Talk:Planck units/Archive 1

message: I think that the table at the end with quantities and dimensions is a bit strange. The idea behind natural units (not all physicists agree with this) is that fundamentally there are no units or dimensions.
If you put h-bar = c = 1, then Time = Length = 1/Mass
If you put c = G = 1 then Time = Length = Mass
Both systems are 1 dimensional unit systems. If you put all the constants equal to 1 you have a zero dimensional system unit system (i.e. no units or dimensions at all). Lengths, squares of lengths, masses, they are all the same quantities.
In no way does this lead to conflicts. Using dimensional analyses, e.g. you can derive that the period of a pendulum should be SquareRoot[L/g] times a constant of order unity. You can still do that in a zero dimensional system. You then define a physical length, time etc. that are obtained by rescaling (using h-bar, c and G) from the dimensionless planck scale quantities. You then demand that the desired relation does not involve infinities in the (independent) limits c->Infinity, h-bar-->0 and planck length --> 0. This is formally the same as dimensional analyses with meters seconds and grams.
Count Iblis 16:42, 11 Dec 2004 (UTC)
thread_title:  Dimensions 

message: Your Planck units of length, mass, etc. have too many significant figures.  The gravitational constant itself is only known within .01%, four significant figures.  Using as many as 6 significant figures on measurements that include G is simply absurd and meaningless.  -RobertDonald 25 Oct 2005
:(Robert, try using four tildes to sign and timestamp your edits)
:G is listed to 5 digits even though the last one is less than the std error.  when you square root, you get another approx 1/2 digit.  the NIST values for: Planck Time Planck Length Planck Mass all are listed to 6 digits.  we just copied their numbers.  if it's good enough for NIST, i think it's good enough for WP.   but you're right, G messes up accuracy.   that's why the Planck Charge has more digits. r b-j 01:47, 26 October 2005 (UTC)
thread_title:  Significant Figures 

message: Lucretius speaking here: I don't agree RBJ that your changes have improved matters. My concern here is that this invariant scaling section looks like a personal opinion, as evidenced by your rhetorical question at the end. I've now removed the rhetorical question (Gamow is unavailable to answer it) but I haven't yet made any other changes. I think even Duff was rather more objective than you have been since he at least includes in his paper (which you link to) the opinions of those who rejected his paper. I also have concerns about the length of this section. It really does lack conciseness. I'm sorry but this section appears to be the Gospel according to RBJ and I still think it is in need of considerable revision if Wiki's claim to being an impartial encyclopaedia is to mean anything. Lucretius 06:58, 31 December 2005 (UTC)
replies: text: you go to sci.physics.research and see how much of a personal opinion it is.  also talk a look at Talk:Variable_speed_of_light#A_changing_C_is_meaningful where i am discussing with "Scott" (he hadn't registered as an editor and created this article as an anon IP) about what the consensus of the physics community is and why (in the opinion of this electrical engineer) they have that consensus.  it is not just my personal opinion, but i could tell that folks like Michael Duff and  John Baez were getting tired of people not getting this and physicists like Paul Davies confusing the issue even more.  this is why i thought putting this in this article was salient.  when the quantities of the universe are measure or described in terms of Planck units there is no speed of light (or those other normalized constants).  if someone thinks there was a cosmological (or a sudden) change in the speed of light and they think they measured such a phenomenon, what changed was the number of Planck lengths in their meter stick or the number of Planck times in the second of their clock or maybe both, and those (dimensionless) quantities are the salient ones that have changed.  that is the whole point of that section.  it is not simply my opinion and certainly not my original research.  but it is my paraphrasing of the language used by Duff and other physicists that i have discussed with this on the moderated newsgroup sci.physics.research. r b-j 18:03, 31 December 2005 (UTC)
replies: text:  i've already provided two links.  they are strictly relevant (but there is a paraphrasing on my part). your rewrite is far less concise. the point is simple.  if our measuring standard is against the Planck units, the speed of light or the graviational constant or Planck's constant or the Coulomb electrostatic constant or the Boltzmann constant do not change.  if, for some reason someone thinks they have, what really changed is the dimensionless ratio of the number of Planck lengths in a meter or the number of Planck times in a second (which is contrary to the assumtion of using Planck units as the standard of measure).   Lucretius, please post to sci.physics.research and ask those guys and banter it about there before changing something like this.
This revert is of course your right. But did you actually read my revised version? This was my second rewrite and it was not the same as my previous rewrite, where I did try to make alterations to the argument. In this second rewrite, I merely tightened up the language but it was YOUR argument I phrased. I included in the revised version the link below, which is to a university sponsored web page that also puts forward your argument in quite simple and entertaining terms. I did not remove your links. I did remove some rhetorical devices you use, such as repetition, which indicate that you have an emotional investment in the article. I also removed redundant phrasing. The present intro, for example, is twice as long as mine without adding anything significant to the meaning. I won't bother to touch this article in future but, in its present form, someone is certain to rewrite it for you, and the next person might not try to honour your intentions, which is what I made a very conscientious effort to do.
I notice that you are using your real name whereas I of course am using an alias. This gives me an unfair advantage, particularly if you think I am using 'banter'. It is hard sometimes to criticize a piece of writing without also appearing to criticize the writer and it may be that I haven't always got the balance right. How does one stop the ball without tackling the man who is running with it? But I do try not to throw any sneaky punches. If anything I have said thus far causes you personal discomfort, you have my permission to delete it.  
I should also add the reason why I originally misunderstood your intentions. There are two reasons:
1) the links to Duff et al are links to controversial papers (Duff for instance argues that no physical constants are truly fundamental, which is extreme even by the standards of his two colleagues. It's also extreme within the context of Planck units, which many believe are indeed fundamental).
2) your treatment of the subject appears controversialist owing to rhetorical devices.
It took me a while to get through these appearances and to realize that your article is not actually controversial but simply a statement of a commonly held position.
Anyway, I've enjoyed this little debate even though I don't much like the final outcome. 
CheersLucretius 23:27, 2 January 2006 (UTC)

text: just to clarify (at least from my understanding), Duff doesn't say that no physical constants are truly fundamental, only that the dimensionful ones are not fundamental.  all physical theories, the Standard model, GR, strings, whatever, can be expressed in their entirety without any dimensionful scaling constants.  yet, according to John Baez, there remain some 26 fundamental numbers (dimensionless) that are needed.  i don't think Duff means to imply that these physical constants are not fundamental to our current physics.  also Veneziano does agree with Duff on that basic concept.  as i read it, from sci.physics.research, there really is not much debate about it, despite the proponents of VSL or variable G or whatever.  r b-j 06:14, 3 January 2006 (UTC)
thread_title:  Personal opinions 

message: I fail to understand, Rbj, why you think the link to Planck force was irrelevant, particularly since you went out of your way to edit that article so as to give primary significance to Planck quantities.Lucretius 03:40, 15 January 2006 (UTC)
replies: text: as i said in the Edit summary, it is already linked two different places, just like nearly all of the other Planck units.  why should the Planck force appear in the See also section and not the Planck mass?  or Planck length? r b-j 04:34, 15 January 2006 (UTC)
thread_title:  Why no Planck force link? 

message: Interesting to read all your above discussion.
In the article it reads now:
"Natural units have the advantage of simplifying many equations in physics by removing conversion factors. For this reason, they are popular in quantum gravity research."
Propose you add a line how this removal of conversion factors works to enable less experienced readers  to better understand how the subsequent tabulation was generated.  
--Oddy 01:14, 24 January 2006 (UTC)
thread_title: Simplification, and basic and derived Planck units

message: okay about anonymous IP User:132.181.160.42 (University of Canterbury, Christchurh NZ) and anonymous IP User:202.36.179.65 (Christchurch College of Education), i strongly suspect that this is the same editor (why not get an account and username?).  not all of your edits make the article better.
some changes back: 
Planck units are not only the base Planck units, just as SI units are not only the SI base units.  Planck units are not the only "natural units".  there are other systems of natural units (Stoney, atomic, etc.) that normalize different natural quantities.  i added a sentence about why Planck units might be "more natural".
the idea of E.T. is not just that E.T. could use or know of natural units but that extra-terrestrial intelligence might be expected (by us or a 3rd party E.T.) to use the same system of units.  this addresses the remote possibilty of one-way communication with E.T., if we receive a message or send one (that somehow the other can decode) and then to make references to distances, sizes of things, etc. how do we communicate this to E.T.?
"The dimensionless fine-structure constant can be thought of as taking on the numerical value that it does because of the amount of charge, measured in Planck units, that nature has assigned ..." this is a qualification and has to do with the fact that it could also, just as legitimately, be thought of the other way around.  maybe the fine-structure constant is the fundamental value and the amount of charge in electrons, etc. take on the value they do because of that.
other changes are hopefully self-explanatory.  we can talk about it. Rbj 06:42, 5 May 2006 (UTC)
thread_title:  edits of 5/5/06. 

message: Just a few silly points : 
1) If we have Planck space, and Planck time, then perhaps Planck "spacetime" is not too bad an idea.  We also have Planck energy - what about Planck "energy density"?  There, perhaps, should be a notion of 'temporal' energy density "Planck energy" per "Planck time".  Essentially, if space-time, matter and, essentially, everything is 'quantised' in the sense of Planck, then some extra Planck unit MIGHT be worthwhile.  
2) Has anyone ever managed to manipulate matter at the Planck scale in space, or to time events to Planck scale in time.  If the notion of Planck energy density makes sense - has anyone ever come close to it (NO, the answer is one one of the wiki-pages).  Is it theoretically/practically possible to contain enough energy within a small enough space so as to interact with the universe at these scales?  (Answer, probably not - but Planck energy located within a Planck space-time event seems like it should be possible.  The energy density would be massive, but the energy is reasonable, perhaps?).  
I think point (1) has some validity.  Perhaps the units may appear to be too much verbiage?  Point (2) is clearly mad.  
Naturallimits 19:11, 23 May 2007 (UTC)
thread_title: "Nature sets a practical limit to things. "