The end all be all of the planck scale

[fet2105]

I have always understood Planck time as being the the smallest amount of time that has any physical significance and the Planck scale as being the region where space and time collapse on each other and all of our mathematics fail. Why are these seemingly magic numbers the end all be all of physics? Can anyone break it down?

 

[Simon Bridge]

tldr: is to do with the uncertainty principle.
http://math.ucr.edu/home/baez/planck/node2.html
http://backreaction.blogspot.co.nz/2012/01/planck-length-as-minimal-length.html

 

[cgk]

Also, those length and time scales are not experimentally accessible, so any such predictions as to what or what does not happen in these regions are technically still *far* in the speculation domain.

 

[Simon Bridge]

And yet there are still peer-reviewed papers concerning physics on the plank scale and possible effects so it is not a banned level of speculation... besides, the question does not call for speculation.

 

[Simon Bridge]

@fet2105: any of this useful to you?

Just to be clear...
The question before us is this:

Why are [plank length and time etc] [considered by some to be] the end all be all of physics? Can anyone break it down?

... the brackets are mine.
We do have to be careful not to indulge in undue speculation since this is fringe stuff.
However, the links in post #2 should explain why the plank length/time tends to be seen as a limiting case in certain ways (details in links).
Even if it were speculation - the rules on speculation are pretty clear:
https://www.physicsforums.com/showthread.php?t=414380

Generally, in the forums we do not allow the following:
...
Personal theories or speculations that go beyond or counter to generally-accepted science

Generally, discussion topics should be traceable to standard textbooks or to peer-reviewed scientific literature. Usually, we accept references from journals that are listed here:
http://ip-science.thomsonreuters.com/mjl/

... it is quite easy to find articles in those journals from that list which refer to plank length physics. Most commonly in terms of quantum gravity.
A quick review of the literature should tell anyone interested the scope of discussion here.

The fact that what happens at the plank limit is basically speculative is the subject of the question ... "how come our models end at that scale?" OP has not asked for speculation or put forward a personal speculation about what happens at the plank scale ... but has asked why the plank scale is (considered by many to be) special.

OTOH: OP could be thinking of something else, I'm making the most favorable interpretation of the question :)

 

[cgk]

I am sorry if it looked like I implied that this question might not belong on this forum. I am not considering this an undue speculation at all. I just wanted to point out that while there are arguments for considering these scales as limiting scales, one should not take these predictions as hard facts: The physics on this scale has not been experimentally observed, and is unlikely to be observed any time soon. So technically one cannot say what happens there. That is all I wanted to say, because OPs question sounded like he/she thinks these issues are completely uncontested (like many highly speculative topics which are presented has hard facts in pop science).

 

[fet2105]

The information provided was very useful indeed. I think that the snippet that sends the overall message home is the question: "how come our models end at that scale?". Thank you very much.