Concerning Dark Matter

[saac]

53 minutes ago, Viktiste said:

 

Why can I not say anything I want in math? Why can somebody else (ok I realize that this may sound stupid...) say anything in math, for example everything existed in a point of 0 diameter at some point? Take the CBR and back calculate - does that make it a fact?

I get the misconception induced by the term "Dark...".  I think because so much of what we observe fits Einstein's Law of General Relativity we are taking it as a fact. So when we see something that does not fit to it, we invent a convenient way out? I'm not claiming to have  the answers, but it makes me wonder. I'm pretty damn sure I will never see any evidence of Dark Matter in my lifetime.

I get what you are saying but I think maybe part of your frustration with maths is maybe a misunderstanding.  Maths, in particular the equation is an expression for "truths",  So at a very basic level with an equation we equate one expression to another , generally with unknowns.  So going back to your 1 apple + 1 apple = 2 apples  well that is correct it does.  It would only mean you physically had 1 apple if that is what it represented . So your statement  that you had no apples in the house was a self fulfilling prophecy and not a problem with the equation.   Maybe a better example   F = G m1 x m2 /r    . This equation shows the relationship between the gravitational attraction of two masses ( m1 and m2 ) and the distance between them .  But it is incorrect, it is nonsense .  The true relationship, the way we observe it in nature , needs the square of the distance (r) .  So we have F = G m1 x m2/r^2        (where r^ 2 means r x r ) ,    So I guess you can write anything you want in a maths equation but it would be like writing musical notation completely randomly - it would result in nonsense.   I don't know if that makes any sense.  Re the name " dark matter"  I genuinely believe these terms do not do the physics community any good  - much like the naming of sub atomic particles and their properties; often the terms do not carry their normal meaning. 

Jim             

Edited August 17, 2021 by saac

[saac]

1 hour ago, Viktiste said:

 

What is it?  We don't know, except we don't know - so why pretend to know? 

You are absolutely right we have no idea what it is .  The only thing we know about it is the effect it is having on the rotational speeds of galaxies - making it higher than it should be due to the observable matter.  But yes totally right we have absolutely no clue what it is.  But I don't think anybody is pretending to know what it is , what we have is theories which need to be validated by measurement and testing . 

Say ultimately it turns out that the higher rotational speeds of the galaxies is due to presence of let's say micro black holes permeating the galaxy.  Well they then become the missing "dark matter"  because they are the cause and that is how we defined dark matter  - ie the property or phenomena that was causing the higher rotational speed.   It does not ultimately need to be matter !  It may well turn out to be a new fundamental force or particle.

Jim 

Edited August 17, 2021 by saac

[Paul M]

I've never really got excited about Dark Matter. It's often struck me as just a diversion en-route to a better theory. But I found this video informative. Sorry, the presenters style isn't for everyone but he does have a way of opening up complex ideas to a non academic audience, i.e. me!

 

 

[Viktiste]

Arghhh saac!

Thinking.  And then thinking some more...

But thanks for responding to my queries! Still, math is just math, not science

 

[Zermelo]

57 minutes ago, Viktiste said:

when we see something that does not fit to it, we invent a convenient way out?

Essentially what Thomas Kuhn was pointing out, in response to Popper's simplistic account of scientific progress. An established scientific theory (or larger body of knowledge) that has persisted for some time and successfully explained many observations is too entrenched to be overthrown easily. Instead, it makes more sense (for defensible, pragmatic reasons) to find alternative explanations for an anomalous observation that don't contradict the existing theory. If the revised theory survives further scrutiny it may persist; but if there are further anomalies and ad-hoc fixes, then eventually it becomes untenable and is ripe for overthrow in its entirety, if an alternative can be found. In the current picture, the "standard model" incorporating quantum field theory and special relativity has been so successful in explaining observations that it is very hard to displace, even by the cosmological anomalies that we have found (though one of those, the discrepancy in the value of the cosmological constant, may not be real, according to one recent paper).

 

1 hour ago, Viktiste said:

Why can I not say anything I want in math?

For example, string theory/M theory etc. , which have attracted an enormous amount of intellectual effort in recent years, while (arguably) providing almost nothing in the way of testable hypotheses in the actual universe (and, therefore, are not science at all). The main driving force seems to be that the mathematics used in modelling these theories is "beautiful" and therefore must be true, when compared with the standard model and its need for many arbitrary constants. Ultimately, the maths must support the theory, but sometimes the tail is wagging the dog.

[saac]

8 minutes ago, Viktiste said:

Arghhh saac!

Thinking.  And then thinking some more...

But thanks for responding to my queries! Still, math is just math, not science

 

No worries  Viktise, hey you are in good company - if anyybody tells you they fully understand this take it with a pinch of salt   The good thing is that you know enough to challenge, at least you are interested , a lot of folk just completely avoid this sort of thinking. 

Jim  

[Viktiste]

Haven't read, but on my list:

[Astro Noodles]

9 minutes ago, Zermelo said:

(though one of those, the discrepancy in the value of the cosmological constant, may not be real, according to one recent paper).

 

Is that the paper which suggests that our methods of measurement based on 'standard candles' may be incorrect or inconsistent ?

[saac]

1 minute ago, Viktiste said:

Haven't read, but on my list:

I may well have a look at that myself Viktiste     Just thinking about what you said re "maths is not science" - I agree with you there.  You mentioned the black hole and the singularity as well  previously.  I've always had difficulty with this notion of the standard definition of the singularity as an infinitely small, infinitely dense state.  That is what the maths tell us but can such a state exist in reality; I don't think it does !  My background is engineering and I was always taught that when you do your stress calculations or thermodynamic calculations and get infinity  (usually dividing by zero) it means you have broken your equation - something is wrong.   In physics (cosmology and particle physics) I think it is also generally accepted that when the equation points to infinity it simply means we have strayed into unknown physics - the equation can no longer describe what you are seeking it to describe.  So yes maths is not science but it is a tool that is astonishingly good at helping describe nature . 

Jim 

[Viktiste]

My background is Engineering too (Electrical Engineering from Heriot Watt in Edinburgh). I wish I had studied computer science instead, but at the time no one did that! It was after the 80's IT bubble. 

Anyways, I guess that is completely besides the point.....

Thanks for arguing with me.

 

[saac]

3 minutes ago, Viktiste said:

My background is Engineering too (Electrical Engineering from Heriot Watt in Edinburgh). I wish I had studied computer science instead, but at the time no one did that! It was after the 80's IT bubble. 

Anyways, I guess that is completely besides the point.....

Thanks for arguing with me.

 

Ah Edinburgh , I went to Strathclyde across in Glasgow, mid/late 80s so sounds like similar timescale.  Heriot Watt always had a good reputation for engineering and still does; we send a good number of pupils onto their engineering courses each year .  Gosh computer science courses in the 80s did they even exist.  I remember Strathclyde giving out ZX Sinclairs to their science students. In the Mechanical Engineering department we used the atari - it was the first computer I came across with a gui - what a difference that made.  With your electrical engineering maths you will be well versed in imaginary numbers then , now that is a bit of maths that always eluded me .  To be honest I was happy when we were allowed to drop maths in our final year.  Our maths lectures would be delivered by pre recorded video - some talking head with a lime green shirt and massive collar , looked like an OU video from the 60s - not exactly inspiring . Happy days nonetheless  

Hey not arguing , just a discussion like we would have in the pub  

Jim 

[Viktiste]

Yes they had computer science classes. I started in autumn of 1989 (I think - its a long time ago).  Had a ZX spectrum as a youngster, advanced to PC -(Atari maybe?), what my kids now would call a 3D PC - meaning a CRT screen,  during  the university years.

[Viktiste]

And just got my 2nd corona shot today. What a strange world!

[saac]

2 minutes ago, Viktiste said:

And just got my 2nd corona shot today. What a strange world!

A 3D pc I love that .  We would have been hard pressed to make up the last 18 months.   I think we may all be getting a third shot in the winter , are they talking about similar in Norway ?

Jim 

[nephilim]

1 hour ago, saac said:

Ah Edinburgh , I went to Strathclyde across in Glasgow, mid/late 80s so sounds like similar timescale.  Heriot Watt always had a good reputation for engineering and still does; we send a good number of pupils onto their engineering courses each year .  Gosh computer science courses in the 80s did they even exist.  I remember Strathclyde giving out ZX Sinclairs to their science students. In the Mechanical Engineering department we used the atari - it was the first computer I came across with a gui - what a difference that made.  With your electrical engineering maths you will be well versed in imaginary numbers then , now that is a bit of maths that always eluded me .  To be honest I was happy when we were allowed to drop maths in our final year.  Our maths lectures would be delivered by pre recorded video - some talking head with a lime green shirt and massive collar , looked like an OU video from the 60s - not exactly inspiring . Happy days nonetheless  

Hey not arguing , just a discussion like we would have in the pub  

Jim 

I studied computer science in the 80's 😂 We were on BBC computers & Commodore 64's. I remember I spent a large part of my time playing Elite & Repton. In fact my sole reason for recently building my gaming PC was so that I could play the new version of Elite although I tend to spend most of my time at the moment with it banging my head against the brick wall that is PixInsight 😬

Edited August 17, 2021 by nephilim

[saac]

11 minutes ago, nephilim said:

I studied computer science in the 80's 😂 We were on BBC computers & I remember I spent a large part of my time playing Elite & Repton. In fact my sole reason for recently building my gaming PC was so that I could play the new version of Elite although I tend to spend most of my time at the moment with it banging my head against the brick wall that is PixInsight 😬

If you figure PixInsight out write a cheat sheet .  I learn how to do something then forget  as quickly by next season - all these astro programmes I find come with a high skill fade , maybe it is an age thing  

Jim

Edited August 17, 2021 by saac

[nephilim]

30 minutes ago, saac said:

If you figure PixInsight out write a cheat sheet .  I learn how to do something then forget  as quickly by next season - all these astro programmes I find come with a high skill fade , maybe it is an age thing  

Jim

@saac I know exactly where your coming from Jim. I just hope there are enough tutorials available to keep me going, as soon as I run out of those & any images to process due to bad weather then all the info I've tortuously learned will start leaking out of my ears 😂

Steve

[Zermelo]

12 hours ago, Astro Noodles said:

Is that the paper which suggests that our methods of measurement based on 'standard candles' may be incorrect or inconsistent ?

There are two broad methods for calculating the Hubble constant, which tells us something about the size and expansion rate of the universe.

The first uses the "standard candles" - cepheid variables, type IA supernovae - to map from apparent to absolute magnitudes, allowing us to calculate the distances of specific objects. The second uses properties of the cosmic microwave background radiation.
Both methods give a range of possible values for the Hubble constant, and both have gradually been refined, to the point where the two error ranges don't overlap - hence the problem. But there was a paper from earlier this year (I can't find the reference now) that proposed a revision in the calculation methods that would mean the two ranges do overlap and could still be consistent.

[George Jones]

16 hours ago, saac said:

Gosh computer science courses in the 80s did they even exist. 

I went to high school in the 1970s in a small (pop. 8000) industrial town in Canada, but the high school was first-rate, and many of its teachers were first-rate. I took computer science classes in high school from 1976 to 1978. By today's standards, the circumstances were strange: the programming language used was Fortran (in high school!); the programs (penciled-in computer cards)  were physically sent by Greyhound Bus to a university in another city, and the cards and hard-copy output were returned by bus. The turn-around time was a least 3 days per run, sometimes to find "execution suppressed" because of a syntax error. The teacher, a computer science graduate from the University of Waterloo, had us work on several projects simultaneously, so that we were always sending and receiving stuff. Good courses and teacher.

Edited August 18, 2021 by George Jones

[saac]

1 hour ago, George Jones said:

I went to high school in the 1970s in a small (pop. 8000) industrial town in Canada, but the high school was first-rate, and many of its teachers were first-rate. I took computer science classes in high school from 1976 to 1978. By today's standards, the circumstances were strange: the programming language used was Fortran (in high school!); the programs (penciled-in computer cards)  were physically sent by Greyhound Bus to a university in another city, and the cards and hard-copy output were returned by bus. The turn-around time was a least 3 days per run, sometimes to find "execution suppressed" because of a syntax error. The teacher, a computer science graduate from the University of Waterloo, had us work on several projects simultaneously, so that we were always sending and receiving stuff. Good courses and teacher.

Gosh I remember Fortran and those punch cards - I dreaded getting them returned to find an error, almost as though the computer was laughing at me! .  Funny thing, it was the last programming language that I could understand , everything just seemed to get complicated very quickly thereafter   Those were the days when a computer with less computing power than a mobile phone filled a room all by itself  

Jim 

[lenscap]

My first computing lessons were in 1969 I think.

We wrote out the programs in "Honeywell Timesharing Fortran" which was transfered to punched tape locally, before being transmitted to a mainframe somewhere in the USA , presumably by trans-Atlantic Teletype. I've no idea if it went by satellite or undersea cable. We got the results a week later.

Having learned a bit of Fortran proved useful about a decade later since the BASIC used by the first PC's seemed to the user to be a simplified version of Fortran.

Happy Days!

[Viktiste]

19 hours ago, saac said:

PixInsight out write a cheat sheet

Have done that, but only for me. What you need to remember is different from what I need to remember.  About Pixinsight I will say this: Probably very hard to learn if you have no experience with image processing,  But a lot easier to learn than anything from Adobe (unless you knowe Adobe stuff  from before). I am impressed by the makers of Pixinsight - you could probably write a book about almost all it's processes. And I like it is a one off payment  (not subscription)!

Still learning it though. I see some people in the IKARUS competition are very good with it. Very....

[saac]

1 hour ago, Viktiste said:

Have done that, but only for me. What you need to remember is different from what I need to remember.  About Pixinsight I will say this: Probably very hard to learn if you have no experience with image processing,  But a lot easier to learn than anything from Adobe (unless you knowe Adobe stuff  from before). I am impressed by the makers of Pixinsight - you could probably write a book about almost all it's processes. And I like it is a one off payment  (not subscription)!

Still learning it though. I see some people in the IKARUS competition are very good with it. Very....

I got my copy about 2 years ago and quickly followed with with a copy of Inside PixInsight by Warren Keller (excellent book) . Last year I also picked up a digital copy of the book written by Rogelio Bernal Andreo (https://www.deepskycolors.com/books.html) , for which I need to request a new password    The various youtube tutorials are a gift and all credit to the people who upload them. I think as a piece of software PixInsight is a joy, and yes I'm really pleased they haven't gone down the subscription route, it is well worth the ticket price.  The problem that I have at the moment is that my image processing sessions are like my image capture with often several months between successive sessions. So my skill fade is huge. I'm looking to really getting on top of the whole image processing thing and PixInsight in general in retirement (hopefully in next couple of years) . 

Jim 

[Lariliss]

The presence of dark matter is implied in a variety of astrophysical observations, including gravitational effects that cannot be explained by accepted theories of gravity unless more matter is present than can be seen. It’s hypothesis started in 1884 and is counting at least 6 of them now. It has its technical definition and indirect observational evidences: galaxy rotation curves, velocity dispersions, galaxy clusters, cosmic microwave background, redshift-space distortions.

Similar story start for black holes, which hypothesis started in 1784. But is came to General relativity theory in format of which observations are done and predictions are confirmed. Still singularity is not a physical solution. And still it is being asked why black hole is ‘black’ and it is a ‘hole’. But we are able to observe thousands of them.

One day a breakthrough might come when we will be able to observe dark matter and wonder why we didn’t do it before..

[bomberbaz]

Revisiting this since my first much earlier post to see how it has expanded <( see what i did there).

After pouring over all the posts, hypotheses and videos, not to mention the beginners class to early computer science 😉, I have found the above post from @space_master meets my own level of understanding and I am happy to leave it at that until the LHC or similar experiment tells me otherwise 😅.

Fascinating input, well done all 👏