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Is it really gravity?

  1. Sep 18, 2005 #1
    I am about to give a complaint against gravity; a fundamental law of nature. I have a problem on how it works and how they describe it. I think I have a better way of describing gravity.

    Note: This is a attempted complaint against gravity, not a theory. Also, I am not trying to disprove Einstien's relativity theory.

    Please note that this has nothing to do with mass; which produces gravity. The mass that produces gravity has nothing to do with this complaint; it is centripetal forces and centrifugal (inertial) forces that I am talking about. So therefore, I will not discuss anything about mass and its effects on gravity. Gravity is the attraction between two masses. I am giving a whole different concept that does not deal with that.

    Now we all know the Earth rotates. This is because an centripetal force is acting on it. Like all masses, it has inertia, so it is trying to resist motion.

    Now if you have been to a carnival, you might have been to a ride where you were pulled back against the wall because the whole ride was spinning very fast. That is because the ride created a centripetal force towards the ride, while a centrifugal force tries to push you outward. That creates artificial, or simulated gravity, which makes you pulled back against the wall like it was gravity.

    Well, the Earth does the same thing; it is creating a centrifugal force, which is actually its inertia while it is spinning, and while in orbit probably; but mostly spinning. Since it spins so fast, it creates a centrifugal force that creates artificial gravity. With that artificial gravity, everything within the earth is pulled down to the ground because the Earth created the centrifugal force to produce the artificial gravity.

    In the process, the Earth while it spins produces an centripetal force pulling things inward toward the center of the earth. In return, a reaction force, called inertia or centrifugal force pushes you out of the center of the earth just like the sensation you felt on that carnival ride I told you about. Therefore, "simuated gravity", which, in return, creates gravity, is created.

    As for other planets and the moon, the gravity, or "simulated gravity" would depend on the how fast the planet and the moon rotate. For example, the moon rotates once per orbit, which is why the "simulated gravity" is weak on the moon. Supposedly, the "simulated gravity" on Venus would be extremely weak because it rotates longer than its year; 243 earth days. The faster the
    planet rotates, the stronger the "simulated gravity". Inversley, the slower the planet rotates, the weaker the "simulated gravity".

    This probably better explains things like why we are sent in the opposite direction when we try to push on something in space and why we are not like that on earth.

    Like I said, this is an attempted complaint, not a theory against gravity.

    Any thoughts, criticisms, comments and objections are welcome.
  2. jcsd
  3. Sep 18, 2005 #2


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    At that carnival, you are projected outwards.
    Gravity projects you inwards.
    Therefore, gravity cannot be due to the rotation of the earth. If anything, the rotation of the Earth counters (ever so slightly) the gravitational attraction of the earth.
  4. Sep 18, 2005 #3
    Okay, I was referring to centripetal force, which produces artificial gravity. Let me explain.

    Imagine that you are in space, where you are inside a spaceship and you drop a book; it just floats. Now say the spaceship starts rotating. The ship produces a centripetal force, which is a "center seeking" force pulling you towards the walls of the ship as if you had weight, along with the ball. The effects are called artificial gravity.

    This is, in my complaint, why the earth spins; if the earth did not spin, there would be no centripetal force, so you would just float. Since it spins, you experience artifical gravity. The centripetal force directs things towards the center of the earth downwards while inertia (centrifugal force) directs things upwards in the radically outward direction.

    Does this make sense? If not, does anything in my complaint sound reasonable?
  5. Sep 19, 2005 #4
    I disagree with you, but thanks for the story.

    I tend to believe Gravity is caused by Micro and Macro conservation of energy (as a whole). This is the Universes way of extending its own life span, by conserving itself. I would recommend researching Conservation of Energy on a completed level, Maybe some of the geniuses in this forum can give a complete formulation to Micro and Macro Conservation of Energy and shed a little light upon the subject.

    Hope I don't get flamed for this one.

    Gerald L. Blakley
  6. Sep 19, 2005 #5
    Even though I have my own thoughts and am tending to stick with my story; I really like and respect your Idea of gravity cuttingedge. It seems like a cool thought. I think it's awesome.
  7. Sep 19, 2005 #6
    hi, maybe i missed this when i read your post...

    i understand what you mean when you describe the gravity felt when you are on the planets, or in the spacecraft etc. but how does your idea explain or adress the gravity existing between bodies, eg. two planets as opposed to a body on a larger rotating body.

    you might not understand my question so to go back to your example of the carnival ride, i understand how you are describing the gravity felt by those in the ride which is spinning, but how does it explain the gravity felt by people outside the ride towards it...

    sorry if this is a stupid question...
  8. Sep 19, 2005 #7
    As we know, black hole has an enormous gravitational force. The core of black hole is a singularity. If what you said is true, I think this will imply that the black hole is rotating at a very high speed, possible near the speed of light for a very big back hole. Whether that is true or not, I am not sure.
    p/s: Please forgive me if I have said something wrong.
  9. Sep 19, 2005 #8


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    However, it appears that it is more of a complaint against your misunderstanding of central force/circular motion in general, and NOT gravity in particular. The source of a central force can be ANYTHING, and it is typically E&M in nature (which ironically is an example you yourself had used). So this has nothing to do with your misunderstanding of gravity, but rather, circular motion.

    And if you have looked in classical mechanics texts such as Marion's, you'll find a whole chapter on motion in non-inertial reference frame. When YOU are rotating, you are no longer in an inertial reference frame. A number of "effects" will occur to make you think that there are other forces acting. Centrifugal and coriolis forces are just two common examples. A non-inertial reference frame is NOT a good frame to determine all the forces acting on a system - it will confuse you to which is the real force, and which is simply due to inertia of your body. There is no confusion here in terms of the physics. We know how to transform one from the other once we figure out what the inertial frame is.

    OK, when I first read your statement saying "Now we all know the Earth rotates. This is because an centripetal force is acting on it. Like all masses, it has inertia, so it is trying to resist motion.", I thought you simply meant "orbit" when you say "rotates". Now I know you meant "spinning". It is wrong to say that the Earth is spinning BECAUSE of a centripetal force! A top did not spin because of centripetal force - it is due to an external torque. However, it stays in one piece during its spinning motion due to the centripetal force via the EM force between the atoms and molecules of the body. The cause and effect here is VERY clear. It is spinning NOT because of the centripetal force.

    In the case of the earth, the initial conditions of the formation of the solar system have a significant influence on its spin. But this has nothing to do with a centripetal force.

    If the earth STOPS spinning, there will still be gravity. This is sufficient to disprove what you just said here. The classical newtonian gravity depends only on the mass distribution and the location of the field point. There are no "spinning" of any kind that is require to generate this gravity. If you are claiming otherwise, then you are contradicting gravitational laws and will be required to submit this to the IR section.

  10. Sep 19, 2005 #9


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    No! The "artificial gravity" produced like that is "centrifugal", toward the outside of the ship, not "centripetal", toward the inside.

    No! spinning does not produce "centripetal" force! That force has to be a centrally directed force that is already there whether there is rotation or not! You could still have rotation without centripetal force- but everything would fly off because of "centrifugal" force (inertia).

    Sorry, not a whole lot! "Centrifugal" force is a fictitious force which is, really, as you say, inertia. "Centripetal" force is the force preventing something from moving in a straight line and is there whether there is rotation or not.

    If you tie a weight to a rope and whirl it around your head, tension in the rope provides the centripetal force keeping it from flying away. If you just let the weight hang at your side that same tension in the rope prevents it from falling down. The force is still there, whether you are swing the weight or not.
  11. Sep 19, 2005 #10


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    In reality, the spinning of Earth acts in the inverse sense of what you think. Things weight a little less because of Earth's rotation. If there was no gravity, we would be sent in space, due to inertia. Gravity provides the centripetal force that keeps us on the surface.
    Rockets launch facilities are situated the nearest possible to the Equator, in order to make use of Earth's rotation for boosting launch. That is why the USA use Florida, Russia uses Baykonur, France uses Kourou at the Guyana and Brazil uses Barreira do Inferno.
  12. Sep 19, 2005 #11


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    modeman -- Look at the numbers. Most freshman physics books give you everything you need to know to show that there's no way the "fictional forces" due to rotation are strong enough to simulate gravity--they also have the wrong dependence on distance, at least for a constant angular speed..

    Reilly Atkinson
  13. Sep 19, 2005 #12
    What I am trying is that inertial forces, mostly inerita is what pulls us to the ground.

    I made a mistake when I said we would be weightless if the earth stopped rotating. We would be sent into space because the earth would produce no more centripetal force to direct everything to the ground. As the centripetal force is removed, the inertia, centrifugal force, or whatever the ground produces sends everything moving along a straight line.

    The centripetal force is the action force of newton's third law. The centripetal force is balanced by a reaction force, an effect of inertia called the centrifugal force. Objects do not fly off by inertia/centrifugal force when released; but when the centripetal force is removed, objects move in a straight line.

    As for the planets, like I said, it depends on the rotational/spin rate of the planet. The planet's rotational speed produces the centripetal force to create the artificial graivty. For the rotational speed of earth, for example, depends on where you are, since the circumference of a circle increases, a single point along it has to travel faster to complete a revolution in the same amount of time. At the equator, it is 1,038 miles per hour. At mid latitudes, the rotational speed decreases.

    Plus, the gravity we know of gets weaker when we move towards the equator
    And gets stronger when we move towards the poles. In this complaint, the centripetal force created by the earth is proportional to the speed of the earth, but is inversely proportional to the radius of it. That would best explain why you are heavier at the poles and lighter at the equator because at the equator, the radius is large while the radius at the poles is small.

    Here are the websites I got to help me out.


    http://www.pschweigerphysics.com/ibcirc.html [Broken]



    http://wise.fau.edu/divdept/physics/jordanrg/LLS/lecture13/VG19.GIF [Broken]

    Now, are there still objections on my complaint?
    Last edited by a moderator: May 2, 2017
  14. Sep 19, 2005 #13


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    None of those references back you up. Remember, you are talking about an issue that has been well understood for centuries, and is an important factor in many ballistics calulations. Further, the potential of gravity goes as 1/r, that for the centripital stuff goes as 1/r*r. How do you account for planetary orbits?

    Do the numbers, as I suggested. Your second reference gives you everything you need.
    If the earth stopped rotating slowly, your feet would stay on the ground. If it stopped quickly, you would be in trouble. Why?

    Reilly Atkinson
  15. Sep 19, 2005 #14
    Okay, so if there was a centripetal force on the earth...something would have to create that force. That force might be.....gravity.....
    Alright, here's the deal, guys; just prove to me how gravity pulls us in to keep us from flying off earth and if nessesary; show how it works as a centripetal force against the effects of inertia. If the proof is complex enough, I will forget about my complaint.
  16. Sep 20, 2005 #15


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    Yes: its getting dangerously close to being gibberish. Did you read anything that anyone wrote in response to your opening post? The things you are saying are beyond wrong - they aren't internally consistent, they make little sense, you are misusing most of the physics terms you are using, and you contradict yourself even while trying to go after your own misconceptions about gravity.

    Stop talking and start listening or you will learn nothing.

    The existing theory correctly explains the shape of the earth and the variations in weight we see. It correctly predicts the weight of an object on the moon. It allows us to put satellites in orbit and send space probes to the outer reaches of the solar system. It works. Drop your idle speculations and learn it. The math isn't even that hard - most people do it in high school. Using Newton's law of gravity, calculate the weight of an object at the equator. Using the equation for circular motion, calculate the effect of the earth's rotation on the weight of that object.
    Last edited: Sep 20, 2005
  17. Sep 20, 2005 #16


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    Permit me to respond to your question with another question, modeman. Do you think your 'weight' [not to be confused with mass] would be different if the earth did not rotate with respect to the stars? [i.e., the location of stars at night never appear to change.] What if the sun appeared to be 'fixed' in the sky? Would that make your weight appear to change compared to this earth, where the sun moves full circle across the sky every day? Propose and quantify what experimental results would confirm or refute your theory. It's hard work, but that's how real science is done, modeman. [Apologies if I merely rephrased what has already been said, I glossed over the replies.]
    Last edited: Sep 20, 2005
  18. Sep 20, 2005 #17

    Even though I was making a complaint, I knew how the current theory of gravity would describe the fact that we are pulled toward the earth. I accept gravity (like all of you), I just thought centripetal forces were a better explaination. I do not have a problem with gravity.

    Also, you did not listen. You were supposed to prove to me how gravity attracts us to the ground (I know that, but to prove it in terms of mass attraction and how my complaint dos not work) and if nessesary, how gravity acts as a "centripetal force". I see that it is gravity and not rotation, but tell me how. Also, do the math.
  19. Sep 20, 2005 #18


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    No, you do the math. Show exactly where in newtonian gravitational law is there a requirement for something to rotate or spin. This is the ONLY way for you to show that you're not up the creek without a paddle.

    Secondly, you made a rather amusing error common to high school students just learning rotational motion. You said:

    If the "centripetal force is balanced by the reaction force.... centrifugal force", then our NET force will be ZERO, ya? If that is true, then why are we still moving in a circular motion? Last time I checked Newton's First Law, it says that when there are no net force acting on an object, the object will either be stationary, or moving with a constant velocity. You and I are NOT moving with a constant velocity, nor are we stationary. We are moving in a circular motion. And in case you missed reading about circular motion, it is an ACCELERATED motion towards the center.

    Furthermore, what you just said doesn't make sense at the poles. There's hardly any "centripetal" forces there. But I don't see antartica flying off the face of the earth. A couple of my friends used to work on AMANDA at the south pole ice caps. They didn't report weight loss of any kind.

    As russ has said, this is bothering on gibberish that any informed high-school physics student could see through. This thread will end if it still can't work itself out of physics 101. If you believe you are correct, then submit it to the IR section.

  20. Sep 20, 2005 #19


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    We were supposed to? Who supposed that? I doubt that anyone knows how gravity "works"- you were the one who was claiming gravity could be explained by rotation and everyone has been pointing out why your arguments are wrong. You seem to be considerably confused as to what centrifugal and centripetal force are.

    Since you mention artificial gravity in a space station caused by rotating it, do you really understand how that works? Suppose we had a spherical "space station" and rotated it about an axis in order to produce "artificial gravity". What would the force be at the poles (i.e. at the axis of rotation). Would the people stand on the inside or outside of the wall? If the radius of the sphere were greater would the force be greater or less?

    Do you see how that differs from what happens on the earth?
  21. Sep 20, 2005 #20


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    Amplification: though I did say that you should do the math, modeman, (I certainly won't unless your attitude changes), it seems your misunderstandings are so basic as to make the math pointless until you can grasp such simple aspects of this issue as what Halls just posted above. If you can grasp those points, you'll see that your idea falls apart even before you try to apply any math to it.

    That is self-contradictory in several ways. If you didn't have a problem with gravity, you wouldn't be asking these questions. And if you understood/accepted the current model for gravity, you'd understand that it is (so far) perfectly in agreement with what we observe (to within the limits of our ability to measure these things). Then you'd see that it is pointless ot look for something "better" than perfect.
    Last edited: Sep 20, 2005
  22. Sep 21, 2005 #21
    This has been an odd thread to read. Could a centripetal force really cause our weight on the surface of the Earth? Absolutely, however, the source of the centripetal force is gravity! Replacing gravity with gravity is a somewhat novel idea. I hope that the originator of the thread has learned something from the excellent replies that he has received and that he continues to think about physics.
  23. Sep 24, 2005 #22
    Oh dear; the best way to explain something is to use as few words as possible (so that he doesn't miss anything) and to use more equations and more pictures. The idea here is not to redicule him for ineptness nor to blame him for not reading your post.

    The fault goes entirely to the instructors ("super mentors") for long and deriding posts. I have a hunch that its possible to set things straight for modeman while following this criteria.
  24. Sep 25, 2005 #23
    And herein lies the crux of the problem. Can't say I know what Modeman is talking about. It doesn't make him wrong, (however) I have firm suspicions that he is. My suggestion might be that Modeman draw up his thoughts so we can understand them, just as he expects others to do regarding gravity.
  25. Sep 25, 2005 #24
    Nobody knows how gravity works so that part is right (i.e. nobody knows the mechanism of gravity, only a description, and a relativistic one at that!). Deriving a conclusion from a piece of information that one person carries does not seem possible to me.

  26. Sep 26, 2005 #25


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    Says modeman

    Also, you did not listen. You were supposed to prove to me how gravity attracts us to the ground (I know that, but to prove it in terms of mass attraction and how my complaint dos not work) and if nessesary, how gravity acts as a "centripetal force". I see that it is gravity and not rotation, but tell me how. Also, do the math

    (RA) Where is it written that we should jump to your tune, when you will not do your homework and freshmen physics? I would hope, frankly, that you are pulling our chains just for the sake of an amusing tweak. Any alternative is difficult to contemplate.

    No one, repeat no one, is supposed to do anything, let alone pay attention to your commands. But fair is fair -- you do yours, then if you are lucky, maybe someone will do theirs.

    So, you are perhaps, King of Physics?

    Reilly Atkinson
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