[rainwildman (OP)]

something that has aways puzzled me, so maybe someone can help....
It is of fundamental importance to the theories of physics that the laws if physics are the same everywhere in the universe.  Also, that space is the same everywhere.  How can we possibly know this? 

If someone can explain to me how we can know this, then fine, but it seems to me almost absurd to say that we KNOW that space and the laws of physics are just the same at the other end of the universe as they are here, yet, if we cannot say that, then none of the grand theories of how the universe was made and stars evolve and so on can be true!!!

oh dear!  Anyone help?

[another_someone]

Laws are whatever you make laws to be.  A law is merely a rule you put in a model.  You can choose which laws work for the particular model you are trying to create.  If the laws you are seeking are something that are universal, then you try to select laws that are universal.

This does not mean that you cannot see different behaviour in different parts of the universe (just as you can see different behaviour in liquid water, ice, and steam; but you create laws that allow you to view these different behaviours as simply different manifestations of the same laws).

Ofcourse, we cannot actually know what happens at the other end of the universe, so we cannot say what behaviours exist there, and so what our laws must explain.  What we can say is what it is we see happening at the far end of the universe, and say that the laws we develop must somehow explain these observations.  If we ever get to visit the far reaches of the universe (a scenario that is at present somewhat unlikely) then it may well be that we will be in for some surprises, and that these surprises will force us to have to change what we consider to be fundamental laws; but that is the nature of science, that as we develop the capability to make new observations, we either reaffirm out existing laws, or force a situation where they must be reviewed.  Science is never definitive, it is always merely state of the art, and tomorrow it may be different.

[Soul Surfer]

It is not totally fundamental that the laws do not change at all. In fact many possibilities exist that fundamental constants like for example the speed of light may change in very extreme conditions.  It is however fundamental that the constants change slowly and evenly with time and/or distance.

There is very good evidence that the main constants and laws do not change over vast distances of time and space as far as the most remote visible objects and even as far as the origin of the cosmic microwave when the whole universe was as hot and dense as the surface of a star and even back to the first few microseconds when the basic elements were being formed when the temperature and density was like the core of a star.

[rainwildman (OP)]

I,m afraid the talk of 'models' does not allay my fears. In fact, quite the opposite, because it makes physics sound like a game of 'fit the image to the stars', you know, looking at the stars and seeing pictures in them, and, really, you can see any picture you like, and especially if you select which stars to include!

It seems to me that the world we live in is incredibly complex, and you could probably make any number of different models to fit it, especially if you select the bits you choose to include.  And now I start thinking to myself (and I should say here that I happen to have heard that the Einstein model of the universe was not the only one on offer at the time, but the others have been forgotten because, well, to be blunt, Einstein had the right friends!)... so, to get back to what I am thinking to myself, is the science that we have today the only model that we could be using?  If there are others, why are we using the one we are using?  Is it because say, Newton or Faraday or Maxwell, had enough clout that they could have their theories oust all the competition?  And then, if we are saying that it is a matter of 'whose' theory it was, rather than which theory might be best, then what are the consequences?  Are we in fact left with a model of the universe which is very inferior to what we might have had if truth had mattered more than vested interest?

The more I go down this road the more uneasy I become.....

Again I have to say... help!!!

[lyner]

Quantum Physics predicts, successfully, quite a lot about the spectra of radiation from atoms and our local observations confirm it. When you observe the light from very distant objects you see the same patterns - just red shifted. That is quite strong evidence that the atoms producing this light are behaving (pretty much) the same as the atoms here. That implies that the constants of Physics are much the same at remote places in the Universe.
Also, you have to start somewhere so . . . 

you could probably make any number of different models to fit it, especially if you select the bits you choose to include.

There won't be that many models which actually FIT all the observed facts. You can only really expect to extend the present model. This may annoy you but the more you know, the more reasonable the existing models (as far as they go)  seem. 
If you treat Science as magic, you can allow just about anything in the way of a model. If you accept that it must be verifiable, when possible, this limits the number of possible models somewhat.
I would say that the present model(s) are not bad, as far as they go. Other models don't go as far.

[another_someone]

I,m afraid the talk of 'models' does not allay my fears. In fact, quite the opposite, because it makes physics sound like a game of 'fit the image to the stars', you know, looking at the stars and seeing pictures in them, and, really, you can see any picture you like, and especially if you select which stars to include!

It seems to me that the world we live in is incredibly complex, and you could probably make any number of different models to fit it, especially if you select the bits you choose to include.  And now I start thinking to myself (and I should say here that I happen to have heard that the Einstein model of the universe was not the only one on offer at the time, but the others have been forgotten because, well, to be blunt, Einstein had the right friends!)... so, to get back to what I am thinking to myself, is the science that we have today the only model that we could be using?  If there are others, why are we using the one we are using?  Is it because say, Newton or Faraday or Maxwell, had enough clout that they could have their theories oust all the competition?  And then, if we are saying that it is a matter of 'whose' theory it was, rather than which theory might be best, then what are the consequences?  Are we in fact left with a model of the universe which is very inferior to what we might have had if truth had mattered more than vested interest?

The more I go down this road the more uneasy I become.....

Again I have to say... help!!!

Very possibly more that one model would fit the observations, but far more would not.

The reason why Einstein's model succeeded had nothing to do with his friends (in fact, most of the ideas were not his - look at the background to Lorenz, Poincaré, FitzGerald, and others), but he put the ideas together in their simplest form, and so created a simple and functional model that explained far more of what was observable with greater simplicity of form than all the other alternatives.

One of the things one should note is the ease with which extremely complex systems can be formed with extremely simple rules, and often the greater the complexity the simpler the underlying rules (look at the construction of cellular automata).

Yes, it is very possible that a totally different set of laws could be constructed to explain the observations available, but given the enormous amount of work over the centuries that have gone into creating the existing set of laws, and showing how they can be used to explain all we see, and it would probably take an almost equal number of centuries to prove any alternative set of laws to be as efficient in describing all we see.

[Kryptid]

If I'm not mistaken, the spectra of elements in other parts of the Universe have been recorded from their light and are the same as the spectra of those same elements on Earth, right (except that they are modified slightly by redshift or blueshift of the light)?

If the spectra of elements is the same there as it is here, then the physics that governs atoms much be the same as well. For example, the EM strength must be the same, as must the quantum numbers that determine electronic structure. The mass of the electron must be the same as well.

Outside of the Hubble Horizon, though, who knows?

edit: sophiecentaur beat me to it.

[another_someone]

If I'm not mistaken, the spectra of elements in other parts of the Universe have been recorded from their light and are the same as the spectra of those same elements on Earth, right (except that they are modified slightly by redshift or blueshift of the light)?

If the spectra of elements is the same there as it is here, then the physics that governs atoms much be the same as well. For example, the EM strength must be the same, as must the quantum numbers that determine electronic structure. The mass of the electron must be the same as well.

If one is going to play devils advocate on this, I am not sure it does mean that EM strengths are the same.  As you say, we have red shifts (occasional blue shifts, but at great distance, I believe they are all red shifts), but what we know is that the relative positions of the spectral lines match up with spectral lines observed on Earth, while their overall position in the spectrum has shifted.  Thus we can surmise that overall structures that cause the emissions are similar to what we have here, but can we preclude that the structures have been scaled in some way, while retaining their same relative energies?

It is not the most likely scenario, but the question is, can we prove it to be a false scenario?

As you say, this only works as far as we can see stars, but beyond the point where we see stars we really cannot say very much.

[DoctorBeaver]

Wouldn't you love to know, though!

[lyner]

Wouldn't you love to know, though!

Are you suggesting that it is necessarily 'knowable' and 'understandable'?

I have enough probs with the story so far.

[lyner]

As you say, this only works as far as we can see stars, but beyond the point where we see stars we really cannot say very much.

you can imply quite a lot, though. If things were, in fact, very different beyond our vision then an observer out there would see different pictures in different directions.
Likely? |It would be a real coincidence; hence the Cosmological principle.

[DoctorBeaver]

Wouldn't you love to know, though!

Are you suggesting that it is necessarily 'knowable' and 'understandable'?

No, I'm not suggesting that. I would just love to know what's there.

[Soul Surfer]

Rainwildman.  All your experience consists of models of reality created by your own brain.  If you are afraid of models (simplified systems that mimic parts of "reality" accurately within defined limits)  you are afraid of your own mind as well as science.

Just like everyone looking at growing grass in sunlight and agreeing that they will call the colour green it is quite possible for you to disagree and call it qwert but you will be in a minority of one.  No scientific theory is ever the work of one person.  One person may originate the idea but many others will try to pick holes in it and eventually agree that the idea has some merit and eventually progress will be made.  That is what peer review is all about.  I agree that ideas can often be missed rejected and lost and then discovered again.  Science is full of examples of people who have had good ideas but failed to explain them properly and they were howled to derision  it is the proving and explaining process that is really important not just the idea.

One of the problems with many of the people who present interesting ideas to the new theories section is that they think that because they have had an interesting idea that might fit one bit of reality better than the current picture  everyone should rush to agree with them.   Some fools do but that is not science.

One of the really big problems with fundamental physics at the moment is that there are literally billions of good ideas but no way of proving which is best.  we are a long way from the last significant breakthrough and  need to find a genius who will understand where things are and come up with a new approach to produce good and testable solution.

[another_someone]

As you say, this only works as far as we can see stars, but beyond the point where we see stars we really cannot say very much.

you can imply quite a lot, though. If things were, in fact, very different beyond our vision then an observer out there would see different pictures in different directions.
Likely? |It would be a real coincidence; hence the Cosmological principle.

One thing you have to bear in mind when you look to the edges of the see-able universe is that you are not only looking into a spacial distance, but into a temporal distance, and in that sense we are in a unique position, in that our own position is the only position which we can view in the present rather than the historic past.

[techmind]

It is of fundamental importance to the theories of physics that the laws if physics are the same everywhere in the universe.  Also, that space is the same everywhere.  How can we possibly know this? 

In the absence of any evidence to the contrary, we postulate that this is true. It has served us well so far.

As others have mentioned, the evidence of (albeit red-shifted) emission- and absorption-spectra in the light from distant stars is a good indication that physical constants are pretty much the same in the furthest places we can see. The red-shift itself fits reasonably into our existing understanding too.

Physics aims to understand all the effects we can observe. Present theories in the main do a good job of describing what we can see. If at some stage in the future it was discovered that some physics was different someplace, then a new theory would be developed... which (mathematically) would tend back to the existing theory (i.e. predict the same observable results) under the condtions/space that the existing theory is valid.
This is what happens with Einstein's relativity - it describes new phenomena which happen at very high speeds/energies... but gives the same results as basic Newtonian motion at everyday slow speeds and energies.


Physics proceeds by getting to the heart of any "problem" or physical "situation". It seeks to find the simplest explanation for the observable facts. You do the experiment, and find that the result depends on A, B, and C. You manage to explicitly test that the result is completely independent (insensitive to) V, W, X, Y, and Z. Furthermore, you observe some evidence of the same phenomena -perhaps some situation where you can't measure or control a host of other potential parameters R,S,T,U - and the observable outcome in this case is still as predicted on the basis of A,B, and C alone. This gives you confidence that your theory is useful (even if there is a small chance that there's some as-yet undiscovered exceptions to the theory).

If we stick with the idea of "simplest possible" explanations, then even if an alternative "verbal"/"descriptive" theory were proposed in future, it's predictions would have to be consistent with the universe with which we are already familiar, and the maths resulting from "alternative" theories would similarly boil down to the existing maths (i.e. by rearranging and substituting into the equations - mere algebraic manipulations).
To avoid having to rewrite the textbooks every few years, and confusing everyone, "new" theories only become accepted if they have a significant advantage over existing theories (e.g. wider validity, demonstrably better fit to *all* existing data, or vastly more logical/easier to comprehend). Sure, in the rel world there can be some politics too, but this is the principle.

Both particle physics and early-universe/big-bang "physics" are mostly observed only very indirectly, under conditions which we cannot easily control or adjust (or re-play/reproduce). It could be argued that some of the theories in these fields are charging ahead of what can be really justified by observation. Such theories are clearly much more "at risk" of being revised than in most other areas of physics. You might say that in some sense such areas are as much philosophy as physics!

[rainwildman (OP)]

OK, someone has been kind enough to play devil's advocate, and the conclusion is that we cannot be sure about physical theories.  Then someone else agreed, and then justified our going with the current theories on the basis of the difficulties of looking for and establishing others. 

Two things about that: in the first place, I thought science was about TRUTH, and if it is, then difficulty is neither here nor there.  This thing about difficulty and cost in time and effort is putting expediency before TRUTH, and surely that cannot be right or healthy?  And talking of health, physics is surely just the base science upon which most others build, and if that is so, then if physics is uncertain, then so too must be all the others, and if that is true, then it applies to medical sciences, and that has my hair standing on end, because I need to be able to trust the medical professionals!


Soul Surfer says my brain is doing the same thing as scientists ... I disagree.  If I fall down, my brain concludes that there is something that makes me go downwards with a bump, as it were, but it would not go off and make work out that it was an inverse square law, and then use that to make predictions about projectiles and planets in orbit and so on.  And if at some later time I was to lose my footing and NOT fall down, it would take that on board and modify my view of the world and my bahaviour accordingly .... in fact, something is just occuring to me as i write, and it is to do with competition:  it seems to me that my brain id fundamentally different in that is ACCUMULATES from experience, takes EVERYTHING on board, which is different from science, where one theory has to COMPETE with another.

And then I am thinking, perhaps the problem is not which theory might be correct, and that we might not have the best one, perhaps the problem is that we only have one theory, whereas the truth is that they are ALL correct, and the prblem might be that we need to BROADEN our way of looking at the world.  Rather than thinking in terms of one theory being correct and the others wrong, we should be thinking in terms of how to reconcile them all.

Well, this is certainly getting me thinking!

[another_someone]

Two things about that: in the first place, I thought science was about TRUTH, and if it is, then difficulty is neither here nor there.  This thing about difficulty and cost in time and effort is putting expediency before TRUTH, and surely that cannot be right or healthy?

Absolute truth is something that exists in the realms of abstract logic only.

You are looking for an idealised situation that does not, and in reality, cannot, exist.

Is this healthy?  In the real world, absolute health does not exist - which is why none of us are immortal.  You do the best you can with what you have, and accept that what you have has its limitations.

And talking of health, physics is surely just the base science upon which most others build, and if that is so, then if physics is uncertain, then so too must be all the others, and if that is true, then it applies to medical sciences, and that has my hair standing on end, because I need to be able to trust the medical professionals!

Simple answer - thalidomide (and that is just the tip of the iceberg).  Scientists, medical practitioners, et. al., are merely human beings, and none should be treated as gods, for they can never be that.

Soul Surfer says my brain is doing the same thing as scientists ... I disagree.  If I fall down, my brain concludes that there is something that makes me go downwards with a bump, as it were, but it would not go off and make work out that it was an inverse square law, and then use that to make predictions about projectiles and planets in orbit and so on.

If someone throws a ball at you, your brain does a fairly good job of making predictions about where the ball is going to travel, and if you want to catch the ball, where you should place yourself to intercept the ball.  In making these predictions, you brain is making a model of the flight of the ball, and is doing whatever calculations it needs to in order to forcast the position of the ball in a few milliseconds time.

It is true that the average caveman did not have the formal tools to make an inverse square law (how would he have written down the notion of what a mathematical square, let alone and inverse square was); but he would have had a good enough intuitive knowledge of the inverse square law to be able to make fairly good calculations of ballistic flight of many objects.  He would also have known enough to know that dropping something from twice the height will give you more than twice the energy.

in fact, something is just occuring to me as i write, and it is to do with competition:  it seems to me that my brain id fundamentally different in that is ACCUMULATES from experience, takes EVERYTHING on board, which is different from science, where one theory has to COMPETE with another.

No difference at all.

The whole point about science is that it too must take everything on board - but you are confusing experiment with theory.  Your experience is equivalent to scientific experiment - and science cannot pick and choose to ignore one experimental result but accept another - if an experiment is repeatable, then the theories chosen must take account of it.  In the same way, an isolated experience you can choose to ignore, but if an experience is repeatable, then you must learn from that experience.

Scientific theory is about prediction.  When you have learnt from experience, then you will start to make predictions about the future; but just like scientific theories, you will have competing means of predicting the future, but you have to choose one that works best.

Going back to the question of ballistics - experimental science will have you throw the ball several times and observe where it will land, while theoretical science will have you calculate where the ball will land while it is still in flight.  You brain and science are doing exactly the same job.  When you want to catch a ball, you will initially have several competing theories about where the ball will land, and will often get it wrong, until you finally get to one theory that always puts you in the right place to catch the ball every time.

Well, this is certainly getting me thinking!

That itself is good.

[rainwildman (OP)]

I'm still thinking, and trying hard to understand.  I am an artist(words and images) by profession, but i took science to a higher level than most artists.  The trouble was that I always felt like a trained parrot, that is to say, that i was just learning stuff by rote and then regurgitating without understanding anything.  So now I am revisiting and trying to put that right.

So, right now I'm battling with a couple of things that were touched on above;
first, what is made of observations of light from distant stars and galaxies (as an artist I certainly love the pictures that come from this!)
If I get this correctly, scientists look at light coming from sources in the sky, and they, as it were, draw a picture of what they see, and then they look at what they have here on earth, and they say that the light from the stars looks just the same as the light from atoms or whatever, that we have on earth, and therefore they must be the same thing.  Well, that is too simplistic, and the can't be right.

I have a friend who is working on a book about, among other things, Freud and Jung, and she has been telling me about some of the methods Freud used to come to his conclusions about what dreams meant.  So, for example, in one dream a snake approaches the dreamer, grows bigger, bites the dreamer, and then shrivells.  Well, says Freud, this is a sex dream, because something that burgeons and then shrivells must be a phallus!  Of course that is nonsense.  The flowers in my garden burgeon and then wither; a balloon being blown up burgeons and then withers when the air is released; a little boy boasting swells with pride and then can be withered by a withering glance ... and so on and so on. 

So, just because two things look alike, one can conclude nothing.  So what is the difference between what scientists are doing with the things they see in the night sky and what Freud (and numerous pseudo-scientist)were doing with the things they were looking at?


Another point, which is not really pertinent, I think, to the understanding of how science works, but has been mentioned above, is the PEER REVIEW SYSTEM.  To me, that is iniquitous, but is politics, not science.  Peer review is the church fathers deciding what is and is not acceptable.  If Einstein(honest its nothing personal, but if you become famous then you have to take the flack) got onto a peer review board, then he could make sure that it was his name that got remembered, and his theories that won out over the competition.

What peer review makes me think of is another famous name: Plato.  One of Plato's major works was THE REPUBLIC.  Now, in that work of philosophy, Plato draws a picture for us of what he has 'reasoned' would be the ideal and best society, and guess who's in charge of this utopia ... that's right, philosophers!  so don't tell me Plato was a philosopher, interested in truth and capable of detached reasoning.  He was not.  he was a poltician making a case for why he and his party should be in charge!  Now I have a lot of trouble with peer review on the same basis.  It smacks of the rule of politics at the expense of detached reasoning and loyalty to personal interest over loyalty to truth.

However, as I said, it is the thing about spectra that really bothers me.

Maybe someone can explain.

[Soul Surfer]

Experiments on earth can determine the mass and electrical charge on a proton and on an electron. putting one proton and one electron together creates a hydrogen atom. The physical laws associated with this combination predict that when excited, hydrogen atoms will radiate very specific sets of frequencies in the optical infra red and ultra violet and radio bands.  Experiments in the laboratory also show that these spectrum lines are accurate.  Similar sets of spectrum lines can be seen in the sun other stars and distant galaxies not just single lines but whole sets with precise separations.  This enables the accurate determination of the relative velocity of the source and the observer.  All other elements and compounds have different sets of spectrum lines predicted, measured and observed in remote objects.  All the velocities measured on the same object are similar.  This gives very accurate information about the composition temperature pressure and radial velocity (including changes with time) of millions of objects this in turn produces and confirms models of stellar evolution the structure if multiple star systems and the structure of galaxies.  Gravitational theory even allows masses of multiple stars to be messured.  All this knowledge is consistent and has been measured by thousands of observers over hundreds of years.

Our knowledge of nuclear physics allows precise models of the origination and evolution of stars to be generated and confirmed by the observation of star clusters which are likely to have originated at a similar time this varies from clusters only a million years old to ones almost as old as the universe.

This list of observations cross linked by many confirming observations gives rise to the information given in popular science books.  it id not the ramblings of one individual but a whole network.

[lyner]

Peer review may seem problematical if you regard Science as a creative art form. But Science doesn't attempt to be one.
Yes, it can suffer from subjectiveness and personal interest but the fictional scenario of which we frequently read in these forums - famous scientist rejects  brilliant idea from young upstart - is very much in the minority. Once a new idea is out, if it really is valid then it will find a way to get accepted. If the feelings of some bright spark are hurt a little then he / she will get over it. If a barmy idea was accepted without a struggle, what damage could be done to Science?
How else and with what other system can we actually make progress and avoid a world of Scientific blind alleys?
It strikes me that people are getting a vicarious displeasure out of these scenarios rather than appreciating that Science must be conservative in order to make any real progress.

Think how the MMR fiasco caused so much potential suffering because the (science-ignorant) media took up the idea of a errant medic and didn't allow the  Science establishment to work properly.