Essay Abstract

In the search for a quantum theory of gravity, it is commonly accepted that the universe must be either digital or analog. Here, I wish to suggest a possible third way: that spacetime may be both discrete and continuous, in the same sense that light is neither particle nor wave, but occupies a dualistic middle ground. I examine three nascent theories of quantum gravity, and posit that, in each case, a dualistic approach has the potential to resolve open questions or, at least, stimulate fresh thinking on old questions. The conventional approaches may yet be proven to work, but that should not imply that other alternatives may not deserve consideration.

Author Bio

Jessica Victoria Bloom is an Honours student in Foundations of Quantum Mechanics at the University of Sydney, Australia. She is passionate about the frontiers of physics and philosophy of science, and enjoys thinking about the universe.

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Sorry - small ammendment! On page 4, I refer to M-theory as "the meta-theory in which the five known versions of string theory are seen as distinguished points in eleven-dimensional spacetime". This should read that the five known strings theories, and 11-dimensional supergravity, are points in multi-dimensional moduli space, moduli space being a form of geometric space used to identify equivalent mathematical objects.

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Hi Jessica, a very nicely written essay and very easy to read yet containing complex study matter. I was particularly taken with this last comment "Perhaps reality IS easy to visualize". I totally agree and think that I have the visual model for the graviton: Archimedes screw. How did Newton miss that one!?

If a graviton helical screw travelled around a wraparound universe then it would emerge on the other side as a force of repulsion i.e. dark matter. Too much of a coincidence imo, what do you think to this backwards idea Jessica?

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The one problem with LQG, causal sets and dynamic triangulation and the rest is that one assigns degrees of freedom to a spacetime manifold. The dynamics is encoded into space as if space were composed of atoms. This leads to a massive accounting of degrees of freedom with entropy S = nNK/2, for N the number of degrees of freedom. This means the universe has intrinsically huge entropy. This is one reason people can’t get LQG to reproduce classical gravity easily, for the classical spacetime has energy or entropy content which is wrong.

In a sense this seems to me as a problem with ether theories over 100 years ago. People insisted there was a dynamical flow to space itself. This was replace by Einstein and Lorentz by a symmetry. In this setting the degrees of freedom in the system are contained in the particles and systems in spacetime, but not in spacetime itself. Curiously we seem to have a similar trend in physics today.

Cheers LC

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Jessica,

I found your essay beautifully written, you definitely have a 'literary' flair. When I saw the title of your essay, I thought of Jonathan Swift and braced myself for a truly outrageous proposition, but, as it turns out, many other entrants to this contest have proposed ideas that seem somewhat similar.

In my view, a duality between things that in their essence appear to be incompatible with one another which fails to show the conceptual bridge between them presents an incomplete picture of the relation between those things, and so I cannot accept that, say, the wave-particle duality alone (i.e. without an explanation of how the two incompatible representations 'fit' each other) is a description that reflects our most fundamental understanding of quantum objects. I think that it really is within our grasp to understand what these kinds of dualities really 'mean', in the sense that a deeper reflection ought to reveal that two concepts related by a duality but apparently mutually exclusive are in some definite sense still compatible with one another.

From this perspective, it seems incumbent upon anyone who proposes such dualities to also explain in what specific sense the two ostensibly incompatible concepts can be understood to be compatible with one another after all. Without this sort of explanation, such propositions run a serious danger of degenerating into a kind of mysticism, in my opinion. Unfortunately, I fail to see much in this regard in the essays that I have read which propose that reality may be both continuous and discrete.

In the case of your essay, I do have the impression that you were actually too modest to venture into this area, as it (unsurprisingly!) will force the proposer to go out on limb and suggest ideas that are likely to be highly unfamiliar. It is not that difficult (or 'immodest') to point out places in a given theory where one or the other concept may be usefully substituted. It is much, much harder to explain in specific terms how the different conceptions can be understood to be connected to each other as clearly as we understand, say, how the the ear and the trunk of an elephant are connected to each other.

Anyway, don't let my criticism discourage you, it is was sincerely meant to be constructive. Within the scope of what you set out to do, you did extremely well!

Take care,

Armin

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Jessica,

I don't get a sense that you believe it is one or the other or both, separating yourself from a decision.

Do you have a preference? I would like to hear it.

Jim Hoover

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Jessica,

I can tell you put a lot of care into this essay. I wish you used a term other than "research programs" in relation to things like string theory. There has been no experiment to prove or disprove string theory, Hawkins radiation or quantum gravity. I know what you mean, there have been great advances in these fields. In a paper like this, that is accessible to non-physicists a small point like this could be confusing.

Overall, this a very good essay.

Jeff

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Jessica

I enjoyed your analysis and modest proposal, definitely worth more than a modest score. Lawrence had a good point about degrees of freedom, but I'm struggling to find anything wrong with an even more modest proposal, that there are simply multiple manifolds. This allows covergence of the quantised mechanism as Newton discovered in our current community leaders essay.

I put this through thorough if naive empirical falsfication in my own essay, (2020 vision, a model of discretion..) which I do hope you'll find time to read and comment on. It suggests a slightly different 3rd way, between an absolute ether and zero field, with the attributes of both, and seems to produce all the results of SR and GR without patches or paradoxes. It's far to simple to believe, but has only yet been faulted on beliif grounds - so also needs some some scientific ones'

I'd really love to hear your views.

best wishes.

Peter

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Thank you, everyone, for your kind and helpful comments!

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Hello Jessica, and a belated congratulatory note on your excellent essay. Hard to keep up with all that is going on with this contest!

I want to share with you an astounding result that just days ago I posted on the web. I think it may help you with your fence-sitting. Two fundamental assumptions made by Einstein more than 100 years ago were the constant speed of light (CSL) that lead to Special Relativity and the Photon Hypothesis (PH) that eventually lead to QM. In my short paper I mathematically prove that CSL contradicts PH! More specifically, I prove the following proposition:

“If the speed of light is constant, then light is a wave”.

It is an easy read! If you have the time, check it along with my essay and comment if you are so inclined. And if you find these results worthy of your support, I ask that you help me put the essay before the panel of experts for review.

Best wishes,

Constantinos

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