Your Gradient Factors?

[Atlantic Explorer]

Its kind of pointless arguing over deco. At the end of the day, there are many personal differences between everyone in many ways, and there are a million different ways to slice the deco cake. Being so exact on deciding a deco plan doesn’t really matter, what matters is following it.

Sure it’s anyone’s guess, the scientists themselves don’t fully understand deco so SBers shouldn’t say which one is better.

 

[tursiops]

Sure it’s anyone’s guess, the scientists themselves don’t know.

This is a cop-out, an appeal to loss of reason. Just because an answer is less than certain, doesn't mean we know nothing. This kind of attitude leads us down a very dark path, ignoring science, ignoring best practices, doing stupid things because "there is uncertainty" hence "no one really knows anything, and my guess is as good as yours."

 

[Storker]

This is a cop-out, an appeal to loss of reason. Just because an answer is less than certain, doesn't mean we know nothing. This kind of attitude leads us down a very dark path, ignoring science, ignoring best practices, doing stupid things because "there is uncertainty" hence "no one really knows anything, and my guess is as good as yours."

Some people don't seem to realize that there's a major difference between "there is a significant, quantifiable uncertainty about the conclusion" and "we don't know shít".

 

[Manatee Diver]

Some people don't seem to realize that there's a major difference between "there is a significant, quantifiable uncertainty about the conclusion" and "we don't know shít".

Do we really know much beyond empirical driven data? Take the dissolved gas model it operates under the assumption that there are no gas bubbles in the blood until you reach critical supersaturation, yet thanks to doppler studies we've found that not only do gas bubbles form before critical supersaturation, but they are even there among people that have never dove.

A lot of diving science is still theory at best, which has resulted in a huge grey area of what is safe and what isn't.

 

[boulderjohn]

Some people don't seem to realize that there's a major difference between "there is a significant, quantifiable uncertainty about the conclusion" and "we don't know shít".

It is the standard basis from arguments relying on the appeal to ignorance. If something cannot be proven 100%, I am justified in believing it is false. If something cannot be disproven 100%, I am justified in believing it is true.

Here is a common example:

Scientists claim the Earth is 4.5 billion years old, but there is no proof of that, and they keep coming out with different estimates. Who can believe anything they say? My church says the Earth is only 6,000 years old, and I have seen no real proof that it is not true. It could very well be true, and that's what I believe.​

 

[scubadada]

Do we really know much beyond empirical driven data? Take the dissolved gas model it operates under the assumption that there are no gas bubbles in the blood until you reach critical supersaturation, yet thanks to doppler studies we've found that not only do gas bubbles form before critical supersaturation, but they are even there among people that have never dove.

A lot of diving science is still theory at best, which has resulted in a huge grey area of what is safe and what isn't.

A bit better than that. I will let someone else comment on Buhlmann

Deco for Divers, Mark Powell, 2014, p 176:

The DSAT Recreational Dive Planner (PADI) model (1987)

The M-values used for the RDP were adopted from the Doppler bubble testing and tested by Dr Merrill Spencer and tested by Dr Raymond E Rogers, Dr Michael R Powell, and the colleagues with Diving Science and Technology Corp, a corporate affiliate of PADI. The DSAT M-values were empirically verified with extensive hyperbaric chamber and in water diver testing and Doppler monitoring.

DSAT has worked OK for me, about 1950 dives. I have run it in parallel to Buhlmann for the last 4 years, about 800 dives. DSAT maps to an approximate GF high of 95,, with several caveats, I have mentioned previously on SB

 

[Celt]

I’m sure someone will correct me in this if I’m wrong. But surely no dive computer builder will allow a user to make an adjustment that might bend them and built into every computer is a ceiling that you don’t go above without deco. So people are playing around with minimum deco and max deco. And any adjustments to the gradient factor is just playing around at the edges?

 

[helodriver87]

I’m sure someone will correct me in this if I’m wrong. But surely no dive computer builder will allow a user to make an adjustment that might bend them and built into every computer is a ceiling that you don’t go above without deco. So people are playing around with minimum deco and max deco. And any adjustments to the gradient factor is just playing around at the edges?

Shearwater will let you run 90/90. Technically, that shouldn't bend you. But I wouldn't try it.

 

[Storker]

Do we really know much beyond empirical driven data?

Is this a general question, or are there some specifics of which I'm not aware?

Generally, science "knows" a lot "beyond empirical driven data". Science "knows" enough that its models form the basis of humanity's technological endeavours. Among a lot of other things. But if you by "know" mean as in "being religiously certain", science knows crap-all. Because it's continuously revising its knowledge according to new facts.

 

[boulderjohn]

A lot of diving science is still theory at best, which has resulted in a huge grey area of what is safe and what isn't.

]But if you by "know" mean as in "being religiously certain", science knows crap-all. Because it's continuously revising its knowledge according to new facts.

Science does not "know" much because of what Storker calls "being religiously certain." A good scientist is always willing to look at new evidence and adjust accordingly.

That means that for a scientist, "theory at best" is pretty darn good. If a concept gets labeled as a theory, it is pretty thoroughly accepted.