Re: [APD] Assumptions

[David Aiken <daiken at iprimus_com.au>]

On 10/11/2005, at 8:23 AM, Jerry Baker wrote:

> David Aiken wrote:
>
>> I never challenged the principles of diffusion. You claimed to  
>> have evidence for what was in the tube and all I said was that you  
>> had no evidence for that claim. You have scientific principles  
>> which are an extremely good basis for predicting what is in there  
>> but, until you confirm that prediction by testing, you have no  
>> evidence for what is  in there and, without evidence, you're  
>> making an assumption. That's  something you happily criticise  
>> everyone else for.
>
> The evidence is the fact that diffusion happens. It's not a matter  
> that is in dispute. To say it might not have happened in this case  
> is to question the principles of diffusion.

Diffusion is not in question, and no one is saying that it might not  
have happened. I'm asking what actually happened. Elsewhere you said:

> Jim Swinford wrote:
>
>> The argument(differance of opinion?) is not whether there is  
>> diffusion but the rates, types and causes of diffusion.
>>
>
> That is exactly what I have been trying to say. We know there is  
> diffusion, but we do not know the extent of it.

And that's what's being asked. Which gasses diffused and to what  
extent? Does supersaturation of one or more gasses influence the  
outcome of diffusion? I understand that Yogi Berra once said  
something like "In theory there is no difference between theory and  
practice, but in practice there is." You said that we don't know the  
extent of the diffusion so why are you so reluctant to test and find  
out exactly what is actually in there? The question is what actually  
did happen and you can't say that without an analysis of what's in  
the tube.

>
>> Until you test, you aren't stating what is in the tube - you're  
>> merely predicting what will be found if you do test. You have  
>> grounds for the prediction. You don't have any evidence for what  
>> is actually in the tube since evidence for that requires testing  
>> what exactly is in the tube.
>
> I would bet on penalty of death that there is *some* oxygen in the  
> tube. There's no way there isn't. What is in question is whether it  
> is something like 0.0001% or 50%.

I won't take your bet because what is at issue is the concentrations  
- as I said above. If the oxygen content happens to be only 0.0001%,  
then for practical purposes it's irrelevant and can be ignored, to  
use one of your favourite phrases. If it happens to be 50%, that is  
way higher than the normal proportion of oxygen in air. In either  
case something unexpected would be going on. So, is something  
unexpected going on or not? I'm using those percentages since you  
raised them, so don't bother trying to prevaricate on the percentages  
here. The question is whether or not something unexpected is going on.

>> As to me doing anything like being "intellectually dishonest" and  
>> trying "to attempt to discredit the results of a scientific  
>> investigation by representing established scientific principles as  
>> open to controversy when they aren't", your test was about  
>> dissolution rates which you were measuring by counting the bubbles  
>> required for the gas to reach a certain volume in the tube. I  
>> didn't question those results at all. I questioned a claim you  
>> made about  something else - the contents of the gas collected -  
>> which you did not test. It's intellectually dishonest to claim  
>> that I was trying to discredit the results of your investigation.  
>> I accepted the only investigative results you reported. I  
>> questioned a claim that was not  the subject of an investigation.
>
> I did not mean that you were questioning my results. I meant that  
> you were introducing a controversy where there is none. Diffusion  
> is a fact of life. It happens without qualification wherever there  
> is a concentration gradient. A bubble of nearly pure CO2 is one  
> such place. If oxygen is present, it *will* diffuse into the  
> bubble. There is absolutely no question about that. Implying that  
> this is not the case appeared to me as though you were trying to  
> make it appear that there
> was a genuinely valid question about whether diffusion had taken  
> place. Of that, there is no question. My apologies if that is not  
> what you intended.

I never indicated that diffusion had not taken place but the point  
here is about intellectual dishonesty. I questioned your claims as to  
what is in the tube because that claim was not the subject of your  
investigation and no evidence for the claim was presented. Yes, you  
did present reasons for making the claim, but not evidence that it  
was correct. You then misrepresented me by claiming I had questioned  
scientific principles - I didn't - in order to throw discredit the  
results of your investigation when I also did not question the  
results of your actual investigation. That misrepresentation is  
actually intellectual dishonesty on your part, and it is totally  
consistent with your tendency to accuse anyone who questions your  
reasoning and conclusions with questioning the laws of science and  
then ignoring the actual question which was raised.

You're the one who has repeatedly claimed elsewhere that small  
differences are irrelevant and can be ignored in the practical world,  
but here you are saying that you don't have to do the tests because  
you know what's in the tube when the tests will also show what the  
proportions are and whether or not we can, for practical purposes,  
ignore the presence of oxygen, nitrogen, and any other components of  
dissolved air.

We can definitely take it for granted that there are pressure  
gradients. In a live planted tank, the levels of dissolved oxygen and  
nitrogen are not in the same proportions as in air and the diffusion  
rate out of solution at the surface will vary depending on the  
dissolved concentrations. When diffusion is into a bubble of pure CO2  
- or at least as pure as it comes from a cylinder - and the water is  
or is not also supersaturated with CO2 as well, we can expect more  
variation in what happens due to the fact that the pressure gradients  
once again aren't the normal ones we would expect for the diffusion  
of dissolved gasses out of water. Charlie Bay said "Fluid dynamics  
are terribly complicated -- we build $500K cell sorters and have  
*lots* of issues with micro-bubbles, turbulence, and other funny  
things dealing with partial pressures of fluids and flow". It's the  
funny things that will affect the result - not the basic laws of gas  
diffusion. The 'funny things' ensure that the basic laws aren't the  
sole determinants of the result, and that's why "In theory there is  
no difference between theory and practice, but in practice there is."  
-  the basic theory often isn't the whole of the theory that's  
required to understand what's going on in real life. I'm interested  
in what is actually happening in practice, not theory.

David Aiken
_______________________________________________
Aquatic-Plants mailing list
Aquatic-Plants at actwin_com
http://www.actwin.com/mailman/listinfo/aquatic-plants