part 1. world in motion

© ABCC Australia 2015 www.new-physics.com

THE WORLD IN MOTION


Motion in the Observable World

In daily life motion is evident when things are moving. Everywhere we see: people move; birds fly. In the cosmos, the sun and moon rise and fall; planets twirl around stars; galaxies whistle through space.

Time moving

Birds moving

Earth moving Sun moving

Galaxies moving

Man moving


Motion in the Microscopic World

Not only that, it has been proven beyond doubt that all the small material bodies in this universe are in a state of motion: molecules vibrating; electrons orbit around nuclei; neutrinos fly in every direction; quarks and gluons twitching inside the elementary particles.

Cells moving

Molecules moving

Atoms moving Quarks moving


Definition of Motion

The word ‘motion’ came from the Greek word ‘motus’ which means change. In ancient Greece, motion includes fluxes, growths, meltings, coolings, heatings . . . etc. The ancient Greek philosophers recognized that the world is transient and is constantly changing.


Translational Motion

To be more precise and scientific in physics, by motion we mean the change of position in space, that is, ‘translational motion’.

Translational motion

Changes


Speed

In translational motion, speed is the perception of how fast an object moves. The concept is a simple one and was well known in the early civilizations or even in prehistoric times. In fact it is so simple that its origin is never noticed.

Slow = Low Speed Fast = High Speed


Ancient Greeks on Speed

Serious consolidation of the concept of motion may have been started with the ancient Greek philosophers when they began to ponder upon the phenomenon of objects in motion.

For example, the great philosopher Aristotle (384–322 BC) had his own notion of motion in that time is proportional to the distance moved. He said:

“For at any moment when a thing is causing motion, it also has caused motion, so that there must always be a certain amount of distance that has been traversed and a certain amount of time that has been occupied.” Aristotle’s Physics VII.

The idea of speed


Galileo’s Investigation

It was probably Galileo Galilee (1564-1642) who first developed the conception of motion in definite and quantitative terms. Through his various investigations such as the slide experiment, he used the mathematical notion of velocity as distance over a period of time.

Dripping water to count time

Ball rolling down slide

Slide tilted to have different angles

𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉= 𝐷𝐷𝑉𝑉𝐷𝐷𝑉𝑉𝐷𝐷𝐷𝐷𝑉𝑉𝑉𝑉 ÷ 𝑇𝑇𝑉𝑉𝑇𝑇𝑉𝑉


Units of Distance & Time

Distance and time are two independent quantities, each with their own measurement units. Distances are measured in cm, m, km etc., in the metric system and inches, feet, miles in the imperial system. For convenience, the metricsystem is used throughout in our discussions with imperial units in brackets if necessary.

Time is more universal. It is measured in seconds, minutes, hours, days, etc. which we are familiar with.

Distance units in cm, m, km, etc.

Time units in second, minutesHours, days, etc


Equation for Velocity

For the special case of uniform motion in which an equal distance (∆𝑥𝑥 =𝐷𝐷𝑇𝑇𝐷𝐷𝑉𝑉𝑉𝑉 𝑑𝑑𝑉𝑉𝐷𝐷𝑉𝑉𝐷𝐷𝐷𝐷𝑉𝑉𝑉𝑉) is covered in equal interval of time (∆𝑉𝑉 = 𝐷𝐷𝑇𝑇𝐷𝐷𝑉𝑉𝑉𝑉 𝑉𝑉𝑉𝑉𝑇𝑇𝑉𝑉), it can be written as:

𝑈𝑈𝐷𝐷𝑉𝑉𝑈𝑈𝑉𝑉𝑈𝑈𝑇𝑇 𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉 𝑣𝑣= 𝐷𝐷𝑉𝑉𝐷𝐷𝑉𝑉𝐷𝐷𝐷𝐷𝑉𝑉𝑉𝑉 (Δ𝑥𝑥) ÷ 𝑇𝑇𝑉𝑉𝑇𝑇𝑉𝑉 Δ𝑉𝑉

Or simply in pure mathematical form:

𝑣𝑣 = Δ𝑥𝑥Δ𝑡𝑡

𝒗𝒗

=𝜟𝜟𝜟𝜟𝜟𝜟𝜟𝜟


Geometric Representation of Speed

Since distance (space) and time are two independent quantities, we can represent them by the two perpendicular coordinates of a Cartesian coordinate system: y-axis take up distance and x-axis looks after time. Velocity become the slanting line or slope across space and time.

Thus speed is measured by meters or feet per second, kilometres or miles an hour.

By interposing, we have the distance:

Δ𝑥𝑥 = 𝑣𝑣Δ𝑉𝑉

Dist

ance

(spa

ce)

Time

Δ𝑥𝑥

Δ𝑉𝑉

𝑣𝑣 =Δ𝑥𝑥Δ𝑉𝑉


The Kinematic Piece

Galileo’s kinematics was accepted by physicists in the subsequent centuries and became the basis of Newton’s work and the foundation of classical mechanics.

Velocity


THE CAUSE OF MOTION IN ANCIENT GREECE


What makes a thing move?With things in motion, there comes the question of what makes an object move. Why do things fall? Who sets the heavenly bodies in motion? What is done on an object to make it achieve a velocity?


It Started with the Greeks

Normally the average person would not have concerned with such a question. Motion is natural. We walk from one location to another; we push and pull so as to make an object move; the sun rises and falls . . . But the ancient Greeks did not stop at that.


Aristotle Physics

The first comprehensive & systematic set of ideas about the physical world was developed by the great Greek philosopher Aristotle (384–322 BC) in the fourth century BC. It is often referred to as Aristotelian physics and the concept of a force is an integral part of Aristotelian cosmology.

Aristotle & his geocentric universe


Observations by Aristotle

Aristotle is a genius with very sharp observation and keen analytic power. However he was heavily handicapped because he did not have the notion of experimental instruments to carry them out. Neither did he has the correct concept of gravitation or the force of friction to start with. This is why he often made astounding but erroneous assumptions which led to complicated but also erroneous deductions. He can be considered as a genius with two heads like the god Janus but with one of them blind.

Blind


Celestial Motion

Aristotle did observe that:

❶ The stars and heavenly bodies circulate permanently around the earth as if moved by angel or god.

According to modern mechanics, celestial motion is the combined effect of linear motion and gravitation. Aristotle did not understand the interaction of gravitation and linear motion and came to the notion that motion is initiated by angels or god himself who decreed that the heavenly bodies should circulate permanently around the earth.

We leave celestial motion to the discussion on circular and orbital motions of celestial objects for later.


Gravitational Motion

❷ Things that have gone up will come done naturally towards the centre of the earth. Example is the fall of Icarus when his wings were melted by the heat of the sun as he went far too high and too close to the sun.

We know that this motion is rectilinear and is caused by the force of gravity. Aristotle did not understand these and so made such a classification.

This class of motion is to be studied in our discussions on gravitation.


Forced Motion

❸ Things on earth move because the application of force. So they are called forcedor unnatural motion by Aristotle.

This is the class of motions we are familiar with in our daily life. They are always interpreted as our bodily effort of a push or a pull.

However Aristotle also observed that things on earth will stop moving in the absence of continuous force application. He did not know that it is actually friction that is working against the motion.

This is the misconception that acts as the prelude to our present discussion.

Force Friction

Forced motion

No motion


Motions with Movers

Aristotle concluded with the assumption that an object cannot move by itself because every movement depends on there being a mover – some body is needed to push or pull them.

Mover

Moved

Mover


Problem with Projectiles

But what about projectiles? They don’t obey Aristotle’s rule because they keep on moving after leaving the thrower or bow without the need of further force applied to them.


Air Behind Projectile Motions

Aristotle maintained that after leaving the shooter’s bow, the arrow still continues to move because a new force is still transmitted to the arrow through a medium such as air. It is the air closing in behind a moving arrow propelled it so that it will keep on moving until it drops.

❸Air turns around and pushes

the projectile forward.

❶ Air being pushed forward by stone in front and so turns back.

❷ Air flows to the side and then back of the stone.


Cannon Ball Trajectory

Thus according to Aristotle, a cannon ball will shoot up straight at first and then drops dead straight to the ground.

A medieval drawing showing cannon ball trajectory.


Medieval Age

The Middle Ages in European history lasted from the fall of the western Roman Empire (circa A.D. 395) to the Renaissance in the 14th or 15th century. During this period, the civilisation of the Greeks and Romans were replaced by barbarism. Most of the ancient teachings and their records were lost or destroyed. Fortunately omeof them were copied and preserved in the Muslim countries.

The devastation of Greek and Roman civilizations


Revival of Greek Learnings

From the thirteenth century onward these writings came to see the light again in Europe. They were recovered as rare copies from forgotten corners in the attic or store rooms. Some of them were also brought back from the Muslim countries translated in Latin. After emerging from a thousand years of darkness, the European civilisation was in a badly retrograded shape. The ancient knowledge and philosophies appeared so far superior to theirs that they were treated with almost superstitious reverence. The teaching of Aristotle in particular became the guiding light of the time.


Authority of Aristotle’s Teachings

The weight of Aristotle's teachings were later further enhanced by St. Thomas Aquinas (1224-1274 B.C.) who brought them in line with the Bible, making them the answer books to all scientific enquiries.

In the centuries to come Aristotle's philosophy was regarded as the ultimate truth throughout Europe. When Aristotle said that a heavy rock falls faster than a lighter one, no one else would have thought otherwise.


John Philoponus

The Aristotelian theory of forced motion encountered criticism in the Medieval age, first and formally by John Philoponus in the 6th century.

Philoponus (AD 490-570) in Greek means "lover of work“. He was so called because he spent most of his time studying.

He was an Alexandrian Christian who disagreed with Aristotle's philosophy.

One of his most important achievements in spear heading Alexandria’s science was his theory of impetus.


Philoponus’ major argument against Aristotle was on the cause of motion. He opposed to the idea of a medium of force such as air because it would resist the motion of a projectile and definitely could not also propel that projectile.

The Medium of Force

Projection motion

Air resistance


Motive Cause - Impetus

Philoponus believed that a stone moved because something like a force had impressed onto it. The stone absorbed the force, moved a little faster and continued to move on. It eventually had to cease motion because of encountering situations such as resistance from the air or collision with another body. The cause of movement or the motive force, Philoponus concluded, resided within the stone itself. He called this something ‘impetus’.

BEFORE

AFTER Impetus


Eternal Celestial Motions

As for the celestial movements Aristotle attributed them to the power of spirits. But Philoponus suggested that the Creator had impressed movement upon the original universe in the first place and the universe went on with the momentum impressed on it. In the same manner as the stone projectile, once the cause of motion was imparted, an object in a void would keep on going because of impetus, without any further push.


Breaking the Earth-Heaven Barrier

This endowment by God did not decay with time. So it was no longer necessary to postulate a variety of angelic movers working on the heavenly bodies.

This is in the truth of the law of conservation of impetus though Philoponus did not explicitly recognized it.This conception, besides establishing impetus as a individually existing entity, it was also a major step in breaking down the difference between the movement of heavenly and earthly objects as conceived by Aristotle.


Philoponus vs Aristotle

To Aristotle, motion is an effect caused by an external agent – an external force. In Philoponus’ theory, motion is an intrinsic property of the moving object itself. Impetus, the driving agent, is first imparted to an object and set the object in motion and later abides within the moving object on its journey.

This is for the first time in a thousand years when the ideas of Aristotle were seriously and challenged and gain acceptance.


What is the Nature of Impetus?

Impetus seems to be something that exists naturally in this world. It appears to Philoponus that it is a fundamental fact of nature and did not give further elaboration on it.

?


The Impetus Piece

Understood or not, we have been able to obtain another important piece for our motion puzzle after velocity – impetus.

Velocity

Impetus


JEAN BURIDANThe Renegade Monk


Jean Buridan

Jean Buridan (1295-1358) was a French priest credited to be the person who sowed the seeds for the Copernican revolution in Europe.

Before Buridan, natural philosophy was only a handmaiden of theology or a mere disciple after the doctrines of Aristotle. After the time of Buridan, it began to have its own legitimacy and developed in a new direction.


Motion of Projectiles

Like Philoponus in the 6th century, Buridan was particularly in discordance with Aristotle’s concept on motion of projectiles.

The trajectory of a projectile by Aristotle


Buridan on Projectiles

Buridan said: “. . . after leaving the arm of the thrower, the projectile would be moving by an ‘impetus’ given to it by the thrower and would continue to move as long as the impetus remained stronger than the resistance, and would be of infinite duration were it not diminished and corrupted by a contrary force resisting it or by something inclining it to a contrary motion.”

IMPETUS


Buridan’s Impetus

According to Buridan in his “Quaestiones on Aristotle's Physics”:

“When a mover sets a body in motion he implants into it a certain impetus:

[𝑀𝑀𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝐷𝐷 = 𝐼𝐼𝑇𝑇𝐼𝐼𝑉𝑉𝑉𝑉𝐼𝐼𝐷𝐷]

. . . a certain force enabling a body to move in the direction in which the mover starts it, be it upwards, downwards, sidewards, or in a circle.

[𝐷𝐷𝑉𝑉𝑈𝑈𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝐷𝐷 𝑉𝑉𝑈𝑈 𝑇𝑇𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝐷𝐷 =𝐷𝐷𝑉𝑉𝑈𝑈𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝐷𝐷 𝑉𝑉𝑈𝑈 𝑉𝑉𝑇𝑇𝐼𝐼𝑉𝑉𝑉𝑉𝐼𝐼𝐷𝐷]


Buridan’s Equation

The implanted impetus increases in the same ratio as the velocity.

[𝐼𝐼𝑇𝑇𝐼𝐼𝑉𝑉𝑉𝑉𝐼𝐼𝐷𝐷 ∝ 𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉]

in fact, Buridan gave it a mathematical formulation:

𝐼𝐼𝑇𝑇𝐼𝐼𝑉𝑉𝑉𝑉𝐼𝐼𝐷𝐷 = 𝑊𝑊𝑉𝑉𝑉𝑉𝑊𝑊𝑊𝑉𝑉 × 𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉

The weight is a constant that does not change. So the impetus is purely a function of velocity. Faster object has greater impetus


INERTIA

Impetus became Momentum

It can be said that what Buridan did was very close to defining momentum in the Newtonian sense 𝒑𝒑 = 𝑇𝑇𝒗𝒗.This impetus theory was revived in the thirteenth century by Peter John Olivi (c. 1248-1298) and has been incorporated into modern physics as momentum.

Buridan’s IMPETUS


Nature of Impetus

Apparently Buridan’s way of thinking was on the right track. But again like Philoponus, he did not investigate further why it should be as he thought. It seemed to him that it was an elementary fact and resumed no further explanation. What is impetus? What is in impetus that is passed on from one body to another to make a body move?

IMPETUS

?

To be continued in Part 2.

part 1. world in motion

Science