SoylentNews

devlux [soylentnews.org] writes:

We're all taught from a young age that spacetime is smooth, continuous and flowing.
In highschool and college we are taught that spacetime can expand or contract, essentially we swap momentum through time for momentum through space and vice versa. The pictures of bowling balls on a trampoline are classic visualizations we're all familiar with to explain the elasticity of spacetime.

Yet Quantum Mechanics tells us there are limits. There is a "smallest small" point in spacetime and at this scale the universe becomes "discreet". A collection of individual points which cannot be subdivided further. This is in direct opposition to relativity.

http://www.askamathematician.com/2009/12/q-howwhy-are-quantum-mechanics-and-relativity-incompatible/ [askamathematician.com]
https://einstein.stanford.edu/content/relativity/a11758.html [stanford.edu]

This is the root of the problem between QM & Relativity. Any theory which seeks to reconcile this disparity must reconcile two theories which posit two completely different models of what "spacetime" actually is.

Quantum Gravity is the name of an effort to find a theory that is compatible with both Relativity and Quantum Mechanics, unifying them into a nearly complete theory of everything.

https://en.wikipedia.org/wiki/Quantum_gravity [wikipedia.org]

This has created a whole new class of theories any of which could be valid, but the question remains how do you test and probe theories at this level?

How do you probe to a depth of 1.616199 * 10^-33 meters?
Compared with the size of a hydrogen atom which is 5.291*10^-11 meters currently the smallest thing we can visualize, we have a long ways to go.

To give you a good example of the scale of difference. Imagine trying to visualize a single atom on earth using a probe located at the edge of the observable universe. https://www.wolframalpha.com/input/?i=13.8+billion+light+years+in+angstroms [wolframalpha.com]

But maybe not that long? A new paper recently published in the Journal of the American Physical Society http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.161303 [aps.org] [paywalled]

Testing Quantum Gravity Induced Nonlocality via Optomechanical Quantum Oscillators

Abstract
"Several quantum gravity scenarios lead to physics below the Planck scale characterized by nonlocal, Lorentz invariant equations of motion. We show that such nonlocal effective field theories lead to a modified Schrödinger evolution in the nonrelativistic limit. In particular, the nonlocal evolution of optomechanical quantum oscillators is characterized by a spontaneous periodic squeezing that cannot be generated by environmental effects. We discuss constraints on the nonlocality obtained by past experiments, and show how future experiments (already under construction) will either see such effects or otherwise cast severe bounds on the nonlocality scale (well beyond the current limits set by the Large Hadron Collider). This paves the way for table top, high precision experiments on massive quantum objects as a promising new avenue for testing some quantum gravity phenomenology."

Original Submission