Is Newton right?

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FromTheAshes

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Amalthea said:
I could tell, and no offence but engineers seem to often not understand physics.
And, no disrespect, but Physicists usually don't have a clue how to build something. Engineers got man to the moon, scientists got a bunch of rocks afterwards.
Again an engineer speaking. Physics is more than real world experiment. By the way Emmy Noether was a woman!
Yes, it's generalizations based of a real-world experiment. Pretty cool that Noether is (was? Is she dead?) a woman. I have a friend who's a math major, and man, half the time I don't have a clue what she's doing.
Noether's theorem is purely mathematical use of the variational principle of calculus. If the 'action' is unchanged under some group of tranformations on the coordinates and the scalar field then there exist conserved quantities. This is physics at the fundamental level. The conservation of energy is the time translational symmetry of spacetime, period.
If it's purely mathematical then it needs experimentation to prove that it has a real-world connection. Either way experimentation is in the links.
Think where a flat spacetime breaks down. On the global cosmological scale there are problems formulating energy conservation and near the Big Bang singularity. The 2nd Law has a similar problem as you cannot define the arrow of time that synopsises the 2nd Law of thermodynamics.
Out of curiousity, it's been suggested that the 2nd law, or the principles behind it, is what defines the one-directional aspect of the arrow of time. If there's any validity in that, what would happen if the second law broke down?
Absolutely incorrect. The laws of thermodynamics originally were based on experiment. See James Joules work for instance.
Exactly! They're expirimentally proven and verified laws. I like them much better then mathematical constructs.
You can approach them theoretically via energy conservation but this technically requires a Minkowskian spacetime. Take that away and you don't necessarily have this. You are putting the cart before the horse and starting off from thermodynamics. You strictly cannot do this. Practically as in an engineering sense you can get away with it but that doesn't make it right. Remember, engineers engineer things, physicists do science.
If the gadget you're building works when you build it right then your theory is fine.
 
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Amalthea

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FromTheAshes said:
And, no disrespect, but Physicists usually don't have a clue how to build something. Engineers got man to the moon, scientists got a bunch of rocks afterwards.
Agreed. But we are talking physics here not engineering.

Yes, it's generalizations based of a real-world experiment. Pretty cool that Noether is (was? Is she dead?) a woman. I have a friend who's a math major, and man, half the time I don't have a clue what she's doing.
She died 70 years ago. Probably the most famous woman mathematician ever.


They're expirimentally proven and verified laws. I like them much better then mathematical constructs.
They are experimentally verified in only the regimes that we can test. We know that they cannot hold if the theoretical reasons behind them were to not occur.

If the gadget you're building works when you build it right then your theory is fine.
That is all well and good. But what you are dealing with here is approximation. Just like not needing relativistic accuracy when sending a probe to the Moon, but that doesn't mean Newtonian meechanis is accurate.

The point I am trying to get across is that from the OP Newtons Laws of Motion have nothing to do with energy conservation. Thermodynamics which states energy conservation were rules developed based upon experiment. The reason behind those laws is theoretically based and we know where to expect them not to hold. But to state that thermodynamics is fundamental in a physics sense is not true. They are flat spacetime consequences of symmetries in nature. This is much more of a fundamental and important statement. Yes, as far as an engineer is concerned this real world practicality is the important thing but let's not confuse that with physics. An analogy would be the zero point of gravitational potential. To an engineer the reference zero potential is most often the Earth's surface but to a physicist it is at infinity. An engineer is most often worried about changes in potential with respect to the Earth's surface whereas a physicist is concerned with the gravitational field in a cosmological sense.
 
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FromTheAshes

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Amalthea said:
Agreed. But we are talking physics here not engineering.
Too true. I mean if you want to talk theoretical equations, pretty much count me out. If I can't build anything with it, it's cool but not proven.
She died 70 years ago. Probably the most famous woman mathematician ever.
Research time! I ought to know my history of the sciences better.
They are experimentally verified in only the regimes that we can test. We know that they cannot hold if the theoretical reasons behind them were to not occur.
If it works then it's verified. If it stops working then it's time to find a new way that does. We "know" that the theoretical reasons behind them are valid because they are working. If the theoretical reasons behind them were to not occur then we'd need new theoretical reasons.
That is all well and good. But what you are dealing with here is approximation. Just like not needing relativistic accuracy when sending a probe to the Moon, but that doesn't mean Newtonian meechanis is accurate.
But it is accurate, for our purposes. It fails to be accurate when you're building a high-energy particle accelerator, predicting the decay rate of particles entering the atmosphere, plotting the course of planets, measuring the speed of light, and a whole lot of other things. Trust me, Newtonian mechanics is MUCH more useful the Einsteinian mechanics when it comes to actually doing stuff. I shudder to think what the equations would look like if we had to actually take into account relitivistic effects (hello changes in the 14th decimal place)
The point I am trying to get across is that from the OP Newtons Laws of Motion have nothing to do with energy conservation.
Which basically goes without saying. Bleh. Newton's laws of motion certainly don't contradict energy conservation (that would be bad) but they don't support it.
Thermodynamics which states energy conservation were rules developed based upon experiment. The reason behind those laws is theoretically based and we know where to expect them not to hold. But to state that thermodynamics is fundamental in a physics sense is not true. They are flat spacetime consequences of symmetries in nature. This is much more of a fundamental and important statement. Yes, as far as an engineer is concerned this real world practicality is the important thing but let's not confuse that with physics. An analogy would be the zero point of gravitational potential. To an engineer the reference zero potential is most often the Earth's surface but to a physicist it is at infinity. An engineer is most often worried about changes in potential with respect to the Earth's surface whereas a physicist is concerned with the gravitational field in a cosmological sense.
True. We like 9.8 Newtons per Kilogram (No, I will not use Engineering English. That system is the devil incarnate), you like a theoretical zero. I'll admit I see your point, and if you show me a really cool gadget I can build of your point I'll stick it together as best I can. Something that strengthened and expanded the weak nuclear force to increase binding energies across an entire structure would be uber-cool for instance (hello infinitely strong steel).

P.S. I'm pretty sure we're refighting the practical/theoretical science battle here. Since engineers/biologists/(some) physicists have been fighting (some) physicists/philosophers along these lines, mostly in friendly debate, for better then a century now shall we call it quits? (I'd say start our own thread, but this one was pointless and silly anyway, so we might as well continue in it. Newton was wrong to begin with, he just came up with some AWESOME approximations).
 
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Amalthea

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FromTheAshes said:
Too true. I mean if you want to talk theoretical equations, pretty much count me out. If I can't build anything with it, it's cool but not proven.
Way too practical. Theoretical physics is such an aesthetic subject. One of the reasons I never considered engineering and I did theoretical physics for my PhD, that plus I was too good at math to do engineering lol.:p


Research time! I ought to know my history of the sciences better.
Always one of my interests, I always lecture with a lot of historical information and anecdotes. Who did what, was taught by whom etc.

If the theoretical reasons behind them were to not occur then we'd need new theoretical reasons.
Agreed, but that is the essence of theoretical physics, understanding the universe from as fundamental a level as possible. Hence quantum gravity research, cosmology, particle physics etc.

But it is accurate, for our purposes. It fails to be accurate when you're building a high-energy particle accelerator, predicting the decay rate of particles entering the atmosphere, plotting the course of planets, measuring the speed of light, and a whole lot of other things. Trust me, Newtonian mechanics is MUCH more useful the Einsteinian mechanics when it comes to actually doing stuff. I shudder to think what the equations would look like if we had to actually take into account relitivistic effects (hello changes in the 14th decimal place)
But that 14th decimal place is important at a fundamental understanding. Practically it may never have import but for ontological reasons it does.

Which basically goes without saying. Bleh. Newton's laws of motion certainly don't contradict energy conservation (that would be bad) but they don't support it.
Agreed. Actually Newton's laws can be shown to derive from the principle of least action.


P.S. I'm pretty sure we're refighting the practical/theoretical science battle here. Since engineers/biologists/(some) physicists have been fighting (some) physicists/philosophers along these lines, mostly in friendly debate, for better then a century now shall we call it quits? (I'd say start our own thread, but this one was pointless and silly anyway, so we might as well continue in it. Newton was wrong to begin with, he just came up with some AWESOME approximations).
Reminds me of an analogy. Mathematician invents some new math. Physicists are using it 20 years later. Chemists about 50 years after that. Engineers about another 50 years later and finally biologists about 200 years after that.
 
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FromTheAshes

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Amalthea said:
Way too practical. Theoretical physics is such an aesthetic subject. One of the reasons I never considered engineering and I did theoretical physics for my PhD, that plus I was too good at math to do engineering lol.:p
You laugh, but it's true. Engineers quit math after computers hit the shelves. Too much time. The debate at this point is modeling. For instance apparently there's a flaw in one of the spring-coupling models of expansion stress on a material that will have some interesting implications. The model's usage needs to be a little more limited then it is now...

Always one of my interests, I always lecture with a lot of historical information and anecdotes. Who did what, was taught by whom etc.
Nicola Tesla did everything better then anyone, so us engineers have our hero (ok, maybe that's not true, but Tesla kicked Edison's ass).
Agreed, but that is the essence of theoretical physics, understanding the universe from as fundamental a level as possible. Hence quantum gravity research, cosmology, particle physics etc.
Meh, kinda cool, no flashy stuff. Give me a way to manipulate gravity and you guys will have done your job.

But that 14th decimal place is important at a fundamental understanding. Practically it may never have import but for ontological reasons it does.
Practically it does have VERY large import in the situations I outlined. The key to engineering is simplifying until you get something you can work with. The key to theoretical physics is exactness. Which is why string theory annoys me (when you're talking approximations of approximations for the equations you should be talking engineering - only it has no evidence and no practical value).

Agreed. Actually Newton's laws can be shown to derive from the principle of least action.
Otherwise known as "The universe is a lazy SOB"

Reminds me of an analogy. Mathematician invents some new math. Physicists are using it 20 years later. Chemists about 50 years after that. Engineers about another 50 years later and finally biologists about 200 years after that.
So true! Especially the 200 years for biologists.
 
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FromTheAshes

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Tesla was just unbelievably cool. He got bored one day, and figured out a way to destroy the earth. He then ran some experiments, and got some exact figures on how to destroy the planet. Because he was curious. This is how insanely cool Tesla is.

I'm still working on my degree, at Union College. Nice little school, upstate New York, and with a liberal arts wing. They're not good for much, but at least we don't have the usual 9:1 male/female ratio, and I can take courses like "Science Fiction in literature." Only downside is you get libbie friends who are like "Do something today!" because they don't have anything that resembles work.
 
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