cincinnati, Ohio, USA Joined: |
Newtonian mechanics is imbedded everywhere in our world. In what way exactly? TTFN, WK
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Monk Member (Idle past 3924 days) Posts: 782 From: Kansas, USA Joined: |
In what way exactly? Hmmm... Why do you ask? As a post-doctoral Research Biologist with an interest in quantum mechanics, surely you know. This message has been edited by Monk, Thu, 08-18-2005 01:18 PM
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Wounded King Member Posts: 4149 From: Cincinnati, Ohio, USA Joined: |
You left out my interest in psychical research.
I ask because I personally don't see Newtonian physics to be embedded in our world, only in our systems of knowledge. On re-reading your post I see that you went on to talk about a variety of human efforts presumably these now constitute 'our world'. I had thought you were making some sort of platonist argument about Newtonian mathematics being integral to 'our world'. TTFN, WK
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Monk Member (Idle past 3924 days) Posts: 782 From: Kansas, USA Joined: |
You left out my interest in psychical research. Yes, I did leave it out mainly because it seemed further removed from your other interest which are more.....shall we say mainstream science? I'd be interested if you started a thread on that topic though and describe the current state of research.
I ask because I personally don't see Newtonian physics to be embedded in our world, only in our systems of knowledge. On re-reading your post I see that you went on to talk about a variety of human efforts presumably these now constitute 'our world'. I had thought you were making some sort of platonist argument about Newtonian mathematics being integral to 'our world'. Yes, my metaphor may have been misleading. I wasn't referring to the natural "world", but the "world" of human endeavors and the use of our "world" of knowledge.
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NosyNed Member Posts: 8996 From: Canada Joined: |
Scientific truth is a continual scale, it’s a matter of degree where truth is measured not in the simple true or false, but in the amount of truth it contains compared to alternative theories. Theories in science are true, but one theory may be more true than another. I believe it is more accurate to say Newtonian physics is true, but Einsteinian physics is more true under certain conditions. I think using "truth" in this context isn't a good idea. In fact, it is my understanding that "truth" is a metaphysical concept and, perhaps, best left out of science discussions. The above reads better if you use the words "accuracy" and "accurate".
Einsteinian physics didn't prove that newtonian physics was wrong, but that newtonian physics contained some amount of falsehood under certain conditions. That’s why I take issue with blanket statements such as Newtonian physics is wrong, incorrect. This implies that it should no longer be used and that another theory should be used under all conditions as a valid replacement. Einsteinian physics shows that newtonian physics gives the wrong answer under all circumstance. However, as you note, the degree of inaccuracy is what matters. Under many circumstances the error of Newtonian physics doesn't matter for the task at hand. It may imply that it should not longer be used but that implication is incorrect and only for those who can't understand real implications of the differences between the theories. There are two different aspects to consider:1) The results that are given by using the theories in such things as space craft navigation or GPS calculations. 2) What the theories tell us about the nature of the universe in which we live. In the first case Newtonian physics may still be acceptably accurate even if it gives answers which are not precisely correct. In the second case Newtonian physics is wrong if GR is right. The very nature of the fabric of our universe is not as described by Newtonian physics. (edited for spelling -- some of it anyway ) This message has been edited by NosyNed, 08-18-2005 06:06 PM
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Monk Member (Idle past 3924 days) Posts: 782 From: Kansas, USA Joined: |
I think we are dancing around the same point of view. Accuracy
Einsteinian physics has its applications under very, very narrow and specialized circumstances. The vast majority of traditional physics gets along quite well without it. As such, I don’t believe Einsteinian physics will replace the use of traditional physics in the vast majority of practical applications at any point in the foreseeable future. My initial objection in this thread was to nwr who said that we don't accept Newtonian physics anymore because it has been replaced with something better, (quantum physics). My point is that we do indeed accept and continue to use Newtonian physics. It has not been replaced except under very specialized circumstances. I didn't intend to be such an ardent supporter of Newton, it just turned out that way. And I’m not minimizing Einstein’s contributions, but I believe Newton’s are equally significant.
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crashfrog Member (Idle past 1466 days) Posts: 19762 From: Silver Spring, MD Joined: |
meh, never mind. Pretty sure it's off-topic and better heads than mine are already on this.
This message has been edited by crashfrog, 08-18-2005 08:13 PM
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nwr Member Posts: 6408 From: Geneva, Illinois Joined: Member Rating: 5.1 |
Einsteinian physics has its applications under very, very narrow and specialized circumstances.
That's not correct. Einstein's relativistic physics as fully superseded Newtonian physics. It is true that there are only narrow specialized circumstances where the difference is large enough to matter, and thus we continue to use the simpler equations.
My initial objection in this thread was to nwr who said that we don't accept Newtonian physics anymore because it has been replaced with something better, (quantum physics).
I was trying to keep it simple, so I only mentioned quantum physics, and omitted relativity. I corrected that when you became argumentative.
My point is that we do indeed accept and continue to use Newtonian physics.
That's not quite correct. We continue to use Newtonian equations as a convenient approximation. However, we have changed the definition of length, for example, from the Newtonian standard to the one based on relativity. That is, the meter is tied to the speed of light, rather than to a platinum rod. That's one indication that we have moved from the Newtonian paradigm.
I didn't intend to be such an ardent supporter of Newton, it just turned out that way. And I’m not minimizing Einstein’s contributions, but I believe Newton’s are equally significant.
I'm a strong admirer of Newton. That his physics has been superseded, does not detract from its value. It is unlikely that relativity could have been discovered, were it not for the research program initiated by Newton and other scientists of that time. One of my desktop computers is named after Newton.
% uname -a
That indicates my respect for him.
SunOS newton 5.10 Generic_118844-08 i86pc i386 i86pc
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