billhinge

1 hour ago, iantaylor2uk said:

You can't write it down to the last digit because there isn't one. The fact we can approximate it surely means it exists though.

yes it exists as a concept but 3.14 does not equal 3.1415926535897932384626433 but both are equally valid answers to what is pi, whatever number you pick I can always give you a different value

If you try to measure a circle it then you have to consider if you live in a flat Newtonian universe or a Riemannian universe, if the universe contains matter it can't be perfectly flat although it may be very, very  close in some places. This doesn't take account of your measuring or drawing equipment

How about imaginary numbers, are they real, do tachyons with imaginary mass exist? why not?

By the way when I say somethings exist as concepts it doesn't mean they don't have physical manifestations, some things do and some don't

If you are religious do demons exist, some would say they are real others that they are metaphors

I am being a bit facetious but there is an underlying point, much of the world is based on models, models are definitely useful and work until they fail but all are approximations of reality

25 minutes ago, iantaylor2uk said:

Pi definitely exists as we define what it is and can measure it, or calculate what it is. If it didn't exist how can it be measured?

can you write it down to the last digit, can you draw a circle and measure it exactly? Even if you 'knew' what it was would you have enough paper or computer RAM to hold it all?

I don't dispute you can get gazillion digit approximations of pi but it isn't pi, its an approximation of the concept of pi

The best you can do is create a useful approximation of pi that is useful to you

23 minutes ago, Moonshed said:

Hi billhinge,

I think we are in danger here of taking our hypothetical cube of nothing and then introducing whatever properties we wish in order to support any given argument. Everyone has their own ideas on exactly what nothing is, so until a unanimous definition can be agreed upon we can make our cube of nothing perform cartwheels if necessary. 😄

Until then, we can argue endlessly regarding what we can do with our hypothetical cube of nothing. 
 

Cheers

Keith
 

Hi Moonshed

Surely we are debating the properties of nothing not hypothetical cubes which by definition are made of something and have 'some' physical rigidity, I'm actually trying to avoiding giving the box any properties 

Not convinced? Take a 2m cubic box full of air and put a plunger on top. If you push the plunger in then the air in the box will resist 

If you pump out the air to create a vacuum (approximation of nothing) then you can push the plunger all the way to the bottom achieving infinite compression of the vacuum space

In the real world if the box were flimsy enough the external pressure itself would crush the box (air pressure, photon pressure, virtual particle pressure on the outside of the box since there isn't anything to resist other than the artificially introduced properties of the box which we eliminate by making it extremely flimsy).

The introduction of a rigid box is the issue here (it isn't nothing and you are letting its properties influence the experiment)

As I said a few days ago, my opinion is nothing exists a concept same as Father Christmas, pi, imaginary numbers(?) but it doesn't exist in this Universe as a real physical thing that you can measure or see, but as you say everyone has an opinion and this is mine

23 minutes ago, billhinge said:

Since nothing doesn't contain any fermions and therefore not subject to Pauli Exclusion Principle why can't you stack both cubic metre volumes inside one another, there is nothing to interact with or repulse each other causing outward pressure. Furthermore you could pour the nothing into a container half the size  ad nauseam till you get to infinitesimal size  (since we are putting nothing in )

For the confused ...

Imagine Maxwells Daemon, you tell him to take each cubic component of nothing and stack them so that they will fit into a box half the size of the original (like filling a box with building blocks), since you can stack each nothing block on top of each each other you can always stack nothing into a smaller volume (it has no physical properties to prevent this). Therefore nothing is infinitely compressible to an infinitely small size, why would you expect anything else, what pushes back if you try to compress it? (forget the artificial construction of the box since it is not nothing)

This is akin to asking what does the universe expand into? Nothing, there is no embedding space

13 hours ago, Moonshed said:

Hi Olly,

I would suggest that a cubic metre of nothing is defined as being that size by the mass that surrounds it and puts that constraint on its size, for without being surrounded by something that we can measure we cannot say what the volume of nothing would be. Adding another cubic metre of nothing gives us two cubic metres of nothing, again determined by the mass that surrounds it. Therefore you will need two cubic metres of normal space with which to contain them. 
I think that makes sense.

Cheers

Keith 

Since nothing doesn't contain any fermions and therefore not subject to Pauli Exclusion Principle why can't you stack both cubic metre volumes inside one another, there is nothing to interact with or repulse each other causing outward pressure. Furthermore you could pour the nothing into a container half the size  ad nauseam till you get to infinitesimal size  (since we are putting nothing in )

On 10/04/2023 at 19:03, ollypenrice said:

No, I'm not having this. To quote Wittgenstein (and give my point a bit of gravitas ) language is public and if I asked you, or anyone else looking at my car, what colour it was you would say black. You would not say, 'It has no colour, it manifests the absence of colour.'  Come on now, admit it! 

Olly

You fell into the trap, what you think is black is actually very, very, very , very , very , very dark blue

34 minutes ago, billhinge said:

There is a model called Ogdens or Semantic triangle

https://en.wikipedia.org/wiki/Triangle_of_reference

The Phenomena or Referent of nothing was described in  Sabine's video, the concept  or reference is what is in your head when you think 'what is nothing'

In the 'War of Universals' there was debate as to what was real and what is not -  Are apples real, is the 'state' real, is 'the people' real? if so who are they? is Father Christmas real? 

Plato - a Greek philosopher who argued for the existence of objective, universal forms or ideas.

Aristotle - another Greek philosopher who rejected Plato's theory of forms and argued that universal concepts are derived from particular objects through abstraction.

In the real world does 'nothing' really exist if fields are everywhere? Does pi exist as real thing or only as a concept, if its real can you write it down?

 

 

Sorry I couldn't resist this https://www.quantamagazine.org/the-electron-is-so-round-that-its-ruling-out-new-particles-20230410/

Imagine an electron as a spherical cloud of negative charge. If that ball were ever so slightly less round, it could help explain fundamental gaps in our understanding of physics, including why the universe contains something rather than nothing.

I was looking up quantum computing algorithms and found it ...

There is a model called Ogdens or Semantic triangle

https://en.wikipedia.org/wiki/Triangle_of_reference

The Phenomena or Referent of nothing was described in  Sabine's video, the concept  or reference is what is in your head when you think 'what is nothing'

In the 'War of Universals' there was debate as to what was real and what is not -  Are apples real, is the 'state' real, is 'the people' real? if so who are they? is Father Christmas real? 

Plato - a Greek philosopher who argued for the existence of objective, universal forms or ideas.

Aristotle - another Greek philosopher who rejected Plato's theory of forms and argued that universal concepts are derived from particular objects through abstraction.

In the real world does 'nothing' really exist if fields are everywhere? Does pi exist as real thing or only as a concept, if its real can you write it down?

would never of happed in the old days

Something different

Three time dimensions, one space dimension: Relativity of superluminal observers in 1+3 spacetime

https://phys.org/news/2022-12-dimensions-space-dimension-superluminal-spacetime.html

...the crucial ingredient of any spontaneous symmetry breaking mechanism is a tachyonic field. It seems that superluminal phenomena may play a key role in the Higgs mechanism.

https://iopscience.iop.org/article/10.1088/1361-6382/acad60

While it wasn't the best I'm surprised by the strong reaction against. I thought it was a decent 6/10 in terms of balance. If i'd been a youngster say 11 years old I'm sure most wont be familiar with multiverse, QM or black holes so it may spark an interest. If you want a more technical description there are lots of alternatives which may be the point. 40 odd years ago there was no internet and Sky at Night was one of the few programs out there and no competition, now we are spoilt for choice and its easy to compare apples and oranges and people here may be more knowledgeable on these topics than the public

As someone else pointed out, I think the issue was it was too short for the things it tried, each topic could be an episode

On 15/10/2022 at 17:09, pipnina said:

I'm looking to use the APM riccardi flattener/reducer with it, which means I need at least 2.5" clear barrel, and I figure getting a 3" focuser will prevent any vignetting. At the moment there is a fair bit of vignetting on my APS-C sensor, and I'd like it to be as camera-upgradable as possible. Since the focuser must be changed anyway due to being defective, I may as well do a full-blown upgrade in size while I'm at it!

I was looking at either the feathertouch R&P 3" (M109 x 1mm thread), or the TS 3" R&P (M117 x 1mm thread).

I am going to go into work on monday and see if they'll let me machine it in there (they are often quite relaxed about these things so it may be possible). If that is the case, I just need to decide definitively on which of those focusers I want, cut the flange off (sawing seems to be the most popular method in this thread so far) and hopefully by that point it just becomes a matter of machining and fitting that focuser, and gluing the flange back on...

If it works, hurrah! If it goes wrong, I will have to reconcile a lot of emotions regarding a lost £2000 haha.😬

Why didn't you say. That's what I'm doing with my TMB 115, fortunately only screws to deal with. If you are going to use the Riccardi reducer it will change the back focus so chopping the tube is beneficial to obtaining focus.  Theoretically it could change the internal baffle spacing/size 

It had a  native 2" feathertouch but wanted to use the Riccardi's.  I wanted the 3" or 3.5"  feathertouch but they are hard to find  due to issues at the company and if you can then they are very expensive. You also need the adapter to fit the focuser to the tube. If your tube is non standard diameter getting the adapter is a challenge. (I drew my own and 3d printed one). Rather than getting the feathertouch I bought the APM 3.75". Its half the price and the feathertouch really isn't worth twice the price

You could always try. https://www.photoniccleaning.com/category-s/164.htm

365 sell it

I suppose its possible, this JWST pic has curly whirly bits in it

Best black hole video - the rotating Kerr black hole , extended ring singularity, repulsive gravity, 2 event horizons, escape through future white hole, super luminal speed , time travel to the past and multiverse (providing you don't get cooked by the inner horizon)

13 hours ago, Macavity said:

In "our day", we didn't have the "joy" of the Internet? lol. Scientists didn't
have a (largely lay?) "fanbase", to whom I / we / they could "appeal"? lol
N.B. I use the term *appeal* in the way Cricketers shout: "How's That"! 🥳

https://backreaction.blogspot.com/2022/09/ive-said-it-all-before-but-here-we-go.html
The above could be summarised: "But yeah I’m having FUN for sure."? 🤔

Reminded of: “Of all tyrannies, a tyranny sincerely exercised for the good of
its victims may be the most oppressive"... (Seemingly from C.S. Lewis?) 😉

And science is (genuinely) hard - For most of us? The "field is vast" etc.
Personally, I HOPE that there will always be "young scientists", who (like
me once!) wanted to "take up science". just because *it* inspired us? 😎
 

I didn't read it that way, I thought Sabine made a very good reasoned argument. Whether you agree with her depends on what side of the fence you sit on. If you are a particle physicist I'm sure you well never agree, it isn't in your interest. If you have already nailed your colours to the mast I doubt anyone will convince you otherwise, and nor should they expect to. But if I were a particle physicist I would be thinking of the comment  'And soon enough governments are going to realize that particle physics is a good place to save money that they need for more urgent things.' - rightly or wrongly (I'm happy to pay tax for these things by the way)

I don't always agree with everything she says but I think she is quite incisive. Science maybe hard but it doesn't mean that a proposed bollockon partice is real either

Now throw in a hypothetical quintessence particle (dark energy quantum field 'particle' which could be considered having long range anti-gravity properties)  or even a rare magnetic-monopole ( supposed to exist but hidden by inflation) so that the hole has a net magnetic charge

strange on a mac I didn't have to do anything? Just check for upgrade and restart

Did you restart PI? - just installed it a couple of minutes ago. I'd been meaning to but hadn't got around to it (it used to come preinstalled)

On 22/09/2022 at 17:42, PeterC65 said:

My take is that given the vast number of galaxies in the Universe, the vast number of stars in each galaxy, and the recent evidence that many of these stars are orbited by planets, it is very likely that life exists elsewhere, indeed it could be commonplace. At the same time, I think that so called intelligent life is likely to be very short-lived, given our experience on this planet, and that is why we haven't found any evidence for it nearby in the short time humans have been (will be) around.

This may be a good thing because if we were ever visited by extra-terrestrial intelligence, they would probably conclude that humans are a parasitic infestation of the Earth and seek to cull us. Just as we react to overpopulation of animals and plants.

Funny how people assume aliens may be hostile based on historic actions of earthlings, if they evolved past our technology and survived, surely they are more likely ultra-woke Star Trek Discovery types

Don't select the play 'Global Thermonuclear War option' - doesn't end well

From the ever reliable https://en.wikipedia.org/wiki/JPL_Horizons_On-Line_Ephemeris_System

There are 3 ways to use the system and all of them can be automated:

Web (partial access)
Email (full access)
Telnet (full access)

https://ssd.jpl.nasa.gov/horizons/manual.html for v4

This is the web interface. https://ssd.jpl.nasa.gov/horizons/app.html#/

I assume you are using Telnet?

You can access to JPL space telescope data as anonymous so maybe / probably?

Best I can do, Pixinsight

Used  StarXTerminator to split galaxy and stars - star image had the trails

Edited the star image using clone tool - not as tedious as it sounds - I inverted image to black on white so the trails are clearly visible

Zoomed in really close, by repeated click and drop I was able to run along the trails quite easily most of the way, didn't take as long as you may think

re inverted when finished and did standard tweaking with crop dynamic background elimination, curves, wavelets etc

used pixelmath to put star and galaxy image back together

There is a linearPatternSubtraction script, it sees the lines but for some reason it doesn't remove them, hence plan B with clone tool

I saw most of it till the end of the entropy example which was good, but it didn't cover all the Hilbert Hotel infinities such as infinite number of infinite buses and finally guests with infinitely long names of 2 letters who couldn't fit in the infinite hotel

3 hours ago, Louis D said:

Artemis 1 is pretty nimble after all. 😉

I must admit I love the crawler back from Saturn V days - cool video!

1 hour ago, Louis D said:

 

Alright, as a Yank, I had to look up these references since even us oldies are only vaguely aware of the Thunderbirds shows.  I found the below clip to clarify your references:

If y'all do launch for the moon or Mars someday, we'll hold you to launching from beneath a retractable pool. 😁

Shows how far advanced our Brit design is compared to NASA  😜