Sunday, December 04, 2016

Collisional cross sections

The kinetic theory1 of gases connects the properties of individual molecules with the behavior of the bulk gas.  For example, if you know the mass of a particular gas present in a bottle of known volume and temperature, the idea gas law (PV=nRT) lets you predict the pressure in the bottle.  Since the pressure of a gas is related to how often the molecule hit the walls of the container, collision rates are a fundamental part of the theory.

How often molecules collide is of interest to chemists because getting molecules close together (really close together, within tenths of nanometers) is fundamental to their ability to react, to change into other things.  Molecules bump into each other more often when the temperature is high (they are moving faster and so cover more territory) and when the pressure is high (there are more of them to hit).  But collisions also increase when the target area is larger.  Think about trying to move through a crowded grocery store with a big cart versus when you just need to grab a gallon of milk.  The surface area you present to other shoppers is large when you have that cart and you are more likely to run into other things.2  This surface area is the collisional cross section.

I've been moving fast lately and the pressure has been high, which if I were a gas would mean I would be having more collisions, but in reality has left me feeling like all I do is wave as I race past people in the hallway or on campus. Sorry, can't talk now, have to run. Whoosh.  The semester is winding down, with the gift of a Friday with no classes or meetings on it.  Not only that, but this was the very same Friday that The Egg is singing as part of a quartet at his SoCal college. A most welcome collision on my calendar.  

I booked a flight, and now I am here. Not only that, but Math Man figured out he could take a day off and come, too.  So this morning, I met The Egg on campus and as we walked to get breakfast, we "ran into" Math Man on the sidewalk.  Surprise!

But there was more collisional fun to be had. A delightful colleague was in Philly to give a talk which I couldn't go to (vide infra).  We booked a time for tea and Skype later in the month, a moment to virtually collide, if not literally.  But on Thursday evening, while headed to my gate at PHL, my phone rang. The number was delightful colleague's.  "Are you by any chance at PHL?" she asked.  "I am."  We were flying out from adjacent gates.  Which resulted in two women running (literally) into each other at PHL, and we enjoyed twenty wonderful minutes to hug, hang out and catch up on the really big things that had happened to each other.  And some of the small delights. 

A high collisional cross section?  Almost worth the pressure.

1. Theory in the sense scientists use it, meaning a coherent system of ideas used to explain something,  not theory as it is often used outside of scientific circles, where it carries the connotation of something unlikely to be realized in actual practice, or notions that are not yet and probably won't  proved true. 
2.  To get a sense of how lightly populated a gas is, a molecule at room temperature on average travels about 300 times its length before hitting another molecule, the equivalent of my walking 500 yards without getting close enough to anyone to shake their hand.  Not my experience of the grocery store after work!

Thursday, December 01, 2016

Column: Advent 1: This very moment the pavements are laid in carnelians

A column for the first week of Advent which appeared at CatholicPhilly on 29 November 2016.





O afflicted one, storm-battered and unconsoled,
I lay your pavements in carnelians,
your foundations in sapphires;
I will make your battlements of rubies,
your gates of jewels,
and all your walls of precious stones. — Isaiah 54:11-12

“What do I need to cook a turkey, besides a big pan?” wondered my oldest son, staging Thanksgiving hundreds of miles from home. “Time,” I texted back. “Time to defrost it and time to cook it.” Time, I thought, wishing I could jot it on the shopping list next to onions and potatoes.

Time feels in short supply right now. It’s the end of my semester, so time for advising and writing letters of recommendations needs to be found amid classes and review sessions. My pile of grading stretches into eternity, and deadlines sprout on my calendar like dandelions, one puff and there are four more tasks rooted in my to-do list. And very little can wait for another week, or perhaps even another day.

I long for the luxury of waiting, of having time to sit and watch, to take long stretches for prayer. But the Advent I dream of is not the Advent I have. So I take heart in theologian and Jesuit Father Walter Burghardt’s encouragement to be aware of what is right before us: “This very moment, for all its imperfection and frustration, is pregnant with possibilities, pregnant with the future, pregnant with love, pregnant with Christ.”

This very moment is the only one that I have; can I see what it holds? An undisturbed five minutes to drink a cup of tea, washed in the sunlight of an early morning, the psalter open on my lap. The single leaf that floated past my office window, reminding me that seen or unseen, aware or not, God is at work in creation. The pool of quiet that emerged on the sidewalk outside of the post office on Saturday afternoon, a breath of stillness in the midst of a long list of errands, a reminder to be still, let go my grasp and know that God is with us. The student who, seeing me struggle with a stack of books for class, turned around on the stairs and helped me carry them to my classroom, Christ before me.

Perhaps Advent is as much a time for rousing, as it is for quiet waiting. “Now is the hour for you to awake from sleep!” cried St. Paul in the reading we heard on Sunday.  Stay awake, be alert to the signs of God among us.

Advent reminds me that, even in these storm-trammeled days, despite my imperfections, this moment is ever pregnant with possibilities, this moment is always charged with God’s grandeur. Look around, the pavements are laid in carnelians, the walls of precious stones. Now and always.


I wrote this with Michael Joncas' In our hearts be born.  A link to that and more resources for reflection are at CatholicPhilly.

Sunday, November 20, 2016

Putting air in the tires

Spider plants and Klein bottle. 
I put air in the Mini's tires today.  The low pressure light has been on for...well, longer than a week, and longer than I would like to admit.  Surprise, the car drives better when the tires are properly inflated.  But I just haven't had the time to do it.

I needed air, too.  Work has been chaotic, so much to do, and no breathing room at all.  This week I had more than 30 scheduled work hours on the books -- meetings, classes, talks, office hours.  Everything else — two manuscripts to edit and return, class prep, grading, letters of recommendation to write and submit, administrative planning, and dear God, the email, the email — had to be shoehorned into the remaining waking hours. And still they knocked on my door. Every 10 minutes one afternoon.

By Thursday, the email was flowing into my box at a rate that exceeded my rate of response.  I would answer an email, click back to the main screen to find three or four new ones.   No, I had to tell students, I can't meet with you this week, and perhaps not next either, as the molten lava of commitment creeps across my calendar, leaving ashes in its wake.  The good news was that saying "no" at this point was easy. There was no more time to give away.  The bad news, I was desperate for air.  For space to breathe.

On Friday, I had a lunch time appointment with my spiritual director. And this weekend, I had no work committments that required my presence elsewhere (for the first time since the middle of August).  And I declared a day of rest.  A sabbath of sorts.

I wrote yesterday.  I transplanted the spider plants and their offspring.  I got my hair cut.  I went to the farmer's market. I did my laundry and folded the towels.  I got my flu shot. I prayed.  I put air in my tires — and in my soul.




Lessons for young faculty (and others with high demand, high autonomy jobs) in learning to say no.  Or in my case, re-learning.

Wednesday, November 09, 2016

#imwithher

I am with her: the sobbing child, whose mother cannot afford medical care for her ear infection.

I am with her: the mother in the shelter, who does not know where she will live next week, next month, or perhaps tomorrow night.

I am with her: the mother whose child died of their mental illness.

I am with her: the mother in Aleppo, the mother in Mosul, their bodies wrapped around their children, sheltering them from the unthinkable.

I am with her: the mother in Virginia, sleeping in her car in the heat of July to get glasses for her children, and dentures so she can eat.

I am with her: the mother whose children were bullied and beaten and killed because of their race, their ethnicity, their religion, their gender or their sexual orientation.

I am with her: my student, whose faith in God has been impugned, dismissed as evil.

I am with her: my student, who cannot afford to complete her degree.

I am with them:  those who live in fear, those whose lives are in peril, those who are hungry and naked and sick and trapped by forces they do not control.


Here is where I stand.  I stand with Mary Magdalene and Mary the mother of James and Joseph, and the mother of the sons of Zebedee.  I know where I stand.  At the foot of the cross. Unwilling to look away from the suffering. Willing to witness. Willing to pick up the bodies and care for them.

Here is where I stand. 
‘Lord, when did we see you hungry or thirsty or a stranger or naked or ill or in prison, 
and not minister to your needs?’ 
He will answer them, ‘Amen, I say to you, what you did not do for one of these least ones, you did not do for me.’

#imwithHim

Wednesday, November 02, 2016

Boycotts, dovecots and apricots

In my course on contemplative practices yesterday we spent time looking at plans of monasteries (thank you, Bryn Mawr Art & Archeology library), ranging from an Egyptian monastery built in the 4th century and continuously occupied (and updated) until the 19th century, to a much later Carthusian charterhouse.

The questions to wrestle with included how the rule of life was supported by the architecture, but students also noted the practical sides of life which needed to be provided for.  Kitchens and infirmaries. And dovecots, to provide a ready supply of domestic pigeons.

One student joked if a dovecot was a place to keep doves, what did that make a boycott? ...and what about apricots?

So now I know that boycott is an eponym, for Charles Boycott, an Irish land agent who was shunned for his demands during the Irish Land Wars.  The tactic of refusing to use a service or good now bears his name.

And apricots get their cot from precocious, through the Latin praecocia - they ripen early.