The Planck length is defined as the shortest measurable length in physics, approximately 1.6 x 10-35 meters, where quantum gravity effects become significant. Above this scale, quantum mechanics operates effectively without the need for a quantum gravity theory. The discussion highlights the distinction between quantum mechanics and theories of quantum gravity, specifically contrasting String Theory and Loop Quantum Gravity (LQG), with LQG being favored for its simplicity and testable predictions.
PREREQUISITESPhysicists, students of theoretical physics, and anyone interested in the foundational concepts of quantum mechanics and gravity theories.
There's a lot of misleading stuff written about the Planck length, and definition you've found is an example. Give this Insights article a try: https://www.physicsforums.com/insights/hand-wavy-discussion-planck-length/Lunct said:The definition of the Planck length I have found is that it is the shortest length that has meaning. What is meant by that? Can someone give be a better definition of what it is?
So does quantum theory only apply to things smaller than the Planck length? That cannot be right.Nugatory said:There's a lot of misleading stuff written about the Planck length, and definition you've found is an example. Give this Insights article a try: https://www.physicsforums.com/insights/hand-wavy-discussion-planck-length/
You're right, it's not right.Lunct said:So does quantum theory only apply to things smaller than the Planck length? That cannot be right.
Thanks for the help.Nugatory said:You're right, it's not right.
The Planck length is the approximate distance at which quantum gravity starts to matter. Quantum mechanics has not been completely and successfully integrated with gravity, but works just fine above the Planck length, where we don't need a theory of quantum gravity.
Your right, but what I am saying is the LQG has more testable proof. Also Occam's Razor suggests LQG as it is much more simple than having the 11 plus dimensions.FactChecker said:Theories can be supported or can survive a test, but that is not the same as being totally proven. If string theory can not be proven or disproved, that is good enough. It means that it is consistent with reality.
Good points. Simpler is better. And if it is stronger and allows some testable predictions that string theory does not, then that is better (assuming that it passes the tests). Simpler and stronger together are much better.Lunct said:Your right, but what I am saying is the LQG has more testable proof. Also Occam's Razor suggests LQG as it is much more simple than having the 11 plus dimensions.
thanks for the repliesFactChecker said:Good points. Simpler is better. And if it is stronger and allows some testable predictions that string theory does not, then that is better (assuming that it passes the tests). Simpler and stronger together are much better.