Tuesday, July 27, 2004
This was written by me and copied from the message board - please drop by to add your two cents worth!
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Back before the days when the world wasn't flat, there was a Centre Of The World somewhere, and it was usually not too far from where you were standing. Thesedays, we understand that we live on a globe, a sphere that orbits a star, our Sun. This understanding is a relatively recent thing, considering how long we've been able to point at the stars and communicate our feelings of insignificance to those around us willing to listen. Only in the past few hundred years has humanity worked out what goes on above our heads, and thus been able to work out where we are in relation to it all.
Until this time, the world was flat, and thus was the Word Of God. The Pope saw to it that those who did not see the world as the church saw it, had bad things happen to them. This ranged from excommunication, to house arrest, up to death in some cases. It was not a good idea to speak your mind, nor to explain what you saw in ways other than those approved by the authorities.
Galileo was a man who spoke out - explained what he saw in scientific terms, from first principles. It was hard to disprove, but deaf ears and blind eyes are the staple of those in power, and things were no different then. He was hounded by officials, forced to retract his findings, and lived his final days a broken man under guard in his own home. It was only recently that the current Pope officially apologised for what happened centuries ago, and thereby acknowledged that perhaps the world was not flat after all.
Understanding the way things move in our solar system was brought forward in leaps and bounds by Newton. He simplified things in his three laws of motion, which basically state that
(1) all motion stays the same unless something forces it to change, (anything travelling will ALWAYS remain at the same speed unless an outside force causes it to slow down),
(2) if something DOES force a change, then the acceleration is in proportion to both the force and the mass of the object, (for the same force, heavy stuff accelerates slower and to get the same acceleration for something heavy you need more force),
(3) for every action there is an equal and opposite reaction.
For that last one, stand in a small boat on a lake, next to a jetty. Now jump off the boat to the jetty. Your action of pushing yourself towards the jetty has pushed the boat in the opposite direction. The same thing happens when you walk - each step you take pushes you forward, but pushes the Earth in the opposite direction. So you're making the speed of the Earth's rotation change with every step! But remember the second law? You are small, and the Earth is very massive, so the change in acceleration you are causing to the planet is very, VERY small. So small in fact, that it's cancelled out by the drag of the atmosphere, as well as the steps of someone walking in the opposite direction to you.
So knowing how the planets interact with each other, using Newton's laws, it was possible to predict where planets would be with accuracy, and so make predictive almanacs. These tables of numbers helped navigators sail around the world, and not get lost (too often). They mapped the planet before we got into space and took pictures of how we KNEW the world looked already.
But maps have been around longer than the scientists of the Golden Age. Ptolemy wrote "The Geography" almost 2000 years ago, and Mercator advanced his ideas greatly, 1500 years later.
All these guys are heroes of mine.
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Back before the days when the world wasn't flat, there was a Centre Of The World somewhere, and it was usually not too far from where you were standing. Thesedays, we understand that we live on a globe, a sphere that orbits a star, our Sun. This understanding is a relatively recent thing, considering how long we've been able to point at the stars and communicate our feelings of insignificance to those around us willing to listen. Only in the past few hundred years has humanity worked out what goes on above our heads, and thus been able to work out where we are in relation to it all.
Until this time, the world was flat, and thus was the Word Of God. The Pope saw to it that those who did not see the world as the church saw it, had bad things happen to them. This ranged from excommunication, to house arrest, up to death in some cases. It was not a good idea to speak your mind, nor to explain what you saw in ways other than those approved by the authorities.
Galileo was a man who spoke out - explained what he saw in scientific terms, from first principles. It was hard to disprove, but deaf ears and blind eyes are the staple of those in power, and things were no different then. He was hounded by officials, forced to retract his findings, and lived his final days a broken man under guard in his own home. It was only recently that the current Pope officially apologised for what happened centuries ago, and thereby acknowledged that perhaps the world was not flat after all.
Understanding the way things move in our solar system was brought forward in leaps and bounds by Newton. He simplified things in his three laws of motion, which basically state that
(1) all motion stays the same unless something forces it to change, (anything travelling will ALWAYS remain at the same speed unless an outside force causes it to slow down),
(2) if something DOES force a change, then the acceleration is in proportion to both the force and the mass of the object, (for the same force, heavy stuff accelerates slower and to get the same acceleration for something heavy you need more force),
(3) for every action there is an equal and opposite reaction.
For that last one, stand in a small boat on a lake, next to a jetty. Now jump off the boat to the jetty. Your action of pushing yourself towards the jetty has pushed the boat in the opposite direction. The same thing happens when you walk - each step you take pushes you forward, but pushes the Earth in the opposite direction. So you're making the speed of the Earth's rotation change with every step! But remember the second law? You are small, and the Earth is very massive, so the change in acceleration you are causing to the planet is very, VERY small. So small in fact, that it's cancelled out by the drag of the atmosphere, as well as the steps of someone walking in the opposite direction to you.
So knowing how the planets interact with each other, using Newton's laws, it was possible to predict where planets would be with accuracy, and so make predictive almanacs. These tables of numbers helped navigators sail around the world, and not get lost (too often). They mapped the planet before we got into space and took pictures of how we KNEW the world looked already.
But maps have been around longer than the scientists of the Golden Age. Ptolemy wrote "The Geography" almost 2000 years ago, and Mercator advanced his ideas greatly, 1500 years later.
All these guys are heroes of mine.
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