Q&A: The Earth's Rotation on Its Axis
The Earth's Rotation on Its Axis
Question
Hello,
I saw that there was discussion about the relationship between the Earth and the sun.
I wasn’t sure that if I added a question there you would see it, so I opened a separate question.
I saw that regarding the relationship between the Earth and the sun you said these are just different definitions, and it can be defined this way or that way.
Can one define that the Earth does not rotate around itself? The problem is that if so, the entire universe revolves around us once every day, and that involves speeds higher than the speed of light. Thanks
Answer
I see every comment everywhere.
Indeed, from a kinematic standpoint that is possible. And true, the speed can be greater than the speed of light. In relativity there are more complicated transformations between frames of reference in which you would not get a speed greater than the speed of light.
Discussion on Answer
When a car drives on a road,
can one say that the road is moving?
Both.
It is indeed strange, but it is a question of definition. Think about two bodies, one of which revolves around the other. If you sit on the revolving body, you will see the first one revolving around you. The question is where you are sitting.
The question of energy is a subtler matter, but it belongs to dynamics (forces, how the rotation happens) and not to kinematics (the mathematical definition of motion).
With a car and a road too, it is only a question of definition.
The point is that the concept of motion itself is not absolute. Motion is always defined relative to something. You cannot say, “the body moves.” You have to say, “it moves relative to x.”
From Wikipedia:
In December 1613 Galileo wrote a letter to his former student Benedetto Castelli, and in the spring of 1615 he wrote the "Letter to Christina of Lorraine" (which was also addressed, indirectly, to Church theologians). In these letters Galileo wrote that he saw the heliocentric model as physical reality and not merely a tool for mathematical calculation, as this model was regarded by the Church in those days. He further argued that the passages in the sacred scriptures that speak about the course of the sun should be interpreted allegorically and not taken literally. In addition, he expressed his hope that the Church would change its position regarding the prohibition of the Copernican books, because in his opinion the Christian faith must not rely on the facts of science.
Does this fit with what the Rabbi said?
What is the question? Is this a reading-comprehension question? Why should I care whether Galileo agreed with me or not?
To the Rabbi,
Is the issue whether the sun revolves around the Earth or the Earth around the sun?
Or is the issue the sun around the Earth or the Earth around itself?
In addition, how can one say this is a question of definition? After all, it is a matter of reality; motion is real.
So one moves and one is at rest?
Or maybe they both do half the way?
After all, motion has to come from energy.
So on which one is the energy acting?