Okay, about 10-15 years ago, I taught some eighth graders. It's coming up on
Thanksgiving, holiday and we've just finished doing Newtonian mechanics and basic physics. We're about to start on thermodynamics,
so I say ah, I know what to do. Here's your homework.
Over Thanksgiving, make a graph of the temperature of a turkey on Thanksgiving Day.
You know, from morning to afternoon,
you know, put the units down, you know, temperature - make sure you've got units.
Well, okay, the students are in America,
Thanksgiving is an American holiday,
turkeys are North American birds - all the same
it would be nice if you used Celsius, but if you have to, okay.
Meanwhile, there's students in my class, and I'm telling them:
okay, I know; some of you are vegetarian so you don't even have turkeys.
Some of you don't celebrate Thanksgiving.
Some of you are gonna be travelling. Some of you -
you know, I don't even have any thermometers to give you.
Doing science means you're gonna figure this out and do the experiment,
you're gonna find your own equipment.
If you don't have a turkey around,
measure the temperature of lasagne!
Or measure the temperature of uh, chow mein.
Just give me a graph
across time and temperature.
Really, what I'm trying to do is I'm trying to say, oh
we're gonna study a little bit about thermodynamics coming up.
We've finished Newtonian mechanics.
Upcoming is:
how does heat flow? You know, and this leads into some truly wonderful
partial differential equations and gradients and, and for a heat flow. But of course, I'm not going to go there,
I just want them to realise that heat moves from cold - you know,
there's a heat flow that never goes from cold to hot, it always goes from hot to cold. So that's
motivating me. And my usual thing with homework is if you hand it in you get an A, if you don't hand it in
you get an F. Hand this out - give me your name, oven temperature and temperature. Make sure you give me units. Come Monday after Thanksgiving
comes
30 different
things.
30 different reports, I get 'em I'm gonna start looking at them. Immediately,
it's obvious who copied from who. It's right away obvious who just, you know, copied somebody else's.
Some of the graphs you're seeing look like this. They're - people have scribbled things that
where they put one dot over here at
seventy degrees F, 1 dot over here at the oven temperature of
of...
whatever they - whatever their mom set it to;
350 degrees Fahrenheit.
Through a straight line between there and this was like 9 a.m,
this is 3 p.m. You know, they just said - oh straight line like this. Others you saw a graph that went like...
ohh
here's a dot here, dot here. Oh it ducked down a bit.
You know, even though the - even though the oven temperature was set to 350, it never got much above
ohh
160 or so degrees
Fahrenheit. Other students did it in Celsius. One, one kid wrote everything - used Kelvin! In the ideal world
there'd be a phase change
from a
frozen turkey across
and
then, through boiling and up higher but you know, in fact willing to stay in this region here. Really the slope of this line
tells us about the - for a heat equation, that says the gradient of
temperature determines how fast heat flows across it. It's parents' night, and parents come in the evening and want to know, how's,
how's my kid doing in class? And I described the experiments that we're doing and what the kids are doing in school,
and it's, it's way fun and
afterwards,
three parents: two moms and a dad come up to me separately and they say:
that thing with it with the Thanksgiving
experiment was
wonderful for my kid! Because it's the first time
that my kid
came into the kitchen on Thanksgiving!
Over and over and over again, every half hour, my son would open the oven door, put a
thermometer in the turkey - measure the temperature, write it down, add a dot to the graph and keep going like this. It's the first time
my kids
spent,
spent time in the kitchen on Thanksgiving! And the parents were delighted! And I thought yeah, you know it's so -
but the coolest thing -
coolest? The warmest thing of all,
was one,
[laughs]
one of my students
took, took this seriously, and graphed the temperature of a,
of the turkey on Thanksgiving and ended up with a graph - rather than going up across the day,
rather than, you know, going
along there.
This,
this student, made it - handed in a graph
where from morning to evening,
the temperature
remained exactly the same.
If I remember right she wrote down 104 degrees.
And I looked at it and I asked: why is the temperature the same? She says
it's a live turkey.
(Brady: Where did she stick the thermometer?)
[Turkey gobbling]
I have no idea.
You know, she completely slam-dunked me.
Absolute, you know -
there's somebody
who gets an A+ at it!
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