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A few questions about gravity, space, and reality in general

  1. Sep 9, 2012 #1
    I'm just curious and like thinking about how reality works. I don't now where or if I could find the answers to these questions already written.

    From what I've seen and read, gravity is cause by space being bent by mass the same way a person standing on a trampoline bends the trampoline.
    1. Would enough mass packed into a single point be able to bend space to the point of tearing?
    2. Is a black hole a point in space that was torn like in the above question?
    3. If space is bent like a person bends a trampoline down, where is the mass pushing space to bend it?

    I have read about antimatter being made and have a few questions about that too.
    4. Would an anti hydrogen used to make a bomb like hydrogen was, would it actually work?
    4b. Would it have the same or greater power?
    5. If you annihilated antimatter and matter in a vacuum and somehow stopped it immediately when the two are destroyed, what would be left?
  2. jcsd
  3. Sep 9, 2012 #2


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    Depends on your coordinate system ;). The analogy of space as a trampolin does not really work for black holes.

    It is a simple model, and you try to push it way too far.

    Antihydrogen (with the right isotopes) can fuse to antihelium, this would work similar to a hydrogen bomb. However, if you have a large quantity of antimatter, you would not care about fusion - just set it free, it will annihilate with matter around it and give a big explosion - bigger than any fusion bomb can do with the same mass.
    Fusion gives the same power (probably - it cannot be tested yet), but annihilation gives about ~100 times more per mass.
    Stopped what? It depends on the annihilated things. Electrons+Positrons would usually give two high-energetic photons, while protons+antiprotons would give some high-energetic pions (plus photons maybe). Those pions decay in other particles afterwards: Neutral pions decay into photons, charged pions into muons (usually) plus a neutrino, and muons then decay into electrons/positrons (depends on their charge) and neutrinos.
  4. Sep 9, 2012 #3
    If the trampoline analogy is too simple to accurately explain how space bends, exactly how does mass bend space?

    With that antimatter bombs idea, I was thinking if you used fusion to disperse the antimatter before annihilation. Would the fusion reduce the overall power of the annihilation, or just spread it out a little?

    Let me rephrase my last question. Is there a stage between annihilation and photons or pions?
  5. Sep 9, 2012 #4


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    It changes the curvature of spacetime. Physics won't tell you "why", General Relativity is just the description which fits best to observations.

    It would not give any significant changes. As soon as matter reacts with antimatter, the whole things is heated up anyway and you get a big, nearly point-like explosion.

    Annihilation directly produces photons and pions.
  6. Sep 9, 2012 #5
    If you could make a device that bends space, would it be possible to bend two points until they become the same point, or close to it?

    Different dimensions

    1. If we could travel in four dimensions, could the multiverse be arranged like a hallway and each universe is like a different room?

    2. Could the big bang have been another universe forming a bubble that is now our universe?

    3.Could the multiverse be arranged like groups of bubbles inside of bubbles, inside of even larger bubbles?

    Thanks for answering the questions of someone that knows almost nothing about physics and the math behind it.
  7. Sep 10, 2012 #6


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    Probably not.

    You would first have to describe such a universe with 4 (spatial?) dimensions.
    Otherwise, the question is meaningless.

    There are some ideas in that direction, but it is just educated speculation.

    The question does not make sense. "arranged" needs space, and there is no space "between" (not even that word makes sense) different universes (if those exist at all).
  8. Sep 10, 2012 #7
    1. In this question, I mean the fourth dimension is perpendicular with our three dimensions. I'm trying to ask if the fourth could be the way to parallel universes, while those universes are three dimensional.

    3. Wouldn't there have to be something between the universes to keep them from interfering or destroying each other(some kind of wall or membrane?)? I am assuming that other universes exist, and that they are not separated just by being on a different frequency.

    New question: Do you know about sacred geometry? If so, do you think it is relevant to the study of the universe? I apologize for putting something a bit religious on here, but it is primarily geometry.

    Assuming we will end up typing more, I always assume there to be many more dimensions than the three, and that time is not one of them.
  9. Sep 10, 2012 #8


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    The question simply does not make sense.

    There is no "between". Space exists within universes only.

    That TV series is pure fiction, not science ;).

    Nothing special.

    No. Is there any reason why the construction of churches and similar things should be relevant in science (apart from questions about church statics)?

    Science is not about what "is", but what is used to describe observations. The description of time as a dimension is a wonderful concept, and it would be really tricky to describe General Relativity without that concept.
  10. Sep 10, 2012 #9
    1. I guess the way I think about dimensions differs from most people.

    What TV series? When thinking about these things, I also include certain spiritual and religious beliefs that make at least a little sense. You have to consider that there are many things we can't possibly understand with today's technology.

    Sacred Geometry isn't just how they build religious buildings and such. It's a geometry that uses structures and patterns found in nature. http://www.geometrycode.com/sacred-geometry/ This explains it better than I can. Just try to ignore the religious bits and view it as geometry. It basically says that life follows a few set rules of geometry, and so does the rest of the universe.

    I just don't see time as a dimension, because if someone goes back in time and does something, that makes the world branch off onto it's own path. Like on a computer game, if you load a save from before where you just were, you either make a new save, or you overwrite the previous one, destroying it. If it doesn't do that, then if time travel ever becomes possible, it has already happened.

    Viewing the past without actually affecting it, using math or technology that follows matter going backwards in the same way it's used to predict where something is going... Can that be done?
  11. Sep 10, 2012 #10


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    This concept is a staple of a lot of science fiction. About the only thing vaguely similar to this I can think of this in modern physics is some forms of "Brane" theories. However, I'm not extremely familiar with Brane theories, they are outside the scope of general relativity.

    You might have better luck asking about them (preferably by name, and omitting the speculative stuff) in another forum (beyond the standard model would be the PF forum I think) or just doing some research.

    Wiki has the following to say (it seems reasonable to me, but remember, I don't know much about brane theory):


    As far as the concept of dimension goes, the physical and mathematical concept is a lot less restrictive and more general than your personal one- and time fits the more general definition(s) of a dimension that's used in math and physics.

    I could try and get into it a bit more, but it can get somewhat involved. I'll just say that the most primitive concepts of dimension can be defined in topology, and that the only thing you need to use these primitive concepts is the concept of "neighborhood" , sometimes called "open sets" or "open balls". This leads to the idea of "covering dimension" - there's a bunch more as well, "dimension" is a term used to describe a group of related concepts.

    It's generally more productive if you adapt your personal definitions to the ones used in the field, if you insist that the field adopts your own personal ones, it's probably not going to cooperate :-).
  12. Sep 11, 2012 #11


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    The answer must be 42.
  13. Sep 11, 2012 #12
    I'm not unwilling to adapt my definitions, I've just never read about physics. All my knowledge and ideas come from using common knowledge, ideas from many religions, and never being able to stop thinking about how the universe really works. I have no education after highschool, besides culinary arts, so I still have much to learn.

    The way I learn and understand things is to construct models in my mind using what I already know and applying it to the new information. My brain doesn't like math, so it will take a while to understand all this new information. I love learning these new things though.

    Time being a dimension; I always pictured it to be like a movie. That we'd be the characters in the story. If there were some sort of being outside our spacetime, they'd be watching, and no matter how many times they went back, we'd never know because to us, nothing had happened. We'd just go on repeating until it's destroyed. Now I see it more like we are in a game and even if there were a being outside our spacetime, they couldn't rewind or anything, but they could view the log of what has happened. Are either of these views even remotely accurate when you see time as a dimension?
  14. Sep 11, 2012 #13
    I hope that's just a joke.
  15. Sep 11, 2012 #14
    It is hard to comment on what an imaginary being would or wouldn't be able to do, since it is fictional to start with.
    But I think most would agree that if you 'played back' the universe exactly then no-one in it would notice. Though the if in that statement is an impossible if :)
  16. Sep 11, 2012 #15


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    If it cannot be understood today, you should not try to make up some mystic stories about it. They will end like the gods for thunder, the gods responsible for moving the sun around earth, and so on.

    Well... strucutes and patterns found in the universe can be relevant to the study of the universe - that is trivial.

    That is a very problematic claim, as it can lead to all sorts of misconceptions. While it is true that you can find similar geometric shapes in different situations, it does not imply any causal or other connection between them.

    How do you go back in time? If you cannot do that, it is just pure speculation.

    Fine. Stack all movie images on top of each other, and you get a 3-dimensional stack with a 2-dimensional movie. Stack 3-dimensional "images", and you get a 4-dimensional stack with a 3-dimensional "world movie".
  17. Sep 11, 2012 #16
    Has anyone attempted to use all the known laws of physics to generate a world inside a computer?

    Is there even a computer powerful enough to to generate and keep a world the size of a solar system, or maybe a single galaxy going while obeying all the laws of physics?

    Would such a thing be helpful in finding any gaps in the current understanding of how the universe works?
  18. Sep 11, 2012 #17
    First of all, there's probably no computer powerful enough to generate and keep track of a world the size of a dust mite. Even if there were, Quantum Mechanics would give us some problems, as software algorithms cannot generate truly random numbers. Also, it's not known how gravity works on the microscopic scale, trying to use our laws that appear to work perfectly on macroscopic scales yields total and utter nonsense.
  19. Sep 11, 2012 #18


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    A computer cannot simulate anything more complex than itself (here: mainly determined by the number of particles), it cannot even store the required data (the computer would be able to simulate itself, if it simulates a solar system with a computer in it).
    Real computers are far away from this theoretical limit. Even quantum systems with ~100 elements can be too time-consuming, if I remember that number correctly.

    Simple solution: Use a deterministic interpretation of QM. In case of MWI, this has the nice side-effect that the computation produces all [possible] results at the same time, and their relative amplitude. However, it increases the computation time exponentially.

    That is a real problem, unless we neglect gravity.
  20. Sep 11, 2012 #19
    Could it be that because the particles are so small, even if they do have their own gravity, it is so weak that it has almost no effect on surroundings? That gravity only plays an important role when it comes to larger objects?
  21. Sep 11, 2012 #20
    Mass does not bend anything.

    The situation is that the relation between the coordinate distance between two point and the physical difference is as if the surface was curved. But nothing is actually bent. And so your question about tearing of space is not a valid question.
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