# User talk:Dauto

Welcome!

Hello Dauto, and welcome to Wikipedia! Thank you for your contributions. I hope you like the place and decide to stay. Here are a few good links for newcomers:

I hope you enjoy editing here and being a Wikipedian! Please sign your name on talk pages using four tildes (~~~~); this will automatically produce your name and the date. If you have any questions, check out Wikipedia:Where to ask a question or ask me on my talk page. Again, welcome!  Fawcett5 18:07, 19 October 2005 (UTC)

You were right that there was a problem with a sign, but it's not a good idea to just delete a minus sign without a reason. I corrected the sign error by taking the integral over M in the correct direction. 75.45.210.119 (talk) 18:32, 4 February 2009 (UTC)

## Barnstar

You deserve a barnstar. Best wishes. Axl ¤ [Talk] 18:32, 2 March 2009 (UTC)

 The E=mc² Barnstar To Dauto, for contributions to scientific articles. Axl ¤ [Talk] 18:32, 2 March 2009 (UTC)

## Science desk question

I asked a follow-up to one of your answers on the science desk regarding quantum mechanics and predetermination. Your responses there are usually very helpful and appreciated. Thanks mislih 00:04, 24 April 2009 (UTC)

## Relativity, exponential curves, infinity of time(ish)

You gave a truly patient and correct response to a convoluted question. Cuddlyable3 (talk) 18:31, 12 June 2009 (UTC)

## Nuclear force binding energy constant

Hi Dauto. Thanks for the reference desk answer -- I needed you help in seeing how simple it was. I'm not trying to pick nits here, but when you wrote "I forgot to include the energy realeased from two electrons" I assume that it was the mass of the electrons themselves that you had forgotten to include, because I get you initial number of 0.0068500 from 1 - mα / (4 mp). I am also assuming that your second number, 0.0071224, had a typo and you meant 0.0071204. Thanks again. -- Thinking of England (talk) 09:29, 23 August 2009 (UTC)

## Weight diagram

Hi Dauto,

thanks for SO(10) diagram -- just one last question. I get everything except the vertical column of arrows and numbers on the right hand side. How do they work?

Do you have a similar diagram for the Pati-Salam model?

--Michael C. Price talk 14:51, 2 November 2009 (UTC)

Obviously I understand less than I thought. What is a "level"? It seems I need to understand that to get your Pati-Salam explanation.

Incidentally, my interest in Pati-Salam was piqued when I read that it doesn't predict proton decay. Since minimal SU(5) has been ruled out by the lack of proton decay, this seems to be a plus for Pati-Salam. Strangely, there seems very little in textbooks (and nothing on Scholarpedia) about Pati-Salam, which makes life frustrating. --Michael C. Price talk 18:12, 2 November 2009 (UTC)

Obviously I understand less than I thought. What is a "level"?

It's really pretty simple. The top component of the weight diagram (The anti-neutrino for that specific diagram) is labeled as being level zero. Now go down the diagram (walking with your fingers if you will) following the links. Your first step will take you down to an up quark which is labeled as belonging to the level 1. Your second step take you down to another up quark (of a different color) which is labeled as belonging to the level 2. Work your way down to the bottom of the diagram which (for that diagram) will be level 10. It is just a way to help label the different components of the diagram to make it easier to refer to them. Dauto (talk) 20:18, 2 November 2009 (UTC)

I'm none the wiser, perhaps I should just ignore the levels and connections since they don't seem to have any physical significance - they're not helping me at all, at the moment. Could you produce a Pati-Salam weight diagram? I think that would be most helpful, for me and for the Pati-Salam article. Basically something that will realise
${\displaystyle Q=Y/2+T_{3L}+T_{3R}}$ (?) and retain ${\displaystyle X+2Y=5(B-L)}$ etc
--Michael C. Price talk 10:48, 3 November 2009 (UTC)
Forget about the levels. They are not that important. I uploaded a weight diagram for the matter content of the Pati-Salam model. There is a link for it at my user page. BTW you probabily meant :${\displaystyle Q=(B-L)/2+T_{3L}+T_{3R}}$. Dauto (talk) 21:29, 3 November 2009 (UTC)
Yes, just realised my mistake. Thanks - it's making sense now. I think the -1 in the positron should be +1. --Michael C. Price talk 22:00, 3 November 2009 (UTC)
Yes, absolutely. The -1 in the positron is a typo. I'll fix it. Dauto (talk) 22:06, 3 November 2009 (UTC)
If you want to dig a little deeper and really learn some of that stuff, I recomend reading that book by Georgi and that paper by Slansky. I never read that book [ABE: paper] by Das and Soni but the title seems promissing. Dauto (talk) 23:21, 3 November 2009 (UTC)
Putting all the data from the weight diagrams into tabular form is very instructive. It makes Pati-Salam seem inevitable from SO(10).
Does X have a name?
--Michael C. Price talk 11:15, 4 November 2009 (UTC)
As far as I know it is simply called the X-Charge (or X'-charge in some of the literature). It sounds better than super-dee-duper-charge which is where the trend started by hypercharge might eventually lead us to. Dauto (talk) 14:44, 4 November 2009 (UTC)

I'm having troubling downloading the Slansky paper (lack of cryllic skills). Do you have any links that give the langrangian for Salam-Pati? I couldn't find any on the physics archives that explained just the basic model, as opposed to some SUSY extension.--Michael C. Price talk 14:52, 4 November 2009 (UTC)

Just click the bottom most link above the "Report abuse to this file" button. You may have to wait a few seconds for the link to load.Dauto (talk) 17:00, 5 November 2009 (UTC)
You can also find it here but you may have to pay for it if you don't happen to have free access to this database. That's why I like the other site. Dauto (talk) 17:09, 4 November 2009 (UTC)
You won't find many people doing GUT model building without SUSY nowadays. That's just how things are right now. But you should be able to extract a non-SUSY lagrangean almost by inspection just by looking at the field content of any particular model.The particular field content may vary a bit from model to model. Just remember that the lagrangean must be a Yang-Mills singlet Lorentz single every-thing-singlet. The Pati-Salam model page has one possible choice of fields. Dauto (talk) 18:56, 4 November 2009 (UTC)

Here's my rather unpolished attempt to summarise the ferrmion SU(4)c, SU(2)L and SU(2)R quantum numbers for Pati-Salam:

Quantum numbers
2I1 2I2 2I3
L/R fermions u1 d1 -1 0 1
u2 d2 1 -1 0
u3 d3 0 1 0
${\displaystyle \nu }$ e- 0 0 -1
2T3L/R 1 -1
2T3R/L 0 0

Where ${\displaystyle B-L={\frac {4I_{1}+2I_{2}+6I_{3}}{3}},}$

${\displaystyle X=-4T_{3R}+3(B-L)\,}$

${\displaystyle Y=2T_{3R}+B-L\,}$

${\displaystyle Q={\frac {B-L}{2}}+T_{3L}+T_{3R}={\frac {Y}{2}}+T_{3L}}$ --Michael C. Price talk 00:47, 7 November 2009 (UTC)

I have a few points to make.

• I was a little lazy earlier with the notation and used ${\displaystyle I_{1},I_{2},I_{3}\,}$ instead of the more proper ${\displaystyle I_{3,1},I_{3,2},I_{3,3}\,}$. If you are using ${\displaystyle T_{3L},T_{3R}\,}$, than you should use the latter for consistency.
• When moving from the SO(10) to the Pati-Salam fields: ${\displaystyle SO(10)\rightarrow SU(4)\times SU(2)\times SU(2)}$ it's necessary to change the labels of the generatos like this

${\displaystyle I_{3,1}\rightarrow I_{3,L}}$
${\displaystyle I_{3,3}\rightarrow I_{3,2}}$
${\displaystyle I_{3,4}\rightarrow I_{3,1}}$
${\displaystyle I_{3,5}\rightarrow I_{3,3}}$
${\displaystyle I_{3,1}+2I_{3,2}+2I_{3,3}+I_{3,4}+I_{3,5}+\rightarrow -I_{3,R}}$
Note how the SU(4) generators are out of order.

• Your choice for numbering the three possible color for a quark is also non-standard. To get to the standard from yours make the changes ${\displaystyle u_{1}\leftrightarrow u_{3}}$ and ${\displaystyle d_{1}\leftrightarrow d_{3}}$

Of course the last two points are just a matter of convention, but they lead to a staircase-like structure for the eigenvalues which is easier to remember

Quantum numbers
2I3,1 2I3,2 2I3,3
L/R fermions u1 d1 1 0 0
u2 d2 -1 1 0
u3 d3 0 -1 1
${\displaystyle \nu }$ e- 0 0 -1
2T3L/R 1 -1
2T3R/L 0 0

The expression for B-L has to be changed accordingly: ${\displaystyle B-L={\frac {2I_{1}+4I_{2}+6I_{3}}{3}}.}$ Dauto (talk) 05:31, 9 November 2009 (UTC)

Very nice relabelling. Makes B-L easier to remember also. Is there a similar assignment for the Higgs field(s)?

### Use in articles?

I just noticed your nice diagrams on your home page and wanted to find out more about them, but it seems they aren't used in either Pati–Salam model or weight diagram. That's a shame! Why aren't they? — Sebastian 19:45, 8 March 2013 (UTC)

## Sterile neutrino mixing

Hi Dauto,

Thanks for all the help with SO(10) etc. I'm trying to apply some of this to neutrinos at the moment.

I've seen it was stated on one of the neutrino talk pages that sterile neutrinos can oscillate with "normal" neutrinos. I'm not clear whether "sterile" just means "right-handed within the SO(10) model" or not. If sterile neutrinos are just right-handed neutrinos then it seems to me that they will have different weak hypercharge (0 for right-handed neutrinos, -1 for the left-handed neutrinos) and X charge. If so, wouldn't that prevent the right handed / sterile neutrinos from mixing or oscillating with the left handed neutrions?

--Michael C. Price talk 12:05, 21 November 2009 (UTC)

Michael, sterile neutrinos can be any particle that on the one hand mixes with normal neutrinos while on the other hand do not part take on the weak interactions and therefore will (by design) have different electroweak quantum numbers. I'm not a big fan of these kind of models exactly for that reason. If if turns out to be true, they will require a deep restructuring of our understanding of the origins of the Standard Model. The reason they became popular for a while was that atmospheric neutrino experiments, solar neutrino experiments and the LSND experiment seemed to require three different scales of squared mass difference which require four different masses making an sterile neutrino almost unavoidable. The MiniBooNE experiment designed to try to verify (or refute) the LSND results have so far provided a negative result which means that LSND was probabily a fluke making sterile neutrinos unnecessary at this point. Dauto (talk) 15:03, 21 November 2009 (UTC)

Okay, let's see if I've followed that:

1. the right handed SO(10) neutrino is not a sterile neutrino
2. sterile neutrinos fit into a sort of 4th generation which doesn't feel the electroweak force
3. sterile neutrinos do not fit into any natural extension of the Standard Model

Is that right? --Michael C. Price talk 21:12, 21 November 2009 (UTC)

## PreviousPost: Relativity of simultaneity help in the following case

You said “Yes” to my question posted on dated Nov 22, 2009 in the following link

http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Archives/Science/2009_November_22

But I don't know why relativity pundits hesitate in saying “Yes” to my original question which is the reverse play of Einstein experiment in which two bolts of light strike the longitudinal sides of moving train.

Please ignore all if you dislike. 68.147.38.24 (talk) 19:03, 1 December 2009 (UTC) khattak

## User:Neptunerover's question about a no-maths solution to gravity

Hi, Dauto. I noticed you reverted my removal of your comment and the ones that followed, at the end of User:Neptunerover's question regarding his no-maths solution to gravity. As I stated in the edit summary (and on the talk page), I think we should refrain from making such characterizations of our questioners. I have therefore moved the section in question to the talk page. Your opinion would be most welcome there. --NorwegianBlue talk 21:46, 2 January 2010 (UTC)

## Pati-Salam proton decay

Hi Dauto, I finally tracked down a copy of the original Pati-Salam paper, Lepton number as the fourth "color". I'm puzzled by a few things (actually a lot of things). They say that B-L is preserved (although they define L as -L, so they call it B+L), but at the end of the paper they also say that the proton decays into three neutrinos and a pion:

 p → 3ν + π+

But this seems to violate B-L. Do they mean 2 anti-neutrinos and a neutrino, in addition to the pion? --Michael C. Price talk 00:10, 14 February 2010 (UTC)

Hard to say without reading the paper myself, but I wouldn't be surprised if that was the case. Different people often use different notations that are not entirely consistent. BTW I actually personally know Belyaev from whom you got the paper. We published two papers together. Dauto (talk) 05:42, 14 February 2010 (UTC)
Thanks. I've also posted a query at the physics notice board.[1] --Michael C. Price talk 11:44, 14 February 2010 (UTC)

## Pati-Salam gauge bosons

Hi Dauto,

do the new gauge bosons predicted by PS, aside from the W' and Z' bosons, all have B-L=4/3? And do they have an electric charge of 2/3?

--Michael C. Price talk 01:54, 1 May 2010 (UTC)

## Barnstar

 The Reference Desk Barnstar For this particularly astute response, thank you! Calliopejen1 (talk) 17:44, 20 January 2011 (UTC)
Thanks. Dauto (talk) 16:32, 21 January 2011 (UTC)

## Refdesk

Thank you for a clear and thorough answer to my question on half-life and decay constant. jftsang 23:25, 21 February 2011 (UTC)

      1. The U-turn wasn't avoided at all, since the spaceship still reverses direction of motion and comes back to earth.


[@@@@ Thanks for commenting. Reverse is a poor description of what happens. The point of furthest travel isn't detectable to the ship, or clock. If you maintain that these "know" of a U-turn, then describe by what force or means @@@@]

      2. The principle of equivalence doesn't work the way you think. The gravity on the planet
is NOT equivalent to the acceleration of the spaceship and here is why.


[@@@@ The gravity on the planet is equivalent in this case since the earth-bound twin and clock stay at a constant elevation - no tidal effects. http://en.wikipedia.org/wiki/Equivalence_principle "The equivalence principle proper was introduced by Albert Einstein in 1907, when he observed that the acceleration of bodies towards the center of the Earth at a rate of 1g (g = 9.81 m/s2 being a standard reference of gravitational acceleration at the Earth's surface) is equivalent to the acceleration of an inertially moving body that would be observed on a rocket in free space being accelerated at a rate of 1g. Einstein stated it thus:" @@@@]

From the point of view of the observer on the planet he is at the bottom of the planet's gravity well while the ship is outside of the well - that is further up the gravitational potential, and the difference between their gravitational potentials is constant throughout the trip. The planet's gravity isn't very strong so this effect is almost negligible. From the point of view of the observer in the spaceship sometimes the other observer is further up the gravitational potential gradient and sometimes he is further down, depending on whether he is acceleration towards the planet or away from it. [@@@@ The spaceship is outside of the planet's gravity well. It has an artificial gravity of its own, such as being on, say, Mars. General Relativity's Strong Equivalence Principle says that the effects of either acceleration and gravity will be identical for our time dilation problem. @@@@]

He interprets his a acceleration as uniform gravitational field (Yes, that is different from the non-uniform gravitational field of the planet hence the fact that a gravitational field is equivalent to an accelerated reference frame only locally. This problem doesn't satisfy locality since the distance between the observers is at times quite large). [@@@@ General Relativity is invoked to satisfy locality: "In 1905 Albert Einstein's Special Theory of Relativity postulated that no material or energy can travel faster than the speed of light, and Einstein thereby sought to reformulate physical laws in a way which obeyed the principle of locality. He later succeeded in producing an alternative theory of gravitation, General Relativity, which obeys the principle of locality. http://en.wikipedia.org/wiki/Principle_of_locality @@@@]

Because of that the difference between their equivalent gravitational potential can be extremely large and that effect is NOT negligible. Trying to bring General relativity into that problem is unnecessary and makes the problem much harder to understand. [@@@@ I don't understand this statement. We're only talking about 1G forces. @@@@] @@@@[I'm experimenting with methods to make your reading of my comments easier - it all seems to jumble up sometimes]@@@@

Dauto (talk) 03:52, 26 February 2011 (UTC)

GQuickstad (talk) 16:24, 26 February 2011 (UTC)

There is much more you don't understand than my last statement. You don't understand how the equivalence principle works. What's important is not what your local gravitational acceleration is. The important thing is what is the difference of gravitational potential between the two observers. That difference is negligible for the planet's gravitational potential but is non-negligible for the spaceship because from the point of view of the ship, the planet is either way way up in a constant gravitational field or way way down in a constant gravitational field. What is important here is the way way up/down which will be several lightyears. Turns out that those effects are very large but cancel each other exactly, except for the planets gravity which is negligible anyways. That's not surprising since that problem can be solved without using general relativity at all. Dauto (talk) 20:13, 26 February 2011 (UTC)
Yes, there is much I don't understand. Gravity is a mysterious force. I hadn't yet happened upon the "gravity well" solution to the twin paradox. It seems that it has far reaching effects. How about we avoid gravity and go with "a" = shuttle, "b" = mother ship, and "c" = shuttle. "a" and "c" leave the "stationary" mother ship and travel at high fractional C speeds in opposite directions using the 1g acceleration protocol and the 180° rotation in the middle of their respective trips from the mother ship "b". "a" and "c" have the proverbial twins aboard. Is there a "twin paradox" encountered between "a" and "c" as to their aging and shuttle-board clock systems when they reunite? (to refresh, they each accelerate away from the mother ship at 1g, perform a 180° rotation (thrusters always on at 1g) at the halfway points of their respective journeys, thrusters never turning off and causing a constant 1g deceleration and an undetectable 0 velocity point where the shuttles start again towards the mother ship. Back at the center of their respective journeys the shuttles again perform the rotation while still under constant 1g thrust and eventually arrive at the mother ship.)

GQuickstad (talk) 16:37, 7 March 2011 (UTC)

No, there will be no age difference in this case since as you can surely see the situation is completely symmetrical. Dauto (talk) 19:39, 7 March 2011 (UTC)
Please, I wonder if you are being serious. How can it be that the two shuttles, with extremely different relative velocities, are in symmetry to each other? It is their velocity difference that gives them different reference frames and exposes them to time dilation in regard to each other and their onboard twins. You seem to be just comparing the shuttles to the mother ship, which would observe symmetry in the cases of the two shuttles. If you maintain that there is time dilation occurring with each shuttle in reference to the mother ship, what is it due to? Velocity differences? Acceleration differences? Why would these not occur with each twin in respect to the other? You notice that I've tried to avoid gravity wells here so I hope you can't find sufficient gravity anywhere in this case. GQuickstad (talk) 18:03, 10 March 2011 (UTC)
May be I misunderstood the situation but it sounded to me that you were describing a situation where both shuttles accelerate with identical accelerations equal to g but in opposite directions and then reversed their motions after some time coming back to the space station simultaneously. That situation is symmetric and the twins (one in each shuttle) will have aged the same amount after the trip rendering no twin's "paradox". Dauto (talk) 01:53, 11 March 2011 (UTC)
I'll do some more reading and get back. I see that there are discussions that Einstein had with critics that touch on this subject. Thanks for your input.GQuickstad (talk) 01:59, 14 March 2011 (UTC)

## Please cite why I'm out of luck

...when it comes to donating skin and fat cells. That sounds like a quicker way to lose weight anyway, so why not? Re: Your Ref Desk reply.--98.190.13.3 (talk) 23:13, 31 March 2011 (UTC)

I didn't say you're out of luck. I said I think you're out of luck. I don't need a citation for my thoughts. Dauto (talk) 23:37, 31 March 2011 (UTC)

## Political correctness

You asked why I think that some questions or articles would be (considered by some to be) politically incorrect. Looking around, not only on wikipedia, there clearly are people who act as if science, especially nuclear science and space exploration, would be somehow offensive.

Look at the comment on this User_talk:76.64.30.242 talk page. Do you think the question about how to catch or kill a housefly would have been removed for the same reasons given? 5BYv8cUJ (talk) 10:46, 19 June 2011 (UTC)

The question got that (unwarranted) response because it appeared to be speculative in nature. I don't think political correctness played a role in here. Dauto (talk) 15:42, 19 June 2011 (UTC)
Please have a look at all the other questions that where not deleted, if they "appeared to be speculative in nature". And please have a look at http://en.wikipedia.org/w/index.php?title=Wikipedia%3AReference_desk%2FScience&action=historysubmit&diff=435534518&oldid=435533796 .
Me, too, was once blocked when I tried to fix a typo and was assigned an ip by my internet provider that had been blocked before, twice. If "you (the wikipedia community as established right now)" would like no "outsiders" in, "you" should state that right on the main page and not lure people into helping and contributing and then throw them out for quite arbitrary reasons. 5BYv8cUJ (talk) 00:03, 22 June 2011 (UTC)
I think you are being paranoid. Dauto (talk) 00:42, 22 June 2011 (UTC)

## CP violation

HI,

This is with regard to the undoing of my additional information regarding the theory and experimental Data, about the effect of galactic spin On spacetime.

any particular reason? — Preceding unsigned comment added by Chimesmonster (talkcontribs) 12:59, 21 July 2011 (UTC)

Yes, there were three main reasons.

• 1st, You addition wasn't very well written. Wikipedia is an encyclopedia, not a blog. Just adding a one-liner at the end of an existing article that doesn't seem to connect in any way with what came before is not the way to go. Your text was to colloquial, starting with "As of July 14th" which is bound to become outdated within a year.
• 2nd, The new addition wasn't well referenced. You linked to two blogs and a picture with no caption.
• 3rd, It is dubious whether that addition meets Wikipedia's notability requirements.

Dauto (talk) 16:58, 21 July 2011 (UTC)

## Eta meson mixing

Hello, Dauto. You have new messages at Talk:Meson#Eta_meson_quark_content.3F.
You can remove this notice at any time by removing the {{Talkback}} or {{Tb}} template.

23:58, 28 July 2011 (UTC)

## Definition of Physics

Dauto: What do you mean by study of quantities? Here is my favorite definition: Physics is whatever physicists do.

Saeed: Thanks. definition was improved to: "the science of quantities." more explaination was added to Talk:Physics

Dauto: The definition of physics is a ontological matter, not a scientific one. Complaining that a definition includes words such as matter and energy on the basis that those things are subjects of ontology makes no sense. Dauto (talk) 16:48, 29 July 2011 (UTC)

Saeed: A really wise feedback. answered here.

 The Brilliant Idea Barnstar I was analyzing different definitions of physics, Thanks for giving me the Idea to analyze the concepts usually used by those definitions. this can allow analyzing more definition in less paragraphs. -- Saeed 20:30, 29 July 2011 (UTC)

Dauto: Chemistry is a branch of physics, so the subject of chemistry IS part of the subject of physics. Dauto (talk) 17:15, 29 July 2011 (UTC)

Saeed: Almost correct. Chemistry is a branch of physical Science, but not Physics. Physical science is a study. An action distinguished by it's method, not a field of information, distinguished by it's subject.

Dauto: No, not almost correct. Exactly correct, chemistry is indeed a branch of physics. Dauto (talk) 20:38, 29 July 2011 (UTC)

Saeed: Ok, I'm working on formulating reason for my claim. To understand what you exactly mean by branch, would you pleas answer a few questions? I

• Is Cosmology (Astronomy, Meteorology, Geography, Geology) a branch of Chemistry?
• Is Cosmology a branch of Physics?
• Is Biology a branch of Cosmology or Chemistry or Physics?
• Is Psychology a branch of Biology or Cosmology or Chemistry or Physics?
• Is Sociology a branch of Psychology or Biology or Cosmology or Chemistry or Physics?

--Saeed 23:57, 30 July 2011 (UTC)

Dauto:

• Why do you put Astronomy, Meteorology, Geography, and Geology in parenthesis when you talk about cosmology? They are not branches of cosmology. Read cosmology and you will see that it talks about the universe, its origins and properties. No cosmology, Astronomy, Meteorology, Geography, and Geology are not a branches of Chemistry.
• Yes, Cosmology is a Branch of physics
• No, Biology is not a branch of Cosmology or Chemistry or Physics.
• No, Psychology is not a branch of Biology or Cosmology or Chemistry or Physics.
• And no, Sociology is not a branch of Psychology or Biology or Cosmology or Chemistry or Physics.
Dauto (talk) 02:14, 31 July 2011 (UTC)

Saeed:

Astronomy = Science of outer space.
Meteorology = Science of planets' atmosphere
Geography = Science of planets' surface
Geology = studying the body of planets
Cosmology = the study of the structure and changes in the present universe. Source: NASA
"They are not branches of cosmology?" maybe. but they are in a same science, because they share subject (the world that exists) and differ only in boundaries of the subject.

Please answer carefully. because it indicates I have to support my claim. Thanks.

Is astronomy, or Meteorology, or Geography, or geology a branch of Physics?
How to recognize something is a branch of another? for example, is it by the way universities classify disciplines and sub-disciplines? is it by subject? Is it because Physics is prerequisite for Chemistry? if yes, is it the only reason? (please also comment on my reply about cosmology) Is it based on library classifications? like library of congress classification? Is it based on scientific papers (in information science) that classify science? is it based on a wikipedia's classification standards?

--Saeed 17:02, 31 July 2011 (UTC)

Dauto: It's not an easy task to pin point a definition for physics and that's why a like the definition that physics is whatever physicists do. Just take a look at the article econophysics. If you really must have a clear definition for physics, and I can't see why anybody would need one, but if you rally must have one, a simple definition is that physics studies matter and its properties. Chemistry studies atoms and their interactions paying particular attention to the bounding of atoms. That definition falls within the first one so clearly chemistry is a branch of physics. Similar claims could be made about Cosmology, astrophysics, Meteorology, Geology, but not biology, geography, psicology, and sociology. Dauto (talk) 20:00, 31 July 2011 (UTC)

Saeed:

"It's not an easy task to pin point a definition for physics"

That's why It took me eight years to do it.
It's not that hard. you just have to read one or two elementary books is Logic, Math, Physics, Chemistry, and Astronomy, carefully enough.
Even a precise definition is not hard after practicing. I've practiced eight years.
What's hard to get is a "globally accepted" systematic defining method.

"Just take a look at the article econophysics"

I've already produced a classification for all such fields and more. I call it "The Atlas of Science."

"I can't see why anybody would need [a clear definition for physics]"

For many many many reasons.

"a simple definition is that physics studies matter and its properties. Chemistry studies atoms and their interactions paying particular attention to the bounding of atoms. That definition falls within the first one so clearly chemistry is a branch of physics."

Now we get to it. Is chemistry a branch of physics? a paper by Mario Bunge.

--Saeed 01:57, 1 August 2011 (UTC)

## centrifuge follow-up

Wow! That is fascinating. I never thought of it before! So fundamentally it is the change in the geometry of spacetime caused by a given scenario that determines whether the given scenario will result in time dilation or not. I would like to learn more. Is there any book that I can read that can teach me how to do calculations to allow me to figure out whether there would be time dilation, and by how much, there is in any given scenario, be they black wholes, traveling twins, centrifuges or other scenarios involving forces/relative motion/other scenarios of GR/SR/Q. Thanks for teaching me. I feel enlightened. L33th4x0r (talk) 13:30, 18 September 2011 (UTC)

## A beer for you!

 Thanks for bringing me enlightenment. L33th4x0r (talk) 13:30, 18 September 2011 (UTC)

## hi - on entropy

hi, so wrt the reference desk - is it fair then to say that the amount of thermodynamic entropy in an object is strictly equivalent to the amount of entropy you would have to send over the wire to a replicator that was capable of perfeclty creating it? Thanks. 178.48.114.143 (talk) 20:51, 10 December 2012 (UTC)

Thanks for the response. Very, very helpful. Thanks. 178.48.114.143 (talk) 21:30, 10 December 2012 (UTC)

## Hi

Hi Dauto, hope you don't mind me buzzing you on your talk page just for a greeting. I noticed your conspicuous absence from the ref desk around early last year, and didn't realise you had returned. Your edit history shows you've been back a while, but I only just noticed you were here again. You have helped me once or twice, and I have learned a lot from your answers to other people's questions. We need people like you, so a belated welcome back! IBE (talk) 19:01, 6 January 2013 (UTC)

## Astronomy

Let me restate the question: ""Galaxies X and Y appear equally bright in the night sky. When a radio spectra of both galaxies are taken, the 21cm line of galaxy X is twice as wide as that of galaxy Y." So is 21cm line indicate how big the the galaxy is? How is that mean the hydrogen line? I know the bigger the universe would mean the faster it rotate. If I assume 21 cm line is the size of galaxy Y then I can get the correct answer but not sure if that's the right way to do it. Hope you can help me with this!174.20.15.246 (talk) 20:47, 6 January 2013 (UTC)