out on a limb without a wave to hop on

merle van osdol
merle van osdol
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Topic 197978

Lets just say that GW's don't exist and action at a distance does. Where does theoretical physics then focus its attention. I know I'm way out there and perhaps creating my own waves. Please just humor me.
I also ask the impossible when I ask for a layman's interpretation of it all. I am serious re. my questioning.

merle

What is freedom of expression? Without the freedom to offend, it ceases to exist.

— Salman Rushdie

Mike Hewson
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out on a limb without a wave to hop on

Quote:
Lets just say that GW's don't exist and action at a distance does. Where does theoretical physics then focus its attention. I know I'm way out there and perhaps creating my own waves. Please just humor me.
I also ask the impossible when I ask for a layman's interpretation of it all. I am serious re. my questioning.


That's a great question Merle ! :-)

It would I think have to be some other alternative entirely ie. it may not be either fields or action-at-a-distance. Certainly not in the currently understood senses.

Pure Newtonian gravity had no time delays and thus fails when that matters. Even Newton wasn't comfortable with that aspect, pretty much glossed over that, and settled for a predictive description which worked well with the data of the day.

Throwing fields away ( and you'd have to do that as fields imply waves ) discards a model where one part of spacetime informs an adjacent part of what it's up to ( ... etc to the next bit and so on over long distances, with time delay thus inbuilt ). I think it is clear that some sort of differential scheme is needed ( where adjacent parts of something are compared to yield an effect ) eg. why does an apple fall down not up ? Apart from the obvious language point that 'down' is defined as that direction in which test masses go, it still leaves the real issue that there is such a preferred direction at all. If you go for 'local realism' then there must be something about the near surroundings of the apple that is asymmetric ie. some difference is having an effect. The field construct connects all the little local realities at different locations in spacetime.

So that leaves a bunch of negatives to describe some other theoretical alternative : no differentials, no local realism, no mechanism for time delays etc. You could keep some field qualities but not with respect to the dimensions that we immediately are aware of. Now there's a mouthful to swallow indeed ! But it gets worse because however many/type of other dimensions you then invoke, that will discard cause-and-effect as we traditionally know of it. In turn that de-references to the issue of the meaning of 'time' ie. is it a basic quality at axiomatic level or emergent from who-knows-what beneath ? And so it goes ......

... though do remember what happened with the Michelson-Morley experiment. What! No aether? Surely not ..... :-)

Cheers, Mike.

( edit ) I think this may sum the situation up :-) :-)

... that isn't you on the branch Merle! Science has this special quality of deliberately being falsifiable ie. a 'good' theory is one which has a mechanism available for it's own potential disproof - we call that experiment. That way it is up to reality to decide upon physical truth and thus the value of candidate ideas. In fact that is precisely the commonest reason for despising science : it can't be talked/spun away. You have to get out of your own head and that is often hard work. In my experience many just don't possess the neurology for that. That doesn't make them bad or inferior people etc. Not at all. They are simply different and that requires some gentility and respect of that situation.

NB Ideas are inside people's heads. Reality is the part of the universe on the outside. You can't equate the two ....

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Mike Hewson
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I probably slid through

I probably slid through 'local realism' a bit too quickly.

It's a general approach to physical descriptions. A sort of philosophy about how the universe works. It means that for some chunk of the universe, what happens next to that chunk is purely dependent upon that chunk's properties and immediate surroundings. The various fields that we talk of : electromagnetic, gravitational, nuclear etc are part of that immediate surroundings.

However these fields are extended entities that span across - in theory at least - the entire universe. They are hence a component to be reckoned with for all surroundings of all chunks. The field is the connection apparatus that links what we like to think of as a cause 'over here' having an effect 'over there'.

So for the apple falling toward the Earth ( when not otherwise held in position ) we reason thus :

- the Earth has produced a contribution to the gravitational field.

- the apple is sitting in the gravitational field.

- the subsequent mechanics of the apple ( moment to moment ) depend upon it's response to the gravitational field at it's momentary position.

.... this is logically symmetric for the apple influencing the Earth's motion, so I could correctly say :

- the apple has produced a contribution to the gravitational field.

- the Earth is sitting in the gravitational field.

- the subsequent mechanics of the Earth ( moment to moment ) depend upon it's response to the gravitational field at it's momentary position.

But the magnitudes are far different and this comes back to the mass of the objects. The apple is tiny, the Earth is huge ( relatively ). So the Earth is making a large field contribution for which the smaller apple will display a large response. Obversely the apple is making a tiny field contribution for which the large Earth will display a small response. Thus we say, as a language construct :

'the apple falls to the Earth'

and not :

'the Earth falls to the apple'

... even though theory says that both occur. This becomes more evident in generality ie. systems containing bodies of comparable mass. The solar system is our best studied example of this. Interestingly it is often said that 'the Sun is the centre of the solar system'. It is better to say that the Sun is the dominant mass in the solar system, and that it may be simplest to model/consider that system with Sun-centric co-ordinate systems. Basically that is what Copernicus said/did. Note that Copernicus had even more epicycles than Ptolemy - I mention that as it is often erroneously claimed that Copernicus eliminated them. He didn't. He shifted the 'origin' of the co-ordinates.

[addendum]
Sharp punters will spot a difficulty here. What is the contribution of the apple to itself ? Meaning that if it produces a field component then how does it react to that ? This is generally known as 'self-energy' and is also a conundrum with other physical fields as well. Ways to manage it :

- ignore it, thank you very much. Just phrase your thinking and the maths especially to not include the apple-influencing-itself component.

- sweep it under the rug. This is the QED contribution of Feynman/Schwinger/Tomonaga called 'renormalisation'. The trick* here is to just assign some total field effect at the surface of some ( vanishingly ) small volume around the point of interest, make that value c/w measurement, and don't look inside that surface.

- worry about it more than that. Come up with a better theory. Strings ? :-) :-)
[/addendum]

Cheers, Mike.

* To be a good boy I must admit : I am giving an equivalent explanation here. The full horror is to offset one high-order effect with another, which in turn implies I am limiting the energies to be nett-summed, and that in turn means not getting in too close ....

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

merle van osdol
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Thanks Mike. Is nuclear a

Thanks Mike.

Is nuclear a separate field?
There is what; the strong force of the atom binding and the weak force of radiation (like radium).

Gravitation operating at great distances and nuclear operating at small distances.

Sorry that I am bouncing around so much but I don't have the background to do otherwise and my curiosity just won't quit.

Why does current thinking seem to be so much against, action at a distance.
I grew up in the 50's thinking just that. Stars, planets, etc. They simply tugged at each other and the bigger guy won the most influence in this totality.
I know I have nothing to base it on but it just seems that GW doesn't make sense.

When you want to quit this Mike, I shall understand completely.

merle

What is freedom of expression? Without the freedom to offend, it ceases to exist.

— Salman Rushdie

Mike Hewson
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RE: Is nuclear a separate

Quote:
Is nuclear a separate field?


Yes. Two actually. The weak and the strong.

The weak has been combined with electromagnetism as the 'electroweak' force. It is involved in nuclear decays for instance. The basic event ( at everyday energies ) is the decay of a down quark into an up quark with the release of an electron and a neutrino type. This is why a neutron ( 2 downs + 1 up ) all on it's own will decay to a proton ( 1 down + 2 ups ) in about a quarter of an hour, on average. Inside nuclei there are various similar reactions. It is called 'weak' due to it's intrinsic strength being above gravitation but below electromagnetism. It is very short range of the order of nuclear dimensions.

The strong is the strongest of all. It's range is of the order of a proton/neutron width. It has this weird behaviour of getting weaker if real close in and getting stronger further out. To separate a group of quarks to individual ones would require infinite energy. So that doesn't happen. What does happen if separation is attempted is the creation of more quarks. So they've only been seen in relatively stable groups of two or three, sometimes as very short lived 'jets' of very many. A legitimate question is 'how do we know what quarks are if we never see them alone ?' The answer is moderately complex. If one fires, say electrons, at protons then there will be close encounters b/w the electrons and the quarks and the results can be studied. Over very many such interactions one can deduce the quark parameters that would consistently give the observed outcomes.

[ One especially interesting result here is that a down quark has mass/energy of ~ 5 Mev and an up has ~ 2 Mev. So a neutron's mass/energy from such 'valence' quarks ought be ~ 12 Mev. This is way lower than the ~ 940 Mev as measured 'on the outside' as it were. The remaining mass/energy is that of the strong interaction, or put another way, the energy of the gluons .... ]

Quote:
Gravitation operating at great distances and nuclear operating at small distances.


Electromagnetism is also long range.

Quote:
.... my curiosity just won't quit ....


Excellent! :-)

Quote:
Why does current thinking seem to be so much against, action at a distance. I grew up in the 50's thinking just that. Stars, planets, etc. They simply tugged at each other and the bigger guy won the most influence in this totality. I know I have nothing to base it on but it just seems that GW doesn't make sense.


I've delayed answering this because I've had to think 'well, what is the problem here?'. Exactly why* does action-at-a-distance ( call it AAAD ) fail ? I'm going to have a longer think about that before replying. I want to identify and isolate the key components better ...

Quote:
When you want to quit this Mike, I shall understand completely.


It's fine. You ask good questions ... :-)

Cheers, Mike.

( edit ) So the forces are ranked ( strongest to weakest ) :

strong nuclear > electromagnetism > weak nuclear > gravity

... with the method of ranking being a wee bit obtuse in everyday terms, but is defined in terms of constants that determine the degree of 'coupling' between the matter particles and the relevant force carrying particles. NB also that matter particles are under the heading of 'fermions' with the force mediators being 'bosons'. Essentially fermions cannot be stacked together in the precisely the same place : if there are two or more, one of more of them has to move on. Which is good as the matter of the entire universe would wind up all in the one spot otherwise. Whereas bosons can be grouped together, or not, as you please.

* Such exercise is good for the psyche and soul. I've been reading a recent book by Jim Baggott called Farewell to Reality: How Modern Physics Has Betrayed the Search for Scientific Truth ( it seem you can only publish a book - perhaps in the USA at least - only if it has several titles ). While naturally bagging string theory as prediction failure par excellence, it also has a crack at a number of other theory topics too. It's not so much that theory awaits proof/disproof on some experimentalist's workbench, but that some theoreticians actually believe physical demonstration may be foregone and the moniker of 'science' still applied. It seems the string theory rot is spreading. Recurrent readers of my posts will note that I do keep going on about this. This is probably my medical training & background. I literally cannot imagine practising medicine in a likewise reality-be-damned manner ....

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Phil
Phil
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RE: I literally cannot

Quote:
I literally cannot imagine practising medicine in a likewise reality-be-damned manner

Good God man! You are still practicing? When are you due to get your license? I've heard it takes a long time to become a doctor, but jeez.

:-)

Phil

Mike Hewson
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Now that I come to think of

Now that I come to think of it : I started the medical course in January 1980 .... oooh, I see your point. :-0

Cheers, Mike.

( edit ) ... and this from a guy who used to jump out of planes for a living ? Like that's easy, right? There is no way that you'd miss the planet. Your work's already done for you from the get go ... a lazy use of gravity if you ask me ! :-):-)

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

merle van osdol
merle van osdol
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Thanks again Mike,

Thanks again Mike,

merle

What is freedom of expression? Without the freedom to offend, it ceases to exist.

— Salman Rushdie

merle van osdol
merle van osdol
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Mike, I don't understand the

Mike,
I don't understand the part about a neutron decaying into a proton in about a half an hour.

I seem to remember from chemistry, the table of elements. Each atom had a fixed number of protons and a fixed number of neutrons. Maybe my memory is incorrect or there is something else going on here.

Thanks for the explanation of the difference in neutron/protons in terms of the up/down quarks.

merle

What is freedom of expression? Without the freedom to offend, it ceases to exist.

— Salman Rushdie

Mike Hewson
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RE: Mike, I don't

Quote:

Mike,
I don't understand the part about a neutron decaying into a proton in about a half an hour.

I seem to remember from chemistry, the table of elements. Each atom had a fixed number of protons and a fixed number of neutrons. Maybe my memory is incorrect or there is something else going on here.

Thanks for the explanation of the difference in neutron/protons in terms of the up/down quarks.


'all on it's own'

... is the key thing. It would seem that it needs to keep company in order to not decay. A lone neutron is unstable. Weird huh ? Unless disturbed/nudged a lone proton is stable - at least for the lifetime of this universe.

If you look at the periodic table in terms of isotopes - same number of protons, differing number of neutrons - then the most stable forms of each element tend to have a mild excess of neutrons. Though nuclei which are called even/even - multiple of two protons and multiple of two neutrons - are especially stable. Now you can bash anything to bits if you whack it hard enough so stability here is measured by the amount of energy required to break something up ( hence the older term 'atom smashing' ). It it falls apart simply because you watched and waited then the decay is termed as spontaneous. Very stable means I have to really clout it in order to see pieces. Now even/even nuclei are also multiples of the helium 4 nucleus - two protons + two neutrons - otherwise known as the alpha particle when seen alone ( helium atom stripped of electrons ). In any case nature seems to like multiples of alpha particles .... or failing that an extra neutron or two ! :-)

Some nuclei are just hopeless for stability. Francium for instance, and this applies to most of it's isotopes, can barely last a second. But a few of it's isotopes will stay around for a half hour. In fact the term 'metastable' is sometimes applied to refer to not instantaneous breakup, but not very much longer lived either! It took years to characterise because it simply fell apart in your fingers, as it were. So Francium ( 87 protons ) is an example of the group of odd/odd nuclei which - you can now guess - are all pretty rubbish at stability, certainly with respect to those nearby to them in the table.

Cheers, Mike.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

merle van osdol
merle van osdol
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Thanks Mike, Sorry it took so

Thanks Mike,
Sorry it took so long to get back here.
I had to go back a refresh myself on the periodic table.

merle

What is freedom of expression? Without the freedom to offend, it ceases to exist.

— Salman Rushdie

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