We know that there is a gravitational force between the earth and the sun, which forces the earth to move around the sun. However, how can I explain to the primary school students the reason of not falling of the earth on the sun? They only know the gravity force. They say that we stick on the earth and we can not fly due to gravity force.
Actually the Earth is endlessly falling into the sun! The easiest way to demonstrate this is by attaching a light mass (or a ball) to one end of a rope or a string and rotate the other end above your head such that the mass orbits around your head in a horizontal plane. The rope is always pulled straight by the centrifugal force of the mass, you can demonstrate that force by letting go the rope and the ball flies off in a straight line just as the Earth would do if the sun were not there.
Flying through space is falling to the sun and miss.
Take a magnet and show that it attracts metal screws and nuts. Then let them drop a nut past a table on the floor. Then let them place the magnet at the edge of the table and let them repeat the experiment. The nut will either get caught by the magnet or end up on a different place on the floor. It started falling to the magnet. When it falls on the floor it did miss the magnet. Hitting the magnet or missing the magnet depends on the initial conditions, like the direction and speed of the nut close to the magnet.
With the magnet we have two forces. Magnetic and gravity force. With the sun we have one force. If we start with the right direction of falling and the right speed (initial conditions), then we keep falling to the sun and mis. There are many different paths possible around the sun. Only the paths that are stable can keep objects long enough to become a planet and support life. The other paths did either make objects fall into the sun or onto the planets.
I hope this helps them to understand it. Of cause the rope example above is also important.
Paul Gradenwitz
Hi Majid!
The answer is very simple: the earth does not fall on the sun just because it moves quickly enough (inertia law) . The same would happen with any object quickly ejected from the ground, but unfortunately the speed that we get during, for example, long jump is not enough :-). Greetings from Poland for your students and You
Jerzy
The approach that I use with the earth-moon system is that the moon is continuously falling around the earth. For each unit distance of fall towards the center of the earth there is a compensating motion tangent to the moons orbit such that the moon, indeed, falls around the earth. The earth likewise falls around the sun.
Let the children describe what happens if they throw a ball. What line does it follow? Let them assume they had more power. What happens then? Finally you can conclude with them that if the throw the ball with extreme power, it will follow an orbit around the earth.
Very good books: The Feynman Lectures on Physics! In the Volume I he said about Gravitation: "the gravitational effects are so weak that the need for a quantum theory of gravitation has not yet developed"! I discovered a Quantum Gravity theory! “Starting from STR, it is not possible to find a Quantum Gravity theory” Adrian Ferent
“Einstein was on the wrong way: from STR to GTR” Adrian Ferent
“Starting from STR, Einstein was not able to explain Gravitation” Adrian Ferent
“Starting from STR, Einstein was not able to explain Gravitation, he calculated Gravitation” Adrian Ferent
“Einstein's equivalence principle is wrong because the gravitational force experienced locally is caused by a negative energy, gravitons energy and the force experienced by an observer in a non-inertial (accelerated) frame of reference is caused by a positive energy.” Adrian Ferent
“Because Einstein's equivalence principle is wrong, Einstein’s gravitation theory is wrong.” Adrian Ferent
“Because Einstein’s gravitation theory is wrong, LQG, String theory…are wrong theories” Adrian Ferent
“Einstein bent the space, Ferent unbent the space” Adrian Ferent
“Einstein bent the time, Ferent unbent the time” Adrian Ferent
“I am the first who Quantized the Gravitational Field!” Adrian Ferent
“I quantized the gravitational field with gravitons” Adrian Ferent
“Gravitational field is a discrete function” Adrian Ferent
“Gravitational waves are carried by gravitons” Adrian Ferent
In STR and GTR there are continuous functions.
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