Newtonian Physics?
Posted on: September 19, 2008 - 10:46pm
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Newtonian Physics?
...Are Newton's theories just considered junk, more or less, in modern times? I continually hear that Newton was wrong (no surprise, given his total lack of knowledge of the atomic / subatomic world), but then I also continually hear about Newtonian Physics being used in various applications.
I don't understand. Was he just 'sort-of' wrong or something?
Quote:
"Natasha has just come up to the window from the courtyard and opened it wider so that the air may enter more freely into my room. I can see the bright green strip of grass beneath the wall, and the clear blue sky above the wall, and sunlight everywhere. Life is beautiful. Let the future generations cleanse it of all evil, oppression and violence, and enjoy it to the full."
- Leon Trotsky, Last Will & Testament
February 27, 1940
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No, Newton wasn't wrong, more of refined. Newtons laws were more approximations.
The problem with Newtonian is that it does not work on the quantum level. So you can use Newton's laws on large objects, but once you get at the quantum level, it breaks down.
For example:
Clasically:
momentum=mv
In modern physics:
Momentum=mv/(SQRT(1-v2/c2))
The Lorentz factor (The SQRT(1-v2/c2)) is pretty much 1 given objects with low velocity much smaller than c, so the classical mv works.
So for large objects, yes Newtonian physics works.
If what I remember from my (admittedly far more brief than I would have liked) College Physics Education is correct then I believe, while not entirely accurate, Newton's laws of motion are useful approximations in certain circumstances (I believe these circumstances are the objects in question being not too massive or too small, but I don't know the specifics, DeludedGod could you clarify?). They are useful because they get results very close to accurate under their good conditions, and the equations are vastly simpler.
Hence why they are still taught in the beginning of early Physics classes, to give the students a fairly easy step into the science instead of bludgeoning them over the head with an equation with five different differential terms.
Again, My memory may be wrong, but that's what I remember being taught.
When you say it like that you make it sound so Sinister...
Newton, Galileo .... godly prophets, and the religious leaders of course hated them.
Ah, it works for large ones, not small ones. Thanks Captain.
emphatically NO!
Newton assumed some grounds for his hypotheses, as you do (it's just necessary), and his conclusions reinforce those grounds in the sense that the true stuff tows along false stuff with it.
Newton's Laws are rightly formulated and it is expected that they will derive neatly as approximations to a fundamental hypotheses, this hypotheses will hopefully also explain why Newton was able to glean his accurate results from questionable abstract premises.
So basically, Kevin, if someone says to you 'Newton was wrong' they are either referring to his abstract premises or they are just bullshitting.
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Ahh I see Cpt has already posted an example of this principle. Newton inferred a static background, Einstein inferred a dynamic background, presently there is inference of no background at all. In Cpt's example we can demonstrate how Einstein's dynamic background acts approximately static, per Newton, under certain conditions, explaining how he could be correct even though his premise was eventually disproven.
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The day when it is proven all is ONE .... heck, I will long gone. Ahh sucks.
Newton's theoretical model of the universe is incorrect. However, his mathematical models are so useful that they find applications in virtually everything: Electromagnetism, fluid dynamics, astrophysics, vector calculus etc. etc. Newton's theoretical model states that there is a universal gravitational field which permeates all of space. This is wrong. However, It is conceptually useful to start thinking of gravity in terms of field lines which cannot break except form where they originate. It is so useful, in fact, that we still use it to send rockets to space. Newton's model also state that quantities like velocity are variant under Galiliean coordinate transforms. This is also wrong, although he can be forgiven for this error as well, as it was a perfectly reasonable assumption in his time (and tensor analysis hadn't been developed). Notice how I said his theoretical model was "incorrect", not "junk". An example of "junk" would be N-rays or polywater. The two are fundamentally different. No student of physics could claim to have any meaningful understanding of any physical concepts without a firm background in Newtonian mechanics.
"Physical reality” isn’t some arbitrary demarcation. It is defined in terms of what we can systematically investigate, directly or not, by means of our senses. It is preposterous to assert that the process of systematic scientific reasoning arbitrarily excludes “non-physical explanations” because the very notion of “non-physical explanation” is contradictory.
-Me
Books about atheism
DG , real science, fuck yeah ....
Most science is often an approximation very very close one to all observable and predictable events. Why religious nuts never use this is beyond me basically I suppose they are thick.
Maybe one day someone will show that evolution is part of something bigger but it won't be shown to be wrong.
I remember at school being told atoms were little physical nuclei with little ball like electrons flying around them (not true but good enough at that level to make some extremely predictions on how the world works)