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8 April 2010

My Essay (Part IV) - Clockwork Universe

The moon - Like any other celestial object are bounded by gravity. Gravitational attractive force is pulling moon closer to earth but this force is countered and balanced by the outward rotational (centrifugal) force which results an orbit.

Because of the three immutable laws, Newton is able to synthesise a new equation that describes the motions of planet. This is what we affectionately call “Newton’s Universal Law of Gravitation”. This law is powerful because it is so short – barely five characters in the equation. Enough to predict how much force it needed to propel a rocket to space, how much force pulls us on the surface of the earth, how much force the moon need to stay in orbit. In fact, Since the discovery, the equation is still being used now by all space agencies to launch anything into orbit! Here’s the nasty bit:

Here’s how it works. The F which means the attractive force between two bodies in space is equal to the product of mass 1 (object A in space) and mass 2 (object B in space) divided by the square of distance between them. Do not mind the G. It’s a constant which has a fixed value. What this means is that for any two objects in space, now there’s a formula to apply and we get the value for the forces between them. The motions of everything in this universe became calculable.

Newton’s law stated that gravitation is always attractive. That is bodies in space will always attract each other no matter what they are made of. This has a logical flaw which is pointed out by Richard Bentley, another brilliant thinker at his time, sending a letter to Newton. That innocent looking letter packed with such a load that blows Newton back thinking about this: “If all things in this universe are attractive in nature, shouldn’t the stars all come onto each other crashing? The universe is unstable.”

In reply towards Bentley’s letter at 1691, Newton argued that such case will only happen if there are finite number of stars and finite volume of space between them. So, he proposed that in the universe, there should be infinite stars separating from each other in equal distances and space is infinite in volume. Also, God has to intervene once in a while to nudge the stars so that they will not move towards one another destroying the stability of the universe.

Newton’s law is elegant, in the sense that the law is simple yet it could predict the motions of stuff in our experiences. Take a stone and throw for example. Using Newton’s law (knowing the mass of the stone) we could predict how high the stone will fly and with a computer, we can draw a path of its precise trajectory. Ironically, it was precision that render Newton’s law at describing some astronomical observations, wrong.


Anonymous said...

"Also, God has to intervene once in a while to nudge the stars so that they will not move towards one another destroying the stability of the universe."

are those your words or Newton's pray tell.

Andrew C. said...

"Gravity explains the motions of the planets, but it cannot explain who set the planets in motion. God governs all things and knows all that is or can be done." - John H Tiner. Isaac Newton: Inventor Scientist and Teacher, Mott Media, ISBN 0-91513406-3

"Opposition to godliness is atheism in profession and idolatry in practice. Atheism is so senseless and odious to mankind that it never had many professors." - Brewster, Sir David. A Short Scheme of the True Religion, manuscript quoted in Memoirs of the Life, Writings and Discoveries of Sir Isaac Newton Edinburgh, 1850.

"Sir Isaac Newton and his followers have also a very odd opinion concerning the work of God. According to their doctrine, God Almighty wants to wind up his watch from time to time: otherwise it would cease to move. He had not, it seems, sufficient foresight to make it a perpetual motion." - Leibniz, first letter, in Alexander 1956, p. 11

or perhaps this will suffice;

"This most beautiful system of the sun, planets, and comets, could only proceed from the counsel and dominion of an intelligent Being. [...] This Being governs all things, not as the soul of the world, but as Lord over all; and on account of his dominion he is wont to be called "Lord God" παντοκρατωρ [pantokratōr], or "Universal Ruler". [...] The
Supreme God is a Being eternal, infinite, [and] absolutely perfect." - Principia, Book III; cited in; Newton’s Philosophy of Nature: Selections from his writings, p. 42, ed. H.S. Thayer, Hafner Library of Classics, NY, 1953.

Or you can refer to this:

Third paragraph, sixth line.

I hope I've done enough citations to support my statements..

jefferyseow said...

Nice blog. I have not really done anything with both of mine. LOLz.

Anonymous said...

when will the next installment of your essay be published mrPhysicist?

Anrdrew.C said...

Jeffery: Update then! :D

Anonymous: WOW. Flattered I am that you still follow this blog despite it's lack of updates for so long...

But I'll update it as soon as my semester starts. Which is mid july. Hope to hear more from you later. ;)

jefferyseow said...

hehehe. bit bit lazy lor. i do give updates. on facebook. LOLz.