Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: McQueen on 23/10/2005 14:22:45
-
Reading several posts in this Forum relating to the motion of objects , led me to re-read Newton’s Laws of Motion and to realize how extraordinary they really are : “If an object is moving in a straight line it will continue moving in a straight line forever, unless it is acted upon by something else ( a force ). At that time its direction and speed will be altered , depending upon the magnitude and direction of the force which it encounters. Further every action is accompanied by an equal and opposite reaction. “
Think about how extraordinary this statement(s) is. Observation would lead us to believe that just the opposite takes place , namely that objects in motion have a tendency to come to rest , and in fact for over two thousand years , ever since Aristotle , this was the accepted wisdom : “That an object in motion would return to a state of rest.”
Even more incredible was the fact that Newton presented these theories with the premise of “ Hypotheses non fingo “ ( I make no hypotheses) meaning that he based his laws of motion on sound experimental evidence and nothing else. Which of course reminded me of Einstein and his Nobel Prize Lecture , he had received the Nobel Prize for his explanation of the photo electric effect , but he made no mention of this in his lecture , presenting instead his theory of special relativity ! What can one say , great minds think alike.
(Edit)I should add that it was not my intention to attribute frivolous motives to either of the two great scientists referred to in this thread. I am well aware that Einstein’s theory of relativity was supported by his equation E = mc^^2 , which in turn was based on experimental evidence , while Newton’s Laws of motion were founded on a vast amount of astronomical data , which led to his truly amazing and detailed explanation on the effects of Gravity. Although no-one has as yet been able to explain why Gravity works in the way it does. As Newton himself put it : …that one body may act upon another at a distance through a vacuum without the mediation of anything else , by and through which their action and force may be conveyed from one to another , is to me so great an absurdity that , I believe , no man who has in philosophic matters a competent faculty of thinking could ever fall into it.” The aspect which I was trying to emphasize was the amazing flair for presentation and for the dramatic that both these scientists possessed to a high degree.
-
I would imagine that Newton would have had to accept perpetual motion (in the absence of any force) not on the basis of experiment so much as upon the observation of astronomical bodies, which his observations would have indicated are in perpetual motion.
As for general relativity, as I understand it, it was proven by looking the irregularities in the orbit of mercury. E=MC^2 is a consequence of the theory of special relativity, but as i understand it, it was not observed to happen until the splitting U235 was shown to lose mass and gain energy. As I understand it, this was not anticipated, but once it was observed, it consequences were immediately apparent.
-
Actually, the special theory of relativity was engendered by Maxwell's equations. When a moving magnetic field gives rise to a current in a conductor, the form of the equations is completely different than when a conductor moves through a stationary magnetic field. I remember encountering this, and immediately recognizing that the equations must be wrong. Of course they give the right answer, but they are not describing correctly what is happening. Einstein's contribution was in correcting the Maxwell's equations to give the right description for both cases.
Of course, Maxwell was following Newton's lead, because he used an absolute coordinate system. This gives the wrong equations, since only the relative movement needs description.
"F = ma, E = mc^2, and you can't push a string."
-
quote:
Originally posted by gsmollin
Of course, Maxwell was following Newton's lead, because he used an absolute coordinate system. This gives the wrong equations, since only the relative movement needs description.
What does Newton have to say on the propagation of light :
“Those that are averse from assenting to any new discoveries but such as they can explain by an hypothesis , may for the present suppose , that as stones by falling upon water put the water into an undulatory motion , and all bodies by percussion excite vibrations in the Air , so the rays of light excite vibrations in the refracting medium or substance ……… that the vibration thus excited in the refracting or reflecting medium or substance , much after the manner that vibrations are propagated in the Air for causing sound , and move faster than the rays so as to overtake them………… And that every ray is successively disposed to be easily reflected or transmitted by every vibration which overtakes it. But whether this hypothesis be true or false I do not here consider.”
Newton was strongly pre-disposed to the idea of light as a beam (or ray) of particles. The above is his explanation of how a beam of particles might behave like a wave. It is interesting to note that he takes exactly the same route that was eventually adopted by Quantum Mechanics , namely that of the group velocity and phase velocity of waves. Of course when applied to light this implies faster than light (FTL) communication.