Gomboc: World's First Self-Righting Object

The "Gomboc" is a mono-monostatic object, a three-dimensional thing that has only one way to stand up. Like a weeble, you might offer. (I'd be right there with you.) But apparently, no. While a Weeble could in theory be balanced on its opposite, egg-shaped side, the Gomboc is only stable at a single point. It is therefor always self-righting. (Plus, the Weeble rights itself because of extra weight in its ample bottom, while the Gomboc is the same density throughout.) The scientists who discovered the Gomboc shape are now selling acrylic versions of the same online, each with a special serial number and certificate. Unfortunately, each one starts at €900, with an additional cost based on its serial number. Seems a bit over the top for what is ultimately just a lump of plastic. Self-Righting Object, The [NYTimes.com] Project/Product Page [Gomboc.eu via Metafilter]
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18 Responses to Gomboc: World's First Self-Righting Object

  1. Anonymous says:

    I had one of these from the discovery store when I was like 8. It was a couple dollars – and that store was overpriced as shit.

  2. Anonymous says:

    That’s not a Gombic. That is a glass cube that has a 3-d engraving that makes it look like a Gombic. It comes with some other stuff.

  3. Anonymous says:

    or maybe it IS a Gomboc. Can’t tell after reading. Wording is unclear.

  4. certron says:

    If anyone remembers seeing this object a number of months (years?) ago, did they not also have a contest for creating non-concave objects of a certain shape that would similarly be completely self-righting, with a bonus for the least number of sides. I remember seeing a shape similar to this one in connection to the contest, but I don’t know if this object displayed here is the same or the product of evolution or the contest. Can anyone else shed some light upon this, or am I making up some crazy fantasy?

  5. derPlau says:

    Please please please note the distinction between an equilibrium and a “stable point”. Both a Weeble and a gomboc have two equilibria, one of which is stable and the other is unstable. The unstable equilibrium is the one on which the object “could, theoretically, be balanced;” the fact that it moves to the other point if it’s perturbed even slightly from the unstable point is what makes it unstable.

  6. jrtom says:

    #6: There were rumors of such a contest (the version that I saw was offering a prize of N divided by the number of sides), but I was never able to confirm them.

  7. Anonymous says:

    No. The one who costs 80 EUR is definitely a glass cube. You can verify that on the official website, where you can order for a gomboc for 1000 EUR at least (the price grows when you choose a little serial number) :


  8. vik says:

    A type of Indian tortoise has a shell much the same shape

  9. Halloween Jack says:

    Wait two years, get it for $4.95 from The Sharper Image after these “geniuses” do the math.

  10. ernie says:

    This will be the “test print” page of desktop 3d fabbers in 10 years.

  11. Anonymous says:

    Wait a minute. Didn’t Doctor Who destroy these things back during the second season?

  12. Anonymous says:

    The difference between a weebl and a Gomboc is that the Gomboc has a uniform mass density. A weebl always has a weighted bottom and a low-density top.

    In terms of the stability conditions, they are the same: one stable and one unstable equilibrium.

  13. nex says:

    While a Weeble could in theory be balanced on its opposite, egg-shaped side, the Gomboc is only stable at a single point.

    I think this is wrong, please check/correct. According to the Gömböc web site, both the Weeble and the Gömböc are stable at a single point, and both have a second point on which you could balance them, which is unstable. Thus, the difference is only in the density distribution — this isn’t a ‘plus’ aspect, but actually the entire, err, point.

  14. cha0tic says:

    A nice project for someone with one of those 3D printers.

  15. fenderbasher says:

    Looks a lot like a tangible representation of a non-orientable surface mathematical thingie (Cross-Cap, Boy’s surface, Roman surface…). Interesting.

  16. Anonymous says:

    That gomboc.eu website has a virus – don’t click it

  17. Anonymous says:

    Looks like you can also get a non-numbered one without the DVD and other fancy stuff for EUR 80, which is considerably cheaper than the EUR 900 mentioned in the post.


  18. Heteromeles says:

    Depending on the range of surfaces over which this object rights itself, it might be useful for space probes or similar mechanisms that have to be oriented a certain direction after falling.

    Now all we have to do is come up with a baked-bread version of this, so that we can butter the top and see if it will land butter side up, or whether it will hover spinning in midair :)

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