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Question of the Week / Re: QotW - 24.08.02 - What is the universe expanding into?

« on: 12/10/2024 12:23:34 »

That is a good question and guess what? I can't answer it! The universe is by definition "all that there is",

Yes ,that is how I inderstand the "universe".
However ,since that definition gets us nowhere close to understanding intuitively what happens (we just have models which seem to do a great job until someone spots an anomaly) that is to me an indication that the definition ,whilst logical  is not fit for purpose.

If you think about it , the definition itself is a part of that defined universe and so ,again using "logic" cannot be used to describe   it as that would be to describe itself  as a corollary  setting up a chain reaction or a feedback loop.

Unless we assume mental constructions are not part of the physical universe (something that I would not do-I think they are a strange subset of the physical universe  that ,once again we are prevented from understanding  ,there being some questions that are indeed unanswerable  -actually perhaps we could say that unanswerability  is the default position and that all answers to all questions are just  holding positions)

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Physics, Astronomy & Cosmology / Re: Did the Sun change from orange to white 15 years ago?

« on: 11/04/2024 21:33:49 »

Nor in my 71 years. Can anyone beat that number?

Yes  ,but I am not saying  ;-)
I think it did turn black a few days ago, but I missed it.

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Physics, Astronomy & Cosmology / Is there a connection between slow motion filming and time dilation?

« on: 29/03/2024 13:42:32 »

This seems like such an obvious question that I am surprised it is the first time it has occurred to me .

When we speed up the recording of a film and play it back at a slower speed we see everything slowed down.

Again , if an object is in relative motion to our frame of reference we "see" things slowed down  in it (as in the twin astronauts scenario and others)

If we speed up the recording of the film to the maximum the speed of the replay goes to zero.(with no loss of detail)

Is this just an analogy for time dilation or is this more or less how time dilation actually works?

(I realize ,I think that the doppler effect plays no part in slow motion filming but I am not concerned with it for this question.)

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Physics, Astronomy & Cosmology / Re: What is the relationship between an object and its field?

« on: 13/03/2024 22:00:03 »

@Eternal Student

Thanks.That was informative.Yes ,I appreciate that different ways of looking at things should really have consequences  to be of interest.
Still it was mostly for my own benefit and curiosity that I was asking.
Hopefully when our notions are disabused we can pick up on another path(as well as sometimes validating  some of our vague suspicions to a degree)

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Physics, Astronomy & Cosmology / Re: What is the relationship between an object and its field?

« on: 13/03/2024 16:00:34 »

If you start with the field, you need to produce a mechanism for generating mass, and  a reason why the field appears to be radially isotropic from a point. It's a lot easier to assume that the field is a characteristic of the object, since this model also works for large objects like magnets and wires.

Thanks.
Is it normally accepted that the object and the field are two aspects of one "overarching" entity?

Could there be (is there?) a mathematical equation  where the object is defined in terms of the field? (along the lines of energy and mass in relativity)

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Physics, Astronomy & Cosmology / What is the relationship between an object and its field?

« on: 13/03/2024 00:09:25 »

As an example an electron and its electric field?

In QFT the former is described as an excitation of the latter,I believe.

Are there other ways of looking at it?

Can we imagine the field as an extension of the object(the two being aspects of the greater whole)?

Or is it just  easier to imagine it the other way round with the object being  some kind of  an "appendage" of the field ?(that would be more  along the lines of the QFT model ,I think)

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Physics, Astronomy & Cosmology / Re: Time dilation caused by relative motion.

« on: 07/02/2024 00:42:24 »

I have also seen it stated that it is possible to produce  two scenarios with the same accelerations but with different resulting time dilations(because of  different relative motions ,presumably)

There were some specific examples at the bottom of this post:
https://www.thenakedscientists.com/forum/index.php?topic=86033.msg697485#msg697485

The first shows identical accelerations (just at different times), and significantly different differential aging. The second shows very different acceleration (continuous, one a thousand times the other) with identical dilation over indefinite time.

OK, you wanted an example of same magnitude of acceleration, but different dilation. I'm sure I've posted something of that nature, but it's easier to do it again. Remember that time dilation (due to speed at least) is a coordinate effect, not a physical one. Differential aging is a physical effect, meaning the difference isn't frame dependent.

First of all, something flying by Earth at 0.4 c is dilated far less relative to Earth than something flying by at 0.8c. There's no acceleration at all in that example.

Second example: Bob and Alice have identical ships that accelerate at 2g continuously for 7.5 Earth years. They both start on Jan 1, 2000. Bob accelerates a year (his clock) outward, two years to reverse direction, and a year to stop at Earth, and thus ages 4 years.  Alice turns the ship around in a month, so she visits Earth about 15 times instead of just once. Alice ages just under 7.5 years, having aged only 10 days less than had she stayed home.  Bob returns early July, 2007, having aged over 3.5 years less than had he stayed home.

Thanks .
So  Alice's and Bob's acceleration are identical (even if they can be characterized  as  broken up into smaller segments,one than the other) and ,as I requested the time dilations differ.

How does that work out with the relative motions /velocities of either Alice or Bob wrt the Earth?

Is it a complicated (tedious) calculation of all the various relative speeds involved followed by an integration of all the time dilations along the respective paths?

Are the actual distances travelled by Alice and Bob  the same?(I suppose that  is not an important thing to know,or might it be?)

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Physics, Astronomy & Cosmology / Is time dilation caused just by relative motion(not acceleration)?

« on: 06/02/2024 23:11:15 »

I understand that the idea that time dilation is caused by acceleration  is a mistaken one(one that I laboured under for some time)and that it is actually relative  motion that is the cause.

I have also seen it stated that it is possible to produce  two scenarios with the same accelerations but with different resulting time dilations(because of  different relative motions ,presumably)

I did not see(I mean they were only mentioned in passing and not described specifically) any such actual examples .

Can anyone here produce such an example,just for my curiosity?

Ps I have changed the title of the thread so it now reads as a question ,as we are supposed to do.

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Physics, Astronomy & Cosmology / Re: Are quantum systems dynamic?

« on: 03/01/2024 20:23:16 »

If we observe 2 stars at a very great distance  and the light arriving from them only amounts to a very low number of pixels , are there any quantum effects involved  in the observation?

Let's say it a is binary system.

How many pixels would you need to form any kind of a judgement  as to position and relative moment between them?

Would quantum effects come into play if the amount of light reaching the receptor was small enough?

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Physics, Astronomy & Cosmology / Re: Are quantum systems dynamic?

« on: 01/01/2024 23:31:54 »

@Eternal Student
I have read and reread (once) your post.

I think I may have got most of he gist of it.

So  if an observable of a quantum object is measured the waveform  suddenly  changes to a new waveform  which has a probability  attached to the "amplitude " of the particular observable at the time.

I see you listed several components of the waveform with corresponding coefficients

What might be the maximum number of coefficients for a typical quantum object  and what  might they correspond to?

Alternatively what might be a typical quantum object with very few such coefficients?

Might there  be such an object with ,say only 4(to represent spacetime)or 5 or 6 (to represent additional properties)?

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Physics, Astronomy & Cosmology / Re: Are quantum systems dynamic?

« on: 31/12/2023 03:50:04 »

@Eternal Student
just to acknowledge  your lengthy reply.

It may take me a  good few days to read and reread it.

Hopefully I will have something to answer it with then(yes,I had heard  of that Zeno effect.Quite weird .Maybe you have provided a context for me to understand it in.I'll see)

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Physics, Astronomy & Cosmology / Re: Are quantum systems dynamic?

« on: 28/12/2023 21:33:51 »

Thanks. Do the quantum systems evolve in discrete  ways rather than continuously?

I thought I just answered that question.  If your asking just about quantum particles then the answer is quantized or discrete.

I think I was trying  to distinguish between quantum particles and quantum  systems.

Does a quantum system lie between a quantum  object and a classical  system?

Can that distinction  be made?

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Physics, Astronomy & Cosmology / Re: Are quantum systems dynamic?

« on: 28/12/2023 20:28:06 »

Large objects are made up of quantum particles.  The individual particles act in a quantum fashion and the large object acts in a classical fashion

Thanks. Do the quantum systems evolve in discrete  ways rather than continuously?

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Physics, Astronomy & Cosmology / Are quantum systems dynamic?

« on: 28/12/2023 17:53:46 »

A classical system is clearly dynamic.

Can the same be said about a quantum system?

Can quantum system be said to evolve (I think so)?

Do they ,then evolve in discrete ways and not in a continuous fashion except when viewed as part of a classic system?



Hope the question makes some kind of sense as I don't have a very deep acquaintance with QM.

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Physics, Astronomy & Cosmology / Re: How Can We Know The Cosmos Age If We can Only See The Observable ?

« on: 01/10/2023 03:50:25 »

Usual problem of ambiguity about "the universe". For all practical purposes, it means the observable universe. Only human vanity would presume that there is nothing else, so it is entirely reasonable to assume that there is more in the "entire" universe that we can't observe, and therefore cannot meaningfully ascribe any properties such as age. How old is the unobservable fairy who may or may not be standing behind me?  Since it is unobservable, it cannot affect me and its age doesn't matter.

Is it possible to hypothesize that  that part of  the universe that we cannot observe but yet  believe exists  was in the past    concentrated in a small region that we can now observe (the Cosmic Background  Radiation)?

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Physics, Astronomy & Cosmology / Re: Talking about Physics

« on: 14/07/2023 16:23:50 »

Aether does not exist.

'twas  said in jest(not joust).

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Physics, Astronomy & Cosmology / Re: Talking about Physics

« on: 13/07/2023 21:27:08 »

Maybe not, but it was quoted in the NC even if they didn't coin it.  Maybe that's why so many people still think about aether - the Dept of Education's only physics textbook is 100 years out of date!

With all the water vapour  out there it can't be long before they track down the aether.

https://roboticsandautomationnews.com/2021/01/20/scientists-have-found-more-water-in-space-than-they-ever-knew-possible/39771/#:~:text=The%20cloud%20of%20water%20in,accounting%20for%20its%20remarkable%20size.&text=The%20gas%20cloud's%20higher%20temperature,in%20space%20is%20constantly%20heated.

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Physics, Astronomy & Cosmology / Re: How do or can we measure entropy in a system?

« on: 18/06/2023 17:30:50 »

Quite a bit of heat is lost from your head/brain but I would say that the entropy there is just part of the heat loss for the whole body.

Isn't entropy a measure of the degree of order in a physical system?

Well ,is a system of connected minds  also an ordered system?

Can the concept of entropy apply in those cases as well ?

Or is the concept of entropy only applicable in physical systems?

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Physics, Astronomy & Cosmology / Re: How do or can we measure entropy in a system?

« on: 18/06/2023 16:54:50 »

If this is possible can we measure the entropy of an individual  mind or a system of  minds?

Do you mean entropy of a brain?  What in the world is a 'system of minds'.

Yes ,the brain (but the mind is   a "property" of the brain)

A system of minds? Could be the interactive network of any group of people or living, sentient beings.

A book club.A pack of hounds.A political grouping   with constituent parts that interact with each other


Fo those groupings exhibit   degrees of entropy ?They are ordered, aren 't they?

And what about  the purely physical observable universe
?
How do we measure  its entropy?Does it have a number?

Can we compare its number to that of the groups ,I listed above?

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Physics, Astronomy & Cosmology / How do or can we measure entropy in a system?

« on: 18/06/2023 13:57:28 »

If this is possible can we measure the entropy of an individual  mind or a system of  minds?

And what about the observable universe ,would there be any rough number associated with it?