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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 / 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: 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: Are there any philosophical or other implications to the underlying randomness

« on: 07/06/2023 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: 07/06/2023 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 / 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: 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)

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Physics, Astronomy & Cosmology / Re: Are both electrons and photons modeled as excitations in a field?

« on: 17/04/2023 22:37:07 »

Thanx for that Link G!

I read pretty much All of it, won't say i Understood it all.

I've obtained another doubt from it thou lol.

Why is a UFT required?

I don't know  and others will give you a better answer but I suspect a ToE (what you mean by UFT I think) is necessary to understand the conditions  even earlier in the life of the universe than we do already.

But don't take my opinion for it as I  only.listen to what more knowledgeable  people have to say on the subject.

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Physics, Astronomy & Cosmology / Re: Are both electrons and photons modeled as excitations in a field?

« on: 11/04/2023 00:06:43 »

Much appreciated @evan_au  and @Eternal Student
Whilst my ambition  to learn many  things in this subject is very low I do welcome the prospect of hopefully   not making the exact same mistakes in my questions in the future (although doubtless I will) as well as learning one or two things I am not likely to forget.

And let us hope that others can also learn something from your answers.

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Physics, Astronomy & Cosmology / Re: Does anyone understand Roger Penose's view of cyclic universe?

« on: 26/01/2023 23:27:20 »

Yep!
Exactly my point.

I failed to find any consensus or agreement Online on the CCC Topic.

The ones against it pop up at top spots in the Goggle search engine.

The only ones i could find in favour of CCC were Sir Roger Penrose's own videos on Utube.

Thou, there is one thing i wish to ask here...
In his video He draws the shape of the Universe like a pointy conical.
(it begins n slowly spreads out)
The images/diagrams i've seen of the Universe show a large bloating right at the beginning.
(possibly showcasing Inflation)

So, where does the CCC stand on Inflation?
Is Inflation also embedded into & is a part of the CCC Model?

Do you want to take a look at this fairly recent discussion?

https://www.reddit.com/r/cosmology/comments/jfu7mm/is_conformal_cyclic_cosmology_really_debunked/

I have only read the first few contributions  so far  and am not sure yet of the overall flavour .

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Physics, Astronomy & Cosmology / Re: Does anyone understand Roger Penose's view of cyclic universe?

« on: 25/01/2023 21:18:50 »

I am not well enough informed to get a  feel for how reliable those articles are.

The flavour of them is certainly  that CCC seems very unlikely to become a successful theory as all the supposed data supporting it seems to be contested for now and stronger data seems a  far distance away.

To have a better idea I think one might need there to be a debate between a strong advocate for and a strong  advocate against  CCC.

Perhaps such a debate exists out there on the internet

It might be interesting if it was  discovered and dug up.

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Physics, Astronomy & Cosmology / Re: Does anyone understand Roger Penose's view of cyclic universe?

« on: 20/01/2023 19:59:23 »

Penrose's theory assumes that the universe has enough mass to slow down the expansion of the universe, so that it eventually contracts into a "Big Crunch" (or "Gnab Gib", as some palindromically express it).

This theory took a (possibly fatal) beating in the 1990s, when it was discovered that the universe is expanding at an accelerating rate.
- This suggests that Penrose's proposed contraction does not seem possible.
https://www.scientificamerican.com/article/the-2011-nobel-prize-in-prize-physics/

Are you sure it is predicated on a Big Crunch?

I imagined it might be that the condition at the "end" of the universe (ie an absolutely total heat death) might provide a circumstance  where  the very large spatial distances were identical to the  very small distances (zero distances?) that may have prevailed before or just after the birth of the universe.

I have not looked into Penrose's idea apart from the one or two times I have heard it     mentioned but I thought it must surely be more than just a kind of Big Crunch.

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Physics, Astronomy & Cosmology / Re: What is a black hole made of?

« on: 28/06/2022 02:01:10 »

I have read that black holes might be viewed not as objects at all but  as extreme spacetime  curvature 

Is that correct or have I perhaps  misconstrued?

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Physics, Astronomy & Cosmology / Re: How would we know whether space,time or spacetime were continuous or discrete?

« on: 12/06/2022 17:52:36 »

. I suspect geordief likes these continued discussions

Yes he does.It takes me a lot of effort to follow the replies ,though after my  question has been answered in the main.

And I may no longer be able to contribute  but  I follow as far as I can.

I find the world as built up of "events" rather than objects /systems evolving in time very interesting  and find the former to be equally acceptable (more so actually) on an intuitive level.

Apparently spacetime is a model  designed to be just a coordinate system (a local one) without any objects  necessarily occupying  any particular location  but I have also wondered if  those  locations could be populated by  real events.(ie if  the real events  could define the location in spacetime)

Seems ,maybe it can be one or the other but not both at the same time?

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Physics, Astronomy & Cosmology / Re: What are the properties of space?

« on: 10/06/2022 01:05:40 »

What is it that makes stuff separate from itself? (rarified?)

Why is it not happy just being together with itself,with no distance between its constituent parts?

Are all the separate bits of stuff  forever connected or forever  separate? (both?neither?)

Is that a very poor philosophical question as well as a poor scientific question?

Do we just start with what we observe and not try to second guess  what is out there and in here?

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Physics, Astronomy & Cosmology / Re: What if the universe really is infinite?

« on: 21/10/2021 22:59:58 »

Does the big bang theory cause a problem for the infinitely expanding universe theory? Our universe is currently expanding and my understanding is that a reduction of that expansion would bring us to the big bang. But wouldn't that mean that the reduction would also have to be infinite?

(think my head just expanded   )

Well could you have it so that some of the universe did fall back on itself but some was just too far distant and "out of reach" so that it  continued its expansion "to infinity and beyond"   ?

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Physics, Astronomy & Cosmology / Re: What if the universe really is infinite?

« on: 18/10/2021 21:33:23 »

I'm obviously talking about something being identical to within a particular volume

But isolated systems don't exist.

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Physics, Astronomy & Cosmology / Re: What if the universe really is infinite?

« on: 18/10/2021 21:21:29 »

@Kryptid I see it the other way round.For there to be an identical system to another it has to have identical connections to its environment.

Taken to the extreme that would mean that system A would be a part of an identical universe (including its past ,since the universe is dynamic)  to that of system B.

So system A =system B

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Physics, Astronomy & Cosmology / Re: What if the universe really is infinite?

« on: 18/10/2021 13:47:58 »

But can we begin to tentatively assume that the observable universe may well  be part of an (dynamic) infinite structure?

Rather than hedging our bets as it were,can we just let it sink in to our "world view" that this ,or something very similar can be the starting block  that all our other ideas and theories have to accord with?

A bit like Einstein and the invariance of the speed of light.Just accept it and build around it.

It makes me wonder where the energy "came from" to keep "all this" going.

Is it related to asymmetry?

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Physics, Astronomy & Cosmology / What if the universe really is infinite?

« on: 18/10/2021 13:02:08 »

Watching a Horizon programme last night on BBC 4 (Sean Caroll was one of the contributers)

Apparently the Cosmic Microwave Background Map is like an expanding bubble around anywhere in our "neighbourhood" and its features have now been mapped in enough detail to "draw" a huge triangle from here to there.

The triangle ,according to the programme is evidence that  space (spacetime?) is probably flat and as a result the universe outside the observable part is  of infinite extent.

What might be the implications if this,startlingly  is true and can we now posit this provisional result as a stone to build our edifice of how "everything" works.

Can we ditch the "universe may be finite" for good unless we get  some new unexpected observations in the coming years or centuries?