- #1
xwolfhunter
- 47
- 0
Sorry for the ineloquent title, I had some space issues.
First, a little backstory, as this is my first post and I'm new to the realm of physics.
I am currently taking an AP physics class at my high school, and as I am also taking AP calc, I got interested in some of the historical figures responsible for these branches of reasonable thought. After a while, I got into Galileo, and am reading his Dialogue Concerning the Two Chief World Systems. As I was reading this earlier this evening, a sentence about the natural state of the Earth sparked my imagination into asking this question: What if people at some point in time thought that gravity was explained by a constant upward motion in the ground, before it was proven that the Earth is spherical? This got me into thinking about the effects of actual Earth movement on the forces we experince, and I came to a question: How do our relative gravities change throughout the day (excluding the presence of the moon, since I can't visualize that too and wanted this to be a simple thought experiment)?
Basically, since I'm sure this has been thought of by every physics major after learning about centripetal force and gravitational force, the two forces that I thought applied to the situation, I thought I'd come here to see if I'm right. So here I shall propound (a word I picked up from the Galileo book :) my thoughts on the subject:
First, I decided to exclude all points on the globe except for the equator, since it was the easiest to visualize and I thought the experiment would apply to all infinitely small horizontal slices of the earth, except for of course the points at the equators.
I then decided that the Earth's rotation in the experiment would be along the y-axis, since it was simpler to visualize and still, I think, hold's true even though the axis does tilt, since the x-distance from the sun still changes as time passes.
Then I decided to see if the Earth's rotational motion would affect the outcome of the experiment, to which I thought no, since it is equal along all points at which it can be measured, again, on a single infinitely small horizontal slice of the earth.
The last point which I took into account in setting up my visualization was this: That the Earth's rotation would take one year to complete, simplifying the scenario further, giving me only two points to keep track of, namely the point closest to the sun, and the point furthest; and that it would ultimately not affect the outcome of the experiment as at noon one is at the former point; and that at midnight, the latter.
So, excluding rotational forces and following all those restraints which I have applied to the experiment, I thought I should decide which forces apply to the situation. Knowing only basic classical, I would guess, physics, I came to the conclusion that, to my obviously limited knowledge, only centripetal and gravitational forces would apply.
The rest of the experiment is actually quite simple. I decided that, as both points follow the same period, the outside one obviously must have a greater centripetal force, and the inside one a smaller. I also decided that as the force of gravity is determined in part by distance, the closer point must be experiencing more force due to gravity than the outer point.
Now came the point at which I decided the outcome of the experiment. As I did not know the points which will be discussed momentarily, I could not lean more heavily on one outcome than the other, so as I stand currently the probability of either outcome, or a third to be discussed in the next sentence, is equal. But I found it to be that if the force of the sun's gravity were more powerful than the centripetal force on earth, we would be heavier during the night than the day, since the sum of the forces of gravity on the two would be greater than those of the centripetal force; but that if they were equal, the directional nature of the forces would cancel out exactly, leaving an [itex]\chi[/itex]-[itex]\chi[/itex] situation; and if they were lesser, we would be heavier during the day than the night, as the sum of the centripetal forces on the two points would be greater than those of the sun.
This is how I stand currently, and I would appreciate knowing which of the forces on Earth is stronger, that of the sun or that of the centripetal force. Also, and as I am a rank beginner at this I would not doubt it in the least, if there is a flaw in my logic or a concept I have failed to grasp properly, I would appreciate it being pointed out to me as well.
Thanks!
-XWolfHunter
First, a little backstory, as this is my first post and I'm new to the realm of physics.
I am currently taking an AP physics class at my high school, and as I am also taking AP calc, I got interested in some of the historical figures responsible for these branches of reasonable thought. After a while, I got into Galileo, and am reading his Dialogue Concerning the Two Chief World Systems. As I was reading this earlier this evening, a sentence about the natural state of the Earth sparked my imagination into asking this question: What if people at some point in time thought that gravity was explained by a constant upward motion in the ground, before it was proven that the Earth is spherical? This got me into thinking about the effects of actual Earth movement on the forces we experince, and I came to a question: How do our relative gravities change throughout the day (excluding the presence of the moon, since I can't visualize that too and wanted this to be a simple thought experiment)?
Basically, since I'm sure this has been thought of by every physics major after learning about centripetal force and gravitational force, the two forces that I thought applied to the situation, I thought I'd come here to see if I'm right. So here I shall propound (a word I picked up from the Galileo book :) my thoughts on the subject:
First, I decided to exclude all points on the globe except for the equator, since it was the easiest to visualize and I thought the experiment would apply to all infinitely small horizontal slices of the earth, except for of course the points at the equators.
I then decided that the Earth's rotation in the experiment would be along the y-axis, since it was simpler to visualize and still, I think, hold's true even though the axis does tilt, since the x-distance from the sun still changes as time passes.
Then I decided to see if the Earth's rotational motion would affect the outcome of the experiment, to which I thought no, since it is equal along all points at which it can be measured, again, on a single infinitely small horizontal slice of the earth.
The last point which I took into account in setting up my visualization was this: That the Earth's rotation would take one year to complete, simplifying the scenario further, giving me only two points to keep track of, namely the point closest to the sun, and the point furthest; and that it would ultimately not affect the outcome of the experiment as at noon one is at the former point; and that at midnight, the latter.
So, excluding rotational forces and following all those restraints which I have applied to the experiment, I thought I should decide which forces apply to the situation. Knowing only basic classical, I would guess, physics, I came to the conclusion that, to my obviously limited knowledge, only centripetal and gravitational forces would apply.
The rest of the experiment is actually quite simple. I decided that, as both points follow the same period, the outside one obviously must have a greater centripetal force, and the inside one a smaller. I also decided that as the force of gravity is determined in part by distance, the closer point must be experiencing more force due to gravity than the outer point.
Now came the point at which I decided the outcome of the experiment. As I did not know the points which will be discussed momentarily, I could not lean more heavily on one outcome than the other, so as I stand currently the probability of either outcome, or a third to be discussed in the next sentence, is equal. But I found it to be that if the force of the sun's gravity were more powerful than the centripetal force on earth, we would be heavier during the night than the day, since the sum of the forces of gravity on the two would be greater than those of the centripetal force; but that if they were equal, the directional nature of the forces would cancel out exactly, leaving an [itex]\chi[/itex]-[itex]\chi[/itex] situation; and if they were lesser, we would be heavier during the day than the night, as the sum of the centripetal forces on the two points would be greater than those of the sun.
This is how I stand currently, and I would appreciate knowing which of the forces on Earth is stronger, that of the sun or that of the centripetal force. Also, and as I am a rank beginner at this I would not doubt it in the least, if there is a flaw in my logic or a concept I have failed to grasp properly, I would appreciate it being pointed out to me as well.
Thanks!
-XWolfHunter