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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?

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Physics, Astronomy & Cosmology / Re: Can we ever truly describe space as empty?

« on: 07/10/2021 16:20:48 »

I don't know what you mean by that

Well apparently particles (via the virtual particle process) can appear out of nowhere**

Can they similarly disappear into nowhere (causing the universe itself to leak in a similar way to black holes)?

**I don't personally understand  how virtual particles work,except for learning that some physicists wish they had never been so named...

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Physics, Astronomy & Cosmology / Re: What is TIME?

« on: 03/10/2021 19:40:20 »

The definition Alan quoted above works quite nice for time as an integral part of spacetime, and it works for other interpretations as well. So it is a far better definition

Thanks,I missed that.

Other events are independent or subject to less constant conditions but their sequence can be located on a time line established on the basis of constant-dependent events

Could I ask if you have any examples?

I had been  wondering whether all pairs of events are connected,either from A to B or from B to A depending on circumstance(eg I cannot influence my mother's early life but she could (and did?) mine-as a specific example of what I was assuming would be the general case)

To clarify the specific case above, if she took ,say 5 minutes extra to do the shopping on a day before I was born ,I am saying that that extra 5 minutes would have changed the course of the universe and my  life (and all others ) would be included in that changed universe.

So her shopping and my , say fit of coughing would be connected events  but only in the direction of her to me .

So to my mind all events in the universe are connected but sometimes only  in one direction.

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Physics, Astronomy & Cosmology / Re: What is TIME?

« on: 03/10/2021 12:43:35 »

Is there a definition  or description of time as it applies to the time that is an integral part of spacetime?

What does the space part refer to and what does the time part refer to?

I think there is a well known quotation (by Minkowski?)  where he says that henceforth both time and space in the then accepted sense would be replaced by a kind of union between the two.

Can anyone flesh  that out at all?

Is the time in that quotation simply a reference to what clocks measure in moving frames of reference or was he driving at something else? Some physicality to the concept?

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Physics, Astronomy & Cosmology / Re: Is "Space" distinct from "nothingness"? (and the Vacuum)

« on: 08/08/2021 23:44:29 »

geordief  -  If you still have questions or are seeking more discussion, just say something here.   I'm sorry that your thread seems to have become complicated and difficult to follow.

Quite often ,I start a thread and ,after a few replies (if I get them) I have taken in all I can digest and so ,when others take over the thread ,so to speak I can lose interest as the conversation goes over my head

Sometimes ,as you may have observed someone can necro an old thread for perhaps not good reasons but in this case Yoron  did ask me to clarify a passage I had written earlier (yes,a long time earlier)
Of course I did my best to explain  my thinking

I don't think I accidentally misattributed  any passage as Yoron correctly quoted me in post#38 and I then answered him  in post#40.

(When I do quote anyone ,I often highlight the salient passages in the post and then look for the "quote selected" facility under the Actions tab at the top left of the post.

Simply using the "Reply" facility at the bottom of the post can imo often make for very long posts.)

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Physics, Astronomy & Cosmology / Are possibly all massless particles just travelling waves in particle fields?

« on: 05/08/2021 21:36:15 »

That is an uneducated question and I anticipate answers  along the lines of "of course not",

Still the idea of that possibility just occurred to me .Is there /could there be anything to it at all?

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Physics, Astronomy & Cosmology / Re: If sound could travel through space, what would the Sun sound like?

« on: 06/07/2021 02:12:39 »

I think Janus once  explained to me** that the wave motions of galaxies reverberating through space might be considered a form of extremely ,extremely long wavelength sound transmission.

   I'm not Janus but might they have been talking about   the Baryon Oscillation Spectroscopic Survey?
See "Ancient Sound Waves sculpted galaxy formation."  https://www.newscientist.com/article/dn21653-ancient-sound-waves-sculpted-galaxy-formation/

Maybe that is a related phenomenon but as I recall ,and hopefully understand it was just that galaxies interacted (=ran into) each other  and the effect was some extremely ,extremely  low frequency waves that might be termed "acoustic" were formed (that propagated through the vacuum)

If I find the thread I will update you on what was actually said  but I hope others here might  know about this effect (if it exists)

Or ,maybe Janus will drop by and explain (if it was indeed  he who pointed this out in the past -and if he is not under too much duress in the  heatwave on the Pacific North West at present)


EDIT:This is more or less what I had in mind

https://www.sciencealert.com/sound-can-travel-through-space-after-all-but-we-can-t-hear-it

Still can't find that old thread but that link seems to broadly cover the idea.

Basically no 100% vacuums exist on a large scale and so sound can travel ,albeit  at enormous wavelengths.

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Physics, Astronomy & Cosmology / Re: Can we see the universe from the outside?

« on: 06/05/2021 22:54:15 »

Actually, no I couldn't.  I agree with your assessment, there isn't enough places on this forum.  Many other science forums do have a much bigger selection of places for discussion where the policies on sticking to mainstream science have been relaxed and more general philosophy can be discussed.   

I wonder if there could be a space for the interpretation of  established scientific theories?

On another forum there is an ongoing discussion of virtual particles which apparently may be something of a misnomer,being as they apparently are disturbances in the waves in the fields that may be related to particles - but not really particles.

Maybe those kinds of discussions are a kind of halfway house between philosophy and general scientific discussion?

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Physics, Astronomy & Cosmology / Re: Can we see the universe from the outside?

« on: 06/05/2021 22:23:16 »

Outside is a relative term. I am inside my house but outside the kitchen. I am inside my garden but outside my house. Define what outside means in this context.

What about  in my reply#6 above?

Might my attempt  there to bring in causality  have in a sense  addressed  the inside/outside question.?

Can a system of events lie outside or inside  the causality region of another system.?

Would that be a more productive  definition,perhaps?

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Physics, Astronomy & Cosmology / Re: Can we see the universe from the outside?

« on: 06/05/2021 15:37:41 »

There are other sections of this forum (and also other forums) that seem better suited to your discussion.

Could you suggest  another section of this forum?Were you thinking of the "Just Chat" section?
Would be happy if a mod thought  this thread should be relocated there ,or elsewhere(fairly sure New Theories  would be inapplicable and that is all I can see apart from Just Chat)

I realize it can be a pain weeding out idle speculation from hard science....

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Physics, Astronomy & Cosmology / Re: Can we see the universe from the outside?

« on: 06/05/2021 12:52:09 »

Best Wishes to you, sorry I couldn't be more help.

Could I pare down the question to "Could  there have been  anything in the universe  that had a potential causative  relationship    to the configuration we understand  "prior" to the Big Bang but was not in a reciprocal  causative relationship with it?"

Or "Might it (one day)  be possible to detect objects in the universe whose provenance was not from the Big Bang?"

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Physics, Astronomy & Cosmology / Re: Can we see the universe from the outside?

« on: 05/05/2021 13:50:58 »

If you could make it clear what definition of "the universe" you are considering, it may be possible to continue this discussion.

Hi, well I have had the same idea as you vis a vis adding bits on to any definition and finding that the new piece of the jigsaw was now included  as an integral part of the newly considered "universe".

So ,for the purposes of this  thread ,I was imagining an observer (or simply a physical configuration) that was at a remove (if that is even 100% possible) from the events  unfolding in our arena prior to what is called the Big Bang.

Would that observer,so defined  have a bird's eye view of the process and would his/her/its(other) view actually be any different from the view it may be possible for us to achieve through  mathematical/technological ingenuity, or even in our "mind's eye) ?

I have come across (and possibly suffered from) the misconception that the (loosely defined) universe  has a clearly defined  border or edge border . I think the correct answer may be  just "we don't know but it seems unlikely"   

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Physics, Astronomy & Cosmology / Can we see the universe from the outside?

« on: 05/05/2021 01:36:43 »

Clearly this is something I cannot do insofar as I am presumably a part of this universe (and I think it is also said that the universe has no external boundary).

However is it not possible that the  beginning(if there was a beginning) of the universe was witnessed by an intelligent being (or even just another object?)  and so this being or thing would have had something of an objective view of what happened?

Is that feasible  ?

Would that mean that the universe  did in fact  have a  boundary, even if that boundary  was dynamic and poorly defined ?

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Famous Scientists, Doctors and Inventors / Will I post a link for some new Feynman videos here?

« on: 02/04/2021 17:00:38 »

http://www.thescienceforum.com/links/50272-newly-presented-feynman-lectures.html

I like them a lot  since they are good quality and maybe this is a good place to post a link to them?

https://www.feynmanlectures.caltech.edu/