Feeling Cold

After a week away from school, I took the opportunity to catch up with spring on the campus for a half-hour during first period.  Walking out the door in shirt sleeves (having forgotten my jacket this morning), I was surprised at how comfortable it was compared to my arrival less than an hour before.  By the time I was headed back for the door, I was chilled.  Why?

We commonly predict our comfort outdoors by the air temperature.  This had not changed, but when I came out of the building I was in sunlight, so I benefitted from another source of heat than my own.  Further, the building sheltered me from the wind initially.  Then again, I began to warm up a little as I walked briskly back to the building, generating increased body heat.

So a better question than, "what's the temperature?" might be "how fast will my body lose heat?" or--even better--breeze, sunlight and exercise considered, "what will my body's net heat flow be?"

I returned from a boating trip a few days ago that reminded me of another lamentable (and embarassing) factor: wet clothing.  I had overturned my kayak in cold knee-deep water by a simple-minded error in climbing into it.  I spent the next half-hour wet and wind-blown, until I could get aboard the bigger boat, and get below and change.  Being wet in cool weather can be positively dangerous.  Worse still is staying in the water: you are out of the wind and its evaporative cooling power, but water is  so effective at removing heat from the body that even an hour in really cold water can be a death sentence.  Indeed, water robs heat so effectively that a person can die of hypothermia in New England waters even in high summer, if he stays in the water long enough.

In physics terms, you can think of your body as a container; inside the box thermal energy is generated by respiration fueled by the food you've eaten and enabled by the oxygen you inhale.  Clothing varies in its ability to insulate the box, slowing the flow of heat outward.  Outside the box are a variety of conditions that increase or decrease (on a very warm day, even reverse) heat flow.  The air itself is a fair insulator, but far less if it is moving air; water, by contrast, is an effective absorber of heat.  The idea of wind chill gets at just one of these conditions.  "Net heat flow" encompasses all the factors.

So it seems temperature is only one factor in comfort and safety outdoors.  Besides dressing for the weather, we must consider sun and exercise, and wind and water.  As your heat balance can change many times on even a single outing, the wisdom of dressing in layers becomes obvious, as well as the importance of being able to keep dry when shelter is not close by.

 And shivering, although uncomfortable, is one way your body automatically increases heat production when you're cold: you muscles vibrate, so increase energy output without actually going anywhere--like taking a brisk walk while standing still. 

April 24th: Spring 6

I took these days ago, but was too busy to look at them.  This is where we are four days after the last post.

 

The red maple I've been watching for Nature's Notebook shows the transition from flower to fruit.

The petals of the flowers still show red, but the red-and-green winged fruits are now far bigger than the flowers they are growing from.

 

The Norway maple in the back yard (another Nature's Notebook tree) is just blooming.  In this case of this tree, leaves are emerging together with the flowers; while red maples keep flowers separate.

 

Sugar maples have also begun to flower.  This is one of several sugar maples around the block from me.

 

This maple is a puzzle: the flowers are perfect, like those of Norway maple, 

but the red is suspicious.  Perhaps it is a cultivar.

Spring 5: Happy Easter!

Yup, I found time to check up on Spring even Easter weekend--the dogs need to walk, anyway.

Although nothing seems to be happening with the red maple flowers after a week of blooming, if you look closely you can see the tiny green "wings" just peeking out from the petals.  These will grow and mature into the winged seeds by which maples give their offspring a fighting chance at survival--carried out of the shade of the mother tree by the wind.  

Meanwhile, here is progress in some other species.  

 

Andromeda is an ornamental shrub of Japanese origin.

 

Vinca is my nemesis--but it does have pretty flowers, curse it!

 Paper birch is fairly uncommon around here; a native, but a more northern tree.

This beautiful big tree is in a suburban yard.  The dangling catkins bear flowers preparing to open. 

Spring 4: Animals can "spring," too!

My free period today was at 1pm--late enough, I decided, for the weather to be warm--so I ventured out in shirtsleeves, learning too late that the temperature was in the forties.  I walked almost entirely around the school, looking for new things, catching up with old.  Wandering in a little clearing, I was startled by the sudden crashing of a large animal through the woods a dozen yards away.  The poor thing--a deer, I assume--was as taken aback by my presence as I was by its.  In its haste it knocked down a little rotten tree, bounded across a path (a barely-seen blur of brown), and then splashed clumsily through a series of little vernal ponds.  No photo, of course.  

Certainly deer do pass through parts of Brockton and may even live in the wilder parts, but I somehow never imagined seeing one at school.  Probably because I am seldom there without a few dozen kids accompanying me.  

 

This rotted old birch tree made a lot of noise when the deer knocked it over.

 

The male flower are beginning to fall from some trees; their lives are nearly over.

This image is clear enough for you to see a little of the history of this tree: 

 three seasons of growth, marked not only by changes in the color of the twig segments,

but also scars encircling the twig where it ended the summer before.

(Such a scar is clear between the buds just left of the flowers.)

 

I thought this was another alder, but the fuzzy male catkins now whisper, "willow."

 

This oak's buds have barely expanded yet.

 

The rose leaves are becoming big enough to be recognizable.

 

The velvet leaves of this common mullein (Verbascum thapsis) 

were probably already growing when there was still snow on the ground.

 

A couple of mystery plants; I'll probably be able to identify them in a few weeks.

 

I tend to ignore cultivated plants, but my wife's beloved lilacs are well along.

 

This pignut hickory is one of the trees I'm keeping a "professional" eye on

for the Nature's Notebook project of the National Phrenology Network.

Spring 3 A Wintry Interlude

The ground white with snow startled me this morning.  "Sleet" my wife corrected.  Even so, my mind and the flowers and bursting buds all agreed that it was spring.  But it was cold enough that much of the white stuff survived most of the day, even where sunlight reached.  What effect did this weather have on the flowers?

Sleet on the ground set off the little white pines and hairy cap moss to advantage.

Apparently no harm done.

 

 

Silverberry leaves continue to expand.

 Although a few red maple trees had  flowers scattered beneath them, 

I suspect these flowers were "done" and discarded by the tree, rather than fallen victim to the weather.

 

 

Forsythia is prized for its cheerful, early flowering habit.

This one at the high school is "escaped from cultivation."

 Norway maples are just getting into the act--about a week behind red maple.  The big tree in my backyard has most flower buds just beginning to break, and about 5% open with open flowers.

This is the red maple whose debut I missed.

Maples flower before the leaves emerge.  Specialized flower buds produce only flowers.  In red maple, a single leaf bud is surrounded by between one and five flower buds, each of which produces five flowers.  The leaf bud (pink like the flower buds) is just visible in the center of the flower buds, in line with the twig.

I have long been acquainted with red maple for many years, but I am only coming to know it by close observations such as these.  Thoreau said, "It's not what you look at that matters, it's what you see."

Spring 2 A Blustery Day

It rained today, a blustery day.  I took these during a lull in the rain, though not the wind.  All are around the high school grounds. 

 Roses by the pond are leafing out, well-ahead of any trees I've seen.

 

Yesterday's alder catkins are draggled in today's rain.

 

The swamp behind the school has a nice tangle of  willow.

Silverberry is an exotic, and sometimes borders on invasive, but I have to admit I like it anyway.

The silvery mature foliage and berries make it look as if painted with a delicate brush.

 

White pine leaves last two years; it wears its year-old leaves through the winter, 

and buds new leaves in spring.  This tree's leaf buds aren't ready to break yet.

 

Hairy cap moss, looking like miniature trees, stays green year-round, giving it a head-start in spring.

 

A lot of the action in spring goes unnoticed because you'd have to look down.

This milfoil (aka yarrow) will produce large clusters of white flowers in summer.

Enjoy Spring With Me

At long last, after weeks of getting ready, things are popping out all over.  I had been watching the red maple buds redden and expand, then I was distracted for a few days.  Today they are all in full bloom.  I shouldn't have blinked!  I walked around at the high school for awhile today, discovering alder flowers blowing in the wind.  The buds of the Norway maples are huge: they, too, will bloom in a few days time.  In the coming days, I plan to keep up with the changes as best I can.  

 

Long catkins blowing like flags from this alder are clusters of male flowers.

They are shedding pollen to be carried by wind to female flowers.

(Male and female flowers are borne on the same tree, though they generally cross with other trees.)

 

Very windy day today.

 

Cluster of red maple male flowers, showing the long, yellowish stamens that produce the pollen.

 

Female red maple flowers; the stigmas that dangle like antennae will receive the wind-blown pollen.

Their flowers are small but many, making red maples easy to pick out beside the highway right now.

Red maples in the wind.

We love the small willows that are nicknamed "pussy willows."

What, in the middle of the woods, could make a sound like a creaking door?

The answer came as I watched trees move in the wind, and saw an old oak with two trees fallen against it.  As the oak's crown twists in the wind, the fallen trees probably rub against it.

 

That's right: you have to put your head sideways to watch it.

Just don't let anyone see you lying on your desk.

(The annoying tapping sound is me trying unsuccessfully to hold the camera still.)

This was another visit to "my" newly-discovered Wild Place.  I decided to stay an hour or so, look around a bit, and set awhile in my Thinking Place.

 

Me on the comfy rock in my Thinking Place.

 

The woods around my Thinking Place.

Making a (very small) Virtue of Necessity

As I climbed to the third-floor classroom yesterday, I got to wondering how much energy I was burning.  I was predisposed to think of stair-climbing in term of calories (rather than, say, heart health) because I have put on a few pounds lately.  (Okay--more than a few.) 

This could be quite complicated as a biology question, but in terms of physics, it can be done--very roughly but adequately--in five minutes on the back of an envelope.  In fact, with some simplification it can be done in your head.

The first thing to realize is that height is a kind of energy (potential energy).  Consider a car about to roll down a hill in neutral: when that car steam-rolls you at the bottom, you will have experienced that potential energy converted into the form of motion (kinetic) energy.  By the same token, energy is "stored" in an object as it is raised to a height.  That means the energy I burn in walking up the stairs is roughly equal to the amount I gain in potential energy in going up two floors. 

A moment's thought will convince you that potential energy depends on both the mass of the object, and how high it is.  (An anvil falling on your head will affect you differently than a marble from the same height.)  It also depends on the "acceleration of gravity" (symbolized "g"), which describes how quickly a falling object on earth accelerates, and is equal to 9.8m/s².  (This translates: a falling object increases its speed by 9.8 meters per second for each second that it falls.)  The actual equation for potential energy (E_p) is:

                                           E_p=mgh               

--where "m" is mass in kilograms, and "h" is height in meters.  (E_p is in Joules; a Joule is the amount of energy needed to accelerate a 1kilogram object by 1 meter per second every second.)

I'm guessing the floors of the school to be 4 meters apart, so 8m total height.  Taking g to be nearly 10, and my mass to be almost exactly 100kg, we have:

                               100kgX10m/s2X8m=8000J

Sounds like I'm burning a lot of energy on my climb!  Now to turn that into a more familiar unit: a calorie is four-point-something Joules--call it four even for simplicity.  Now I have burned about 200 calories on my climb.  But wait! in one of the stupider coincidences in science, there are two kinds of calories**: the regular sort used by physics, and the Calorie (big "C") used in considering food.  A Calorie is equal to 1000 calories.  So my climb actually only burned about 2 Calories. 

Bummer.

According to the sugar bag in my pantry, a teaspoon of sugar--not much more than I put in my coffee--has 15 Calories.  So every time I walk up to the third floor, I burn through only a few sips of my morning brew.**

Deep funk.

I suppose the take-home lesson is one I already knew: you can't exercise yourself into weight loss (unless maybe you're the athletic type, in which case you probably don't have to); you have to control your eating.  (Yes, there's more to it, but it's still unavoidable.)  Probably I should stop making hermit cookies, full of deadly brown sugar, molasses and butter.  From the scientific point of view, it's pretty cool (and scary) how much energy food contains. 

*Another definition: a calorie (small c) is the amount of energy needed to warm one gram of water by one degree Celsius.  Therefore a Calorie can warm a whole kilogram by the same one degree.


**Okay, so it isn't really that simple: since I am assuming our bodies are 100% efficient at converting chemical (food) energy--via muscles, joints, etc.--into potential energy.  What if our bodies were only 25% efficient? or 15%?  I still don't burn that whole cup of coffee!