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Dr. Robert Forward's curvature gradient detector

  1. Sep 20, 2007 #1
    In a response by Pervect to another topic, he mentioned a device called a Forward mass detector, named after its inventor Dr. Robert Forward.

    It's an intersting device with the claim that it can detect small gradients in the curvature of spacetime.

    I couldn't find any info regarding someone that has built one, but I might just give it a try. Maybe I'll see if Jodi Foster wants to take a ride in it. ;-D

    He passed away in 2002. Here's a link to his website:


    Also, I created a pdf of the patent for the detector (U.S. patent 3,273,397), but it's larger than this forum will allow to be posted (the pdf is 1.6MB). If anyone wants it they can email me at bwalance(at)roadrunner.com

    I have attached a couple of pics from his book showing the detector.

    Thanks for the tip, Pervect.

    Bob Walance

    Attached Files:

  2. jcsd
  3. Sep 20, 2007 #2
    Interesting, this reminds me of the experiments to detect Gravitational Waves, postulated by General Relativity. While his idea is of sound basis (from a theoretical standpoint), I think that the size would make it insensitive to any but very large changes in the static field. The gravitational wave detector at Stanford (I may be incorrect about the University, this hasn't been my study for quite awhile) is nearly 2km in length and operates, approximately, by the same principles. To date, nothing has been detected by the Stanford team.
  4. Sep 20, 2007 #3


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  5. Sep 20, 2007 #4
    Actually, this device is used quite often to map out gravitational inhomogeneities of the earth. Since it actually measures a static curvature (it's called a gravity gradiometer for a reason), it's best suited to measuring large, slow changes. A practical use is to measure the gravitational multipole moments of the Earth, and thus get the subsurface structure; the oil industry uses this in a fairly serious way. In a 1970 prototype, the sensitivity was about "Riemann curvature produced by a two-bilometer high mountain, idealized as a two-kilometer high cub, at a distance of 15km." (Gravitation, MTW, Box 16.5).

    Seriously people, MTW is one of the best physics books ever made, by some of the best physicists to grace the earth. It's big, and it needs re-reading to understand the logic (which is sometimes fragmented by the book's need to cater to differing levels of mathematical sophistication). But I've yet to see a problem that people have raised, on GR or related subjects, which isn't covered by the book.
  6. Sep 20, 2007 #5


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    I like MTW too.

    A quick google for gravity gradiometry (optionally with oil) also gives a lot of information. One very interesting paper is


    The Grace experiment is another interesting experiment being done.

    There's a gadget called http://www.superconductorweek.com/pr/0106hgf/arkex1.htm [Broken] that's interesting as well, but I haven't been able to find out much about how it operates (it may be proprietary) .
    Last edited by a moderator: May 3, 2017
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