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MIKE SHORT: OK, guys.

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Welcome to the first filmed
and hands-on installation

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of 22.01, Introduction
to Ionizing Radiation.

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I'm Mike Short.

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I'm the department's
undergrad coordinator.

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I'm also your 22.01 instructor.

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But I also want to introduce
you to Amelia Trainer

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in the back, who one of the
three TAs for the course.

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She took it last year.

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Everything is still very
fresh in your head, I bet.

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AUDIENCE: More or less.

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MIKE SHORT: Cool.

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So she'll be-- she and
Ka-Yen Yau and Caitlin Fisher

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will be with us all
throughout the term.

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So if there's something that you
don't like my explanation for,

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you've got three people
who just took the course,

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and struggled through
my own explanations,

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and can say it in
a different way.

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So let's start off by taking
your knowledge of physics

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from the roughly 1800s education
of the GIRs, the a General

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Institute Requirements,
up till 1932

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when the neutron was discovered.

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And I would argue that
this particle is what

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makes us nuclear engineers.

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It's the basis behind reactors.

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It's what differentiates us
from the high energy physics

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folks and everything,
because we've studied these

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and use them quite a lot.

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And so we want to
retrace Chadwick's steps

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in discovering the neutron.

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And this is the only
time you're ever

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going to see me have a
bunch of words on a slide.

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It's not a presentation
technique I like,

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but this paper is awesome in
the clarity and expressiveness

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of him saying I
ran this experiment

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and found something unknown.

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I'll use basic conservation
of energy and things

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you learned in 8.01
and 8.02 to prove

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that it has to be a neutron,
that a neutron must exist.

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It's elegant and
brilliant, and I want

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to walk you guys through it.

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Did any of you get a chance to
read the Chadwick article yet?

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OK.

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I'll show you where that is,
because hopefully by now you're

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all aware that we have
a learning module site.

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It's where I'm going
to post everything.

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It's where you're going
to submit everything

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for the class.

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But I'll save to the
end of this class

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to go through the
actual syllabus

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because I want to
get into the physics.

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So let's bring your knowledge
from classical mechanics

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and E&M up till about 1895 when
Wilhelm Roentgen used X-rays

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and used them to, well, image
something for the first time

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ever.

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Showing the contrast
between bone and tissue,

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he was able to illuminate
the bones in a hand.

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And then about a year later, the
X-rays got a whole lot better.

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So by then, it was known that
there were high-energy photons

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that had differential contrast
between different types

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of material.

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A year later, after
the nicer X-ray,

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J.J. Thompson
conclusively proved

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that there is an electron
by taking these cathode

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rays, as they were
called at one point,

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and sending them through
two charged plates.

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And he was able to show
a slight deflection.

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So these cathode rays, as they
pass through an electric field,

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change direction a little bit.

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And from the change
in direction,

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you may not know the
mass or the charge,

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but you can get the
mass to charge ratio.

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Because if you guys remember
from 8.02, from electricity

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and magnetism, as
a charged particle

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passes through an electric
field, it's deflected.

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And the amount of that
deflection, or the curvature,

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is based on the mass
to charge ratio.

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So Chadwick knew that
electrons existed.

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This was a known thing, as well
as alpha, beta, and gamma rays.

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So the electrons that
came out of the nucleus

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were later renamed beta rays.

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And at around the same time,
Ernest Rutherford and Paul

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Villard, working in
Canada and France,

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discovered that there are some
heavy charge particles that

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have very little penetrating
power, while Paul

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Villard discovered that there
are some other radiations--

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I think he called it produced
by disintegration of nuclei--

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that have very high
penetrating power.

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And they named them
alpha, beta, gamma

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in order of their penetrating
power or their range.

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And so it was later figured
out that these were also

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high-energy photons.

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So this is something to note is
that gamma rays, x-rays, light,

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whatever, it's all photons.

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However, once this pops
back up, gamma rays

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emanate from the nucleus.

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So when we refer
to a gamma ray, we

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mean a photon that came out
of a nuclear interaction

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or a nuclear disintegration,
not an electron transition.

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So this is one-- this is what
makes a gamma ray a gamma

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ray, is where it comes from.

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Otherwise it's a photon.

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It behaves just
like any photons.

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So what did Chadwick
see in 1932?

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This is the first
one-page article

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that he sent out to Nature to
say, I found something weird.

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So he found out that when
you take alpha particles

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from polonium-- so let's say
we had a source of polonium

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sending off alpha particles,
which I haven't told you

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what they are yet.

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It emits a radiation of
great penetrating power

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when it hits a
foil of beryllium.

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And it was not known
what these things were.

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So in goes the
alphas to beryllium.

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Something happens,
and something comes

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streaming out that couldn't be
explained by current theories.

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It was also noticed
that when hydrogen

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was placed in front of it,
when a piece of hydrogen

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in the form of wax, which
contains a lot of hydrogen,

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was put in front of it,
the amount of ionization

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increased, as measured by
what's called an ionization

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chamber and an
oscillograph, nothing

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more than an
almost-sealed chamber,

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a piston with some charge on
it that would then deflect.

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As it were to pick up
positive or negative charges,

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it would move
inwards or outwards

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and send an electrical signal to
something like an oscilloscope.

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So this was a way that
you could figure out

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how many ions were
created by this highly

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penetrating radiation
interacting in the ionization

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chamber.

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And they estimated that
with the old theories,

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if this highly penetrating thing
were a photon or a gamma ray,

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it would have to have
an energy of 50 times 10

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to the 6 electron
volts, or 50 MeV.

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He said, OK.

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Well, if that's to be basically
the experimental observation,

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say, a 50 MeV photon must be
responsible for the ionizations

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that we saw.

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And so again, this is
what the experiment

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looks like where you've got
a polonium source naturally

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emitting alpha rays.

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They hit a foil, a beryllium.

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They produce what he did not
know at the time was neutrons.

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We actually do know that
beryllium produces neutrons

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pretty well.

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Beryllium is an interesting
neutron multiplier.

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It undergoes what's called
an n 2n reaction where

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one neutron comes in, two
neutrons can come out,

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and it transmutes
into something else.

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And we'll go over what
this notation means, what

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these nuclear reactions mean.

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If you don't understand
it, don't worry.

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The whole point of today
is to open up questions

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that we'll spend the rest of the
semester closing and answering.

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So again, if you're
lost, don't worry.

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It's the first day of class,
and it's your first day

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of Modern Physics.

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So not to worry.

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And this is an actual
picture of what

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it looked like in the
paper, a simple polonium

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source on a disk that was made
by the natural decomposition

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of radium into polonium, a piece
of beryllium, a vacuum chamber.

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Because it was already known
that the alpha particles

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coming from polonium have
an extremely short range.

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We're going to figure out
why as part of this class.

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But without that vacuum
there, the alpha particles

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wouldn't make it
to the beryllium.

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So that much was known.

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What wasn't known was why are
we getting so many ionizations.

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They attributed it to
what they called a process

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similar to the Compton effect.

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To tell you what
that is, in 1923,

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Arthur Compton figured
out, among other things,

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Compton scattering, where a
photon can strike an electron.

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The photon changes energy.

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The electron picks
up some energy.

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They exit at very
well-known angles,

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and they transfer very
well-known amounts of energy.

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So this is how they knew how
much energy the photon, if it

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were to exist, should have.

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And they said the process
was analogous to Compton

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scattering because
they said in this case,

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a proton would be ejected.

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It would take a lot of energy to
eject a proton using a photon.

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And Chadwick saw
this and said, well,

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if we ascribe this phenomenon
to a Compton recoil,

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we should see about 10,000 ions.

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We actually saw about 30,000.

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So there was more
ionization going

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on than can be explained
by what's going on.

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In addition, those
protons should

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have a range in air of
about 1.3 millimeters,

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and they saw much more.

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So this is something simple--

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theory and experiment
don't match.

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There's got to be a different
theoretical explanation

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if the experiment was correct.

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And so finally, what I love--
the last sentence in this--

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the quantum
hypothesis-- a quantum

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was the way they
referred to a photon.

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It was called a
quantum back then,

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a little packet of energy.

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Can only be upheld if we
forget about conservation

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of energy and momentum.

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Now, I'll ask you guys
from 8.01 to 8.02.

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So Sean, when can you throw
out energy and momentum

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conservation?

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AUDIENCE: [INAUDIBLE]

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MIKE SHORT: That's
pretty much right.

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You can't.

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A situation probably
wasn't given to you

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where you can just
throw away conservation

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of momentum and energy.

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In fact, nature gives
us three quantities

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that we can measure
and conserve--

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mass, momentum, and energy.

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And throughout this course,
if something is not conserved,

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you've probably got the
math or the physics wrong.

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So this is something to
remember throughout the course

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and our derivations and
in your problem sets,

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is conserve mass, conserve
momentum, conserve energy, just

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like what was taught
in 8.01 and 8.02.

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So I'll call your
answer correct.

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You don't remember a situation
because, well, it didn't exist.

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And that's what Chadwick noted.

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He said theory and
experiment don't

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work unless we throw
out conservation

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of energy and momentum.

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Whether this was a kind of
passive-aggressive thing

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to say-- well,
this clearly can't

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exist-- or he was suggesting
maybe it doesn't work,

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I don't know.

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I wasn't there.

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But later on,
about a year later,

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he published a follow-on
paper confirming the existence

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of a neutron by reconciling
these differences

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in theory and experiment.

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So he restated
what he saw before.

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This was the first
paragraph of it.

248
00:10:37,320 --> 00:10:40,920
And again, it said that
radiation excited in beryllium.

249
00:10:40,920 --> 00:10:43,260
Whatever happened after the
alpha particle came out.

250
00:10:43,260 --> 00:10:47,070
It had a highly penetrating
radiation, distinctly greater

251
00:10:47,070 --> 00:10:48,727
than that of any
gamma radiation found

252
00:10:48,727 --> 00:10:49,810
from radioactive elements.

253
00:10:49,810 --> 00:10:52,500
Something is different.

254
00:10:52,500 --> 00:10:54,580
And I want us to take
a sec to digest this.

255
00:10:54,580 --> 00:10:56,770
This is the part I actually
want you guys to read,

256
00:10:56,770 --> 00:10:59,680
so take a minute and read
through some of this stuff.

257
00:10:59,680 --> 00:11:02,080
And then we'll begin
explaining his argument.

258
00:11:26,628 --> 00:11:28,420
Let me know when you
guys are done reading.

259
00:11:37,660 --> 00:11:38,160
OK.

260
00:11:38,160 --> 00:11:40,660
I see some folks
starting to look down.

261
00:11:40,660 --> 00:11:43,260
So let's take this
apart and figure out

262
00:11:43,260 --> 00:11:44,940
what was Chadwick saying.

263
00:11:44,940 --> 00:11:48,360
He was saying that if a
quantum was responsible

264
00:11:48,360 --> 00:11:50,610
for this energy,
a photon, then we

265
00:11:50,610 --> 00:11:53,130
can write a nuclear reaction.

266
00:11:53,130 --> 00:11:55,120
I'll write it in the
notation that we use now,

267
00:11:55,120 --> 00:12:00,660
which would be beryllium-9,
the only naturally occurring

268
00:12:00,660 --> 00:12:04,290
isotope of beryllium,
plus an alpha particle

269
00:12:04,290 --> 00:12:09,840
would lead to carbon-13
plus a gamma ray.

270
00:12:09,840 --> 00:12:12,060
And that gamma ray
would take away

271
00:12:12,060 --> 00:12:14,100
the energy from this reaction.

272
00:12:14,100 --> 00:12:17,400
So now we can start to figure
out, is energy conserved?

273
00:12:17,400 --> 00:12:19,360
Could this gamma
ray actually exist?

274
00:12:19,360 --> 00:12:22,050
And if it does, does it
account for the ionizations

275
00:12:22,050 --> 00:12:23,640
that Chadwick saw?

276
00:12:23,640 --> 00:12:26,280
So for each of
these isotopes, we

277
00:12:26,280 --> 00:12:28,170
know a few different quantities.

278
00:12:28,170 --> 00:12:36,570
We know what's called its rest
mass energy, which is this.

279
00:12:36,570 --> 00:12:38,920
It's rest mass times
speed of light squared.

280
00:12:38,920 --> 00:12:40,960
This should look
familiar to everyone.

281
00:12:40,960 --> 00:12:43,630
I've seen it on t-shirts
all over campus.

282
00:12:43,630 --> 00:12:45,400
And it may take
two or three weeks

283
00:12:45,400 --> 00:12:49,840
to really wrap your head around
what Einstein's equation really

284
00:12:49,840 --> 00:12:50,770
means.

285
00:12:50,770 --> 00:12:53,050
It is that mass and
energy are equivalent.

286
00:12:53,050 --> 00:12:56,810
You can express mass in terms
of energy, and vise versa.

287
00:12:56,810 --> 00:13:00,760
And you will be doing so
to conserve energy and mass

288
00:13:00,760 --> 00:13:03,940
in nuclear reactions, one of
which is written right here.

289
00:13:03,940 --> 00:13:07,210
So if each of these things
has a given rest mass energy,

290
00:13:07,210 --> 00:13:10,120
let's say a rest mass
energy of beryllium

291
00:13:10,120 --> 00:13:13,360
and a rest mass energy
of an alpha particle,

292
00:13:13,360 --> 00:13:16,570
and this alpha particle maybe
had some kinetic energy--

293
00:13:16,570 --> 00:13:18,100
it was moving pretty
fast, so we'll

294
00:13:18,100 --> 00:13:21,502
give that the symbol
t for kinetic energy,

295
00:13:21,502 --> 00:13:23,710
because that's what you're
going to see in your notes

296
00:13:23,710 --> 00:13:25,600
and in the reading
and everywhere.

297
00:13:25,600 --> 00:13:27,520
And then this
carbon-13 nucleus has

298
00:13:27,520 --> 00:13:32,850
got to have a rest mass
and a kinetic energy,

299
00:13:32,850 --> 00:13:35,560
and then this gamma
ray, it's going

300
00:13:35,560 --> 00:13:37,870
to have some e gamma energy.

301
00:13:37,870 --> 00:13:40,770
Now, the question is,
is the mass and energy

302
00:13:40,770 --> 00:13:42,558
conserved in this equation?

303
00:13:42,558 --> 00:13:44,100
What we're actually
starting to write

304
00:13:44,100 --> 00:13:48,000
is what's called the q
equation, or the universal mass

305
00:13:48,000 --> 00:13:51,540
and energy balance for any
kind of nuclear reaction.

306
00:13:51,540 --> 00:13:55,440
So let's say we have a
large initial nucleus

307
00:13:55,440 --> 00:13:59,520
i and some small
particle i moving

308
00:13:59,520 --> 00:14:02,460
at it with some great speed.

309
00:14:02,460 --> 00:14:05,580
And after some
reaction occurs, you

310
00:14:05,580 --> 00:14:08,720
have a small, final
particle leaving

311
00:14:08,720 --> 00:14:12,240
and a different, large
final particle leaving.

312
00:14:12,240 --> 00:14:15,160
They don't necessarily
have to be the same.

313
00:14:15,160 --> 00:14:22,410
Let's give these particles
designations 1, 2, 3, and 4.

314
00:14:22,410 --> 00:14:24,780
In the end, we should be
able to write the difference

315
00:14:24,780 --> 00:14:27,060
in either total
energy or total mass

316
00:14:27,060 --> 00:14:30,840
of the system as this value q.

317
00:14:30,840 --> 00:14:34,200
q is, let's say,
the amount of energy

318
00:14:34,200 --> 00:14:36,242
that turns into
mass, or vise versa.

319
00:14:36,242 --> 00:14:37,450
So let's say energy transfer.

320
00:14:42,840 --> 00:14:45,420
And so if we start writing some
mass conservation equation,

321
00:14:45,420 --> 00:14:48,840
we can say that the
mass of nucleus 1

322
00:14:48,840 --> 00:14:51,540
plus the mass of
nucleus 2 should

323
00:14:51,540 --> 00:14:56,250
equal the mass of nucleus 3
plus the mass of nucleus 4

324
00:14:56,250 --> 00:15:01,680
plus however much energy
from nuclei 1 and 2 turned

325
00:15:01,680 --> 00:15:04,853
into energy into 3 and 4.

326
00:15:04,853 --> 00:15:06,270
We could also write
the same thing

327
00:15:06,270 --> 00:15:08,130
for their kinetic energies.

328
00:15:08,130 --> 00:15:12,468
In this case, the
finals are on the end.

329
00:15:12,468 --> 00:15:13,010
So I'm sorry.

330
00:15:13,010 --> 00:15:14,910
I should use t for
kinetic energy.

331
00:15:26,200 --> 00:15:29,350
So what this is saying is
that if some mass has turned

332
00:15:29,350 --> 00:15:31,450
into energy at the
end, that energy

333
00:15:31,450 --> 00:15:33,370
had to come from somewhere.

334
00:15:33,370 --> 00:15:36,220
It had to come from the initial
kinetic energy or conversion

335
00:15:36,220 --> 00:15:38,993
of mass to energy
from this reaction.

336
00:15:38,993 --> 00:15:40,660
And so notice that
now, you can actually

337
00:15:40,660 --> 00:15:44,380
express the masses of the
nuclei in terms of their energy,

338
00:15:44,380 --> 00:15:46,875
of their initial and
final kinetic energies.

339
00:15:46,875 --> 00:15:48,250
And this right
here is what we're

340
00:15:48,250 --> 00:15:51,640
going to be spending the first
two or three weeks deriving,

341
00:15:51,640 --> 00:15:55,030
using, and exploring in order
to balance nuclear reactions

342
00:15:55,030 --> 00:15:58,400
and explain why they
are the way they are.

343
00:15:58,400 --> 00:16:02,200
So let's make sure-- we'll keep
this nuclear reaction up here,

344
00:16:02,200 --> 00:16:04,960
because Chadwick proposed
a different one to explain

345
00:16:04,960 --> 00:16:07,190
what he saw.

346
00:16:07,190 --> 00:16:09,320
And some of the
evidence for this

347
00:16:09,320 --> 00:16:12,710
was that he put
some aluminum foil

348
00:16:12,710 --> 00:16:20,520
in between the beryllium where
things were being liberated

349
00:16:20,520 --> 00:16:23,710
and the ionization
chamber and oscilloscope,

350
00:16:23,710 --> 00:16:26,070
or oscillograph, as
he liked to call it.

351
00:16:26,070 --> 00:16:29,090
And that way, by putting
more and more pieces of foil

352
00:16:29,090 --> 00:16:30,680
in there, you can
deduce what's called

353
00:16:30,680 --> 00:16:37,230
the range, or the distance
that the radiation will travel

354
00:16:37,230 --> 00:16:40,373
before it stops by losing
energy through a whole host

355
00:16:40,373 --> 00:16:42,540
of different processes that
we'll be working through

356
00:16:42,540 --> 00:16:43,620
together.

357
00:16:43,620 --> 00:16:47,200
If this were to be
ascribed to a proton,

358
00:16:47,200 --> 00:16:50,640
then it should have had
a certain range in air

359
00:16:50,640 --> 00:16:52,740
by this curve b right here.

360
00:16:52,740 --> 00:16:55,680
Instead, he found this curve a
where things moved about three

361
00:16:55,680 --> 00:16:57,120
times farther than
could have been

362
00:16:57,120 --> 00:17:00,330
explained if that
were a proton to be

363
00:17:00,330 --> 00:17:02,100
liberated by all this stuff.

364
00:17:02,100 --> 00:17:05,670
So he's saying, OK, something
has got more penetrating power.

365
00:17:05,670 --> 00:17:07,829
We know now that part
of the reason for this

366
00:17:07,829 --> 00:17:12,577
is if there's a neutron,
and there's no charge on it,

367
00:17:12,577 --> 00:17:15,119
then it's not going to interact
with the electrons in matter.

368
00:17:15,119 --> 00:17:16,680
It won't even see them.

369
00:17:16,680 --> 00:17:18,359
Whereas protons or
any other charged

370
00:17:18,359 --> 00:17:20,910
particles will see the
electrons in matter

371
00:17:20,910 --> 00:17:23,950
and will interact with the
electrons and the nuclei.

372
00:17:23,950 --> 00:17:25,950
So a little flash
forward to say,

373
00:17:25,950 --> 00:17:28,720
we can explain this pretty
simply with what we generally

374
00:17:28,720 --> 00:17:29,220
know.

375
00:17:29,220 --> 00:17:31,080
But this was the
first time somebody

376
00:17:31,080 --> 00:17:33,213
had to come up with
[INAUDIBLE] explanation,

377
00:17:33,213 --> 00:17:34,130
and it was quite hard.

378
00:17:37,300 --> 00:17:39,220
And so moving on,
he can say, well, I

379
00:17:39,220 --> 00:17:42,820
know what protons should
be injected from paraffin.

380
00:17:42,820 --> 00:17:47,410
I know a formula to describe
what quantum or photon

381
00:17:47,410 --> 00:17:49,990
energy had to create them.

382
00:17:49,990 --> 00:17:52,960
And then instead, he says-- this
is where his major hypothesis

383
00:17:52,960 --> 00:17:53,650
is--

384
00:17:53,650 --> 00:17:55,630
either we relinquish
conservation

385
00:17:55,630 --> 00:18:00,910
of energy or neutron or
adopt another hypothesis.

386
00:18:00,910 --> 00:18:05,170
And this was already put
forth by Rutherford back

387
00:18:05,170 --> 00:18:06,940
in the '20s that there
may be a neutron,

388
00:18:06,940 --> 00:18:08,620
but there wasn't any proof.

389
00:18:08,620 --> 00:18:11,260
And this is what
provided the proof.

390
00:18:11,260 --> 00:18:14,530
He gave an alternate
nuclear reaction

391
00:18:14,530 --> 00:18:16,540
if there were to be
a neutron which had

392
00:18:16,540 --> 00:18:18,830
roughly the mass of a proton.

393
00:18:18,830 --> 00:18:20,620
Then let's write a
second one down here.

394
00:18:20,620 --> 00:18:23,320
I'm going to erase
these extra notation,

395
00:18:23,320 --> 00:18:26,740
and we'll write the competing
nuclear action below.

396
00:18:26,740 --> 00:18:34,960
And he said that-- let's say
we start with beryllium-9

397
00:18:34,960 --> 00:18:38,050
plus an alpha
particle could instead

398
00:18:38,050 --> 00:18:42,840
become carbon-12 and a neutron.

399
00:18:47,530 --> 00:18:50,080
So I'd like to ask you guys
right now to work this out.

400
00:18:50,080 --> 00:18:53,560
Are both of these reactions
balanced in terms of mass?

401
00:18:53,560 --> 00:18:56,810
Are there the same number
of protons, neutrons,

402
00:18:56,810 --> 00:18:58,930
and electrons at either side?

403
00:18:58,930 --> 00:19:01,390
And just to let you
know, an alpha particle

404
00:19:01,390 --> 00:19:05,080
is better known as
a helium nucleus.

405
00:19:05,080 --> 00:19:08,170
So that means that
there's two protons.

406
00:19:08,170 --> 00:19:11,410
There's four protons
plus neutrons,

407
00:19:11,410 --> 00:19:22,730
and beryllium-9 has four protons
and nine protons plus neutrons.

408
00:19:22,730 --> 00:19:26,650
And carbon-12 has six protons.

409
00:19:26,650 --> 00:19:29,015
A neutron has zero protons.

410
00:19:31,890 --> 00:19:34,780
So in each of these-- and I'll
fill in the other ones here.

411
00:19:34,780 --> 00:19:39,690
So that's a 4, 4, 2, and 6.

412
00:19:39,690 --> 00:19:41,820
Do we have the same number
of protons and neutrons

413
00:19:41,820 --> 00:19:43,680
on both sides of both equations?

414
00:19:47,030 --> 00:19:50,930
I see a number of heads and
one person saying yes, we do.

415
00:19:50,930 --> 00:19:54,200
So both of these reactions
are balanced in terms of mass.

416
00:19:54,200 --> 00:19:57,410
The next thing to do is balance
them in terms of energy.

417
00:19:57,410 --> 00:20:00,080
Now, they can both be
balanced in terms of energy

418
00:20:00,080 --> 00:20:04,700
because you could attribute the
change in the amount of mass

419
00:20:04,700 --> 00:20:07,280
from here to there
and attribute that

420
00:20:07,280 --> 00:20:09,650
to the energy of the photon.

421
00:20:09,650 --> 00:20:16,040
That's when you'd have to have a
photon of energy around 50 MeV.

422
00:20:16,040 --> 00:20:17,240
But if a proton--

423
00:20:17,240 --> 00:20:19,700
I'm sorry-- a photon
of energy around 50 MeV

424
00:20:19,700 --> 00:20:21,430
can't explain what we saw.

425
00:20:21,430 --> 00:20:24,440
Instead, if there is something
like a neutron which also

426
00:20:24,440 --> 00:20:31,300
has its own rest mass and
its own kinetic energy,

427
00:20:31,300 --> 00:20:33,550
and that neutron were
highly penetrating,

428
00:20:33,550 --> 00:20:37,030
it could explain
what Chadwick saw.

429
00:20:37,030 --> 00:20:40,030
And so the masses and
things of these nuclei

430
00:20:40,030 --> 00:20:43,030
were fairly well known
back then to, well,

431
00:20:43,030 --> 00:20:46,000
six significant digits
based on some very careful

432
00:20:46,000 --> 00:20:47,290
experimentation.

433
00:20:47,290 --> 00:20:48,730
And all he did is
say, all right.

434
00:20:48,730 --> 00:20:51,610
Let's take all of the
energies in this reaction.

435
00:20:51,610 --> 00:20:54,040
Remember how I
told you over here,

436
00:20:54,040 --> 00:20:55,690
you can write any
nuclear reaction

437
00:20:55,690 --> 00:20:57,730
in terms of its
kinetic energies,

438
00:20:57,730 --> 00:20:59,990
and the difference will
give you the q value,

439
00:20:59,990 --> 00:21:03,610
which you can attribute to the
conversion of mass to energy?

440
00:21:03,610 --> 00:21:05,740
That's what Chadwick
did right here.

441
00:21:05,740 --> 00:21:08,560
He took the full
reaction, saying here's

442
00:21:08,560 --> 00:21:12,520
the mass of beryllium, the
mass of the alpha particle,

443
00:21:12,520 --> 00:21:15,035
the kinetic energy of
the alpha particle.

444
00:21:15,035 --> 00:21:17,410
Note that he assumed that the
kinetic energy of beryllium

445
00:21:17,410 --> 00:21:17,950
was zero.

446
00:21:17,950 --> 00:21:20,290
It was just sitting
at room temperature.

447
00:21:20,290 --> 00:21:22,870
Does anyone know the approximate
kinetic energy of atoms

448
00:21:22,870 --> 00:21:25,880
at room temperature?

449
00:21:25,880 --> 00:21:28,440
Order of magnitude, even?

450
00:21:28,440 --> 00:21:33,330
It's around 1/100 to 1/1,000
of an EV, or an electron volt.

451
00:21:33,330 --> 00:21:35,730
So when we're talking
about beryllium,

452
00:21:35,730 --> 00:21:40,470
whose kinetic energy, we'll
say, is around 0.01 EV,

453
00:21:40,470 --> 00:21:44,400
and the alpha particle whose
kinetic energy was around 4

454
00:21:44,400 --> 00:21:49,920
times 10 to the 6th EV, you
can see why it's neglected.

455
00:21:49,920 --> 00:21:51,120
And you can do that too.

456
00:21:51,120 --> 00:21:57,090
You do not have to account
for the initial kinetic energy

457
00:21:57,090 --> 00:21:59,070
of a nucleus at rest.

458
00:21:59,070 --> 00:22:00,930
This is the first
approximation that we

459
00:22:00,930 --> 00:22:04,522
tend to make to the q equation
to just have fewer variables.

460
00:22:04,522 --> 00:22:06,480
And don't worry if you
don't remember this now,

461
00:22:06,480 --> 00:22:09,930
because we have a whole
lecture on the q equation.

462
00:22:09,930 --> 00:22:11,720
And so finally, he
said, all right.

463
00:22:11,720 --> 00:22:13,350
We'll subtract all the masses.

464
00:22:13,350 --> 00:22:16,260
We're left with the kinetic
energies and a little bit

465
00:22:16,260 --> 00:22:19,200
of excess rest mass.

466
00:22:19,200 --> 00:22:21,830
That's got to be--

467
00:22:21,830 --> 00:22:22,970
this has got to exist.

468
00:22:22,970 --> 00:22:27,890
And so this inequality has to be
satisfied, which indeed it was.

469
00:22:27,890 --> 00:22:30,530
Using this inequality,
he said that the velocity

470
00:22:30,530 --> 00:22:33,920
of the neutron has to be
less than its kinetic energy

471
00:22:33,920 --> 00:22:36,860
if it had all of that
energy, 3.9 times 10

472
00:22:36,860 --> 00:22:38,630
to the 9 centimeter per second.

473
00:22:38,630 --> 00:22:40,190
Indeed it was lower--

474
00:22:40,190 --> 00:22:43,460
not by that much, but it still
satisfied this criterion.

475
00:22:43,460 --> 00:22:45,290
So things are checking out.

476
00:22:45,290 --> 00:22:47,210
That's pretty cool.

477
00:22:47,210 --> 00:22:49,400
He looked at another
nuclear reaction

478
00:22:49,400 --> 00:22:50,870
that was known at the time.

479
00:22:50,870 --> 00:22:54,110
If you were to bombard
boron-11 with helium,

480
00:22:54,110 --> 00:22:57,950
you end up with
nitrogen-14 and either--

481
00:22:57,950 --> 00:23:00,620
either end up with
nitrogen-15 and a photon

482
00:23:00,620 --> 00:23:03,710
or nitrogen-14 and a
neutron, explaining

483
00:23:03,710 --> 00:23:07,380
another reaction that
wasn't as well known before.

484
00:23:07,380 --> 00:23:10,737
So I'd like to write
this nuclear reaction,

485
00:23:10,737 --> 00:23:13,070
because I want you all to get
very familiar with writing

486
00:23:13,070 --> 00:23:14,880
nuclear reactions.

487
00:23:14,880 --> 00:23:19,910
Let's say boron-11 plus
an alpha particle--

488
00:23:19,910 --> 00:23:22,610
we'll say it has a mass of 4--

489
00:23:22,610 --> 00:23:26,540
becomes nitrogen
14 and a neutron.

490
00:23:29,810 --> 00:23:31,460
We also have a
shorthand of writing

491
00:23:31,460 --> 00:23:33,050
this nuclear reaction
which I'll use

492
00:23:33,050 --> 00:23:35,180
on the board for speed's sake.

493
00:23:35,180 --> 00:23:39,740
Usually if you put
the initial nucleus

494
00:23:39,740 --> 00:23:42,980
and the initial incoming
radiation, comma,

495
00:23:42,980 --> 00:23:48,810
the exiting radiation,
and the final nucleus,

496
00:23:48,810 --> 00:23:51,140
these two right
here are equivalent.

497
00:23:51,140 --> 00:23:53,780
This is just a shorthand
for nuclear reactions.

498
00:23:53,780 --> 00:23:56,000
This is what you'll
tend to see because it's

499
00:23:56,000 --> 00:23:59,240
a lot easier to write this
shorthand and parse it visually

500
00:23:59,240 --> 00:24:02,680
than it is to parse a
whole nuclear reaction.

501
00:24:02,680 --> 00:24:05,180
So I just want you to know if
you don't know what these are,

502
00:24:05,180 --> 00:24:07,670
just remember to
stick the arrow here,

503
00:24:07,670 --> 00:24:09,530
stick plus signs in
for the parentheses,

504
00:24:09,530 --> 00:24:11,300
and you've got the same thing.

505
00:24:11,300 --> 00:24:14,120
And using these, you should be
able to very quickly determine

506
00:24:14,120 --> 00:24:15,350
is this reaction balanced.

507
00:24:15,350 --> 00:24:16,940
What's actually going on?

508
00:24:16,940 --> 00:24:20,240
And there will be tabulated
values of q values or energy

509
00:24:20,240 --> 00:24:22,228
amounts for these
sorts of reactions

510
00:24:22,228 --> 00:24:24,020
in all sorts of tables
I'll be showing you.

511
00:24:27,500 --> 00:24:30,170
And so finally, he
figured out what

512
00:24:30,170 --> 00:24:33,830
the energy or the mass defect
of the neutrons should be.

513
00:24:33,830 --> 00:24:35,630
Does anyone know what
a mass defect is?

514
00:24:38,210 --> 00:24:40,460
This is another core concept.

515
00:24:40,460 --> 00:24:44,210
Let's say you were to want
to make an atom of helium.

516
00:24:44,210 --> 00:24:49,220
So you would have to take
two protons whose masses are

517
00:24:49,220 --> 00:24:53,920
very well known,
and two neutrons,

518
00:24:53,920 --> 00:24:54,920
and bring them together.

519
00:24:59,760 --> 00:25:01,340
So if you were to
have-- let's say

520
00:25:01,340 --> 00:25:04,900
the initial mass
would be 2 times

521
00:25:04,900 --> 00:25:10,930
the mass of a neutron plus 2
times the mass of a proton.

522
00:25:10,930 --> 00:25:16,290
And the final mass is just
the mass of a helium nucleus.

523
00:25:16,290 --> 00:25:18,630
You'll actually find that
the initial mass does not

524
00:25:18,630 --> 00:25:22,080
equal the final mass.

525
00:25:22,080 --> 00:25:25,555
In bringing nuclei
or nucleons together,

526
00:25:25,555 --> 00:25:27,930
they actually release what's
called their binding energy.

527
00:25:27,930 --> 00:25:30,330
It's what keeps the
nucleus bound together.

528
00:25:30,330 --> 00:25:32,880
There's a little bit of
mass turned into energy.

529
00:25:32,880 --> 00:25:36,030
And so you know how we like
say the whole is usually

530
00:25:36,030 --> 00:25:37,355
more than the sum of its parts?

531
00:25:37,355 --> 00:25:38,730
In nuclear
engineering, the whole

532
00:25:38,730 --> 00:25:40,740
is a little less than
the sum of its parts.

533
00:25:40,740 --> 00:25:42,930
It definitely is not equal.

534
00:25:42,930 --> 00:25:46,740
And Chadwick was proposing
that a neutron should actually

535
00:25:46,740 --> 00:25:53,700
be made up of a
proton and an electron

536
00:25:53,700 --> 00:25:55,535
in very close proximity.

537
00:25:55,535 --> 00:25:57,660
And since the masses of
the proton and the electron

538
00:25:57,660 --> 00:26:00,330
were known, he said, well,
if we bring the proton

539
00:26:00,330 --> 00:26:03,090
and electron very
close together to have

540
00:26:03,090 --> 00:26:06,900
an overall neutral
neutron particle,

541
00:26:06,900 --> 00:26:11,220
it should have roughly that
mass defect or that difference

542
00:26:11,220 --> 00:26:14,850
between the energy of
its constituent nucleons

543
00:26:14,850 --> 00:26:17,550
and the energy of the
assembled nucleus.

544
00:26:22,380 --> 00:26:24,520
And you'll hear the
words "mass defect"

545
00:26:24,520 --> 00:26:26,050
and "binding energy" used.

546
00:26:26,050 --> 00:26:29,740
Mass defect is in terms
of mass in either--

547
00:26:29,740 --> 00:26:33,740
you can give it in kilograms
or in atomic mass units,

548
00:26:33,740 --> 00:26:40,952
or AMU, or in, let's
say, MeV c squared.

549
00:26:40,952 --> 00:26:43,160
And you'll also hear of the
binding energy just given

550
00:26:43,160 --> 00:26:46,210
in things like MeV.

551
00:26:46,210 --> 00:26:48,910
I want to show you where you
can find these things now.

552
00:26:48,910 --> 00:26:53,140
I'll give you the single
most useful website

553
00:26:53,140 --> 00:26:55,260
that you'll be referring to.

554
00:26:55,260 --> 00:26:57,730
And I've posted it up on
the Learning Module site,

555
00:26:57,730 --> 00:27:01,840
so now is a good time for me to
show you that the site exists.

556
00:27:01,840 --> 00:27:03,690
And let me just clone
my screen real quick.

557
00:27:07,140 --> 00:27:11,368
It's a wireless HDMI thing, so
it takes a sec to pop back up.

558
00:27:14,360 --> 00:27:15,410
Great.

559
00:27:15,410 --> 00:27:18,620
Has anyone not been
to the site yet?

560
00:27:18,620 --> 00:27:19,120
It's OK.

561
00:27:19,120 --> 00:27:20,110
You don't have to
be embarrassed.

562
00:27:20,110 --> 00:27:20,610
OK.

563
00:27:20,610 --> 00:27:21,790
About half of you.

564
00:27:21,790 --> 00:27:25,120
I recommend tonight that you
start looking through the site.

565
00:27:25,120 --> 00:27:27,190
One, make sure that
you can log in,

566
00:27:27,190 --> 00:27:30,160
because you'll need to log in
to see some of the copyrighted

567
00:27:30,160 --> 00:27:32,740
materials that I've posted,
and two, because this is where

568
00:27:32,740 --> 00:27:34,810
you'll be posting
all your homeworks,

569
00:27:34,810 --> 00:27:37,120
getting the assignments,
checking due dates.

570
00:27:37,120 --> 00:27:39,940
Especially if I
postpone a problem set,

571
00:27:39,940 --> 00:27:42,160
I'll put out an announcement
and post it here.

572
00:27:42,160 --> 00:27:45,070
So this is the place
to look for everything.

573
00:27:45,070 --> 00:27:47,620
And in addition, I've posted
a lot of useful materials

574
00:27:47,620 --> 00:27:50,240
for you guys.

575
00:27:50,240 --> 00:27:51,990
They're all at the
bottom, and the top one

576
00:27:51,990 --> 00:27:55,890
is the [INAUDIBLE]
table of nuclides.

577
00:27:55,890 --> 00:27:58,050
Anyone seen this
kind of thing before?

578
00:27:58,050 --> 00:28:00,690
We have posters of it down on
all the first-floor classrooms

579
00:28:00,690 --> 00:28:02,160
in Building 24.

580
00:28:02,160 --> 00:28:03,600
This is our go-to chart.

581
00:28:03,600 --> 00:28:06,480
When you want to find out
all of the nuclear half-life,

582
00:28:06,480 --> 00:28:09,150
radioactive decay
and decay of energy,

583
00:28:09,150 --> 00:28:11,700
probability of certain
direction, whatever,

584
00:28:11,700 --> 00:28:13,570
this is where you go.

585
00:28:13,570 --> 00:28:16,443
So let's take a look
at, well, helium-4

586
00:28:16,443 --> 00:28:17,860
since we've been
talking about it,

587
00:28:17,860 --> 00:28:19,690
better known as
an alpha particle.

588
00:28:19,690 --> 00:28:23,080
And you'll notice a few
different quantities visible.

589
00:28:23,080 --> 00:28:29,770
The atomic mass, 4.0026032 AMU.

590
00:28:29,770 --> 00:28:32,290
And this is another tip I want
to give you guys right now.

591
00:28:32,290 --> 00:28:34,750
Don't round these numbers.

592
00:28:34,750 --> 00:28:36,730
That's one of the
major trip up points.

593
00:28:36,730 --> 00:28:40,390
If you say that's
approximately 4 or 4.003,

594
00:28:40,390 --> 00:28:43,150
you probably won't get
the p-set questions right,

595
00:28:43,150 --> 00:28:47,500
because 1/1,000 of an AMU can
still represent almost an MeV

596
00:28:47,500 --> 00:28:48,970
of lost energy.

597
00:28:48,970 --> 00:28:51,250
So let's say you have
a nuclear reaction that

598
00:28:51,250 --> 00:28:55,750
liberates a 1 mega electron
volt or one MeV gamma ray,

599
00:28:55,750 --> 00:28:57,910
and you get the
fourth digit wrong

600
00:28:57,910 --> 00:28:59,410
in one of your
mass calculations.

601
00:28:59,410 --> 00:29:01,330
It's like that gamma
ray didn't exist,

602
00:29:01,330 --> 00:29:03,070
and you won't get
the answer right.

603
00:29:03,070 --> 00:29:06,430
So again, word to the
wise-- do not round.

604
00:29:06,430 --> 00:29:09,730
You'll also see what's known as
the excess mass or the binding

605
00:29:09,730 --> 00:29:10,240
energy.

606
00:29:10,240 --> 00:29:12,820
So this binding
energy right here,

607
00:29:12,820 --> 00:29:16,300
if you were to take two
protons and two neutrons

608
00:29:16,300 --> 00:29:20,140
and bring them together and
look at the difference in masses

609
00:29:20,140 --> 00:29:23,140
from, let's say, the same
old formula as before,

610
00:29:23,140 --> 00:29:33,880
you would get a difference of
28,295 keV, or about 28.295673

611
00:29:33,880 --> 00:29:34,810
MeV.

612
00:29:34,810 --> 00:29:36,585
Again, don't round.

613
00:29:36,585 --> 00:29:37,960
Let's figure this
out right here.

614
00:29:37,960 --> 00:29:46,540
So we have 28.295673 MeV.

615
00:29:46,540 --> 00:29:49,570
And there is a conversion factor
that you should either memorize

616
00:29:49,570 --> 00:29:50,440
or write down.

617
00:29:50,440 --> 00:29:51,970
Either way, it's good.

618
00:29:51,970 --> 00:29:59,470
It's about 931.49 MeV
per atomic mass unit.

619
00:29:59,470 --> 00:30:02,140
This is your mass
energy equivalence

620
00:30:02,140 --> 00:30:04,360
that you'll be using over
and over and over again.

621
00:30:04,360 --> 00:30:06,070
And again, don't round.

622
00:30:06,070 --> 00:30:10,550
Those last two
digits are important.

623
00:30:10,550 --> 00:30:13,460
So by taking this energy and
dividing by this conversion

624
00:30:13,460 --> 00:30:17,180
factor, you can figure out
how many atomic mass units are

625
00:30:17,180 --> 00:30:19,670
lost in terms of
actual mass when

626
00:30:19,670 --> 00:30:23,900
you assemble an alpha particle
from its constituent pieces.

627
00:30:23,900 --> 00:30:26,202
And the rest of the stuff
we will get into later.

628
00:30:26,202 --> 00:30:28,160
It's not really relevant
to today's discussion,

629
00:30:28,160 --> 00:30:32,660
but it's definitely
relevant to today's course.

630
00:30:32,660 --> 00:30:34,620
Cool.

631
00:30:34,620 --> 00:30:36,190
OK.

632
00:30:36,190 --> 00:30:37,793
And then on to--

633
00:30:37,793 --> 00:30:39,460
one of the last things
that he mentioned

634
00:30:39,460 --> 00:30:43,670
is some predictions to say, OK,
let's say this neutron exists.

635
00:30:43,670 --> 00:30:45,340
It doesn't have charge.

636
00:30:45,340 --> 00:30:48,070
Most matter interacts
with other matter

637
00:30:48,070 --> 00:30:50,920
by virtue of Coulombic
or charge interactions.

638
00:30:50,920 --> 00:30:53,110
If the neutron has no
charge, it shouldn't really

639
00:30:53,110 --> 00:30:55,790
see matter except for nuclei.

640
00:30:55,790 --> 00:30:59,020
This is exactly what he
said, is an electrical field

641
00:30:59,020 --> 00:31:01,760
of a neutron will be
extremely small except

642
00:31:01,760 --> 00:31:05,290
at small distances, because
he proposed that a neutron is

643
00:31:05,290 --> 00:31:07,120
a proton plus an electron.

644
00:31:07,120 --> 00:31:09,700
So once you get to around
the radius of the neutron,

645
00:31:09,700 --> 00:31:13,180
you might start to see some
charge, but not before.

646
00:31:13,180 --> 00:31:14,800
And so most other
matter, unless you

647
00:31:14,800 --> 00:31:20,170
have a head-on collision with a
nucleus, neutrons won't see it.

648
00:31:20,170 --> 00:31:22,180
And that helps explain
why the neutrons

649
00:31:22,180 --> 00:31:24,970
had such high penetrating
power or high range--

650
00:31:24,970 --> 00:31:27,970
because they just went streaming
through most materials,

651
00:31:27,970 --> 00:31:29,920
invisible to the electrons.

652
00:31:29,920 --> 00:31:33,770
So very forward thinking, and
turned out to be very correct.

653
00:31:33,770 --> 00:31:37,330
And then finally, as a kind
of mic drop conclusion,

654
00:31:37,330 --> 00:31:42,460
came up with the final
concluding statements.

655
00:31:42,460 --> 00:31:44,500
OK, we know there's a neutron.

656
00:31:44,500 --> 00:31:46,090
We know its mass.

657
00:31:46,090 --> 00:31:52,930
The actual mass of the
neutron is about 1.0087 AMU so

658
00:31:52,930 --> 00:31:57,760
within 0.1% of Chadwick's
calculations and predictions

659
00:31:57,760 --> 00:32:02,410
based on 1930s equipment,
which is strikingly awesome.

660
00:32:02,410 --> 00:32:04,130
And there you have it.

661
00:32:04,130 --> 00:32:06,318
That's the discovery
of the neutron using

662
00:32:06,318 --> 00:32:08,860
most of the concepts that we're
going to be teaching you here

663
00:32:08,860 --> 00:32:10,360
in 22.01.

664
00:32:10,360 --> 00:32:12,550
So right now, I'd say
your scientific knowledge,

665
00:32:12,550 --> 00:32:14,410
if we don't count what
you read on the news,

666
00:32:14,410 --> 00:32:16,930
is roughly around
1850 when all the E&M

667
00:32:16,930 --> 00:32:18,420
stuff was being figured out.

668
00:32:18,420 --> 00:32:21,280
We are going to bring you
screaming into the 1930s.

669
00:32:21,280 --> 00:32:24,670
And by about month 1,
we'll hit the present day

670
00:32:24,670 --> 00:32:27,100
when we can start to talk
about the super heavy elements

671
00:32:27,100 --> 00:32:29,650
like the ones that were
discovered last year.

672
00:32:29,650 --> 00:32:31,403
I think there was
even some this year.

673
00:32:31,403 --> 00:32:33,820
But we'll look at the Physics
Today article from last year

674
00:32:33,820 --> 00:32:35,920
to get to the
point of explaining

675
00:32:35,920 --> 00:32:38,200
why super heavy elements
might be stable.

676
00:32:38,200 --> 00:32:39,940
Why are we even
looking for them?

677
00:32:39,940 --> 00:32:41,645
Where do cosmic rays come from?

678
00:32:41,645 --> 00:32:44,020
How do we know that they're
cosmic rays and not something

679
00:32:44,020 --> 00:32:44,650
else?

680
00:32:44,650 --> 00:32:47,170
How can you tell a reactor
turns on anywhere in the world

681
00:32:47,170 --> 00:32:49,810
by measuring different
bits of radiation, which

682
00:32:49,810 --> 00:32:52,090
is an active defense
project that folks

683
00:32:52,090 --> 00:32:53,530
are pursuing right now?

684
00:32:53,530 --> 00:32:55,960
Lots of really fun questions.

685
00:32:55,960 --> 00:32:58,150
And speaking of
questions, do you guys

686
00:32:58,150 --> 00:33:00,850
have any questions about
what we've explained here,

687
00:33:00,850 --> 00:33:03,670
how we've retraced Chadwick's
discovery of the neutron

688
00:33:03,670 --> 00:33:05,650
from basic nuclear
science principles?

689
00:33:08,830 --> 00:33:12,820
So who here has seen these
nuclear reactions before?

690
00:33:12,820 --> 00:33:13,320
Cool.

691
00:33:13,320 --> 00:33:14,778
This is something
that I hope folks

692
00:33:14,778 --> 00:33:15,990
would cover in high school.

693
00:33:15,990 --> 00:33:17,785
But with a general
trend of watering down

694
00:33:17,785 --> 00:33:20,160
science education, I didn't
want to make any assumptions.

695
00:33:20,160 --> 00:33:22,740
I'm glad to hear
this was covered.

696
00:33:22,740 --> 00:33:25,510
Was this coveted at MIT?

697
00:33:25,510 --> 00:33:27,960
Are you guys relying on
high school knowledge?

698
00:33:27,960 --> 00:33:29,550
OK, good.

699
00:33:29,550 --> 00:33:31,917
Not good.

700
00:33:31,917 --> 00:33:33,000
Good I know where you are.

701
00:33:33,000 --> 00:33:35,010
Not good that MIT doesn't
teach anything nuclear

702
00:33:35,010 --> 00:33:36,180
until year two.

703
00:33:36,180 --> 00:33:37,320
That's OK.

704
00:33:37,320 --> 00:33:39,310
You guys, along with
the Physics Department,

705
00:33:39,310 --> 00:33:43,290
will get at least a 20th-century
knowledge of physics and 21st

706
00:33:43,290 --> 00:33:45,780
by the end of month 1.

707
00:33:45,780 --> 00:33:50,250
So I want to come back
to the Stellar site,

708
00:33:50,250 --> 00:33:51,720
and specifically the syllabus.

709
00:33:51,720 --> 00:33:55,050
I've taken a lot of care to
write a very detailed syllabus

710
00:33:55,050 --> 00:33:59,490
of what we're going to do,
what I expect of you guys, what

711
00:33:59,490 --> 00:34:01,530
you can expect of
me, and what we'll

712
00:34:01,530 --> 00:34:02,950
be doing every single day.

713
00:34:02,950 --> 00:34:04,590
So if you want to
know what we're

714
00:34:04,590 --> 00:34:06,780
going to be doing, if you have
a class that you miss, and you

715
00:34:06,780 --> 00:34:08,655
want to know what notes
you're going to miss,

716
00:34:08,655 --> 00:34:10,530
it's all written up here.

717
00:34:10,530 --> 00:34:13,440
I want to get right
into assignments,

718
00:34:13,440 --> 00:34:15,989
because everyone wants to know
what am I responsible for.

719
00:34:15,989 --> 00:34:17,699
Well, not too much--

720
00:34:17,699 --> 00:34:20,580
nine problems sets,
three quizzes.

721
00:34:20,580 --> 00:34:22,860
The final exam is just a quiz.

722
00:34:22,860 --> 00:34:26,518
It's only worth 24% of
your grade instead of 20

723
00:34:26,518 --> 00:34:28,560
to get the math to work
out, because I eliminated

724
00:34:28,560 --> 00:34:32,550
one problem set to avoid running
afoul of MIT regulations,

725
00:34:32,550 --> 00:34:35,190
but not assigning things
at the last week of class.

726
00:34:35,190 --> 00:34:37,800
But there are three quizzes,
so the final exam is just

727
00:34:37,800 --> 00:34:38,909
another quiz.

728
00:34:38,909 --> 00:34:41,130
It's not a super
high-stress, crazy thing,

729
00:34:41,130 --> 00:34:43,889
because I don't see a
point in doing that.

730
00:34:43,889 --> 00:34:46,440
You can make your
assignments however you want.

731
00:34:46,440 --> 00:34:49,440
I don't care as long
as I can read them.

732
00:34:49,440 --> 00:34:51,989
But I do ask that in the
end, you submit a PDF

733
00:34:51,989 --> 00:34:53,570
file on the Stellar site.

734
00:34:53,570 --> 00:34:55,320
And the reason for
this is my first course

735
00:34:55,320 --> 00:34:57,900
that I ever taught at
MIT as a professor were

736
00:34:57,900 --> 00:35:01,770
the graduate modules, 22.13,
Intro to Nuclear Systems,

737
00:35:01,770 --> 00:35:05,040
and 22.14, Intro to
Nuclear Materials.

738
00:35:05,040 --> 00:35:07,200
I accepted paper submissions.

739
00:35:07,200 --> 00:35:10,020
And by week 3, I had
to microwave them.

740
00:35:10,020 --> 00:35:13,320
Because three or four times,
I definitely saw blood.

741
00:35:13,320 --> 00:35:15,630
And there were also
some weird stains

742
00:35:15,630 --> 00:35:16,950
that I didn't want to explain.

743
00:35:16,950 --> 00:35:20,520
So I added the habit of
unstapling, microwaving,

744
00:35:20,520 --> 00:35:23,130
and re-stapling the
p-sets before grading.

745
00:35:23,130 --> 00:35:25,860
So in the digital
world, it's sterile.

746
00:35:25,860 --> 00:35:26,970
I'm not a germophobe.

747
00:35:26,970 --> 00:35:29,200
I just don't like
blood in my house,

748
00:35:29,200 --> 00:35:30,750
especially if it's not mine.

749
00:35:30,750 --> 00:35:34,860
So I ask that you guys submit
PDFs on the Stellar site.

750
00:35:34,860 --> 00:35:37,860
They're due at 5:00 PM to
make sure that you're done

751
00:35:37,860 --> 00:35:41,108
and you can go home and relax
or work on something else.

752
00:35:41,108 --> 00:35:42,900
I used to some have
things due at midnight,

753
00:35:42,900 --> 00:35:46,020
and I had every
submission was 11:59 PM.

754
00:35:46,020 --> 00:35:47,490
I'm not going to
do that anymore.

755
00:35:47,490 --> 00:35:49,450
Do make sure to submit
15 minutes early.

756
00:35:49,450 --> 00:35:52,140
So if your computer or the
Stellar site has trouble,

757
00:35:52,140 --> 00:35:54,638
send me an email or a
text or whatever saying,

758
00:35:54,638 --> 00:35:56,430
I'm trying to submit,
and it's not working.

759
00:35:56,430 --> 00:35:59,850
Here is a backup, or I'm leaving
something under your door.

760
00:35:59,850 --> 00:36:01,440
And if you want my
cell phone number,

761
00:36:01,440 --> 00:36:02,650
that's also my office number.

762
00:36:02,650 --> 00:36:03,990
It's also my only number.

763
00:36:03,990 --> 00:36:05,792
It's in the MIT directory.

764
00:36:05,792 --> 00:36:08,250
So if there is some emergency
you need to make me aware of,

765
00:36:08,250 --> 00:36:09,360
please do communicate.

766
00:36:09,360 --> 00:36:12,270
I'd rather you tell me than be
worried about not telling me

767
00:36:12,270 --> 00:36:13,743
and then find out later.

768
00:36:13,743 --> 00:36:14,910
So are we all clear on that?

769
00:36:17,980 --> 00:36:20,350
As far as what the
assignments are,

770
00:36:20,350 --> 00:36:23,380
each assignment is going to be
about 50% basic calculations,

771
00:36:23,380 --> 00:36:26,320
working out things like these
to make sure you've mastered

772
00:36:26,320 --> 00:36:28,030
the material, that
you understand

773
00:36:28,030 --> 00:36:31,330
writing nuclear reactions,
you can balance a q equation,

774
00:36:31,330 --> 00:36:33,010
you can tell me about
what your cancer

775
00:36:33,010 --> 00:36:34,977
risk would be from a
certain dose of material.

776
00:36:34,977 --> 00:36:37,060
So this is like when you
go out in the real world,

777
00:36:37,060 --> 00:36:38,470
the sort of
calculations everyone

778
00:36:38,470 --> 00:36:42,320
would expect you as a nuclear
engineer to be able to do.

779
00:36:42,320 --> 00:36:44,350
And then 50% of each
problem set is either

780
00:36:44,350 --> 00:36:48,250
going to be analytical questions
of considerable difficulty.

781
00:36:48,250 --> 00:36:49,540
This is MIT.

782
00:36:49,540 --> 00:36:52,000
We're not just here
to give you the basics

783
00:36:52,000 --> 00:36:53,620
so that you can
regurgitate a textbook

784
00:36:53,620 --> 00:36:55,520
onto the first person who asks.

785
00:36:55,520 --> 00:36:57,520
We're here to make sure
that you can go farther.

786
00:36:57,520 --> 00:36:59,680
Because you guys are
the future of this very

787
00:36:59,680 --> 00:37:02,950
small and diminishing field
at the moment if you look

788
00:37:02,950 --> 00:37:04,960
at the nuclear power in the US.

789
00:37:04,960 --> 00:37:07,190
I would say growing
in terms of the world,

790
00:37:07,190 --> 00:37:08,315
but not in terms of the US.

791
00:37:08,315 --> 00:37:10,815
And you guys are going to be
in charge of leading this field

792
00:37:10,815 --> 00:37:12,468
and determining where
it's going to go.

793
00:37:12,468 --> 00:37:14,260
So you've got to be up
at the cutting edge,

794
00:37:14,260 --> 00:37:17,500
and we're going to take you
to the edge of your abilities.

795
00:37:17,500 --> 00:37:19,480
My favorite kind of
problem is to give

796
00:37:19,480 --> 00:37:23,560
one sentence for the question,
five or 10 pages for the answer

797
00:37:23,560 --> 00:37:25,210
if you don't get the trick.

798
00:37:25,210 --> 00:37:26,340
Now, that's OK.

799
00:37:26,340 --> 00:37:30,083
It's perfectly fine
not to figure out

800
00:37:30,083 --> 00:37:31,000
the answer in the end.

801
00:37:31,000 --> 00:37:33,640
In fact, I'll usually
give you the answer

802
00:37:33,640 --> 00:37:35,590
for the analytical
questions because I

803
00:37:35,590 --> 00:37:37,330
want to see your approach.

804
00:37:37,330 --> 00:37:39,640
I'm not interested in
you nailing the answer.

805
00:37:39,640 --> 00:37:41,830
I'm interested in
seeing how you think.

806
00:37:41,830 --> 00:37:45,190
And copious partial credit will
be given for the way you think.

807
00:37:45,190 --> 00:37:47,562
So if you have a missing
step, and you say,

808
00:37:47,562 --> 00:37:49,770
I don't know the step, I'm
going to assume variable a

809
00:37:49,770 --> 00:37:51,610
and keep going,
you will get credit

810
00:37:51,610 --> 00:37:53,550
for the subsequent steps.

811
00:37:53,550 --> 00:37:56,230
I want to see how you
think from start to finish

812
00:37:56,230 --> 00:37:59,610
and how you cover for holes
that you can't get through.

813
00:37:59,610 --> 00:38:01,050
So everyone clear on that?

814
00:38:01,050 --> 00:38:03,090
Partial credit, yes.

815
00:38:03,090 --> 00:38:06,260
Use it to your fullest ability.

816
00:38:06,260 --> 00:38:07,850
The other half of
the problem sets

817
00:38:07,850 --> 00:38:10,780
will have take-home
laboratory assignments.

818
00:38:10,780 --> 00:38:12,590
It's not just enough
for me to tell you

819
00:38:12,590 --> 00:38:14,120
about nuclear engineering.

820
00:38:14,120 --> 00:38:16,220
You have to see it
for yourself, and you

821
00:38:16,220 --> 00:38:17,910
have to feel it for yourself.

822
00:38:17,910 --> 00:38:20,330
And once in a while, you'll
get a mild electric shock

823
00:38:20,330 --> 00:38:23,030
by yourself if things
go wrong, but that's OK.

824
00:38:23,030 --> 00:38:25,160
It happens to the best of us.

825
00:38:25,160 --> 00:38:26,113
I got zapped by our--

826
00:38:26,113 --> 00:38:28,030
you guys have all made
Geiger counters, right?

827
00:38:28,030 --> 00:38:30,700
Has anyone not made
a Geiger counter yet?

828
00:38:30,700 --> 00:38:31,480
Oh, OK.

829
00:38:31,480 --> 00:38:33,890
It sounds like we need
to run another workshop.

830
00:38:33,890 --> 00:38:37,750
Well, our Geiger counters
rely on a neat little boost

831
00:38:37,750 --> 00:38:40,300
converter power supply
that takes 9 volts

832
00:38:40,300 --> 00:38:44,380
and steps it up to 400 volts
via some switching things.

833
00:38:44,380 --> 00:38:46,658
That means you have 400
volts on a big metal tube.

834
00:38:46,658 --> 00:38:48,200
And if you're working
on your circuit

835
00:38:48,200 --> 00:38:51,250
and you happen to brush against
it, you get zero current,

836
00:38:51,250 --> 00:38:56,020
so it doesn't hurt you in the
medical sense, but it hurts.

837
00:38:56,020 --> 00:38:58,930
I also have a dance I
call the 60 Hertz shuffle.

838
00:38:58,930 --> 00:39:01,300
It's the high speed
shaking that you

839
00:39:01,300 --> 00:39:03,398
do when you're
connected to 60 Hertz

840
00:39:03,398 --> 00:39:04,690
somewhere from the wall outlet.

841
00:39:04,690 --> 00:39:06,398
None of you guys will
be exposed to this,

842
00:39:06,398 --> 00:39:08,200
but I've done it
enough times that I

843
00:39:08,200 --> 00:39:10,300
have a name for the dance.

844
00:39:10,300 --> 00:39:12,640
If you get 400 volts,
you'll just kind of scream.

845
00:39:12,640 --> 00:39:15,730
And I don't care how
manly men you guys are.

846
00:39:15,730 --> 00:39:19,480
Everyone makes the same
pitch scream with 400 volts.

847
00:39:19,480 --> 00:39:24,010
We're all equal in the
eyes of electricity.

848
00:39:24,010 --> 00:39:25,780
For these laboratory
questions, I'm

849
00:39:25,780 --> 00:39:28,180
going to ask you to both
complete an assignment where

850
00:39:28,180 --> 00:39:31,720
you'll, for example, measure
the half-life of uranium,

851
00:39:31,720 --> 00:39:34,930
measure the radioactivity
of one banana, confirm

852
00:39:34,930 --> 00:39:37,060
or refute the
linear no threshold

853
00:39:37,060 --> 00:39:38,860
hypothesis of the dose.

854
00:39:38,860 --> 00:39:41,170
And the experiment itself
won't take that long,

855
00:39:41,170 --> 00:39:46,000
but I want you to write it up in
proper documented format using

856
00:39:46,000 --> 00:39:46,760
these sections.

857
00:39:46,760 --> 00:39:48,427
So I'm going to be
teaching you guys how

858
00:39:48,427 --> 00:39:50,940
to write scientific articles.

859
00:39:50,940 --> 00:39:53,890
So actually, this is kind of
a good time to ask you guys.

860
00:39:53,890 --> 00:39:56,910
How would you define
the word "science?"

861
00:39:56,910 --> 00:39:57,910
Luke, what do you think?

862
00:40:00,530 --> 00:40:03,410
AUDIENCE: It's a process
of getting knowledge

863
00:40:03,410 --> 00:40:08,568
by fitting theories
to empirical evidence.

864
00:40:08,568 --> 00:40:10,610
MIKE SHORT: Gaining
knowledge by fitting theories

865
00:40:10,610 --> 00:40:11,550
to empirical evidence.

866
00:40:11,550 --> 00:40:12,050
OK.

867
00:40:12,050 --> 00:40:14,660
So I hear knowledge
gaining by some sort

868
00:40:14,660 --> 00:40:18,090
of well-justified and
accepted means, right?

869
00:40:18,090 --> 00:40:21,110
Monica, what do you think?

870
00:40:21,110 --> 00:40:24,960
AUDIENCE: Science is the
study of the natural world

871
00:40:24,960 --> 00:40:30,450
through patterns and
mathematics, I suppose.

872
00:40:30,450 --> 00:40:31,440
MIKE SHORT: Cool, yeah.

873
00:40:31,440 --> 00:40:33,482
Let's say the studying,
modeling, and abstraction

874
00:40:33,482 --> 00:40:37,230
of the natural world into
ways we can understand.

875
00:40:37,230 --> 00:40:40,182
Jared, what would you say?

876
00:40:40,182 --> 00:40:41,015
AUDIENCE: Which one?

877
00:40:41,015 --> 00:40:43,470
MIKE SHORT: Oh,
there's two Jareds.

878
00:40:43,470 --> 00:40:46,200
I want to hear both,
and then I'll--

879
00:40:46,200 --> 00:40:47,970
yeah.

880
00:40:47,970 --> 00:40:49,725
AUDIENCE: Science is--

881
00:40:53,306 --> 00:40:55,730
I'd probably go with
it's the same thing

882
00:40:55,730 --> 00:41:00,480
Luke said, gaining knowledge
through experimentation

883
00:41:00,480 --> 00:41:01,920
and trial.

884
00:41:01,920 --> 00:41:02,800
MIKE SHORT: Cool.

885
00:41:02,800 --> 00:41:04,050
And other Jared?

886
00:41:04,050 --> 00:41:08,230
AUDIENCE: I think what Luke
said about fitting theories

887
00:41:08,230 --> 00:41:10,750
to empirical evidence and
testing them that way.

888
00:41:10,750 --> 00:41:11,678
MIKE SHORT: OK, cool.

889
00:41:11,678 --> 00:41:12,220
I like these.

890
00:41:12,220 --> 00:41:14,590
And these are the
generally accepted theories

891
00:41:14,590 --> 00:41:16,800
and descriptions I've
heard of science.

892
00:41:16,800 --> 00:41:18,940
And I want to pose a
question to you guys.

893
00:41:18,940 --> 00:41:21,700
If a tree falls in the woods
and nobody is around to hear it,

894
00:41:21,700 --> 00:41:22,880
can it win the Nobel Prize?

895
00:41:27,880 --> 00:41:29,120
It's kind of an expression.

896
00:41:29,120 --> 00:41:33,010
So if somebody
discovered the neutron,

897
00:41:33,010 --> 00:41:34,480
and they wrote up
their findings,

898
00:41:34,480 --> 00:41:37,270
and proved that it exists,
and they put it in their desk,

899
00:41:37,270 --> 00:41:39,700
and the house burned
down, and the person died,

900
00:41:39,700 --> 00:41:43,710
was the neutron discovered?

901
00:41:43,710 --> 00:41:45,080
What does discovered mean?

902
00:41:50,030 --> 00:41:53,570
So to me, science is
equal parts everything you

903
00:41:53,570 --> 00:41:56,620
guys said and communication.

904
00:41:56,620 --> 00:42:00,040
If you discover something
and you don't tell anyone,

905
00:42:00,040 --> 00:42:03,870
the information
technically doesn't exist.

906
00:42:03,870 --> 00:42:05,010
It dies with you.

907
00:42:05,010 --> 00:42:06,503
And you don't want
that to happen.

908
00:42:06,503 --> 00:42:08,670
So I want to make sure that
you guys both understand

909
00:42:08,670 --> 00:42:13,050
the science and understand the
importance of communicating it

910
00:42:13,050 --> 00:42:13,980
effectively to people.

911
00:42:13,980 --> 00:42:15,522
Because that's the
other thing you're

912
00:42:15,522 --> 00:42:17,670
going to be doing as
leaders in this field

913
00:42:17,670 --> 00:42:19,360
is explaining things.

914
00:42:19,360 --> 00:42:22,110
You better believe when
Fukushima happened--

915
00:42:22,110 --> 00:42:23,460
I was a postdoc at the time.

916
00:42:23,460 --> 00:42:27,630
I was not a person, I guess,
in the academic sense.

917
00:42:27,630 --> 00:42:29,190
People here treated
me very well,

918
00:42:29,190 --> 00:42:32,100
but I was also very aware that
I was not one of the greats.

919
00:42:32,100 --> 00:42:34,470
Still I am not old enough yet.

920
00:42:34,470 --> 00:42:37,260
I was getting calls all
day, all night from news

921
00:42:37,260 --> 00:42:39,060
agencies saying, you're at MIT.

922
00:42:39,060 --> 00:42:40,680
I saw your name
on the directory.

923
00:42:40,680 --> 00:42:44,330
Do a radio interview and tell
us all if we're going to die.

924
00:42:44,330 --> 00:42:46,740
And you can only imagine what
the professors on this hall

925
00:42:46,740 --> 00:42:47,370
were dealing with.

926
00:42:47,370 --> 00:42:49,370
So folks were traveling
around, answering things

927
00:42:49,370 --> 00:42:50,280
left and right.

928
00:42:50,280 --> 00:42:52,770
I ended up doing some weird
podcast on a Brazilian news

929
00:42:52,770 --> 00:42:54,600
channel that I don't
think ever got aired

930
00:42:54,600 --> 00:42:56,320
and stopped doing it after that.

931
00:42:56,320 --> 00:42:58,950
You as undergrads even
might be called if somebody

932
00:42:58,950 --> 00:43:00,630
wants to know something.

933
00:43:00,630 --> 00:43:03,060
And so it's best that you
not only know the material,

934
00:43:03,060 --> 00:43:05,430
but you can convey
it effectively,

935
00:43:05,430 --> 00:43:09,210
briefly, and in a way that
your audience can understand.

936
00:43:09,210 --> 00:43:12,450
The audience for these
articles is any undergraduate

937
00:43:12,450 --> 00:43:14,550
in any engineering
program anywhere.

938
00:43:14,550 --> 00:43:16,872
That's your lowest
common denominator--

939
00:43:16,872 --> 00:43:18,330
not to say that
that's a bad thing,

940
00:43:18,330 --> 00:43:21,810
but it is the audience that you
want to aim your writing at.

941
00:43:21,810 --> 00:43:23,640
So what I want you
to be able to do

942
00:43:23,640 --> 00:43:28,170
is say what you did, why you
did it, and what it means.

943
00:43:28,170 --> 00:43:32,040
In communication terms, this
means a less-than-100-word

944
00:43:32,040 --> 00:43:36,300
abstract, a very brief synopsis
of what you did and why

945
00:43:36,300 --> 00:43:37,380
it's important.

946
00:43:37,380 --> 00:43:38,190
That's the teaser.

947
00:43:38,190 --> 00:43:40,680
This is the trailer to make
somebody read what you actually

948
00:43:40,680 --> 00:43:42,270
did and see why they care.

949
00:43:42,270 --> 00:43:44,040
This is the main
method and currency

950
00:43:44,040 --> 00:43:45,540
through which
scientists communicate

951
00:43:45,540 --> 00:43:47,860
is articles of this type.

952
00:43:47,860 --> 00:43:50,160
An introduction and
background which

953
00:43:50,160 --> 00:43:52,450
says why are we
studying this problem.

954
00:43:52,450 --> 00:43:54,420
And the answer is not
because I told you to,

955
00:43:54,420 --> 00:43:56,230
and your grade depends on it.

956
00:43:56,230 --> 00:43:59,040
I want you to think about why
this problem is important,

957
00:43:59,040 --> 00:44:01,680
and put it into
context, and give

958
00:44:01,680 --> 00:44:03,900
any of the scientific
background to understand

959
00:44:03,900 --> 00:44:07,530
what's going to come next,
like the experimental section.

960
00:44:07,530 --> 00:44:10,260
Describe what you did in nitty
gritty scientific detail.

961
00:44:10,260 --> 00:44:11,970
This is usually the easy part.

962
00:44:11,970 --> 00:44:16,560
I put this gamma ray in this
bucket, and it made this color,

963
00:44:16,560 --> 00:44:21,180
and I made this noise, whatever.

964
00:44:21,180 --> 00:44:22,800
A results section
where you show all

965
00:44:22,800 --> 00:44:25,480
of your data and a
discussion section--

966
00:44:25,480 --> 00:44:27,040
notice that these are different.

967
00:44:27,040 --> 00:44:29,310
You want to separate
your actual results

968
00:44:29,310 --> 00:44:31,500
from your interpretation
of your results,

969
00:44:31,500 --> 00:44:35,670
because someone else may have
a very different interpretation

970
00:44:35,670 --> 00:44:36,780
of results--

971
00:44:36,780 --> 00:44:39,790
for example, Chadwick.

972
00:44:39,790 --> 00:44:43,930
Somebody found that
beryllium bombarded

973
00:44:43,930 --> 00:44:45,820
by alpha particles
emitted radiation

974
00:44:45,820 --> 00:44:47,050
of great penetrating power.

975
00:44:47,050 --> 00:44:50,680
That's the result. The
interpretation or discussion

976
00:44:50,680 --> 00:44:53,710
said it's probably a
Compton-like effect

977
00:44:53,710 --> 00:44:54,760
from a photon.

978
00:44:54,760 --> 00:44:57,490
By separating your results
and your discussion,

979
00:44:57,490 --> 00:45:00,280
you allow people to mentally
say, OK, I get your results.

980
00:45:00,280 --> 00:45:02,290
I believe that you
found these numbers.

981
00:45:02,290 --> 00:45:03,918
I have a different explanation.

982
00:45:03,918 --> 00:45:05,710
And you all may have
different explanations

983
00:45:05,710 --> 00:45:07,540
for what you see
in your own labs,

984
00:45:07,540 --> 00:45:10,490
because you're also probably
going to get different results.

985
00:45:10,490 --> 00:45:13,330
And then finally, a conclusion
where you quickly re-summarize

986
00:45:13,330 --> 00:45:14,950
your major contributions.

987
00:45:14,950 --> 00:45:16,810
Your abstract is the teaser.

988
00:45:16,810 --> 00:45:19,930
Your conclusion is like your
re-abstract with the context

989
00:45:19,930 --> 00:45:21,190
that people now believe--

990
00:45:21,190 --> 00:45:24,358
or don't-- what you did.

991
00:45:24,358 --> 00:45:26,150
And think about how
you guys read articles.

992
00:45:26,150 --> 00:45:30,140
So who here has read
scientific articles before?

993
00:45:30,140 --> 00:45:31,880
More than half of you.

994
00:45:31,880 --> 00:45:32,930
Let's see.

995
00:45:32,930 --> 00:45:35,945
Alex, what do you read first?

996
00:45:35,945 --> 00:45:38,750
AUDIENCE: If it's a journal,
probably the abstract.

997
00:45:38,750 --> 00:45:41,940
But given that I'm mostly
interested in the topic,

998
00:45:41,940 --> 00:45:43,678
I tend to go to the
conclusion section.

999
00:45:43,678 --> 00:45:44,720
MIKE SHORT: That's right.

1000
00:45:44,720 --> 00:45:45,200
OK.

1001
00:45:45,200 --> 00:45:46,010
I'm glad you said that.

1002
00:45:46,010 --> 00:45:47,180
That was my next question.

1003
00:45:47,180 --> 00:45:48,590
You read the abstract.

1004
00:45:48,590 --> 00:45:50,660
The next thing you
read is the conclusion.

1005
00:45:50,660 --> 00:45:52,160
The next thing you
usually read is

1006
00:45:52,160 --> 00:45:54,110
you skim through the
results and the figures

1007
00:45:54,110 --> 00:45:55,700
and see if it's
worth looking at.

1008
00:45:55,700 --> 00:45:58,490
Then if you're like, OK,
this is worth my time,

1009
00:45:58,490 --> 00:46:00,920
then you slog through
and read everything

1010
00:46:00,920 --> 00:46:02,870
to make sure you
understand it all.

1011
00:46:02,870 --> 00:46:04,640
So when you're writing
these articles,

1012
00:46:04,640 --> 00:46:07,803
think about who's reading
them and how they read them.

1013
00:46:07,803 --> 00:46:10,220
Because if you guys don't tend
to read an article from top

1014
00:46:10,220 --> 00:46:12,290
to bottom, neither
will your audience.

1015
00:46:12,290 --> 00:46:13,250
And that's true.

1016
00:46:13,250 --> 00:46:16,010
Most scientists skim things
because we have a lot to read.

1017
00:46:16,010 --> 00:46:17,460
So that's OK.

1018
00:46:17,460 --> 00:46:20,750
And I am very interested
in you guys completely

1019
00:46:20,750 --> 00:46:22,130
documenting your experiment.

1020
00:46:22,130 --> 00:46:25,040
Pictures are also
awesome to use.

1021
00:46:25,040 --> 00:46:26,660
Accuracy of results
and analysis--

1022
00:46:26,660 --> 00:46:29,360
so did you round when
you weren't supposed to?

1023
00:46:29,360 --> 00:46:32,380
Did you have a clear numerical
typo that you can't explain?

1024
00:46:32,380 --> 00:46:34,070
And the readability
of the report--

1025
00:46:34,070 --> 00:46:37,400
I want you to spend time
making this readable.

1026
00:46:37,400 --> 00:46:39,260
I expect that this
part of the assignment

1027
00:46:39,260 --> 00:46:42,830
will take roughly five hours,
whereas the basic questions

1028
00:46:42,830 --> 00:46:45,020
will take roughly three
to four hours depending

1029
00:46:45,020 --> 00:46:46,310
on how well you're doing.

1030
00:46:46,310 --> 00:46:48,470
And that leaves three
hours of class time

1031
00:46:48,470 --> 00:46:51,380
and a couple hours for
whatever else happens in life,

1032
00:46:51,380 --> 00:46:53,730
let's call it.

1033
00:46:53,730 --> 00:46:55,817
Since you've never
written these before--

1034
00:46:55,817 --> 00:46:56,400
wait a minute.

1035
00:46:56,400 --> 00:46:57,275
I shouldn't say that.

1036
00:46:57,275 --> 00:46:59,370
Who's written these
kinds of things before?

1037
00:46:59,370 --> 00:47:01,530
Anyone here wrote a
scientific article?

1038
00:47:01,530 --> 00:47:02,030
Two.

1039
00:47:02,030 --> 00:47:03,380
OK, three.

1040
00:47:03,380 --> 00:47:04,193
Cool.

1041
00:47:04,193 --> 00:47:05,610
So most of you
haven't, and that's

1042
00:47:05,610 --> 00:47:07,470
where I assumed you'd all be.

1043
00:47:07,470 --> 00:47:10,470
We have a whole lab dedicated to
scientific communication called

1044
00:47:10,470 --> 00:47:12,900
the Comm Lab run by
someone, who happens

1045
00:47:12,900 --> 00:47:14,820
to be my wife, four doors down.

1046
00:47:14,820 --> 00:47:17,580
We live and work
next to each other.

1047
00:47:17,580 --> 00:47:18,840
It's pretty cool.

1048
00:47:18,840 --> 00:47:20,970
And you get an automatic
three-day extension

1049
00:47:20,970 --> 00:47:23,760
on the lab assignment if
you go to the Comm Lab.

1050
00:47:23,760 --> 00:47:25,420
There are three
reasons for this.

1051
00:47:25,420 --> 00:47:27,750
One, I want you to
get better grades,

1052
00:47:27,750 --> 00:47:29,730
so I want you to learn
how to communicate.

1053
00:47:29,730 --> 00:47:32,340
Two, I don't want to spend
time trying to figure out

1054
00:47:32,340 --> 00:47:33,870
what you were trying to say.

1055
00:47:33,870 --> 00:47:37,050
So better articles means
less grading time for me.

1056
00:47:37,050 --> 00:47:40,410
And three-- OK, let's
just say it's two reasons.

1057
00:47:40,410 --> 00:47:42,180
That's enough.

1058
00:47:42,180 --> 00:47:45,000
And for everything
except for the quizzes,

1059
00:47:45,000 --> 00:47:47,070
it's perfectly OK
to work together

1060
00:47:47,070 --> 00:47:49,860
as long as you
attribute who did what,

1061
00:47:49,860 --> 00:47:52,890
you write your own articles,
don't Xerox anything,

1062
00:47:52,890 --> 00:47:54,360
and say who took the data.

1063
00:47:54,360 --> 00:47:56,820
So if the whole class wants
to get together and take one

1064
00:47:56,820 --> 00:47:59,150
set of data and
work for that, fine.

1065
00:47:59,150 --> 00:48:00,900
If you all want to do
the labs yourselves,

1066
00:48:00,900 --> 00:48:03,090
which I highly recommend, fine.

1067
00:48:03,090 --> 00:48:05,100
But I'm not going
to tell you how

1068
00:48:05,100 --> 00:48:08,040
to do the lab assignment
in this, as long as you

1069
00:48:08,040 --> 00:48:09,600
say what you did.

1070
00:48:09,600 --> 00:48:12,330
And I want all of you,
if you haven't yet,

1071
00:48:12,330 --> 00:48:16,740
to head to integrity.mit.edu
to see our official policies

1072
00:48:16,740 --> 00:48:19,500
on what is considered
plagiarism, what is considered

1073
00:48:19,500 --> 00:48:22,920
working together, what's
considered academic honesty.

1074
00:48:22,920 --> 00:48:25,050
I will assume, because
it's on the syllabus

1075
00:48:25,050 --> 00:48:27,750
and I'm telling you now,
that you've all read this,

1076
00:48:27,750 --> 00:48:29,210
and that there will
be no cheating.

1077
00:48:29,210 --> 00:48:32,040
It's just not something that's
part of my job description,

1078
00:48:32,040 --> 00:48:33,525
and I don't want
to deal with it,

1079
00:48:33,525 --> 00:48:34,900
which means I
won't deal with it,

1080
00:48:34,900 --> 00:48:38,170
which means the
consequences will be severe.

1081
00:48:38,170 --> 00:48:41,700
So I don't think I'll
have to worry about that.

1082
00:48:41,700 --> 00:48:43,930
And then for the late
policy, it's just 10%

1083
00:48:43,930 --> 00:48:46,780
of the value of assignment
for each calendar day, not

1084
00:48:46,780 --> 00:48:48,200
each business day.

1085
00:48:48,200 --> 00:48:50,620
So if you're running really
late and you haven't started

1086
00:48:50,620 --> 00:48:54,700
an assignment the day it's due,
better to take the 10% penalty

1087
00:48:54,700 --> 00:48:58,430
and do really well than
hand in nothing on time.

1088
00:48:58,430 --> 00:49:00,160
So keep in mind how
can you maximize

1089
00:49:00,160 --> 00:49:01,930
the points in this course.

1090
00:49:01,930 --> 00:49:04,330
I'd rather you hand
in something good late

1091
00:49:04,330 --> 00:49:06,080
than terrible on time.

1092
00:49:06,080 --> 00:49:10,180
So if you really need that extra
day if MIT gets crazy, take it.

1093
00:49:10,180 --> 00:49:13,030
10% of a problem set is
0.4 points on your grade.

1094
00:49:13,030 --> 00:49:16,340
It's not that big a deal.

1095
00:49:16,340 --> 00:49:19,430
Then as far as the syllabus, I
want to show you very quickly.

1096
00:49:19,430 --> 00:49:21,470
We've got when things are due.

1097
00:49:21,470 --> 00:49:24,140
I'm going to change these dates
to basically just shift them

1098
00:49:24,140 --> 00:49:25,790
all forward by
one day to account

1099
00:49:25,790 --> 00:49:28,580
for the new Tuesday,
Thursday classes.

1100
00:49:28,580 --> 00:49:30,860
So I've got when the
problem sets are due.

1101
00:49:30,860 --> 00:49:33,530
And Friday is
recitation activities.

1102
00:49:33,530 --> 00:49:35,300
If there aren't
too many questions

1103
00:49:35,300 --> 00:49:37,400
on a particular
Friday, I have a lot

1104
00:49:37,400 --> 00:49:39,020
of fun stuff in store for you.

1105
00:49:39,020 --> 00:49:40,690
For example,
tomorrow we're going

1106
00:49:40,690 --> 00:49:44,060
to be talking about radiation
utilizing technology, including

1107
00:49:44,060 --> 00:49:47,000
plasma sputter coders, one of
which we have set up in my lab,

1108
00:49:47,000 --> 00:49:48,230
and I'd like to show you.

1109
00:49:48,230 --> 00:49:49,730
Because it's a way
that you can coat

1110
00:49:49,730 --> 00:49:51,530
materials and other
materials, and you

1111
00:49:51,530 --> 00:49:54,800
have to generate this beautiful,
glowing purple plasma in order

1112
00:49:54,800 --> 00:49:55,800
to do so.

1113
00:49:55,800 --> 00:49:58,820
So you ionize nitrogen. You
induce sputtering, which

1114
00:49:58,820 --> 00:50:01,400
is a radiation damage process
which we'll be going over,

1115
00:50:01,400 --> 00:50:03,632
to coat things in other things.

1116
00:50:03,632 --> 00:50:05,090
There will be once
in a while where

1117
00:50:05,090 --> 00:50:08,030
I have to shift a class into
recitation because I'll be

1118
00:50:08,030 --> 00:50:10,210
at Westinghouse or in Russia.

1119
00:50:10,210 --> 00:50:12,530
And I think that's only
twice during the whole year.

1120
00:50:12,530 --> 00:50:13,790
So you won't miss any classes.

1121
00:50:13,790 --> 00:50:15,770
We'll just use the
recitation time.

1122
00:50:15,770 --> 00:50:17,780
And then other,
times we'll be doing

1123
00:50:17,780 --> 00:50:20,480
measuring the radioactivity
of banana hashes.

1124
00:50:20,480 --> 00:50:23,270
Or once we talk about
electron interactions,

1125
00:50:23,270 --> 00:50:26,720
we're going to go use a
scanning electron microscope.

1126
00:50:26,720 --> 00:50:29,120
The carrot at the end of
the stick to make sure

1127
00:50:29,120 --> 00:50:31,280
that you guys do well--

1128
00:50:31,280 --> 00:50:35,330
the top two people performing
on the quizzes get to pilot

1129
00:50:35,330 --> 00:50:39,020
and choose the samples for
the SEM and elemental analysis

1130
00:50:39,020 --> 00:50:41,360
and the focused ion
beam demonstration.

1131
00:50:41,360 --> 00:50:44,870
So you guys get to pilot
something that's, let's

1132
00:50:44,870 --> 00:50:47,480
say, as complicated as a
space shuttle but deals

1133
00:50:47,480 --> 00:50:49,340
with things much, much smaller.

1134
00:50:49,340 --> 00:50:50,840
So I'll put you in
the driver's seat

1135
00:50:50,840 --> 00:50:52,070
in the machines of
our lab, and you

1136
00:50:52,070 --> 00:50:54,153
get to bring whatever you
want to analyze and find

1137
00:50:54,153 --> 00:50:57,325
the elemental analysis of
and use the world's smallest

1138
00:50:57,325 --> 00:50:58,700
machining instrument
that can cut

1139
00:50:58,700 --> 00:51:01,940
5-nanometer slices of things
using processes that we're

1140
00:51:01,940 --> 00:51:03,508
going to discuss in this class.

1141
00:51:03,508 --> 00:51:05,550
So the better you do, the
more you get to use it.

1142
00:51:08,390 --> 00:51:10,640
And at the end, we'll
have a nice debate.

1143
00:51:10,640 --> 00:51:12,970
I call it arguing
with Greenpeace

1144
00:51:12,970 --> 00:51:14,720
when we'll talk
about-- now that you'll

1145
00:51:14,720 --> 00:51:17,930
have known all of the nuclear
science and engineering

1146
00:51:17,930 --> 00:51:20,090
and can speak
scientifically about topics,

1147
00:51:20,090 --> 00:51:23,420
we're going to go after a lot
of societal misconceptions.

1148
00:51:23,420 --> 00:51:25,460
Do cell phones cause cancer?

1149
00:51:25,460 --> 00:51:28,910
Does living near a nuclear
power plant cause cancer?

1150
00:51:28,910 --> 00:51:32,010
Does arguing with
Greenpeace cause cancer,

1151
00:51:32,010 --> 00:51:33,110
whatever it's going to be?

1152
00:51:33,110 --> 00:51:35,120
So I want to make sure
that you're well-equipped

1153
00:51:35,120 --> 00:51:37,580
and confident enough to
go out there and hold

1154
00:51:37,580 --> 00:51:40,580
your own in a vigorous debate
with an angry, emotional

1155
00:51:40,580 --> 00:51:41,960
environmentalist.

1156
00:51:41,960 --> 00:51:46,670
You guys will be calm, peaceful,
and informed environmentalists.

1157
00:51:46,670 --> 00:51:49,460
After all, that's why a
lot of us are here, is we

1158
00:51:49,460 --> 00:51:51,470
want nuclear energy
to happen because we

1159
00:51:51,470 --> 00:51:52,610
care about the environment.

1160
00:51:52,610 --> 00:51:54,110
There's other people
that don't want

1161
00:51:54,110 --> 00:51:55,652
nuclear energy to
happen because they

1162
00:51:55,652 --> 00:51:57,080
care about the environment.

1163
00:51:57,080 --> 00:51:59,687
To each their own, I
guess, motivations.

1164
00:51:59,687 --> 00:52:01,520
But I want to make sure
you're well equipped

1165
00:52:01,520 --> 00:52:05,090
to also tackle things like
is food irradiation bad.

1166
00:52:05,090 --> 00:52:08,510
That there's all sorts of
websites with dancing babies

1167
00:52:08,510 --> 00:52:10,730
and weird Geocities-like
graphics saying

1168
00:52:10,730 --> 00:52:12,290
food irradiation is evil.

1169
00:52:12,290 --> 00:52:14,450
You won't find a lot
of scientific articles

1170
00:52:14,450 --> 00:52:15,890
if that's the case.

1171
00:52:15,890 --> 00:52:17,918
And to see if you'll
put your, let's

1172
00:52:17,918 --> 00:52:19,460
say, cancer risk
where your mouth is,

1173
00:52:19,460 --> 00:52:21,770
the last day of class, we'll
have an irradiated fruit

1174
00:52:21,770 --> 00:52:24,920
party where I'll be buying
only the kinds of fruit that

1175
00:52:24,920 --> 00:52:28,220
can be imported into the US
because food irradiation is

1176
00:52:28,220 --> 00:52:29,030
done.

1177
00:52:29,030 --> 00:52:31,810
Otherwise, the USDA would
not let it into the country.

1178
00:52:31,810 --> 00:52:34,910
And this is mostly things like
mangosteens from Thailand,

1179
00:52:34,910 --> 00:52:36,640
pineapple from Costa Rica.

1180
00:52:36,640 --> 00:52:39,050
And interestingly
enough, Hawaii is

1181
00:52:39,050 --> 00:52:42,140
considered a different
country agriculturally.

1182
00:52:42,140 --> 00:52:45,230
It is so far away that they have
different agricultural pests.

1183
00:52:45,230 --> 00:52:46,730
And without
irradiation, we couldn't

1184
00:52:46,730 --> 00:52:48,680
import some of the
produce from Hawaii,

1185
00:52:48,680 --> 00:52:51,810
because it could decimate some
of the crops in the Continental

1186
00:52:51,810 --> 00:52:52,640
US.

1187
00:52:52,640 --> 00:52:54,520
Pretty crazy, huh?

1188
00:52:54,520 --> 00:52:55,150
Yeah.

1189
00:52:55,150 --> 00:52:58,330
It's the-- what, it's the 49th
state, but agriculturally,

1190
00:52:58,330 --> 00:52:59,960
a different country.

1191
00:52:59,960 --> 00:53:03,560
So it's about 5 till, so
I'm going to stop here.

1192
00:53:03,560 --> 00:53:06,620
And we will start with
radiation-utilizing technology

1193
00:53:06,620 --> 00:53:11,180
on Friday, tomorrow,
downstairs in Room 24-121.

1194
00:53:11,180 --> 00:53:14,420
And then we'll move over
to my lab at 2 o'clock

1195
00:53:14,420 --> 00:53:17,080
to see the plasma sputter coder.