Nam Đỗ Blog

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this element that makes it different—the fact that the thoughts go one way and not the 
other. 
Dylan: Okay ... has directions. It sounds logical. And what about the other subjects, such 
as Political Science? There’s no predictable order to that. 
Emily: Well, for that I’d just put my notes in a line, that is, in linear, or straight-line 
fashion, and these notes would use symbols, of course, to save time. 
Dylan: Okay, that just leaves Mass Media. 
Emily: For that, I wouldn’t have any special design at all. As you say, sometimes it’s 
impossible to predict in what way lecturers will present their information, in which case 
the best you can do is pre-write headings, but not specific, just general, as in Main One, 
Main Two, Sub One, Two, and Three, and so on.
Dylan: Okay. 
Emily: But always be prepared to adapt to the nature of the talk, using any one of the 
other methods if it becomes appropriate at the time. 
SECTION 4 
You will hear a lecturer talking about an unusual atomic particle, called the neutrino. 
When considering the smallest unit of matter—the atom — most people know of 
electrons, protons, and neutrons, but almost none know of another particle, even though 
they are constantly emitted from the sun in the trillions, with 100 to 200 billion of 
them regularly passing through your body every second. To repeat, that’s not thousands, 
not millions, but billions, every second. You don’t feel them because they are small, in 
fact, so tiny that we can barely detect their presence at all. These mysterious particles are 
called neutrinos. 

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Despite such an abundance, detecting them is a huge undertaking, and there are many 
reasons for this. Firstly, the neutrino itself is so small that you need to eliminate 
absolutely all other particles around. To do this, you need what is called a clean room, 
one that has an extremely low level of dust, microbes, floating particles, or chemical 
vapours. You probably don’t know it, but the air around you right now has almost 40 
million particles per cubic meter. In contrast, the cleanest of clean rooms has less than 10. 
The second problem is that you also need an environment with absolutely no 
background radiation. At the surface of the Earth, such radiation is all around, from the 
sun and sky, and from TVs and communication devices. The only way to screen out all 
that is to go underground, and I mean deep underground. For example, the Sudbury 
Neutrino Observatory in Canada uses an old nickel mine, one of the deepest in the world, 
and puts the Observatory in its lowest tunnel, more than two kilometers below the 
surface. At such depths, stray radiation is sufficiently screened out to allow neutrinos 
only to pass by. 
The final problem is that you need an elaborate detection system, and this apparatus is 
huge, and its installation in this deep underground cavity presents quite a headache. 
Holding such a weighty construction safe and secure requires complexengineering work, 
such as rock-bolting and support structuring. This obviously requires great care, and takes 
a lot of effort. 
So, I've told you about the difficulty in delecting neutrinos. They are tiny, virtually 
weightless, have no electric charge, and hardly interact with anything at all. Yet 
we can detect them, and to see how, let’s consider the Sudbury installation once again. 
The detector there consists of a spherical container filled with heavy water. This rests 
inside another vessel tilled with normal water, which helps support the weight of the 
inner sphere, as well as providing further shielding from any stray radiation. At the edge 
of this inner sphere are about 10,000 electronic detectors. These tire extremely 
sensitive, able to multiply a hundred million limes any electric current which occurs. 

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