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Thread: Submarine detection by gravitational anomaly

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    Supporting Member spot's Avatar
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    Submarine detection by gravitational anomaly

    That's what the BBC reporters claim anyway.
    Not surprisingly, militaries across the world are also backing research in to quantum sensing.

    Gravimeters in particular offer the potential for detecting your opponent's submarines, for instance. Gravity may be a weak force, but you can't shield against it.

    So while stealth technology may hide your radar signature, it won't hide you from a quantum gravity sensor.

    https://www.bbc.co.uk/news/business-47294704
    Bosh. Bogus nonsense. How on earth is that true.

    Your underwater submarine displaces its exact weight of water. If it didn't it would sink. The principle of buoyancy applies. So how is a gravity measurement, either from the sea floor or the surface, going to twitch in the vicinity of a submerged submarine, quantum or otherwise.

    I am, of course, as always, eager to be corrected.
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    Zero mod strikes. HAH!!! YZGI's Avatar
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    Re: Submarine detection by gravitational anomaly

    I'll do some calculations and get back to you..

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    Proudly humble LarsMac's Avatar
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    Re: Submarine detection by gravitational anomaly

    Curious.

    Surely a submarine mass will be different than that of whatever water it has displaced.
    Especially if the thing is moving.
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    Re: Submarine detection by gravitational anomaly

    Quote Originally Posted by LarsMac View Post
    Curious.

    Surely a submarine mass will be different than that of whatever water it has displaced.
    Especially if the thing is moving.
    It will have a variable density, but why would the mass differ?
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    Senior Member Bryn Mawr's Avatar
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    Re: Submarine detection by gravitational anomaly

    Quote Originally Posted by LarsMac View Post
    Curious.

    Surely a submarine mass will be different than that of whatever water it has displaced.
    Especially if the thing is moving.
    In order for it to float they have to adjust the mass using the buoyancy tanks so that it is exactly equal (OK, technically they could take up some slack whilst they are moving using the trim planes but why would they when they'd have to readjust whenever they stop?).

    Surely the way to detect a sub would be the magnetic anomaly, not the gravitational one.

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    Proudly humble LarsMac's Avatar
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    Re: Submarine detection by gravitational anomaly

    Quote Originally Posted by Bryn Mawr View Post
    In order for it to float they have to adjust the mass using the buoyancy tanks so that it is exactly equal (OK, technically they could take up some slack whilst they are moving using the trim planes but why would they when they'd have to readjust whenever they stop?).

    Surely the way to detect a sub would be the magnetic anomaly, not the gravitational one.
    I understand all that, but the variations in mass due to metal versus air will likely appear as at least an anomaly. It will likely depend on the range from sensor to object.

    I am pretty sure that the water would be not unlike similar readings in air. Water is simply an atmosphere of H2O molecules all wandering about on their own so not likely to appear as a single mass.
    Any object in the water will likely cause a much different reading than the water, itself.

    And again, I suspect the movement of the thing is going to create detectable anomalies, as well.
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    Supporting Member spot's Avatar
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    Re: Submarine detection by gravitational anomaly

    I agree with you that there will be all sorts of detectable anomalies between a submarine and the equivalent mass of water. The question is whether any of those will be gravitational and I still see no reason to think they could be.

    The earth, for example, when considered from any position outside its surface, behaves as a point source at its centre of mass seen from that position. So would the submarine. So would the mass of water in the absence of the submarine. How do those two point sources differ?
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    Senior Member Bryn Mawr's Avatar
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    Re: Submarine detection by gravitational anomaly

    Quote Originally Posted by LarsMac View Post
    I understand all that, but the variations in mass due to metal versus air will likely appear as at least an anomaly. It will likely depend on the range from sensor to object.

    I am pretty sure that the water would be not unlike similar readings in air. Water is simply an atmosphere of H2O molecules all wandering about on their own so not likely to appear as a single mass.
    Any object in the water will likely cause a much different reading than the water, itself.

    And again, I suspect the movement of the thing is going to create detectable anomalies, as well.
    The problem here is the resolution. The current gravity maps are out by two or three orders of magnitude from the level they'd need to be to detect anomalies of the size involved in a sub. Then you have the rate of mapping - given a moving target it would all be a blur.

    As gravity is a weak force I don't see that anyone can improve the detectors quickly enough to catch up given the improvements in concealment that would inevitably happen should such a technology race start.

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    Supporting Member spot's Avatar
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    Re: Submarine detection by gravitational anomaly

    Quote Originally Posted by Bryn Mawr View Post
    the improvements in concealment that would inevitably happen
    I'm listening. Aluminium hull? Plywood partitioning? Helium buoyancy tanks?
    Nullius in verba|||||||||||
    Who has a spare two minutes to play in this month's FG Trivia game!

    The watch of your vision has become reasonable today.

    It’s normal. You must provoke. You must insult the belief of all monotheists. You must make fun of the belief of all monotheists.
    From the upper tier of the Leppings Lane End of the Hillsborough Stadium, I watched the events of that day unfold with horror.
    When the flowers want to oxygen and nutrition, or you’re a wedding or party planner, I will help you too much.
    Write that word in the blood

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    Senior Member FourPart's Avatar
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    Re: Submarine detection by gravitational anomaly

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    Even a fridge magnet is stronger than the earth's gravity. The fact that it sticks to the fridge door instead of submitting to the gravitational force & falling to the earth is proof of that.

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