Newton Physics Emerges

What is the Title?

Isaac Newton was born on Christmas Day, 1642, the same year Galileo died. He did much of his greatest work during a two year period from 1665 to 1667 when he was at the village of Woolsworth to escape the Great Plague which was ravishing London. He died in 1727, at the age of 85. Years later it was discovered that much of his erratic behavior may have been caused by mercury poisoning. Recent samples of his hair showed he had forty times the level of mercury considered normal. Newton discovered the origin of color. He discovered the nature of gravity as an attractive force. He invented calculus as the language necessary to understand how gravity works He used his knowledge or optics to invent the first reflecting telescope - a major breakthru because this will eventually allow larger, more sensitive telescopes to be built.

The genius of Newton was his ability to use calculus and coordinate transformations to reveal and explain the underlying physics.

Calculus as a Language

For example, how do I compute the area of a circle.

A circle is enclosed by a surface when a line of radius r that has been rotated through 360 (2π) degrees.

From the language of Calculus this means the following:

Language should evolve so that communication becomes more efficient; i.e. the above graphic shows how to derive the area of a circle in using the least amount of characters and symbols. It is only meaningful if you understand the language

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Newtonian Physics:

• A Force causes momentum to change with time
• Force operationalizes as Mass * Acceleration (F=ma)
• Mass is that which resists force (this is called inertia).
• Energy is associated with movement and position within a force field.
• Energy is conserved: mgh = 1/2mv²
• impact velocity from free fall independent of mass;
  
  
  
  Note that Galileo does not understand the concept of energy and how it relates to motion. That is he never discovered kinetic energy (1/2mv²). Newton discovered that this concept must exist as a natural consequence of his force law.
  
  Energy means applying a force over some distance:
  • E = F * Δx = maΔx
  • if starting from rest (v_o =o) then
    1/2v² = aΔx (half the square of the velocity of any moving object at any time is equal to the acceleration applied to the object times the distance it has moved)
    now you have E = 1/2mv²

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    Newton invented a scientific method which was truly universal in its scope. Newton presented his methodology as a set of four rules for scientific reasoning. These rules, written in the Principia , are:

    1. We are to admit no more causes of natural things such as are both true and sufficient to explain their appearances

    2. The same natural effects must be assigned to the same causes

    3. Qualities of bodies are to be esteemed as universal

    4. Propositions deduced from observation of phenomena should be viewed as accurate until other phenomena contradict them.

    • What is important about rule 1 and has it been articulated before?
    • What principle do rules 1 and 2 expose and has this been articulated before?
    • What does rule 4 say about the nature of science? Does culture understand this implication?

    
    
    

    An Aside: How Newton Knew he Was Correct:

    Step 1: Assume that M1 is a small mass in a circular orbit about a much larger mass M2 . We can write down the Force law on M1 using Newton's formulations: Step 2: Combining terms yields: Step 3: In an orbit governed by a central force, the centripetal acceleration, a is given by: Step 4: For a circular orbit, the circular velocity, Vc is the total distance traveled (the circumference of the circle) divided by the orbital period, P or Vc = 2p R/P which then yields: in which the harmonic law of Kepler is now apparent as the R3/P2 term.

    Measurements of R and P for any lesser body ( M1 ) in orbit about a larger body ( M2 ) now gives directly a physical quantity, mass. Thus the mass of the sun is determined by measuring the orbital period of the Earth and the distance to the sun. You don't have to go to the Sun and put it on a scale. Wow, what would Aristotle say?

    
    
    
    Newton's Universal Gravity:

    His place in the Gravity Hall of Fame is due to his discovery that gravitation is universal. ALL objects attract each other with a force of gravitational attraction that depends on their masses and separations. ITS A ONE WAY FORCE.

    Upon this realization, Newton's first thought was this:

    Well fine, if gravity is an attractive force, then how come the Universe is still here? (resolution of this?)

    
    
    
    
    
    And his second thought was this:

    Okay then, how come the moon doesn't come crashing into the earth, or the earth into the sun.

    What causes an orbit to be stable?

    An orbit is the balance between inertial (Newton's First Law) and gravitational forces (Newton's second law). That is, the earth is continually falling toward the sun, but inertia also wants the earth to keep moving in a straight line. When these two forces are in balance a stable orbit results:

    

    

    Newton's view of science:

    I do not know what I may appear to the world; but to myself I seem to have been only like a boy playing on the seashore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me. No great discovery was ever made without a bold guess To explain all nature is too difficult a task for any one man or even for any one age. `Tis much better to do a little with certainty,and leave the rest for others that come after you, than to explain all things. Truth is ever to be found in the simplicity, and not in the multiplicity and confusion of things. But Newton is confused by gravity: I have not been able to discover the cause of those properties of gravity from phenomena, and I frame no hypotheses; for whatever is not deduced from the phenomena is to be called a hypothesis, and hypotheses, whether metaphysical or physical, whether of occult qualities or mechanical, have no place in experimental philosophy. More frankly, in a letter to Richard Bentley in 1693, Newton writes that action at a distance is "so great an absurdity that I believe no man who has in philosophical matters a competent faculty of thinking can ever fall into it"