3 hours ago, Bjarne-7 said:

It is possible as I showed in my post-11.

But perhaps it is easier for some to relate to when there is speed included.

The fact remains that you have made a good many claims, some of principle, some numeric and some totally irrlevant to the issue.

But I have not seen a single piece of mathematics or calculation to support them.

1 hour ago, exchemist said:

The French call it jambon persillée. But my recipe comes from an Italian recipe book.

Elizabeth David ?

I believe they originally had a ham joint with the bone in.
Of course you can't get them in England today.

52 minutes ago, sethoflagos said:

One of my favourite childhood memories is that of pea and ham soup based on a 4lb ham shank slow-cooked in 1lb of marrowfat peas. 

I found a recipe at https://foodnetwork.co.uk/recipes/lancashire-pea-and-ham-soup which is very much how my mother and grandmothers used to make it.

Having said that, I roast a cheap ham shank we'd picked up at Tesco's a couple of weeks ago. The resulting ham and mustard sandwiches were gorgeous! 

One very useful tip concerns the roast.
Traditionally cleaning the roasting dish is a chore,

But we take the dish as is the following day, and use it to start off some lentils and vegetables, then some stock and finally a left over worst bits of the meat.
This either becomes a curry or plainer dish or even pea soup base.

The good bit is at the end because all the water added cleans the roasting dish almost as well as our retriever (when we had one) so washing it up is a treat.

Thanks and +1 to both for your input.

What are your (favourite) recipes for cooking ham ?

My family had used the following for generations and most folks we feed the result to seem to think offers significant improvement of the standard method.

Use smoked or plain ham to preference.
First prepare you ham by making small slits in opposite sides or ends with a very sharp knife.
Then insert a sliver of fresh garlic clove into each slit, as deeply as practicable.
Follow this up by inserting one or two cloves into each slit, tailend inwards. These are removed after cooking.
Place the treated ham in a pot deep enough to cover with cold water and place on stove.
Add a rounded desert spoon of soft brown sugar to the water.
Bring to the boil and simmer for 1 hour per kg.
Do not over cook.

Once cooked the ham can be removed to stand.
The ham water can be used to add extra flavour to vegetables such as cabbages, carrots and so on.
Most folks are pleasnatly suprised when they come across this last bit.

I am sorry line 2 of my second quote above should have read

...I am convinced that philosophers have had a harmful effect.....

...I am convinced that have had a harmful effect...

My apologies for that important omission, and the spelling mistake in the first quote, my typing degenerates as the day wears on.

1 hour ago, Bjarne-7 said:

We can easily imagine that a time measurement starts and ends simultaneously, it is technically possible.

Yes it is exactly zero.

By the way

How did we move from a discussion about time

to a discussion about distance ?

4 hours ago, Eise said:

No. It is just as irrelevant.

As irrelevant as what ?

Or did you really mean soemething else ?

4 hours ago, Eise said:

I would suggest you read my exposé again. If you still wonder what philosophy is, then just ask.

The short reaction is: philosophy does not have the same subject as the sciences, so it definitely is not an alternative method to reach empirical truths. 

Here is a quote from a famous Philosopher

Pray tell me what it means

Quote

Now the best bond is one that really makes a unity of itself together the things bonded by it, and this is the nature of things best accomplished by proportion. For whenever of three numbers which are either solids or squares, the middle term between any two of them is such that what the first term is to it, it is to the last, and conversely what the last term is to the middle it is to the first, since the middle term turns out to be both first and last, and the last and first both  likewise turn out to be middle terms, they will all of necessity turn out to have the same relationship to each other. and, given this, all will be unified.

Here is a piece from a famous scientist

Quote

The only justification for our concepts and systems of concepts is that they serve to represent the complex of our experiences; beyonf this they have no legitimacy. I am convinced that have had a harmful effect on the progress of scientific thinking in removing certain fundamental concepts from the domain of empiricism, where they are under our control, to the intangible heights of a priori.

I think it is very important that you separate numbers , units, symbols and the objects which they refer to.

That is you think separately about them, each in their own right.

Let us take an example of this:

Making bread.

Bread has ingredients.

The ingredients are flour, yeast and water.

There are 3 ingedients.

Here the objects referred to are ingredients.

The number 3 is called a quantifier or a coeffiecient.

There are no units involved or if you prefer the unit i 'number or count of'

But there are several types of number and 3, each with their own special features.

So we could have said:

There are 3 ingredients

1st ingredient,, 2nd ingredient, 3rd ingredient.

Or we could have said even more

First ingredient flour
Second ingredient yeast
Third ingredient water.

Which tells us even more.

First second and third are numbers, just a different kind of number.
~They are cvalled ordinal numbers, as they show order.

We could also write a 1 on the jug of water,  a 2 on the tub of yeast and a 3 on the bag of flour.

Then the instructions might read

Mix the contents of 2 with the contents of 3, than add the contents of 1.

We are now using the numbers 1, 2 and 3 as symbols (you mentioned symbols)

We can make the description even more use full if we add units so

Mix 2 of yeast with 400 of flour and then add 250 of water is not very helpful.

But

Mix 2 teaspoons of yeast with 400 grammes of flour and then add 250 mililitres of water is very helpful.

Much more helpful than

Mix 2 teaspoons of  2 with 400 grammes of 3 and then add 250 mililitres of 1.

Although both are strictly correct and Mathematicians and computer engineers like the last as it is shorter.

I have another example to explore but let us see what you make of this one first.

A ROM is a form of truth table.

46 minutes ago, Sensei said:

ps. Not without a reason people invented RTFM.

How w

2 hours ago, johnsri said:

Hello

what is application of Zener diode in smps

ell do those learning English do with acronyms ?  +1

An SMPS is a Switched Mode Power Supply.

Switched mode power supplies often also incorporate a voltage change and use an inductor and or transformer for this.

Inductive switching generates large reverse voltage spikes known as backswing which can damage semiconductors when they are reverse connected.

(see Sensei's graph)

Zener diodes are used as protection to limit (called clamping) the size of the backswing voltage to a safe level.

A second use is to clamp the voltage created on the storageor reservoir capacitor, which stores the switched pulses, to the desired level.

19 minutes ago, sethoflagos said:

The effectiveness of carbon sequestion via weathering of basalt etc. is ultimately limited by actual reaction rates. One only has to consider the rather slow disappearance of such basalt structures as eg the Giant's Causeway (and essentially the entire surface lithosphere of Northern Ireland), Fingal's Cave, Iceland to understand that these carbonation reactions are not lightning fast. Even in finely divided form, a visit to a basaltic black sand beach is scarcely seething with chemical activity.

But that does not make it a factor to be ignored. I cannot be a solution to all our problems but it can help.

I found quite a useful summary of its global relevance at https://www.degruyter.com/document/doi/10.2138/am-2019-6884/html?lang=en. 

I've wondered for a while whether weathering of the calcium silicate content of concrete had a similar effect, and found an interesting Caltech article at https://www.caltech.edu/about/news/weathering-cement-important-overlooked-sink-carbon-dioxide-53134

 

 ... which I found quite interesting.

Not in the least bit suprised. +1 for a proper attempt at evaluation.

Chemically basalt is nothing like portland cement concrete, although both are silicates.

As a material basalt is more susciptible to chemical weathering attack, enhanced by subsequent detrimental attack on its own structure (HAC, ASR, Ettringite, Carbonation) and on any embedded ferrous reinforcement.

This is in direct contrast to Roman lime based concrete, which continues to gain strength and hardness forever on a diminishing curve, from the atmouspheric carbon dioxide.

Since you seem to just want to copy others, rather than answer my questions I will leave you to it.

1 hour ago, mistermack said:

You need energy to extract the basalt. You need energy to transport it to a plant. You need energy to grind it up. You need energy to transport it to suitable farm land. And the farmer needs energy to spread it and plough it in. Nearly all of that at present is done using diesel. So at the moment, it's a big waste of time and effort, and probably adding more carbon than it's fixing. 

What it does do, is allow some big carbon-emitting companies to buy "carbon credits" and carry on emitting, while getting a tax break. 

Maybe in the future, when diesel, petrol and gas have genuinely been replaced with renewables or nuclear, the scheme might make a marginal difference. 

Did I see that knee jerking before you read and investigated

my article ?

The ground up basalt is produced anyway. It used to be discarded as slag waste.

It can be spread along with fertiliser don't forget that this is reduced, they mentioned a fig of 25% saving of fertiliser.

However I do agree with your point about carbon credit trading.

I regard it a scandal.

1 hour ago, TheVat said:

More greenwashing, at this point.  

Really good news for the environment would be masses of people in developed countries bicycling and walking and buying less fungible junk and living in smaller homes and eating more plants,  choices that powerful corporations strenuously want people not to make and fight tooth-and-nail against with enormous campaigns of mass marketing.

So are you saying that new improved technology should not be employed even if it brings environmental benefits ?

To all

I never said this to be a universal panacea.

In the advertising words of one supermarket, "Every Little Helps"

1 hour ago, Bjarne-7 said:

It will not make sense to claim that there is a 41 second difference between Alice's and Bob's perception of simultaneity.

Why not ? you are just dressing up incredulity as something more; I still don't see a problem.

I haven't checked your numbers but it is an observed fact that clocks lower in a gravity well run more slowly so Bob will record less elapsed time for the same interval.

Earlier this year I watched the BBC Earth series, presented by Chris Packham.

One new theory was presented of many years of almost continuous rain on the early basalt eruption surfaces, leading to chemical weathering of the basalt removing significant quantities of acid greenhouse gases, particularly carbon dioxide, from the atmoushphere and chemically 'fixing' it into the ground.

Last Sunday the BBC Countryfile programme had an article about trail replication of this process by spreading the waste products of the aggregate industry (ground up basalt) onto farmland.
The greatly increased active surface of such basalt powder not only reacts quite quickly (ie at human timescales) not only fixing the carbon but also releasing new nutrients to the soil, thereby reducing fertiliser demand.

It is too early to tell just how good this since trials have been going on for little more than a year but apparantly early results are 'encouraging'.

******************************************************************************************************************************************************************

Then I see that someone has done something about waste plastic from laboratories, formerly just burned (5.5 million tonnes in the annually), to make recycling possible.

Well done Helen. Nice to see up and coming graduates succeeding like this.

Quote

https://www.bbc.co.uk/news/uk-england-bristol-67474579

First ever recycling for hidden plastic lab waste

 

19 minutes ago, Bufofrog said:

That's correct.  They will not agree on the time the photon was emitted or the distance, even taking into account the extra distance the photon traveled.

That was going to be my next question.  +1

56 minutes ago, Bjarne-7 said:

It is assumed that both photons follow the same route all the way to Alice.
In principle, we could imagine that there is only 1 photon, and that Alice measures the travel time it took that one photon, - at the exact moment when she reflects this one photon further on to Bob

But the issue here is

How do Bob and Alice know when to start their clocks ticking ?

Obviously they must have lived 14 thousand million years in order to make the measurement, plus a little bit to build their clocks and synchronise them.

3 hours ago, Bjarne-7 said:

The problem is that Bob's watch shows that the photon has travelled 441 seconds less than the time Alice has measured.

So why is that a problem ?

Bob is at the bottom of a gravity well, compared to Alice, so expects his clock to run more slowly.

But you haven't demonstrated that your figures are correct for the time of flight and height difference.

1 hour ago, joigus said:

That surely is the Laplacian operator, which is nabla dot nabla.

"dot" meaning the 3D "dot".

4D nabla dot 4D nabla is called the d'Alembertian, and it's a square (at least in physics).

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

https://en.wikipedia.org/wiki/D'Alembert_operator

Thanks, Joigus. +1

I think you may well be right, although I try to avoid these more exotic non mainstream symbols.

You have done better than the author who had the opportunity to this is what he meant, but chose not to for some reason.

If nabla squared is meant then in my opinion that is what should be said.

The square is often called the box operator but it suffers from the disadvantage that I have seen it confused (used for in lecturres) with the Hodge star operator and also is presented by some parsers as a general symbol when they come across something not in their vocablulary. Word is bad in this respect.

Also remaining is the mathematical demonstration that the second order differential equation obeys the Lorenz transformation, using the speed of sound as an invariant.
The simple fact is that to an inertial observer moving differently from the air, the speed of sound appears different.

15 minutes ago, Bjarne-7 said:

or what ?

Or set the problem out correctly, filling in the missing lines telling us where your figures come from and showing us how exactly the two photons can have followed exactly the same path (world line ?)

2 hours ago, VilJ said:

So you're telling me that I'm supposed to work with r rather than h/2? I found this example which stated that this problem is supposed to be calculated differently. If I calculate with just r then this is super simple.

Guiding would be better than telling.

You still haven't answered my questions.

Since you are doing this in preparation for a real exam it is no good just looking up formulae on the net (especially as I suspect it is wrong but I can't see the rest of what you found).

You need to understand what you are doing.

And that is exactly what both Seth and I are trying to help you with.

So let us go back to first principles and answer my simple questions.

Do you have to derive your equations or have you been given them in lectures ?

Using your knowledge of Physics is the internal ressure greater than or less than the external  ?

Why did I suggest you will have a circular blob ?

You new picture is wrong because the vertical meniscus is not a complete semicircle.

Why do you think this is the case ?

38 minutes ago, Killtech said:

Indeed the topology discussed in that paper is hypothetical since we never observed the universe to have a limited expanse in any direction so far

How's that ?

42 minutes ago, Killtech said:

i had some trouble with the latex.

We all have trouble with the TEX of one sort or another.

I have a ridiculously expensive commercial generator called Mathtype.

Alternatively you can use free sites Codecogs or Sciweavers to have a TEX editor and copy paste from it.

Another possibility (though limited by the inability to produce almost any sort of fraction) is to combine this SF super and subscript and use windows charmap to pick out special characters such as greek letters. You can actually achieve quite a lot this way.

On 11/4/2023 at 7:54 PM, Killtech said:

Let's remember the linear acoustic wave equations is △p−c−2s∂p∂t2=0 in the rest frame of the medium.

I was going to examine your 'mathematics'.

I can't make head not tail of this equation  unless you have nabla the wrong way up ?

If you have written Δp then the equation is nonsense.

On 11/13/2023 at 1:57 PM, Killtech said:

that is if we have a sound equation like ∂2xp−c(x)−2∂2tp=0

You seem to have corrected this few posts further on but a recognisable wave equation is stated and is indeed the equation you seem to have copied from Wikipedia.

Unfortunately you seem not to have read the text where Wikipedia clearly states that this is the equation of a standing wave.

My example involves a travelling wave and Wiki refers you to a simpler first order differential equation, which it call a one way wave equation in its own style.

Quote

n physics, the acoustic wave equation is a second-order partial differential equation that governs the propagation of acoustic waves through a material medium resp. a standing wavefield. The equation describes the evolution of acoustic pressure p or particle velocity u as a function of position x and time t. A simplified (scalar) form of the equation describes acoustic waves in only one spatial dimension, while a more general form describes waves in three dimensions. Propagating waves in a pre-defined direction can also be calculated using first order one-way wave equation.

 

https://en.wikipedia.org/wiki/One-way_wave_equation

20 minutes ago, Bufofrog said:

Well that's surprising.  What are the 'means' by which we can determine the preferred frame?

Note Wiki clearly states these 'preferred frames' to be hypothetical for the purposes of exploring what if there were such a frame.

It makes no guarantees that there is one and indeed states there is not such a frame in an inertial set of frames (as we all know).

2 hours ago, Killtech said:

but size does not equal size.

Love it to bits.

4 hours ago, Eise said:

Yes, and a mass that is twice another mass falls twice as fast. Aristotle said so, and he was (also) a physicist!

Is that incompatible with what I said ?

4 hours ago, Eise said:

The times they are a'changin, and therefore philosophy too.

Glad to hear it.

We need We need philosophers to ruminate, but it is better if they chew on what we know rather than guessing, of if and when they do guess then they cary out testing of their guesses.

Part 1

You are working in the right direction, but if r = h/2cosθ (which is correct)

then how is 1/r  = 1/(h/2) in your first line ?

What makes you think this sort of thing hasn't been done before ?

Apart from a 200km transmission path across the atmousphere (It's much easier for satellites up throught he atmousphere) beig far from isotropic or homogenous,

What is the effect of a 1m, 10m, 100m, 1000m error in the placement of your helicopters on your calculations?

Before we had all the satellite stuff, (and swansont is far better placed than I to discuss them) folks did this sort of thing by an instrument called the Tellurometer. This was invented / developed for the surveys of South Africa, Australia and Canada. Mountain tops, rather than helicopters were used as they do not move about and their positions can be independently verified.
My experience of lasers is that they do not have the range, across the atmousphere, most have a range of a few km at best and the Wild Distomat was really up to a km. They had corner reflectors rather than independent clocks aand there is now such a reflector on the Moon using up through the atmosphere techniques.

You still haven't told me how you are goung to create your pulse for 1000gHz signals.