In short, quantum graininess of space should cause polarization of light traveling great distances. Different wavelengths will experience the polarization to different degrees. A group has been examining data from a powerful gamma ray burst picked up by the ESA's Integral detector in 2004. Comparing polarization of low-energy and high energy rays, they have been able to limit quantum graininess to 10^-48m. The Plank scale calls it at 10^-35m. That is 10,000,000,000,000 times smaller. For all that we know, we still don't know why apples fall from trees. Btw, I have to admit that I take pleasure in another nail candidate for the string theory coffin.
Fully agree but it is something of a conceptual rabbit hole, isn't it? Evolutionary systems seem to require a 'stable platform'. I.e. there seems to be a need for a baseline 'ground of reality'. > the Planck length may be now up for debate I'm with the Greeks on this one. "Number governs the Universe"
I mentioned this in another post, but its relevant to this discussion too- phy