What does "spacetime becomes dominated by quantum effects" mean exactly?

In some forms of quantum gravity, the Planck length is the length scale at which the structure of spacetime becomes dominated by quantum effects, and it is impossible to determine the difference between two locations less than one Planck length apart.

Can someone elaborate? Or point me where can I read more on the subject?

Do I understand it correctly that it actually says that each new time slice of the universe is created by discrete step of Planck length? As mentioned in this article.

• Quantization is not exactly the same thing as discretization. What this means is that instead of getting a precise location you could only get a distribution of values for such a measurement that would have a non-vanishing uncertainty. Having said that, none of the naive concepts of how this could work actually applies, special relativity doesn't play ball with those. There are theoretical models like quantum foams and loop quantum gravity that manage to preserve relativity, but they do so at a great expense of complexity. Commented Jan 2, 2016 at 0:13

You may want to look up the works of Fay Dowker a Professor of Theoretical Physics at Imperial College. Very interesting stuff dealing with the Planck length and the "granulated space-time".

• could you provide a summary of his ideas and links in your post ? TY
– user46925
Commented Jan 2, 2016 at 1:00

You could look up Heisenberg's Uncertainty Principle on Wikipedia (or on this site) which shows that for the physicist, constrained to limit his/her theory to observation as a matter of intellectual honesty, there is a natural limit to his/her ability to observe differences in position (for example) because all physical things have an associated wave and the length of that wave cannot be exactly determined. The limit of experimental exactitude is the Planck length. (Dowker's work on Causal Dynamical Triangulations (mentioned by others) is/was more about building a model of the universe. In it there was difficulty in pursuing the model down to a smooth continuum (i.e. to the limit of smallness) which some might suggest implies that if the model is correct, there must be some minimum length, possibly the Planck length.