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Thread: My Alternative Theory to Dark Matter

  1. #1 My Alternative Theory to Dark Matter 
    Time Lord
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    It's not as developed as it could be..... but it goes like this:

    Maybe the odd behavior of stars on the outer rim of a galaxy could be the result of delayed propagation of gravity? If the star in question is say.... 10 light years out from the center, then maybe it still perceives its own relative location to the core to be where it was 10 years ago?

    I'm not sure how much that would affect things, but it would change the vector of the gravitational force acting on it. Instead of being at a 90 degree angle to its current direction of motion, gravity would appear to be pulling from a slightly smaller angle in front of that motion.

    Another complication that this would introduce is that the gravitational attraction from objects closer to the star (like other stars in the same galaxy) would be subject to this effect to a smaller degree, because information about changes in their relative position is arriving earlier.

    Of course.... this might not be insightful at all. Maybe its already being accounted for and we *still* get dark matter.


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  3. #2 Re: My Alternative Theory to Dark Matter 
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    Quote Originally Posted by kojax
    It's not as developed as it could be..... but it goes like this:

    Maybe the odd behavior of stars on the outer rim of a galaxy could be the result of delayed propagation of gravity? If the star in question is say.... 10 light years out from the center, then maybe it still perceives its own relative location to the core to be where it was 10 years ago?

    I'm not sure how much that would affect things, but it would change the vector of the gravitational force acting on it. Instead of being at a 90 degree angle to its current direction of motion, gravity would appear to be pulling from a slightly smaller angle in front of that motion.

    Another complication that this would introduce is that the gravitational attraction from objects closer to the star (like other stars in the same galaxy) would be subject to this effect to a smaller degree, because information about changes in their relative position is arriving earlier.

    Of course.... this might not be insightful at all. Maybe its already being accounted for and we *still* get dark matter.
    I'd have imagined that this was already being accounted for. The propagation time of gravity is fairly well known and understood by now, isn't it?


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  4. #3  
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    I'm not sure. I haven't gotten that far into it yet. It's hard to find good online descriptions of the specific elements of the model that predicts Dark Matter. I never hear any mention of it being included, but that doesn't mean it isn't.

    It's a question of what your intuitions are about the following thought experiment:

    The sun suddenly moves a light year away. (We'll say God, or Malvolio the wizard decides to suspend the laws of physics and teleports it there) For 8 minutes after that, we still experience its gravity, as though it were still there.

    But the question: Does it still experience our gravity for 8 minutes?
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  5. #4  
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    Quote Originally Posted by kojax
    I'm not sure. I haven't gotten that far into it yet. It's hard to find good online descriptions of the specific elements of the model that predicts Dark Matter. I never hear any mention of it being included, but that doesn't mean it isn't.

    It's a question of what your intuitions are about the following thought experiment:

    The sun suddenly moves a light year away. (We'll say God, or Malvolio the wizard decides to suspend the laws of physics and teleports it there) For 8 minutes after that, we still experience its gravity, as though it were still there.

    But the question: Does it still experience our gravity for 8 minutes?
    Ugh, that hurts my brain. I'm inclined to say yes.
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  6. #5  
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    Quote Originally Posted by kojax
    For 8 minutes after that, we still experience its gravity, as though it were still there.

    But the question: Does it still experience our gravity for 8 minutes?
    No, I would not say so, because it is leaving the reaches of the Earths gravitational field and it does therefore have no influence. Well it has the influence of whatever gravity is left a year ago to where it is (however tiny), but I would not say it would feel our gravity of the moment if it completley left our solar system. It could not by logical definition of Einstein's 2nd postulate of special relativity.

    For instance, imagine I (the earth) am constantly rolling balls at you (the sun). You are also rolling balls to me. If you vanish, I get 8 minutes of the balls you rolled to me. But if you were moved a light year away, my balls that I am rolling relative to the same speed and time where you were will now take a year to reach you instead of 8 minutes, so you are not affected by the ones that I am and am just rolling at you. The second you disappear my ball that took 8 minutes has now got to take just under a year to get to you. But I am still getting your balls for 8 minutes. (You will however be getting balls I rolled a year ago the second you arrive 1 light year away, much smaller balls of course ).

    Did that make any sense?
    "If you wish to make an apple pie from scratch, you must first invent the universe". - Carl Sagan
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  7. #6  
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    Something sounds fishy about this. Gravity travels? Aren't gravitons just mathematical symbols?

    When a particle fluxes, it's field fluxes too right? Would it not be the same effect with gravity on a macro scale?
    Dick, be Frank.

    Ambiguity Kills.
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  8. #7 Re: My Alternative Theory to Dark Matter 
    Moderator Moderator Janus's Avatar
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    Quote Originally Posted by kojax
    It's not as developed as it could be..... but it goes like this:

    Maybe the odd behavior of stars on the outer rim of a galaxy could be the result of delayed propagation of gravity? If the star in question is say.... 10 light years out from the center, then maybe it still perceives its own relative location to the core to be where it was 10 years ago?

    I'm not sure how much that would affect things, but it would change the vector of the gravitational force acting on it. Instead of being at a 90 degree angle to its current direction of motion, gravity would appear to be pulling from a slightly smaller angle in front of that motion.

    Another complication that this would introduce is that the gravitational attraction from objects closer to the star (like other stars in the same galaxy) would be subject to this effect to a smaller degree, because information about changes in their relative position is arriving earlier.

    Of course.... this might not be insightful at all. Maybe its already being accounted for and we *still* get dark matter.
    The reason you don't see it accounted for is that it doesn't happen. It turns out that in GR this "gravitational aberration" effect is canceled out by other effects. The net force felt by the stars acts towards the center of the galaxy and does not pull slightly forward on it.
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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  9. #8  
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    Quote Originally Posted by Bad Wolf
    Quote Originally Posted by kojax
    For 8 minutes after that, we still experience its gravity, as though it were still there.

    But the question: Does it still experience our gravity for 8 minutes?
    No, I would not say so, because it is leaving the reaches of the Earths gravitational field and it does therefore have no influence. Well it has the influence of whatever gravity is left a year ago to where it is (however tiny), but I would not say it would feel our gravity of the moment if it completley left our solar system. It could not by logical definition of Einstein's 2nd postulate of special relativity.
    Yeah, this is how you'd think it would work intuitively, and its how I kind of concluded it at first, but then I had to ask myself: How does this square with the concept of equal and opposite reactions?

    How can the Sun pull on us, and us not pull on the Sun?



    For instance, imagine I (the earth) am constantly rolling balls at you (the sun). You are also rolling balls to me. If you vanish, I get 8 minutes of the balls you rolled to me. But if you were moved a light year away, my balls that I am rolling relative to the same speed and time where you were will now take a year to reach you instead of 8 minutes, so you are not affected by the ones that I am and am just rolling at you. The second you disappear my ball that took 8 minutes has now got to take just under a year to get to you. But I am still getting your balls for 8 minutes. (You will however be getting balls I rolled a year ago the second you arrive 1 light year away, much smaller balls of course ).

    Did that make any sense?
    This only works if we look at gravitons as independent material objects that can have energy transferred to them, and keep the energy without having to transmit it again to something else.

    But, if that were true, then sending these gravitons would cost energy. And, it would cost just as much energy to send gravitons that never hit anything as to send gravitons that do hit something.
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  10. #9  
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    I'm not talking about gravitons, I'm talking about gravitational waves as in Einsteins theory on gravity. I don't even want to think Quantum gravity...

    How can the Sun pull on us, and us not pull on the Sun?
    Well, quite simply put. Because the sun has just completely unnaturally been spontaneously and instantaneously moved 1 light year away. I think when that happens, the fact that physics has been violated in the first place means that ordinary physics aren't going to start making exceptions...

    I'd like to see you try and explain this kind of thing happening with gravtions. Do you know of any particular kind of unnatural phenomena that would occur do to the unnatural movement of the sun? This would help me understand easier... :-D

    Quote Originally Posted by Janus
    ...The net force felt by the stars acts towards the center of the galaxy and does not pull slightly forward on it.
    That supports one of my theories. Thanks Janus!
    "If you wish to make an apple pie from scratch, you must first invent the universe". - Carl Sagan
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  11. #10  
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    Quote Originally Posted by kojax
    I'm not sure. I haven't gotten that far into it yet. It's hard to find good online descriptions of the specific elements of the model that predicts Dark Matter. I never hear any mention of it being included, but that doesn't mean it isn't.

    It's a question of what your intuitions are about the following thought experiment:

    The sun suddenly moves a light year away. (We'll say God, or Malvolio the wizard decides to suspend the laws of physics and teleports it there) For 8 minutes after that, we still experience its gravity, as though it were still there.

    But the question: Does it still experience our gravity for 8 minutes?
    Absolutely brilliant. Exact same conclusion I have come to. My description of gravity is the force resulting from cooling of this region of the universe. Matter is condensing, and its this "condensing" that causes gravity. Somewhere else in the universe is the matter that was pulled away faster than the speed of light, and many of the forces resulting from this account for dark matter. Imagine if you had a bucket of water, and this bucket was within a tub. If you pulled out the bucket, the initial response of the surrounding liquid would be to "follow the bucket" out of the water, and there would be an empty spot for a split second.
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  12. #11  
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    Well, I'm glad someone agrees with this possibility. For me, I'm coming at it from the perspective of quantum mechanics, where causality isn't always a settled matter.

    In QM, it isn't always clear that some event happened first and another followed it. Sometimes it's possible to interpret that the other event might have been the one that happened first, or both might be truly simultaneous.

    When we're talking about things that happen at the speed of light, especially with particles like gravitons that may or may not exist, I think we're in the QM realm. In some sense, it seems like a separation of Distance/C is the closest the universe gets to an event being truly simultaneous.

    Quote Originally Posted by Bad Wolf
    I'm not talking about gravitons, I'm talking about gravitational waves as in Einsteins theory on gravity. I don't even want to think Quantum gravity...

    How can the Sun pull on us, and us not pull on the Sun?
    Well, quite simply put. Because the sun has just completely unnaturally been spontaneously and instantaneously moved 1 light year away. I think when that happens, the fact that physics has been violated in the first place means that ordinary physics aren't going to start making exceptions...
    Well, I meant the whole story as a metaphor. If the sun were 20 light years away, instead of 8 light minutes away, and if it were a supermassive black hole, so we could still feel its gravity that far away, then the question of which one of us counts as "moving" might become more interesting.

    My intuition is that maybe the universe doesn't make a distinction between us moving relative to the gravitational object, or that gravitational object moving relative to us. Maybe both are the same thing.

    I'd like to see you try and explain this kind of thing happening with gravtions. Do you know of any particular kind of unnatural phenomena that would occur do to the unnatural movement of the sun? This would help me understand easier... :-D

    Quote Originally Posted by Janus
    ...The net force felt by the stars acts towards the center of the galaxy and does not pull slightly forward on it.
    That supports one of my theories. Thanks Janus!
    Well, gravitons have never been successfully demonstrated to exist, other than as theoretical particles that help us understand what's happening. A few attempts have been made, but none that yielded any credible results.

    As far as the direction of the net force of stars on the outer rim of a galaxy... I'm not sure anyone has ever shown what direction they're being acted on. Theory predicts what Janus is saying, but I don't know of any observations that have ever confirmed that theory to be accurate in that situation.
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  13. #12  
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    Quote Originally Posted by kojax

    As far as the direction of the net force of stars on the outer rim of a galaxy... I'm not sure anyone has ever shown what direction they're being acted on. Theory predicts what Janus is saying, but I don't know of any observations that have ever confirmed that theory to be accurate in that situation.

    Every observation of a galaxy has confirmed the theory to be accurate.

    Consider what happens if gravitaional aberration were true. The force of gravity would appear to come from slightly ahead of the object in orbit. This means that the force can be divided into two components, one acting towards the center and one acting in the direction of orbital velocity, the vector sum of the two equals the total force felt,. Note that as the direction from which the force is felt shifts more forward, the forward component strengthens and the inward component gets weaker. (BTW this direction would have nothing to do with the distance between gravity source and object, but would be related to the ratio of the orbital speed and the speed of gravity)

    Since the forward vector is constant, it will increase the forward orbital speed over time. As it does so, the object will climb to a higher orbit (made even easier by the weakened inward force vector.) The result would be that gravitationally bound objects like galaxies would tear themselves apart. (In fact, it can be shown that if such an effect did exist, our own Solar system would be too unstable to have existed for as long as it has.)

    But we do not see galaxies tearing themselves apart, instead we see galaxies holding together while rotating at speeds that should tear them apart according to the visiible mass we see.

    Gravitational aberration would have the exact opposite effect that Dark Matter would have.
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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  14. #13  
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    Yeah. That makes sense. I keep wanting to look for ways that the effect could still re-counter itself the other way, but it looks like gravitational abberation would lead to slower orbital velocities, instead of faster ones.
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