Saturday, December 12, 2009

Chillin'.

I need to vent. There is a little bit of physics in this post, but this is more about how arguments start.

I always like to talk about using critical thinking as a way make decisions or draw conclusions without being ruled by one's emotions. I try and paint a picture of dispassionate analysis, and clear logical thinking.
In the real world emotions can run high, cloud ones judgment, and can lead one to draw erroneous conclusions even if one is very good at critical thinking.
It is really hard to think critically during an argument.



Here is an example of how discussions can degenerate to arguments between two well educated critical thinkers.

The other day I was working with some colleagues on taking temperature measurements of an object. The object was made from stainless steel and delrin, and we had an RTD temperature sensor mounted in a small air gap in side the object.
Our plan was to immerse a small area of the metal part of the object in ice water, and measure the time it took to equilibrate to the ice water, then remove the object to air and measure the time it took to equilibrate back to room temperature.

One of my friends said that the two equilibration times would be nearly the same, and that we would not be able to measure the difference within experimental limits of our measurement system, and that at most the difference would be a couple of seconds.

I was pretty darned sure that the difference would easily measurable. The moment he said that the difference would be two seconds, I was wary.
Our RTD sensor is pretty accurate, and has a good response rate. But due to some limitations of the sensor suite we can only sample the temperature every two seconds.
Lets assume that the time it takes for a tennis ball sized hunk of stainless steel partly immersed in ice water and attached to a solid plastic pipe to equilibrate in a few minutes. Lets say 5 min, even though that would probably be an understatement.
If the difference in equilibration times are indeed 2 seconds, that represents 0.7% difference. That would indicate that there would be a very small difference in the thermal conductivity of air and water. Plus a .7% difference just smelled very very wrong to me.

All this went through my head, and I decided to argue the point, and with a smirk/grimace I tactlessly blurt out: "I don't agree, I think there will a signifigant difference it in the two times."

My friends eyebrows rise and he responds:  "Really, why's that?"

"Because the thermal conductivity of water is huge compared to that of air." I respond smugly.

Aside:
I was saying this with a bit of a smug attitude. It is common in physics culture to act a bit cocky and smug and self assured when arguing theory or such with your colleagues. It is commonly done, but it is not taken very personally, and in the end one is always ready to change their opinions in the face of evidence.
This may not be true in chemistry culture, but one data point cannot let me be certain.


My friend shakes his head and replies: "Don't assume I am stupid, I know that it will take longer to equilibrate in air than water, all I am saying is that it will not be measurable with our system. And anyway, the heat capacity of air is huge, and greater than water."

I again smirk: "Actually, water has a greater heat capacity than air. But that does not matter, because at my old job when I did similar experiments we saw large differences, greater than 20% in some cases, and..."

"I don't care what you did at you old job!" He interrupts. "That was a different experiment, and not the same situation!"

Now I was getting pissed, and I retort:
 "Of course it is not the exact same experiment, but from experience and extrapolation the differences will be large!"

"Prove it!" He demands.


Now, know that heating and cooling of bodies is a very non-trivial problem. It is difficult to develop exact models in arbitrary shapes, and even in simple models such as spheres there are difficulties such as volume to surface area ratios, turbulent flow of convection.
Our system was made of various odd shaped materials, so the situation was difficult.

Knowing this, I tried to argue from authority and "common sense".

"I don't have to prove anything. It is common sense that it will take longer to come back to room temperature in air than it took to cool down." I say heatedly.


At this point my other friends interjects: "Hey guys, umm... let's just agree to disagree... OK?"

I round on the poor guy and say: "That is such a cop-out to say that."  (I really do think that, but the reasons are for another blog)

"Look, say I drop a ball here from this height and measure its acceleration. Then I move it two feet over to that part of the floor and do it again... the two values will be nearly the same! Then if I were to tell you that if I moved it to a third spot that the value would again be the same, you would not tell me to prove it. My experience and ability to extrapolate and predict would..."


"What..." he interrupts again: "Are you telling me that there is no difference in the gravity from that point to that other point?"


"Yes... " I start to reply

"Aha!" He triumphantly shouts, "Gravity is not the same, because the Earth is round and there are other masses around..."

"Don't tell me about gravity!" I yell back, "I did thesis work on the topic! Science is predictive, not just something done to verify every freaking propisition! Science can help us avoid testing every case by allowing us to extrapolate and predict from theories we create from observation..."

At this point the argument went way down hill.
He kept insisting that my prior experience was useless in this case, since I had not done "exactly" the same thing.
I kept inisting that my experince was good enough that I could predict the value of the difference. In the end he kept going back to "prove it" and "lets do the experiment".

And truthfully, he had a point. We were arguing about something that could be settled by simple experiment.
He was pissed off at my smugness, and I was pissed that he would not accept my conclusions based on my experience.

I really dislike having my opinion questioned. I know, I should be able to defend my position, and accept questioning with grace. But sometimes I don't want to always be defending what I say. I feel that the time and effort I have spent educating myself should confer a bit of acceptance of my ideas among my peers.
I always say not to blindly acept what someone says. But questining every little thing is pointless and a waste of time.
If I asked a native speaker of Tagalog to teach me the word for water, and then argued with him and ask him "How do you know that is the word for water", I am certain the teacher would give up in disgust.
And this is how I feel when someone questions my about my experience or expertise.
I knew I was right, as both theory and experience coulded with the predictive powers of science were on my side. And probably I could have convinced him if I did not cop to the attitude I had. (Or perhaps not.)

The argument ended with I asserting that the effect would be 20%-25% while he asserting there would be no measurable difference.

At the end of the experiment, the time it took the object to heat back up to room temperature was 30% greater than it took to cool to ice water.

After showing him the data, all I got was a grunt and a shaking of the head. All that arguing for nothing it seems.

So, I was close to right. But, how I approached the discussion was wrong.

Neither of us used much critical thinking. Both of us were talking past each other. My friend could just as easily been in the right, but our tempers did not allow us to discuss the problem rationally and constructively.

It was a case of "I had to be right" for both of us.

What a useless and fucking stressful waste of time.

What I need to take from this is that in future situations like this, I need to chill, and not always have to prove I am right.

Friday, December 11, 2009

Mountain of Meat! (FPOTW)

I must say, I like cows.



Braised, roasted, grilled... you name it.
While eating a nice steak this evening, a friend and I were discussing how nice it was of the vegetarians to leave more meat for us, and that we should come up with a nice Fermi problem to show our appreciation. The basic theme is the number of cattle slaughtered to fill our collective stomachs.

---- Start Fermi Problem ---

How much beef is consumed in the United States each day?

How much in the world each day?

How many cows have to be slaughtered to provide this much beef, for the US and the world respectively?

If you stuffed all the cows in a big cube, what would the dimensions be for the amount slaughtered in the US and the world respectively?

How long until there would be a "mountains" worth of cows slaughtered?

How many cattle are slaughtered each second for the US and the world?

From these numbers can you estimate how many slaughter houses there are?

---- End Fermi Problem ----

Where is the beef?