Vanilla 1.1.9 is a product of Lussumo. More Information: Documentation, Community Support.

    •  
      CommentAuthorgoatcheez
    • CommentTimeFeb 1st 2020 edited
     
    https://www.wired.com/story/a-tiny-glass-bead-goes-as-still-as-nature-allows/

    But this bead is truly still, regardless of whether you are judging it as a human or a dust mite. And at this level of stillness, our conventional wisdom about motion breaks down, as the bizarre rules of quantum mechanics kick in. For one thing, the bead becomes “delocalized,” says Aspelmeyer. The bead spreads out. It no longer has a definite position—like a ripple in a pond, which stretches over an expanse of water rather than being at a particular location. Instead of maintaining a sharp boundary between bead and vacuum, the bead’s outline becomes cloudy and diffuse.
    •  
      CommentAuthorAngus
    • CommentTimeFeb 1st 2020
     
    Indeed. Thanks to Werner.
    •  
      CommentAuthorTrim
    • CommentTimeFeb 6th 2020
     
    Physicists work out the perfect soap mix recipe for blowing giant bubbles - and the secret ingredient is a type of food thickener called guar powder.

    https://www.dailymail.co.uk/sciencetech/index.html

    Wonderful discovery.
    •  
      CommentAuthorgoatcheez
    • CommentTimeFeb 6th 2020
     
    I've never blown Bubbles...she wouldn't go out with me. :(
    •  
      CommentAuthorTrim
    • CommentTimeFeb 6th 2020
     
    -1
    •  
      CommentAuthorgoatcheez
    • CommentTimeFeb 6th 2020
     
    A groan is almost as good as a laugh.
  1.  
    • CommentAuthorAsterix
    • CommentTimeMar 12th 2020
     
    But still no way to harvest that "free" zero-point energy, eh?
    • CommentAuthorkorkskrew
    • CommentTime16 hours ago
     
    At the risk of playing in waters well over my head, a question popped into my head this morning that I don't know enough to even approach an answer or theory.

    LIGO and Virgo seem to have proven that gravity waves propagate at c. I don't get how that is consistent with the theory of inflation at the big bang. They are both fluctuations in spacetime, yes? How is one constrained to propagate at c and the other isn't?

    Is it just that Inflation is the only way we know to get the observable universe, but have no clue how it could happen?
  2.  
    It's the theory that best fits the data, currently.

    Spacetime itself can expand (or indeed contract) at any damn speed it likes.
    •  
      CommentAuthorAngus
    • CommentTime15 hours ago
     
    Yeah. I don't think the idea "speed" really applies to the expansion.
  3.  
    In general relativity, calculations involving any non-trivial system is pure horror.
    • CommentAuthorkorkskrew
    • CommentTime7 hours ago edited
     
    Does expansion and contraction of spacetime not define a gravity wave?

    ETA: or is it the other way around?
    •  
      CommentAuthoralsetalokin
    • CommentTime6 hours ago edited
     
    It is what it is.

    When a GW passes through a detector like LIGO, time actually runs at slightly different rates in the two arms for a moment, and the whole structure changes shape due to the distortion of spacetime.

    Or it is something else entirely and Einstein was an idiot. One or the other.
    •  
      CommentAuthorPathoskeptic
    • CommentTime6 hours ago edited
     
    Posted By: korkskrewDoes expansion and contraction of spacetime not define a gravity wave?

    ETA: or is it the other way around?


    Gravity waves relate to changes of curvature of space-time. Not expansion or contraction.
  4.  
    Posted By: alsetalokinOr it is something else entirely and Einstein was an idiot. One or the other.
    I'm sure there's a fancy name like modus ponens or whatever that a logician would employ to describe what you just did!

    ETA The law of the excluded middle, possibly?
  5.  
    A physical analogy which illustrates a lot of the concepts of GR and cosmology (inflation, curvature, etc.) is to drop one spatial dimension and separate out time, and thus we can imagine inhabiting a two-dimensional surface on a balloon. It's not a perfect analogy because it assumes an embedding into a 3-dimensional space, whereas GR does not assume an embedding into a 4-dimensional space.

    Nevertheless it's a useful model. Starting with a uniform distribution of points on the balloon surface, expansion can be modelled as a blowing up of the balloon. Every point ends up further away from every other point as measured along the surface. Overall universal curvature is modelled by the radius of the balloon. Local curvature due to mass-energy concentrations are modelled by dimples in the surface.

    The maximum speed of information transfer between points on the balloon, an analogue of the speed of light, is a property of the surface material. This is in principle independent of the speed with which the balloon can be inflated, which is what I meant by "Spacetime itself can expand (or indeed contract) at any damn speed it likes.".
  6.  
    No one has ever explained who is blowing up the balloon, though.
    •  
      CommentAuthorAngus
    • CommentTime4 hours ago
     
    Interesting analogy.
    • CommentAuthorkorkskrew
    • CommentTime4 hours ago edited
     
    I still don't get why GW propagation is limited to c, and inflation gets to go as fast as we need it to.