Pushing space

Discussion in 'Astronomy, Exobiology, & Cosmology' started by tashja, Apr 1, 2011.

  1. tashja Registered Senior Member

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    Michio Kaku said in ''Discover Presents Einstein,'' Spring 2009 (page 10), that:

    ''...if you put a bowling ball on a bedsheet and shoot a marble past it. The marble will move in a curved line. A Newtonian physicist would say that the bowling ball exerts a ''force'' that ''pulls'' on the marble, making it move in a curved line. A relativist would say that the ball curves the bedsheet and that the beedsheet ''pushes'' against the marble.''

    ''Now replace the bowling ball with the sun and the marble with Earth. By analogy, gravity does not pull the Earth around the sun. Rather, the sun bends space around it, and curved space pushes Earth so that it moves around the sun.''

    ''Gravity does not pull you into a chair; space pushes on you creating the feeling of weight.''


    Qs: Is space pushing the Earth in a preferred direction? How does space decide in which direction a planet is going to be ''pushed.''
     
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  3. tashja Registered Senior Member

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    I'm thinking something like this:

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  5. Emil Valued Senior Member

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    I feel obliged to defend Einstein.

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    Einstein never said something like that. He said the opposite. (Different people have added something to the Theory of Relativity, or have made different interpretations.)
    ....................................................................................Theory of relativity,Scope
     
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  7. tashja Registered Senior Member

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    I am nonplussed.:shrug:
     
  8. Emil Valued Senior Member

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    If you're interested, please read this.
     
  9. Acitnoids Registered Senior Member

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    Space can't "push" anything. In truth the Earth is in a free fall around the Sun and the path that it follows is caused by the Sun's mass warping the space around it. One of Einstein's greatest revelations stated that a body in free fall will experience the same weightless sensation as an astronaut floating around their shuttle in space (I'm paraphrasing of course). So then why hasn't the Earth fallen into the Sun yet? This has to do with the direction that a planet is falling. When a star begins to form it starts to rotate and in the process it pulls in dust and gas. This matter begins to rotate with the embryonic star which creates angular momentum. That momentum then causes the matter to flatten out into a disc (a.k.a., accretion disc). It is from this concentrated matter that planets form. So its angular momentum that decides which direction a planet will orbit. That being said, there have been observations of distant solar systems were some of their planets orbit in opposite directions. They're still trying to figure out why this is so but it does prove that there is no preferred direction that a planet must orbit.
    .
    To Summerize:
    1: The sensation of free fall is caused by the warping of space (according to Einstein).
    2: In order for a planet (or satellite or moon) to obtain a stable orbit its forward motion must perfectly match its in-falling motion towards the center of a massive body. If the objects forward motion is to great then it will be flung out into space but if its forward motion is to small then it will fall into the more massive body (like the marble analogy).
    .
    The problem with the bowling ball and marble analogy is that the bed sheet creates friction on the marble. If you could take that friction away then it would be possible to obtain a stable orbit around the bowling ball.
     
  10. OnlyMe Valued Senior Member

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    Should have been, "In theory...". Even if a theory works, it is still a theory until proven. Observation and experiment support the involved theory, but haven't yet proven it.
     
  11. SciWriter Valued Senior Member

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    One could think of spacial expansion as being the 4th dimension of 'gravity' that pushes you up.
     
  12. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    Huh?
    "4th dimension of gravity"?

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  13. SciWriter Valued Senior Member

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    I stole the idea from Kaduorkian (sp?) who has a thread here and on some other forums. There were even signs and posters hanging in the subways and around the city, way back, saying "Gravity is the 4th Dimension".

    Darned if I kind of felt the earth or the floor pushing up on me when thinking of it that way, but, of course, that's not a good test of it.
     
    Last edited: Apr 2, 2011
  14. James R Just this guy, you know? Staff Member

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    The explanation in the OP from Kaku is not very good and quite misleading. He ought to know better.
     
  15. nitram22 Registered Senior Member

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    no fabric in space

    The SPECULATION that space can be viewed as "fabric" with the way objects affect its structure has been well defined to the point that many believe this theory to be true. Then again the earth was flat.
    One of the things that brought about this theory was upon observations as distant stars circled each other, when one would pass behind the other the eclipsed star seemed to get distorted as it passed behind the other. This is thought by many to be space itself being bent or warped around the star. Sounds plausible.
    To me it makes no sense.
    On a desert road in the summer the heat distorts your view from the distance as well. But it is not bending the fabric of the road now is it?
    Sometimes if you over think things, you can miss the simplicity of the truth.
    It's matter that distorts the view, not bent space. Think of it more like displacement, as water. The water is displaced around an object, but it's not bent. Space itself has no physical properties that affect moving objects as water would. But it makes a little more sense. The anomalies of the visual distortion is an optical illusion due to the "atmospherical heat" emitted from the star.
    Now I don't have time right now to give you more supporting facts to this. But I will be back the give more to a better set of proofs.
     
  16. James R Just this guy, you know? Staff Member

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    nitram22:

    Ok. Let's assume you're right and space doesn't really bend.

    1. How do you explain observed features such as Einstein rings and multiple images of the same galaxy (currently put down to "gravitational lensing"?)

    2. Can you calculate the correct perihelion advance of the planet Mercury using some theory other than general relativity?

    3. Why do clocks in the GPS satellites need adjustment in order to keep time accurately? The usual explanation is gravitational time dilation. What's your explanation?

    4. Please explain why binary pulsars in orbit around each other increase in orbital period over time. (The usual explanation has to do with gravitational waves. What's your explanation?)

    That will do for a start.
     
  17. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    But he's a crank and has been unable to show that he's anywhere near correct.

    Yup. And according to posters and graffiti I've seen Eric Clapton is god. But I'm fairly sure he didn't create the Earth and everything on it.
     
  18. nitram22 Registered Senior Member

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    James R.

    nitram22:

    Ok. Let's assume you're right and space doesn't really bend.

    1. How do you explain observed features such as Einstein rings and multiple images of the same galaxy (currently put down to "gravitational lensing"?)

    2. Can you calculate the correct perihelion advance of the planet Mercury using some theory other than general relativity?

    3. Why do clocks in the GPS satellites need adjustment in order to keep time accurately? The usual explanation is gravitational time dilation. What's your explanation?

    4. Please explain why binary pulsars in orbit around each other increase in orbital period over time. (The usual explanation has to do with gravitational waves. What's your explanation?)

    That will do for a start.



    I am leaving to work so I'd like to give you this...

    These are matters dealing w/ matter, the gravity generated, and energy and how it all interacts based on the balance of all seen and unseen factors within the dynamics of what is being observed.
    When the big bang occurred "SpaceTime" started for this Universe and everything in it has been expanding from that point until now. As a whole the Universe as we know it has one age. Our perception of time and how we seem to measure it is a Human concept to help us count days and years according to years in "Earthtime"
    Separate from that which you know and look at it this way...
    If you left here for a hypothetical star 4 light years away traveling at half the speed of light, you would arrive there in eight years time. To an Earth based observer it would be 12 years after departure that a signal is received
    about your arrival.
    Its a paradox. But, as you look back at the Sun from 4 light years away it would be 4 years earlier that you see. But earth is still 8 years older than when you left and so are you.
    Its a distance issue not a "Spacetime" issue. Even that 4 year old light you are seeing has aged during its travel. after all it's been traveling for the last 4 years. But all that is within our Universe is the same age as far as matter and energy is concerned. Neither created nor destroyed
     
  19. kurros Registered Senior Member

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    I don't know, I kind of like it. It captures the important point that the Earth stays in orbit due to a local interaction, and he has used that phrasing to strengthen the analogy with the traditional bowling ball on a rubber sheet.
     
  20. James R Just this guy, you know? Staff Member

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    nitram22:

    I asked you four specific questions, and you didn't answer any of them.

    Am I to take it that you have no support for your claim that "space doesn't really bend", then?
     
  21. Motor Daddy ☼☼☼☼☼☼☼☼☼☼☼ Valued Senior Member

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    The orbit of the planets around the sun is best viewed as sending satellites into orbit about the earth.

    The satellite travels away from the earth at an angle and continues to get further away as it travels around the earth.

    The planets left the sun and continue to get further away from the sun, as does a satellite leaving the earth and going into orbit.

    The sun isn't "pulling" on the planets. The planets are traveling around the sun getting further away, as would a marble on a balloon's surface as the balloon increases in size the entire time.

    The sun is "pushing" the planets away, it is NOT "tugging" on the planets.

    Mass is evolving to space, at every level.
     
  22. James R Just this guy, you know? Staff Member

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    Motor Daddy's explanation is nonsense.

    For any object to travel in a circle or an ellipse, a centripetal force is needed. In the case of the planets, the Sun's gravity provides the required force.
     
  23. origin Trump is the best argument against a democracy. Valued Senior Member

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    Sure this is pretty obvious. 50% of c and traveling for a distance of 4 ly would be 8 years, a signal sent back to earth would require and additional 4 years. A total of 12 years.

    What is a paradox? It is obvious.

    Yes, and the sun is also 8 years older and the light you see that is reflected from the earth is also 4 years earlier. What is so intriguing or surprising about this? It takes light 1 year to travel 1 ly (hence the term), so of course the light you see will have left the sun (or the earth) 4 years earlier.

    And finally YOU would not be 4 years older you would be about 3.5 years older. Now that could be termed a bit of a paradox...
     

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