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Thread: Up and Down in Spacetime...

  1. #1
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    Up and Down in Spacetime...

    If you are in space and time, how can you define an upper limit or a lower limit in the aquarium? You cannot, as goes and begs the answer. Without a magnetic pole, there is no north or south directionality.

    If this be the case, then ''gravitational wells'' can be seen the other way around... in effect, a well not going down the way, but rather something moving up the way. There is no math describing a thing going down in spacetime to something that is moving upwards/

    I prefer to see black holes, mind you, as a well, whilst a normal ripple, pr disturbance, or even to call it a distortion of spacetime nothing more than a wall a thing moves into, mush like we can travel land until we reach a bump. If the gravitation is strong-enough, then we hit a mountain... or a hill manifested by some disturbance in space and time.


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    Quote Originally Posted by Occams Ghost View Post
    If you are in space and time, how can you define an upper limit or a lower limit in the aquarium? You cannot, as goes and begs the answer. Without a magnetic pole, there is no north or south directionality.

    If this be the case, then ''gravitational wells'' can be seen the other way around... in effect, a well not going down the way, but rather something moving up the way. There is no math describing a thing going down in spacetime to something that is moving upwards/
    You're referring to the rubber sheet analogy? Well, it is just an analogy, after all.

    I prefer to see black holes, mind you, as a well, whilst a normal ripple, pr disturbance, or even to call it a distortion of spacetime nothing more than a wall a thing moves into, mush like we can travel land until we reach a bump. If the gravitation is strong-enough, then we hit a mountain... or a hill manifested by some disturbance in space and time.

    Ok. A slight variation on the same analogy? Things go up?

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    Yes.... but no...

    What goes up in space and time?

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    Quote Originally Posted by Occams Ghost View Post
    Yes.... but no...

    What goes up in space and time?
    Define "up." Are you talking "up" in terms of a "hill" instead of "hole in the ground/depression" rubber sheet analogy?

    "The problem with quotes on the Internet is that it is hard to verify their authenticity." Abraham Lincoln

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    Quite right!

    In spacetime, you can look down, and it is variably ''up''. Look up, and it is ''down.'' Nothing defines direction in spacetime.

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    Quote Originally Posted by Occams Ghost View Post
    If you are in space and time, how can you define an upper limit or a lower limit in the aquarium? You cannot, as goes and begs the answer. Without a magnetic pole, there is no north or south directionality.
    North and South are arbitrary designations in rotational polar orientation. Magnetic fields just let us locate them more easily.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    If you could map a direction in space and time, then we could have a ''bottom'' in this place... however, thee is no bottom. In fact, space and time is isotropic in nature considering directionality.

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    Quote Originally Posted by Noclevername View Post
    North and South are arbitrary designations in rotational polar orientation. Magnetic fields just let us locate them more easily.

    Tell that to the few around here who seem to think so.

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    Quote Originally Posted by Occams Ghost View Post
    Tell that to the few around here who seem to think so.
    Around where, and who said so?

    As for up/down, like everything else about space, they're relative. To an Earthling, Jupiter is "up" even if it's currently on the other side of the planet, because up is oriented from the center of the Earth. To a Jovian, Earth is "up". On the other foot, the person from the first example could just as easily say Jupiter was "down" to them, because they were orienting using their own body instead of the planet, so whatever their feet point towards is "down". And in half a day, when their head was pointing towards Jupiter, they'd call it "up".
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    as for wrinkles in space such as black holes and other bends in the sheet, I think 'in' and 'out' might be more useful then up and down. Yes it is still reletive, but the point of referance is the one you are dealing with at the moment, no reason to get all cosmic about some kind universal referance frame.

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    I believe Occams Ghost started this thread because of the reaction he got when he started talking about gravitational "walls" and "barriers" in this thread.

    Putting everything together, it looks to me like Occams Ghost prefers his upside-down version of the rubber sheet analogy, and is upset that people are pointing out to him that the conventional version goes the other way and that his version just causes confusion.

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    Whenever I picture the rubber sheet analogy in my head- it is utterly different than the rubber sheet analogy. If that makes sense.

    Although it can be described as a "well" it is more dimensional than that (if THAT makes sense...) and when I picture it it looks (very hard to describe this part) like a warped well wrapped around the body.

    It behaves as a well does- but in any direction. As demonstrated by 3 D bodies in space and even by black holes.

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    Quote Originally Posted by Occams Ghost View Post
    If this be the case, then ''gravitational wells'' can be seen the other way around... in effect, a well not going down the way, but rather something moving up the way.
    But that doesn't reflect the reality of gravity wells. You have to climb against gravity-- up --to get out of one. You can fall into one-- down.

    You can't fall up a hill.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    Wrong... you can fall into a well, but actually turn up in the correct way... so now how does your arguement hold?

  15. 2008-Feb-18, 07:56 AM

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    Quote Originally Posted by Occams Ghost View Post
    Wrong... you can fall into a well, but actually turn up in the correct way... so now how does your arguement hold?
    What?
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    Occams Ghost, aren't you just trying to take the rubber sheet analogy too far? It's an analogy, nothing more. There is no suggestion that gravity really is a depression (or a hill), it's just a way to visualize things in two dimensions to make it simpler to understand. If it doesn't help or confuses, then just forget it. The reality of gravitational theory is much more complex, with tensors and hard maths and stuff. I certainly struggle as soon as I get beyond the pop science.

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    Down is a relative term, it is used relative to the mass with the most gravitational pull on you at the present time. Of course, you could say that the teaspoon that you accidentaly knocked of the table flew up to hit the floor, but that might get you quite a few wierd looks...

    Up and down is therefore not without meaning in space, it is just not common to use them when not in close proximity to a massive object... In and out or towards and away would probably be more common when to far away from the object to feel any significant gravitational pull.

    By the way, by changing the analogy to a mountain instead of a well, you are not changing the directions involved, it takes energy to climb a mountain, and falling off it releases that energy. So really, moving towards a massive object is less like climbing a mountain than going down the well...

    Wrong... you can fall into a well, but actually turn up in the correct way... so now how does your arguement hold?
    Well. Depending on where you want to be at a spesific time, and what you wish to face, you may want to jump in a well, that might be the correct path, but into the well will always be down, or it's not really a well at all...

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    Imagine a black hole... if you enter one, you will appear at a different time in the universe... but what way do you appear? It's like the strange analogy of moving through the earth... if you pass it's center, do you remain with your feet facing australia? No, is the answer, because the force of gravity would keep you at the center... however... in a black hole, you may fall into one, inexorably be sucked by a wormhole threaded with exotic matter, and end up totally the correct way, in a different part of the universe... so a well is really something that you aren't going down, but is a potential tunnel for you to appear in whatever way you had left. But again... there is no up or down. I take no biased opinion either to the rubber sheet.

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    In fact... the equivalance principle prooves that up and down are irrelevant.

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    I disagree, in a gravity well up or down (or in and out, same thing, different terms) are VERY important. Going toward the source of the gravity, or away, are quite different things. Ask any pilot, forgetting up or down is a bad thing to do. Now in empty space, yes they are equivalent, but to call them irrelevant is like calling gravity irrelevant because it doesn't happen in empty space.

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    Quote Originally Posted by Occams Ghost
    Imagine a black hole... if you enter one, you will appear at a different time in the universe...
    Pure conjecture, as it is unknown whether the conditions inside actual rotating black holes will match those needed for such a tunnel.

    Quote Originally Posted by Occams Ghost
    In fact... the equivalance principle prooves that up and down are irrelevant.
    Not true; the equivalence principle has nothing to do with directionality.

    OG, for someone who once referred to himself as a physicist (or was it scientist?), you don't seem very well acquainted with mainstream science. Perhaps you should stick to ATM.

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    Einstein's equivalance principle shows in the Elevator Thought Experiment that one cannot tell if they are moving down or up... this is what i meant... so please... calm down.

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    Wrong again, OG. What the elevator experiment actually shows is that one cannot distinguish between gravity and the pseudo-force generated from being accelerated. One can most definitely, and pretty easily, figure out if one is moving up or down.

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    Not from what was taught. The idea ws, if no windows wher in the elevetor can one tell if he is accelerating or being dragged down by gravity? This is how Einstein linked acceleration with gravity, and acceleration with curvature, because curvature was gravity.

    So please.. again.. calm down.

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    Very good, OG. Now please explain how the equivalence principle shows that up and down are irrelevant, as you tried to claim in comment #19. Because, again, the principle has nothing to do with directionality.

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    Because the results are expressed against the equations of equivalence. Now... give it up... and stop trolling.

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    In other words, you can't back up your claim?

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    Not at all... I've said a lot other than some remedial nit-picking.

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    I'm pointing specifically to your claim that the equivalence principle proves that directions like up and down are irrelevant. Show how this is proven, or retract the claim. It's really quite simple.

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    I gave you an examp The Elevator example is intricate next to Einstein's equivalance principle. So what is wrong?

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