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Thread: space and what it is

  1. #1 space and what it is 
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    Oct 2013
    If I understand it Einstein said there was no such thing as gravity as we usually think of it but that it's a bending of space by the mass of an object. Yet most of us still think of gravity in the old way as a magnetic like force.

    I give credit to those who have studied the subject as a career so I don't want to second guess but I grew up thinking that space was nothing and that's it. It went on forever infinitely. But now they talk of space as having properties and characteristics. I just don't understand.

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  3. #2  
    Moderator Moderator Markus Hanke's Avatar
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    Nov 2011
    Quote Originally Posted by deric View Post
    I grew up thinking that space was nothing and that's it.
    I think most of us would have grown up that way, since General Relativity isn't normally taught in second level.

    But now they talk of space as having properties and characteristics.
    Yes, this is the paradigm shift that Einstein has brought about - you must remember though that we are considering space-time, not just space; the two cannot be separated in modern theories of gravity. The presence of mass and energy affects both space and time. Also in quantum field theory ( another branch of modern physics ), the vacuum is no longer "empty", but a rather chaotic and energetic place.

    I just don't understand.
    It is one of those things in physics where you need to set aside all notions of "common sense", and simply ask yourself which model fits the empirical data ( i.e. measurements taken through experiment and observation ) better. It turns out that the old Newtonian concept of forces works quite well so long as the gravitational fields are weak, and the observer doesn't move at relativistic speeds; however, when stronger fields are considered ( e.g. the gravitation in the immediate vicinity of the Sun ), there are discrepancies between the Newtonian theory and observational data. General Relativity on the other hand fits the experimental data perfectly, and its predictions continue to hold true in all modern tests and observations as well ( see here for latest results ).

    This is what physics is really about - it doesn't search for the truth, but rather for models that best fit the empirical data that the universe throws at us. As such, it is an ongoing effort, and we are still far away from the end goal of a "Theory of Everything", if such a thing even exists, which I am no longer so very sure about. But regardless, so far as General Relativity is concerned, it is the model that best fits all available data, so its premises of space-time having certain degrees of freedom is accepted by virtue of its success in making predictions that continue to hold true, even if it does't necessarily appeal to the common sense of our everyday world of human experiences.

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