Is it possible that the gravity that keeps our feet planted on the Earth is..

Discussion in 'Alternative Theories' started by jiveabillion, Jul 8, 2013.

  1. Fednis48 Registered Senior Member

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    ... huh? Defining gravity is a deep topic, but for the purposes of this discussion, it's enough to define it as "the attractive force between massive, uncharged bodies." In order for the Earth to orbit the sun, there has to be an attractive force between them. And in your description, there is no such force. "Centripetal force" is not an answer, because that's just a label for any force that causes circular motion.
     
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  3. Robittybob1 Banned Banned

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    Your definition of Centripetal Force is a bit short.
    It is Orthogonal to velocity and may not necessarily result in circular motion.
     
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  5. jiveabillion Registered Member

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    Right. But If I am moving at the same speed as the center of the Earth in one direction, I must be made to go slower than the center of the Earth for it to pass me in that direction, no? If I have something in front of me on a moving train, it's not going to just move behind me without something pushing it.


    I am moving in a straight line. The hill is not straight. I might be moving the same speed as the hill, but it is in my way.


    First, how did I get to be moving the same speed as the hill? Something had to push me. Secondly, the hill is in my way again.


    I believe I do understand it. You can't have circular motion without acceleration. The acceleration is outwards from the center of rotation. The velocity is tangent to the rotation, but only if you are attached to the center. I know how it works when you've got centripetal force, but I am saying that there is none in this scenario.


    When I say my body has momentum in the direction away from the D arrow, I mean that, if the Earth were to continue on it's path without me, I would appear to move in that direction. The Earth did not accelerate me towards point A or B, so why would I continue to move in that direction relative to the center of the Earth without the surface pushing against me? Without acceleration, my inertia should keep me right where I was, relative to the center of the Earth.

    As you know, I am no wiz when it comes to physics, but this his how I understand it would go with no gravity:

    Think about it like this. You are out in space like you are standing on an invisible plane (not the airplane type of plane, but the geometry type). Something pushes against your right foot from below.

    What happens to your body? It would rotate, right? Your body has inertia, so you feel the resistance of your body against that force.

    What happens to your left foot relative to the invisible plane? It would pass through it "downward".

    What if the plane was solid and your foot couldn't pass through it? You would tilt on your left foot away from the force pushing on you.

    What if the plane moved downward on the left as much as you were being pushed on the right? You wouldn't tilt relative to the plane, you would just stand there rotating and, relative to the plane, it would look as though nothing is happening, but you can still feel the push on both of your feet.

    What happens when you push away from the plane a little bit with your left leg? Your body's center of mass will shift towards the right leg. But you didn't accelerate your left side enough at the right angle to counter act the force on your right foot and tilt in the opposite direction. But that energy must be conserved, so where does it go? Well, your collision with the plane, even though you were already touching it, was elastic, so that energy comes right back and your left foot "falls" back to the plane.

    What happens if you push away a little bit and then the plane beneath your left foot disappears before you rotate back? You would "fall" past where the plane was.


    Now, take this scenario and replace the invisible plane with the surface of the Earth.
     
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  7. jiveabillion Registered Member

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    I've been thinking about Coriolis force for a few days. I've found some interesting interactive simulations here

    http://severewx.atmos.uiuc.edu/06/online.6.1.html - This one was good for visualizing throwing a ball towards the center of rotation.

    http://www.cleonis.nl/physics/graphlets/coriolis_effect.php - This one was really interesting because it illustrates how I had imagined a planet appearing to orbiting the Sun because of the Coriolis force of revolving around the galaxy and whatever the galaxy is revolving around.

    http://geosci.uchicago.edu/~nnn/LAB/DEMOS/coriolis.html - This one was also very interesting because it shows how something moving back and forth (a pendulum) can look as though it is moving in a circle or ellipse from a rotating reference frame. (Quicktime needed)


    Right now I am thinking about what something that is really moving in a straight line in space would look like to someone on the Earth. The answer is that it would look like it is moving in a curve. For something to actually look like it is moving in a straight line, it would have to actually move in a curve.

    I drew a picture on a piece of paper of an orbit with circles around it representing a planet at different times. Then I drew dots representing where a satellite would be when it is on either side of the planet at those times. After that, I drew a line intersecting those dots. What shape did I get? A wave.

    Now this was only on a 2 dimensional plane, which doesn't give me accurate enough information. This is why I really want a simulation or something that will show me exactly how a satellite moves relative to the Earth, Sun and Center of the galaxy that also lets me trace the paths and view them in 3D. The scale of this simulation would have to be enormous.


    Without that simulation, I'm stuck with the satellite moving in a wave.

    What else moves in waves? Energy.

    What is mass? Energy.

    What is a satellite made of? Mass.

    How does a wave move? Back and forth.

    What else moves back and forth? A pendulum.

    How does a pendulum moving back and forth look to a rotating reference frame? Like an ellipse.

    What else appears to move in an ellipse? A planet. - On that note, here is a cool video that shows how the Earth moves relative to the Sun http://www.youtube.com/watch?v=82p-DYgGFjI


    Now I am inclined to think that all energy moves in waves, no matter what size it is clumped together in as mass, and that a planet's wave just causes interference with the waves of other chunks of mass in the same medium (Space).
     
  8. origin In a democracy you deserve the leaders you elect. Valued Senior Member

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    I assme you are talkiing about the rotation of the earth here. The speed of the rotation of the earth will be added to your velocity of the orbit relative to a a 'fixed' point normal to the orbital plane.

    That makes no sense. When you are in your house sitting in your chair are the walls 'in your way'. Do you contunually slam into the walls? This seems to me more evidence that you are confusing velocity with acceleration

    You have always been moving at this speed from the moment of your conception. Please stop saying "the hill is in my way", it is nonsense and you sound, well, not good.

    I assume you are talking about this comment:
    "5. After reaching point B, does my body not have momentum in the direction away from the B arrow (towards the Sun) and still some momentum away from the A arrow?"

    In which case the answer is still no. All of your velocity due to the rotation of the earth will be in the direction of arrow C. So your combined speed of the orbital speed plus the speed of rotation means that you would move in a straight line in the same instantaneous direction of earth. The earth would continue to orbit the sun (for some reason not made clear by your scenario) but you would continue in a straight line moving ahead of the earth and moving out into space never to be seen again.

    Yep. It would be more of an arc though it is not like a force on one foot would make you rotate around your ankles.

    Yep

    Yep

    First of all you would not rotate with the plane because your center of mass in not on the plane. To have a force pushing on the your foot continually the the plane would have to be continually accelerating so your velocity would be constantly increasing. You would definitely feel the rotation because your head would have a higher velocity than your feet. More than likely you would blow your lunch after about 10 second.

    The first paragraph is too convoluted to address but that doesn't matter because there is one huge difference between the 2 scenarios and it goes back to your basic misunderstanding. In the plane in space there was a FORCE which means there was an ACCELERATION. On earth your scenario says there is NO FORCE only momentum and VELOCITY.

    Lets change the plane is space scenario to your idea where there is only momentum. Now you are standing on a plane rotating at a fixed velocity. In this scenario you will not feel motion but if you move your big toe the you and the plane will separate never to meet again.
     
  9. origin In a democracy you deserve the leaders you elect. Valued Senior Member

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    10,871
    Did this remind anyone else of the 'burn the witch scene' in Monty Python's The Holy Grail.

    Please Register or Log in to view the hidden image!

     
  10. jiveabillion Registered Member

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    252
    I still don't understand why my body's inertia wouldn't cause a normal force when the Earth pushes against me as the surface pushes me around it. At any point on the Earth, it just got through pushing me around from a totally opposite side of the center of the Earth, so why don't I have momentum in that direction that the Earth has to fight against to push me the other way?

    I really don't think we are thinking of it the same way.
     
  11. CptBork Robbing the Shalebridge Cradle Valued Senior Member

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    It reminds me how lucky we are that most people these days side with Galileo.
     
  12. jiveabillion Registered Member

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    How about you explain why you think that thought process is wrong instead of making fun of me? While you're at it, draw a picture from memory depicting the trail of a satellite relative to the center of the galaxy over 5 years, since you seem to know everything.
     
  13. origin In a democracy you deserve the leaders you elect. Valued Senior Member

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    I don't really know how to get he point across to you. A normal force results from a force (F=ma). There is no acceleration, there is no force. Nothing is pushing you. When you are on an airplane flying at 500 mph does your drink fly of the tray - NO there is no force from velocity it takes acceleration.

    You are managing to look at this exactly backwards. The earth is rotating and so are you. You want to go in a straight line. If gravity turned off you would go in staright line right out into space never to be seen again. There is only one reason that your momentum is not sending you off into space and that is gravity. Gravity is holding you on earth, overcoming the momentum of your body that is trying to send you out into space.

    That's for damn sure
     
  14. origin In a democracy you deserve the leaders you elect. Valued Senior Member

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    Aww chill out. I have taken alot of time to answer your questions to the best of my abiltiy. Your comments reminded me of the monty python scene and it cracked be up. What's the big deal.:shrug:
     
  15. jiveabillion Registered Member

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    The acceleration comes from the shape of the Earth. Maybe you should think of it as something that has just collided with the Earth from space.


    I can see it the way you are describing it, just as I always have. I just think you are looking at it wrong. How did my body get momentum? I was pushed by the Earth's surface. How is the Earth going to make my body move in any direction faster than any part it is pushing me with? I really don't think you've spent enough time studying the way the Earth moves and just assume that you are right because of everything else you know.

    This is why I hate discussing this in forum instead of in person. I can't explain anything using visual aids and make sure we are both on the same page before I move on. Right now I'm just extremely frustrated.
     
  16. jiveabillion Registered Member

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    I accept your round about apology. I am also a fan of Monty Python and you are not wrong about the comments being similar to the scene with the witch. I am just already frustrated and poking fun doesn't help.
     
  17. Fednis48 Registered Senior Member

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    725
    Good catch. Either way, though, "centripetal force" is clearly not a valid answer to the question "what force causes the Earth to orbit the sun?" Fortunately, jiveabillion said something that cuts right to the heart of what I was trying to get at:

    This is a good example for the same reason the Earth/sun system would have been a good example: the objects in question never touch each other, so without gravity they can't exert forces on each other. In fact, without gravity, the satellite is experiencing no significant forces of any kind. But according to your own drawing, it has to move in a wave pattern. Newton's 1st Law of Motion is that if no forces are applied to an object, it will move in a straight line. Therefore, the satellite has to be experiencing a significant force to move in the way it does. What could that force be if not gravity?
     
  18. jiveabillion Registered Member

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    What makes light move in a wave?
     
  19. origin In a democracy you deserve the leaders you elect. Valued Senior Member

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    I have no idea what that is suppose to mean.

    When something collides with earth, like a meteorite, then there is a decelertion of that object which of course will impart a force, but I am at a loss how that applies to the discussion.

    I am looking at it based on physics that is tried and true. The way I am looking at it allowed us to land on Mars - seems pretty good.:shrug:

    p = mv

    You are moving with the earths surface not being pushed by the surface. It is like riding in a car at a constant velocity - you are not being pushed!

    Huh?

    That is a bad assumption on your part. I am a big fan of astronomy and space. I have gound my own mirror for a telescope, I have taken an astronomy course (alas jsut one) and have purchased and read other astronomy course text books. I took physics courses to get my degree and had to perform experiemnts prove that the physics work - not just accept that they work.

    The truth is no matter how eloquently you were to explain your postion it would not change the fact that your proposals do not hold water. I truly believe that I understand perfectly what you are saying and I whole heartedly am convinced without a shadow of doubt that you are wrong.

    There is nothing wrong with being wrong - we all are now and again - the problem arises when we disregard information that shows we are wrong and cling to the false idea.
     
  20. gmilam Valued Senior Member

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    Yes, I even hunted for the clip... but realized that all I wanted to do was insult JAB's ignorance. So I decided to drop it instead.
     
  21. Fednis48 Registered Senior Member

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    See, it's comments like this that make me think you're being disingenuous and looking for a reaction, rather than actually trying to learn something. Your original question was whether Newtonian mechanics (momentum, rotation, normal forces, etc) could make people stick to the Earth without gravity. That was a reasonable question, and a number of posters have clearly explained why the answer is a definitive "No." What you seem to be suggesting now is a major change to Newton's Laws, such that an object will not necessarily move in a straight line if no force is applied, but can instead trace out a wave pattern. No matter how simple or how complex a physics problem is, you always have to start with the rules governing how things behave and go from there. If you assume that objects will behave in a way that violates basic physical laws in order to fit your hypothesis, your conclusions will be invariably wrong.

    To answer your question directly, light moves in a straight line, just like anything else. The electric field vector in a beam of light oscillates sinusoidally, so if we draw a graph with electric field strength on one axis and position on the other, the graph will look like a wave. But the electric field axis does not correspond to a spatial dimension, and light does not follow a wave-shaped path through space.
     
  22. CptBork Robbing the Shalebridge Cradle Valued Senior Member

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    And then we just have the wee little problem of explaining what made the pendulum swing in the first place.
     
  23. jiveabillion Registered Member

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    Good question.
     

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