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Physics, Astronomy & Cosmology / Re: Are there any philosophical or other implications to the underlying randomness

« on: Yesterday at 22:56:42 »

*solipsism.

I can't believe you said that ;-)

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Physics, Astronomy & Cosmology / Re: Are there any philosophical or other implications to the underlying randomness

« on: Yesterday at 11:01:46 »

So the decay of the nucleus is only of significance when it is measured (to my mind) and  this "measurement" is a synonym with "interaction"

A whiff of anthropocentrism here! The decay of a nucleus is of huge consequence to the nucleus itself, which ceases to exist or spawns daughters, even if there is no observer.
A lot of philosophical nonsense derives from the technical term "observer" that we use in science simply to denote a plane in spacetime through which information passes.

I just  reread what you quoted  from me.It seems ambiguous  now.When I said  "to my mind" it was just to say "in my tentative  opinion"

Did you think I  was putting my mind  and its powers of observation  at the centre of whether  or not  the physical world exists?

I didn't intend to say that, which would of course be rubbish (but I think I have entertained the notion in the past. Is it called solipscism?

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Physics, Astronomy & Cosmology / Re: Are there any philosophical or other implications to the underlying randomness

« on: Yesterday at 00:57:00 »

As I hope I have understood  Bell's theorem  has clarified the random nature of physical interactions

Did it have much (anything?) to say about randomness?  It seems that quantum theory in the first place (well before Bell came along) demonstrated the fundamental probabilistic nature of empirical things.
There were two principles held shortly after the turn of the 20th century: Realism and locality. The former says that things exist (a system is in a particular state) independent of measurement. The latter says that the effect cannot be separated from its cause in a space-like manner, or that cause-effect cannot move faster than light. Bell demonstrated that (barring superdeterminism), at least one of these principles must be false.

we do only have interactions rather than isolated events don't we?

I don't know what you mean by these things. An interaction is something that happens over time between different systems. An event (as usually used in physics) is a point in spacetime, but it also might be used to describe an occurrence, such as a particle interaction, say that shown by a Feynman diagram. In that sense, an interaction is a form of event. The decay of some nucleus is an event that isn't an interaction since there is but the one system.

So if the random event is something of a ground zero in our understanding  of the physical world  what else can we say  about it aside from just accepting it and building on it?

Again, I don't understand. Our understanding of the world isn't grounded on one event, or a group of them. There's a lot more to it.

Are we still allowed to believe that randomness  can still.be investigate to a deeper level of understanding or is this as far as things go?

My apologies, but again, I don't know what's being asked. Measurements seem probabilistic by nature, but there are interpretations of QM that are not random at all, so the perceived randomness is hardly fundamental since it cannot be conclusively demonstrated.

Thanks for your patience.Clearly I am poorly versed in Bell's theorem and also the localism vs realism question.

Thanks for your descriptions of them

I also  assumed that randomness  was the only interpretation of QM  that  was accepted .

I suppose I may learn more from my errors than by trying to buildi on my imaginings.

I will need a little time for the lessons to sink in.

When I said that interactions were more descriptive  than events (not using  "event"  to mean a geometric  point in spacetime) I was expressing my feeling that everything has to have an environment to play out in.

So the decay of the nucleus is only of significance when it is measured (to my mind) and  this "measurement" is a synonym with "interaction"

As the saying goes ,one hand does not clap and the nucleus decays into or from something ,doesn't it?

Do you stand by your explanation that some occurrences (eg nuclear decay)  take place on their own and without a "partner" in the physical  environment (the wider system they are part of)?

More generally,perhaps are not all systems ,large or small interconnected?

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Physics, Astronomy & Cosmology / Are there any philosophical or other implications to the underlying randomness

« on: 06/06/2023 15:56:57 »

As I hope I have understood  Bell's theorem  has clarified the random nature of physical interactions (we do only have interactions rather than isolated events don't we?)

So if the random event is something of a ground zero in our understanding  of the physical world  what else can we say  about it aside from just accepting it and building on it?

Are we still allowed to believe that randomness  can still.be investigate to a deeper level of understanding or is this as far as things go?

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Physics, Astronomy & Cosmology / Re: Talking about Physics

« on: 05/06/2023 11:20:25 »

Is there any other way we can reproduce  that effect?

And what is "long enough"?

Two dots? Three?

I think I can give a tentative answer to your question, which is, it depends.
In experiments that demonstrate interference, it's nice to see a pattern that we can say is definitely there.
But in quantum computers, the wavefunctions of two particles can be in superposition, such that it's a form of constructive or destructive interference.
We arrange for this to happen that way, and so it must have a nonzero probability of occuring in that case.

So,is that to say that when we have just two.(or even one?) dots on the screen they can be graphically represented as an interference  pattern even though our own optical system (the eyes and the brain) do not process it  that way?

Eventually, with enough dots we do see the underlying interference pattern "with our own eyes "?

Would that be a standard interpretation?

Hopefully  not to cloud  the issue(an ironic analogy,perhaps)  ,but if optical measuring instrumentation  was sufficiently sensitive  might it ,in theory pick up  directly  the interference pattern from one ,two or three dots?

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Physics, Astronomy & Cosmology / Re: Talking about Physics

« on: 03/06/2023 15:48:20 »

Is there any other way we can reproduce  that effect?

And what is "long enough"?

Two dots? Three?

Is the " overall distribution" always there but we only see it above a certain number?

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Physics, Astronomy & Cosmology / Re: Talking about Physics

« on: 01/06/2023 00:57:29 »

Last time I looked, I was definitely an old bloke, and AFAIK this Cambridge is cold, wet, and near the East Coast, just like the other one.

You see, my friend, it all depends on what you think you mean by Cambridge. Is there a universal meme that can be deconstructed as a set of paradigms sufficiently delocalised in spacetime  that your Cambridge and mine are the same but not identical, or identical but not, in whatever sense you think you are talking about, the same? In what sense does the Pythagorean essence of Cambridge heuristically or existentially conflict with the Aristotelian ur-Cambridge such that they cannot coexist?

I could say that in a few minutes I can walk across a bridge over the river Cam, but a philosopher would ask "how do you know that it is really you, and whilst the river was named by the Saxons, since the water that was there at the time is no longer there, is it still the Cam?

Does the idea of a convention  have import when discussing  what "information" is?

Is the idea of a convention the mirror image of solipscism?

In philosophy do we,as conscious beings  travel.through time in the same way as a physical object has its worldline in.the "real" world?

Ps ,what on earth is ur-Cambridge when it is at home?

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Physics, Astronomy & Cosmology / Re: Talking about Physics

« on: 28/05/2023 03:49:38 »

I'd say that depends on what the sentient being knows already

Yes, I thought that too.The brain creates it's own inputs.Any external input goes through a huge amount of processing  before anything like an output can be  observed.

In fact I don't know if it is possible to correlate an individual input with an individual  output.

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Physics, Astronomy & Cosmology / Re: Talking about Physics

« on: 28/05/2023 00:53:17 »

I never really appreciated  that information  could be a learning discipline  in itself.

Suppose a sentient being  received  some sensory input ,is there  a maximum amount of physical sensory inputs it must receive so as to output  something like a work of art(maybe extremely primitive)?

Is there a correlation  between the physical input and the mental output or can a minimal physical  input  produce an unrelated large  mental (informational?) output?

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Physics, Astronomy & Cosmology / Re: Talking about Physics

« on: 17/05/2023 22:40:12 »

What a headache

Or what fun.
Plus ,what is to say that those abstruse considerations may not give rise to practical outcomes  eventually?

What of Einstein's proposal that spacetime was curved? How practical  must that have seemed to anyone else at the time?

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Physics, Astronomy & Cosmology / Re: Can Light Experience 'Time'

« on: 16/05/2023 21:51:09 »

Is it just a convention that c should be a very large number?

I think that sometimes it is given the value 1.

Would it be equally possible  to give it a very small number so that  in the expression e=mc^2 we might have the impression that it would take a numerically  huge  amount of mass to  render a numerically tiny amount of energy?

Or am I just confused?

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Physics, Astronomy & Cosmology / Re: Can Light Experience 'Time'

« on: 16/05/2023 02:06:22 »

Hi.

@geordief   asked about  the speed c.
LaTex isn't working so we can't have mathematical symbols here in the post,  sorry.

    Basically, yes starting from the Lorentz transformation you would quickly obtain the relativistic velocity addition formula - see  https://en.wikipedia.org/wiki/Velocity-addition_formula#Special_relativity

   That will show you that a velocity with magnitude c (which is just what appears in the Lorentz transformation and not necessarily the speed of light) is mapped to another velocity with the same magnitude in any other inertial reference frame.

    The entire discussion was about assuming light may not travel at the speed c.  So, that's why @hamdani yusuf  said what they said (I would think).   In most textbook developments of special relativity it is common to start from an assumption about light and the invariance of its speed.  In this situation, the whole point is that you don't - we assume light has some other speed.

    You could still obtain the Lorentz transformation even if nature had been very unkind to physicists and never given them a massless particle that could be detected.   We were lucky, we had light, it did exhibit properties that strongly pointed us to the development of special relativity.   Assume light wasn't available or did not behave like that.  Provided special relativity is still a rule in nature, then there would have been signposts to it.
   See https://en.wikipedia.org/wiki/Experimental_testing_of_time_dilation   which describes how muons can be produced in earths upper atmosphere when cosmic rays come in.    We use this as a test of special relativity, specifically we suspect that muons moving fast relative to the lab frame would live long enough to reach the surface of the earth before decaying.   The main point is that the effects of relativity like this would still be there, in nature, and eventually we would notice:    Someone would have studied the half-life and decay of particles and they would have noticed that fast moving particles seem to live longer,  they would have said "that's weird, it's as if their clock is ticking slowly".   We now also have particle accelerators and with equipment like that to play with it's almost certain that we would have noticed strange effects when objects have high velocities relative to each other.    Basically, unless the important speed which we are calling c and appears in the Lorentz transformation was many orders of magnitude greater than it actually is, then there would have been signposts to relativity and eventually we would have noticed them.
        With some LaTex mathematical symbols (which, as I mentioned, we don't have the luxury of), we could demonstrate that the Poincare group of transformations is the only set of transformations between reference frames we should consider.   Non-linear transformations are also possible but the words "non-linear" should strike fear into the hearts of anyone who has ever studied some mathematics.   So you can rest assured that every linear transformation between reference frames would have been proposed and examined first.   The basic Poincare transformations like a rotation of the space frame won't explain the results you were getting from experiments so before too long the subset of the Poincare transformations which are just the Lorentz boosts would be all you have left before you move to non-linear transformations.   While mathematicians would be beginning to sweat and fear that  non-linear transformations would be needed, the last set of linear transformations would turn out to be the charm, they would work.  Obviously a Lorentz boost will work, we know that a Lorentz transformation was precisely what we needed.   There would be a constant which we can call c  in those transformations, it would have the dimensions of a speed etc.    The value of c would be chosen to match the experimental results we were obtaining.  Once you have the Lorentz transformations, the rest of the theory of special relativity follows.
   So, summarising all of that,  we could reasonably have obtained the Lorentz transformations just from empirical observations of strange effects when two objects have high velocities relative to each other.   Having a massless particle like light which did travel at c was a great help and it is a clear signpost to relativity.   It probably speeded up the recognition and development of relativity by many years.  Indeed taking, as an axiom, that the speed of light is an invariant will allow you (a lecturer) to develop the theory of relativity on the blackboard in front your students in 1 hour rather than over several lectures.   The key is that it wasn't essential, special relativity is just all the physics which you can obtain from the Lorentz transformation.   You can get to that (the Lorentz transformation) by other routes, you do not need to assume the speed of light is an invariant.   (However, in the world in which we do live, the speed of light is c, so you aren't doing any harm by taking that as an axiom and you will see it done in many textbooks and hear it suggested by many people.   You need this much space on a forum to explain why it isn't quite like that). 

I hope that helps.

Best Wishes.

Ah yes,that has answered my question

When I first started asking questions about this subject some  14  years ago I thought relativity should require some particular way of going from one moving frame to another by virtue of the fact that it should be reversible.

I too assumed this would be a non linear equation of some kind  and  was a bit put out that is was just a plain linear  equation that seemed  to be using complex numbers.

Some people seem to prefer to consider c as a conversion factor between space and time (and other  measurements)

I see that with space and time c has the dimensions of speed.

What about mass and energy ?What would the corresponding   use for c in that situation?

Can there be other situations where c is the conversion factor between physical  properties?

What is mass divided by energy ,I wonder?

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Physics, Astronomy & Cosmology / Re: Can Light Experience 'Time'

« on: 15/05/2023 10:34:44 »

Can I ask you  what are  some of the derivations that show  that c is an invariant speed and which have no connection to the speed of light?

In Special Theory of Relativity, invariance speed of light is taken as a postulate, hence not derived from some more fundamental axioms.

That was not what I was asking -unless your implication is that the invariant speed c  ,(contrary to what  @Janus   said) is completely linked to the speed of light in a vacuum .

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Physics, Astronomy & Cosmology / Re: Can Light Experience 'Time'

« on: 14/05/2023 23:55:58 »

The key here is that it is "c" which is the important thing, not the light itself.  As far as we know, light in a vacuum travels at c.  But even if this turned out not to be the case, it would not change the importance of the speed c as an invariant speed. It would just mean that the photon is not the truly "massless" particle we now consider it to be. 

Can I ask you  what are  some of the derivations that show  that c is an invariant speed and which have no connection to the speed of light?

I feel I should know this  but perhaps I don't  or perhaps you could jog my memory.

Is it perhaps based on the lorentz transformation between moving frames?Does the invariant speed c follow from that?

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Physics, Astronomy & Cosmology / Re: Talking about Physics

« on: 01/05/2023 15:01:59 »

Measurement of one property will cause a wave function collapse and the wave function is then changed.

I seriously disparage this statement!

You can plot the outcome of dice throws as a wave function. You throw the dice and get a number. You haven't done anything to the hypothetical wave function, just chosen one value of it, which you could not predict. If you roll the dice again, you will get an equally unpredictable number. If you had "collapsed" the wave function, you would have restricted the range of future possibilities - the gambler's fallacy.

It is perfectly true that if you measure any property of a subatomic particle you will have altered its state in some way, e.g. by bouncing a photon off it, and thus biased its future state and wave function because you have changed its energy and momentum, but the notion of "collapse" rather militates against Heisenberg.

So collapsing the wave function is a bit like swatting a fly ?

You kill it but there is always another one.....

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Physics, Astronomy & Cosmology / Re: Talking about Physics

« on: 29/04/2023 23:00:30 »

decay of  an atom?
    Are you happy with the answers / discussion so fa

I am not sure I agreed with you regarding yard sticks.

If you create a yard stick for use as a universal unit of measurement  and then wait until (let's hypothesise) the speed of light slows appreciably.

As per what I understand you to be saying  those yard sticks remain unchanged in length but I am wondering  whether their length is dependent on the speed of light  insofar as the bonds holding the Atoms together  are  those of electric attraction.

Since light is em radiation  I was wondering if the force of electric attraction was proportional to the speed of em radiation -ie the speed of light.

If so ,the yard sticks  would change in length.

Am I right?

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Physics, Astronomy & Cosmology / Re: Talking about Physics

« on: 29/04/2023 11:54:17 »

So, if you have anything nearby that you want to measure the length of, your clock is wrong and so is your ruler

Why is that important.?We can never attain absolute accuracy in measurements ,can we?

If the clock was right but the spatial distance was wrong that really would be a problem,surely.

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Physics, Astronomy & Cosmology / Re: Talking about Physics

« on: 29/04/2023 01:20:08 »

Apart from anything else, how do you measure time?

Is  a time unit arrived at  by counting the spontaneous and     random emissions in the radioactive decay of  an atom?

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Physics, Astronomy & Cosmology / Re: Acceleration of light?

« on: 24/04/2023 22:26:21 »

When a photon is ejected from an electron going to a lower energy level, what acceleration does the photon have?

From what I have read  a photon (in a vacuum) does not accelerate and only moves at the one speed(c)

As it transitions between mediums?

I will defer to others here to answer that .....

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Physics, Astronomy & Cosmology / Re: Acceleration of light?

« on: 24/04/2023 01:23:07 »

When a photon is ejected from an electron going to a lower energy level, what acceleration does the photon have?

From what I have read  a photon (in a vacuum) does not accelerate and only moves at the one speed(c)