1

Physics, Astronomy & Cosmology / Re: Emmy Noether's Wonderful Theorem

« on: 17/09/2013 20:24:01 »

Thanks Pete.  I think it might be too technical for me - doing three online courses at present and not sure I have the time for a book that whilst it looks great would require a huge investment of time for an layman like me.

If you don't mind me asking, what is your major? Is it math, physics or both? If so then it might naturally come up as par for the course. If you take math then it would be a good idea to study this anyway somewhere along the road. Especially if you enjoy physics since it will be helpful somewhere along the road.

Pete

My degrees are both in Law - physics is only a hobby to stave of the grind of work (I wish I was the age to be deciding on a degree course again - but that was last millennium).  The online courses I refer to are mostly physics-based, but also a comp-sci course, and an energy course - these are at edx.org   The physics courses are basically 1st year undergrad (8Mrev, 802 from MITx etc)  good fun and challenging as you get weekly assignments and midterm/final exams

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Physics, Astronomy & Cosmology / Re: Emmy Noether's Wonderful Theorem

« on: 16/09/2013 18:25:15 »

Thanks Pete.  I think it might be too technical for me - doing three online courses at present and not sure I have the time for a book that whilst it looks great would require a huge investment of time for an layman like me.

3

Physics, Astronomy & Cosmology / Re: Does time dilatation explain quantum effects?

« on: 15/09/2013 11:26:31 »

niebieskieucho's hijack regarding alternative theories which replace einstein's relativity has been moved to new theories.  please don't invade mainstream threads with speculative ideas - post those in new theories.  thanks

imatfaal

4

New Theories / Re: WMAP balance of the universe by 3D electromagnetic forces

« on: 15/09/2013 11:19:53 »

As guessed - moved to New Theories
-mod

5

Physics, Astronomy & Cosmology / Re: Emmy Noether's Wonderful Theorem

« on: 15/09/2013 11:18:35 »

Peter Paros  might I ask what sort of level it is aimed at? Pop-Sci or math-heavy or more likely somewhere in between - but sounds like an interesting read.

6

Physics, Astronomy & Cosmology / Re: Which one of these sentences best depicts the 'Principle of Least Action'?

« on: 13/09/2013 11:43:44 »

1.  stress and strain are terms of art in physics; and within those definitions this part is simply not correct.  If we do not use the accepted terms then 1 can mean almost anything.

2. but they do not.  the conversion of U to K is dependent on the mechanism - and will happen maximally only to the extent of the mechanism and other constraints.  everything that is not forbidden is compulsory - but lots is forbidden or constrained.
 
3. is dodgy for this definition - whilst completely true.  The principle of least action is that the integral of the Lagrangian is minimized - but, as this is intimately connected with total energy in most investigations. Energy is conserved this is required for the PofLA - but Emmy Noether's work (which shows conservation laws through symmetries) relies on the the PofLA for its proof.  It is too cyclical (although all definitions must be eventually)

Surely 4 is just plain wrong - an apple in mid air has a higher (ie closer to zero from the negative side) U than an apple on the ground.  Nature seeks energy situations which are stable which normally means that there is no easily exploited potential to move them to other situations.  It is the route - not the endpoint - that is crucial in the PofLA; in the route you are looking for minimizations of Kinetic less Potential

5.  I don't think this is correct. 

"Physical processes take the easiest route that their constraints allow"

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Physics, Astronomy & Cosmology / Re: Time Dilation Question

« on: 13/09/2013 11:20:41 »

In travelling close to light speed your perceptions would slow so you wouldn't see things speed up. Your interaction with the universe would be slowed.

Nope.  You are always at rest within your own frame - thus your own wrist watch, brain, bodily functions etc all proceed at a normal pace.  Whether due to gravitational potential or relative velocity - you never notice the change to yourself, only to those in other frames.  You can calculate the change that they would perceive in you - but never observe it.

Travelling toward an object at relativistic speed would blue shift (increase the frequency, decrease the time between peaks and shorten the wavelength) any em radiation  that you encountered.

8

New Theories / Re: The Truth About Geometric Unity

« on: 19/08/2013 13:42:03 »

Further to dlorde

http://arxiv.org/abs/1307.1432

and moving this topic to New Theories

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Physics, Astronomy & Cosmology / Re: Should I add milk sooner, or later for cooler tea?

« on: 07/08/2013 17:04:20 »

I believe loss of heat would be dependent on the difference between the cup of tea and its surroundings.  The difference in temperature is greater without the milk and it will lose more heat to the environment whilst still undiluted with milk - you then add the milk which has a simple mixing effect which will same cooling effect as it would have had if you had done it first. 

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Physics, Astronomy & Cosmology / Re: Does the effect of gravity bend with warped spacetime?

« on: 16/07/2013 14:48:20 »

bizerl - hopefully pete will drop by and post on this question, it is right up his street.  My two-penny-worth: I am not sure it is sensible to talk of gravity and spacetime curvature as separate interacting things.  Gravity - in the realm of General Relativity - IS spacetime curvature.   

Gravity does not cancel or have charges - it is all attractive.  This is why we can approximate all the gravitational attraction of the earth as a point, all the solar system as a point in the sun, all the milky way... so steady gravity is just added together, there is no differentiation.   The propagation of a gravitational attraction change via gravitational waves is a moving distortion of space time; my instinct is that the distortion will be a minor effect on the background curved spacetime near the gravitating mass.

Regarding the ftl bit; there is no shorter route than that which light takes.  It is not that the intervening gravitational well causes light to take a sub-optimal "long route" - it is that the shortest path between two points in space is now a curved route

11

Physics, Astronomy & Cosmology / Re: Richard Feynmann's QED

« on: 21/06/2013 15:55:48 »

Paolo

If I remember correctly it is the vector - representing the state of whatever is being measured at the time - which can be visualized as taking on a direction dependent on time (ie rotating).  Ie the vector sums of various paths can be then added and the directions of the vectors can lead to an analogy of constructive, destructive interference

I have attached a link of the Feynman lectures at the University of Auckland - which I believe were a more popular version of his magnum opus on qm  http://vega.org.uk/video/subseries/8

Not sure if any of above helps - but I hope so

12

Physics, Astronomy & Cosmology / Re: Causality is it violated by quantum entanglement?

« on: 21/06/2013 12:35:43 »

Alan - this is exactly what I was getting at in the other thread.  No where have I said that quantum entanglement is false.   You need to do a lot of basic reading - what you are describing is not entanglement, it is the common and erroneous conception of what entanglement is.   You cannot change the spin (etc) one of a pair of entangled by acting on the other - what happens is that a nondeterminate quantum mechanical state of superposition is determined into a more classical definite state. 

Alter the spin of one particle alters the spin of its twin in the other direction instantaneously.

You are incorrect.

https://en.wikipedia.org/wiki/Quantum_entanglement

13

Technology / Re: What will be the new networks of the 21st Century?

« on: 21/06/2013 11:34:21 »

I think the energy value of fuel should be more properly measured in Mega Joules rather than Mega Watts.

Agree - but the delivery of energy (which was Evan's comment) must surely be measured in joules per second aka Watts

14

Physics, Astronomy & Cosmology / Re: Causality is it violated by quantum entanglement?

« on: 21/06/2013 11:29:58 »

Alan - it is an old and untrue chestnut that you can alter the spin of an entangled particle over a great distance.  An entangles pair of particles will be in an indefinite state - in a quantum superposition; the two particles are in a non-classical state where they can seem to be in a mish-mash /combination of states.   if you measure one particle and determine its state the other is (and seeminly always has been) in the opposite state.  But what you cannot say is that the partner changes state (you cannot possibly have measured/have known the state of the distant partner as that would have collapsed the system into two determined states already) - what happens is that the state becomes defined

I think I know what you mean , that the two particle measures are really like two hands gloves, when you observe the one, the other is always opposite.

However, I am sure that this argument, put forward by no less than Albert Einstein has been disproved.

Alan

I have given the simplest argument shorn of any details - but it is roughly correct.  I can promise you the notion that you can take an entangled pair, then set spin of particle A, and immediately have spin of particle B taking opposite value IS FALSE. 

15

Physics, Astronomy & Cosmology / Re: Why does measuring a particles make its wave-function collapse?

« on: 21/06/2013 11:26:29 »

No - we cannot answer this question.  It is this lack that allows the many different interpretations of quantum mechanics.   Whilst the interpretations are very interesting and sooner or later someone will find a way to experimentally test and disprove some of them - we do not need the interpretations to use quantum mechanics as the maths works fine without the more metaphysical side question of "what is really going on"

I am absolutely not interested in the metaphysical, science should come up with the answer at some point, so why can't we on this scientific forum propose our own scientific ideas on the topic

Alan

Alan further to JP's comments.  You might have interpreted my "we cannot answer" as "can never answer" - this was sloppy wording on my point; at present there is no way we can answer, but that situation may change.  IMHO - in order to propose your own scientific ideas on the topic you need a solid grounding in the subject and for Quantum mechanics that's a tall order; JP and Pete could further elaborate on the difficulty in getting to grips with QM, but remember they both have postgrad physics experience in research and academia.  It is hubris to believe that one can make a significant contribution to an area without a thorough and easy knowledge of the mathematical basis, the theory, and the current work.  That said - feel free to speculate :-)

16

Physics, Astronomy & Cosmology / Re: Why does measuring a particles make its wave-function collapse?

« on: 20/06/2013 12:23:34 »

No - we cannot answer this question.  It is this lack that allows the many different interpretations of quantum mechanics.   Whilst the interpretations are very interesting and sooner or later someone will find a way to experimentally test and disprove some of them - we do not need the interpretations to use quantum mechanics as the maths works fine without the more metaphysical side question of "what is really going on"

17

Physics, Astronomy & Cosmology / Re: Causality is it violated by quantum entanglement?

« on: 20/06/2013 12:19:52 »

Alan - it is an old and untrue chestnut that you can alter the spin of an entangled particle over a great distance.  An entangles pair of particles will be in an indefinite state - in a quantum superposition; the two particles are in a non-classical state where they can seem to be in a mish-mash /combination of states.   if you measure one particle and determine its state the other is (and seeminly always has been) in the opposite state.  But what you cannot say is that the partner changes state (you cannot possibly have measured/have known the state of the distant partner as that would have collapsed the system into two determined states already) - what happens is that the state becomes defined

18

The Environment / Re: What is the meaning of 400 ppm (0.04%) atmospheric CO2?

« on: 31/05/2013 12:20:02 »

The comment which was shrunk was a entirely unwarranted complaint against moderation.  You have been told ad nauseam that links to your blog are both unacceptable as evidence and contrary to our forum acceptable usage policy.   You continue to link to your blog - these are deleted by staff.  When you complain on the forum about these deletions we will shrink your posts that moan. 

Please do not play the lone sane voice whose views are censored by the thought police - you have been given greater leeway and more chances than any previous member of this site.   The fact that you can still post after receiving multiple final-warnings shows the tolerance of the moderators and our desire to maintain a plurality of opinions and outlooks even in the face of personal insults.

19

The Environment / Re: What is the meaning of 400 ppm (0.04%) atmospheric CO2?

« on: 30/05/2013 16:25:18 »

MoreCarbonOK

You have received your last warning (twice) stop linking to your blog and stop moaning about it when you are pinged by the moderators. 

I have shrunk your last post.  There is plenty of peer-reviewed and well-sourced data out there - give links to that, not to your blog.

For your guidance - critiquing the motivation and expertise of person put forward as an expert is not technically an ad hominem.  An ad hominem argument is fallacious due to unsaid proposition that the personality/nature/characteristics of this person, unrelated to the matter at hand, causes his or her argument to be incorrect. 

Peppercorn is advising the membership of the site that the supposed expert has been found to have misrepresented the facts about climate change in the past, has a personal motivation for dissembling in this area, and thus might not be a fair advocate to explain the science; it is a subtle but important difference. 

On the other hand "shows your poor character" - is an insult.  Stop it. 

20

Physics, Astronomy & Cosmology / Re: Supernova seen from UK(London) at 20:13 24th May????

« on: 28/05/2013 17:27:14 »

What was the elevation - must have been pretty close to the setting sun?   Jupiter, Venus and Mercury were all in the lowish sky to the west at that time - and behind them was Orion to the left and Auriga to the right; sorry for the technical terms :-) but I get confused with anything more than left and right up and down. 

Orion has some really bright stars in the belt and capella in auriga can be very bright (I have seen it and thought it looked the brightest in the sky)

I use fourmilab mysky for these sorts of things - its free and amazing, though the interface is a bit cluncky