Monday, April 2, 2007

Classical Thinking in Physics and Newton's Laws of Motion

The discovery of the Newton's Laws of Motion provide many insights into how scientific discovery occurs - there are experiments and observations, consideration of unknown or untested variables in the experimental observations, theories knitted together from results and analogies in other systems, more experiments and use of different experimental paradigms, and finally discussions (and often disagreements) with others until one arrives at a consensus.

It was Aristotle who first noticed that masses of heavier weight tended to move more quickly in proportion to their size. This didn't make sense to Galileo Galilei, though, because he knew that projectiles like cannons didn't move in straight lines, but rather in straight curves. There has been a popular story (perhaps perpetuated by Galileo's biographer) that Galileo dropped two canon balls (one 10 times heavier than the other) from the Leaning Tower of Pisa to refute this law of Aristotle. There still remains some controversy over whether Galileo was actually able to show this, but he did try experiments using inclined planes (rolling balls down planes at different heights) to better control for the rates of acceleration and quantitate his results (in a vacuum or no air resistance), items of different mass should fall at the same rate. A page from one of his notebooks can be seen below.



The year Galileo died was 1642, the same year that Isaac Newton was born. Newton's great insight was to realize that a single law might be able to explain an apple falling from a tree, the curving movement of a cannon, and motions of the planets.

Putting his observations with the concept of Universal Gravitation, Newton imagined that if a cannonball were shot horizontally and fast enough from an iman imagined mountaintop, then it might actually orbit the earth. For an animation of Newton's cannon on a mountain, click here



Newton - What Really Happened with the Apple
PBS: Galileo's Experiments
The Galileo Controversy
Galileo's Notes on Motion

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Previous Latin Sayings of the Week

"Soli deo gloria." - For the glory of God alone.


Christus resurrexit! Vere resurrexit! - Christ is Risen! He is risen, indeed!



"Lex malla, lex nulla." - St. Thomas Aquinas
(A bad law is no law.)


"Cantantes licet usque (minus via laedit) eamus. " - Let us go singing as far as we go: the road will be less tedious.


"Caelitus mihi vires." - My strength is from heaven.

"Magnificat anima mea Dominum, et exsultavit spiritus meus in Deo Salvatore meo" - My soul doth magnify the Lord, and my spirit hath rejoiced in God my Savior (Luke 1:45)

In Omnibus Ipse Primatum Tenens “That in all things He (Christ) might have the preeminence.” (Colossians 1:16-18)


"Qui bene cantat bis orat." - He who sings well, prays twice - (St Augustine)

"Nos fecisti ad te et inquietum est cor nostrum donec requiescat in te." -
Thou hast made us for Thyself, O Lord, and our hearts are restless until they rest in Thee. (St Augustine)

"Caelitus mihi vires
." - My strength is from heaven.

"Ubi caritas et amor Deus ibi est." - Where there is charity and love, God is there.

"Nisi credideritis, non intelligetis ."

Unless you will have believed, you will not understand. - St Augustine

"Deo vindice" - With God as Protector


"Credite amori vera dicenti." - Believe love speaking the truth. (St. Jerome)


De vitiis nostris scalam nobis facimus, si vitia ipsa calcamus." - If we tread our vices under feet, we make them a ladder to rise to higher things. (St. Augustine)

Dei gratia - By the grace of God

Verbum Domini Manet in Aeternum. - The Word of the Lord Endures Forever.

"Est autem fides credere quod nondum vides; cuius fidei merces est videre quod credis." - Faith is to believe what you do not see; the reward of this faith is to see what you believe. (St. Augustine)

"Deo iuvante" - with God's help

"Ut In Omnibus Glorificetur Deus." - That God may be glorified in all things

"Pax vobiscum." Peace be with you.

"Jubilate Deo." Be joyful in the Lord.

"Ille vir, haud magna cum re, sed plenus fidei." He is a man, not of ample means, but full of good faith.

"Facit enim mihi magna qui potens est." - For He that is mighty does to me great things.

"Oremus semper pro invicem." - Let us ever pray for each other.

"Distrahit animum librorum multitudo." - Seneca
A multitude of books distracts the mind.

"Nullam est nunc dictum, quod sit non dictum prius." - Terence
There is nothing said now, that has not been said before.

"Nosce te ipsum." - Plato
Know thyself.

"Non mihi, non tibi, sed nobis" - Not for you, not for me, but for us.

"Primum non nocere." - First, do no harm (Hippocrates)

"Est autem fides credere quod nondum vides; cuius fidei merces est videre quod credis." - Faith is to believe what you do not see; the reward of this faith is to see what you believe. (St. Augustine)

"Deo iuvante" - with God's help

"Ut In Omnibus Glorificetur Deus." - That God may be glorified in all things

"Pax vobiscum." Peace be with you.

"Jubilate Deo." Be joyful in the Lord.

"Ille vir, haud magna cum re, sed plenus fidei." He is a man, not of ample means, but full of good faith.

"Facit enim mihi magna qui potens est." - For He that is mighty does to me great things.

"Oremus semper pro invicem." - Let us ever pray for each other.

"Distrahit animum librorum multitudo." - Seneca
A multitude of books distracts the mind.

"Nullam est nunc dictum, quod sit non dictum prius." - Terence
There is nothing said now, that has not been said before.

"Nosce te ipsum." - Plato
Know thyself.

"Non mihi, non tibi, sed nobis" - Not for you, not for me, but for us.

"Primum non nocere." - First, do no harm (Hippocrates)

"Dei plena sunt omnia." - Cicero (All things are full of God.)