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Re^5: [OT] A prediction.

by Athanasius (Archbishop)
on Apr 28, 2016 at 15:47 UTC ( [id://1161784]=note: print w/replies, xml ) Need Help??


in reply to Re^4: [OT] A prediction.
in thread [OT] A prediction.

Hello BrowserUk,

As jdporter says, the expanding balloon analogy is not the best. The two I’ve seen are:

  1. baking raisin bread (see the animation in Metric_expansion_of_space)
  2. stretching rubber sheet (see http://www.felderbooks.com/papers/cosmo.html, section II)

— the point in each case being that while the “space” (bread dough, rubber sheet) expands, the entities in it (raisins, thumbtacks) do not:

In fact, not everything grows as the universe expands. In the example of the rubber sheet, the distance between thumbtacks keeps increasing but the thumbtacks themselves remain the same size. Similarly, while distant galaxies are pulled away from each other by the expansion, smaller objects like meter sticks, people, and the galaxies themselves are held together by forces that prevent them from expanding. So we expect that billions of years from now galaxies will still be roughly the same size they are today, but the distances between them will on average be much larger.

A minor point:

And if you accept the indivisibility of space & time; that they are aspects of the same thing as General Relativity suggests, ...

I believe that the concept of spacetime is actually a corollary of Special Relativity. If anyone is interested, I can recommend the book Simply Einstein: Relativity Demystified (2003) by Richard Wolfson as an excellent introduction for the layman (like me). It has a section which explains in detail the rationale for viewing space and time as aspects of a unified spacetime in the light of Special Relativity.

BTW, the “taster” paper you cite up-thread seems to say only that the speed of light may not be constant over time. Why do you assume that this implies it is increasing?

Athanasius <°(((><contra mundum Iustus alius egestas vitae, eros Piratica,

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Re^6: [OT] A prediction.
by BrowserUk (Patriarch) on Apr 28, 2016 at 20:32 UTC
    the expanding balloon analogy is not the best.

    Agreed. But it is still the one I've most often seen presented. "The favorite"; rather than my favorite.

    I guess my favorite is the stretchy rubber sheet with heavy spheres represent stars and planets and demonstrating the gravity wells and imprinted lines showing the curvature that results; but it's still an inherently two dimensional analogy (despite that dips give a third dimension).

    I still find it hard to imagine a gravity well in 3 dimensions, and I guess that's because you need be in the fourth dimension to envisage it.

    I have inordinate trouble with going above 3D; but I don't see that as a limitation, but rather as a deeper awareness of the underlying incongruity of trying to visualise something we can never really see. For example, this tesseract animation just demonstrates the limitations of trying to visualise higher dimensions with inherently 3D brains and devices.

    If you want to make your brain go soggy, try to visualise a 4D sphere analog :) Then go here and see if you think the author's animation does it for you? (The write up is ... interesting also.)


    With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority". I knew I was on the right track :)
    In the absence of evidence, opinion is indistinguishable from prejudice.

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