(#40) Nuclear Bombs – English listening with subtitles, script, questions, answers


Okay. Hi. Nuclear bombs. Ten minutes. Go. Right we’re going to talk about nuclear bombs
today. We can’t talk about nuclear bombs without
talking about how they work. So, we have to try and understand two different
processes: fission and fusion. I’m going to try and explain both these processes,
however my background is in English literature not in physics, so I’ll do my best. Here we go. Fission first. Fission means splitting up of something. In this case, splitting up of an atom. What happens in nuclear fission is you get
an unstable isotope, usually something like uranium 235, and what that is is an atom that
has the same number of protons but a different number of neutrons. And they fire a neutron at that atom very
very fast. And when that neutron hits the atom it makes
it unstable and the atom breaks into two halves. In the separation process it releases a vast
amount of energy and also it releases neutrons again, and those neutrons hit another atom
which split that up and those neutrons hit another atom, and this keeps going. We have a cycle. It goes critical. OK? That’s how nuclear fission works. Nuclear fission is used in any nuclear power
station … nuclear reactor. They use nuclear fission to produce energy. They use the energy to heat water. They use this resulting steam to drive a generator
which makes electricity, of course. The problem with nuclear fission is you get
a leftover product. You get a lot of radioactive matter that’s
left behind and that has to be stored and it stays radioactive for tens of thousands
of years. So, they have to bury it in different places. A lot of problems with that. Fusion. Now, fusion means putting things together. If you fuse two things together, you put them
together. So, what happens in fusion is two separate
elements merge to make another one. You have low mass isotopes, something like
hydrogen, which unite under very high pressure and a very high temperature. The sun makes its power … the sun makes
its energy through nuclear fusion. On the sun, you have two materials, tritium
and deuterium, which fuse together to make helium. When these two elements fuse together, they
create a vast amount of energy. Nuclear fusion makes more energy than nuclear
fission. There are also no byproducts. The sun has so much energy … so much material
that it’s going to be doing nuclear fusion for the next 10 billion years. There are many problems with nuclear fusion
we can’t actually do it yet because it has to be ignited under a perfect … in under
perfect conditions. It must be the perfect temperature, not too
hot or not too cold, and it must have an ignition source which is very difficult to do. We’re going to talk about that in a little
bit as well. One of the goals of course for the future
is cold fusion, where you can make a fusion reaction happen without the heat. We’ll talk about that in a bit. Anyway, let’s go back to fission. So, a man called Otto Hahn discovered nuclear
fission in 1934. Now, a lot of research put into that, of course,
but, as with anything, most of the research money came about when World War Two started. A lot of developments in the world come about
because of war, of course. The Manhattan Project, you’ve obviously heard
of. 1942 to 1946, the Manhattan Project were
a team of scientists … nuclear physicists and scientists and physicists from all over
the world who united in America to basically create the first nuclear bomb … the first
atom bomb. OK? Of course, the first bomb they made was a
fission bomb because fusion, even now, fusion is not a perfect science. So, they made a fission bomb. What happens with a fission bomb is you have
the bomb and, it doesn’t hit the ground, of course, it explodes in the sky. A … an explosive fires uranium at high speed
into the trigger and of course this sets off the neutrons firing. And this makes the … the uranium or the
plutonium or whatever is used go subcritical …er supercritical … sorry. That means the chain reaction starts going
and going and going and this releases more and more and more energy of course. The first atomic bombs, of course, were dropped
on Hiroshima and Nagasaki. I’m sure you know that. Those bombs were the equivalent of 18,000
tons of TNT. Now, when a nuclear bomb explodes, what happens? Well, of course, we have the shockwave. I mean you’re releasing all of this energy. There is a shockwave as it pushes the air
through the sky. And this shockwave destroys … well it kills
within a certain region and then it knocks down buildings and it slowly dissipates, but
the shockwave comes first. Then, of course, you have the heat. The heat from the blast in the center causes
fires and, well, basically vaporizes things in that area. And then you have radiation. Nuclear fission … uranium is a very radioactive
material so, after the explosion finishes, you are left with a lot of radiation fallout
in the sky. And you also have an EMP. This is where … electromagnet … an electromagnetic
pulse. This is where neutrons fire out and they destroy
circuitry. So, a nuclear bomb these days would stop any
computer or anything that uses a circuit in the area from working. So, the first bomb dropped on Hiroshima Nagasaki. We’re not going to talk about why. That’s a talk for a different day. That was a fission bomb of course. Fission bombs were gradually improved, gradually
made bigger and more powerful, until the most powerful fission bomb was called The Ivy King
in 1952. This bomb was the equivalent of 500,000 tons
of TNT. Now bear in mind that Hiroshima was 18,000
tons of TNT. We’re already becoming much much more powerful. We have bombs now that can destroy huge areas
not just one city. However, the problem with a fission bomb is
you’re limited by the amount of material you can carry because you can only use the material
you have, the … the atoms split, you need atoms. The more atoms you have the more powerful
it can be. But you’re limited by the amount of plutonium
you can put on one of these bombs. So, of course, we need to improve. If you look through the history of our world,
we’re always trying to find new and better weapons. So, what we come up … well, what they came
up with next is a fusion bomb. Now, we talked about the fusion process. With fusion, you need a huge amount of heat
to start the fusion reaction going. Now, how do you get that with a nuclear bomb? The only way they know to do it is to attach
another nuclear bomb to the nuclear bomb. So, basically, what happens is you have a
regular fission bomb and in the middle of that you have a fusion bomb. So, when the bomb is dropped it reaches its
specific height and the fission bomb ignites, the same way as a fission … a regular fission
bomb, it ignites and what that does of course is it creates a huge amount of energy a huge
amount of pressure and a huge amount of heat. And it heats plastic in a core which melts
and becomes a liquid plasma. And at the bottom of the bomb you have the
fusion material surrounded by plutonium the fission material. And this melted plastic causes another fission
reaction outside and inside and … which sets off the fusion reaction, which releases
huge amounts of energy. There is no way yet to start a fusion bomb
without using a fission bomb. There are ideas to use lasers and things like
that, but it’s … this is talk for the future. The American military has spent hundreds of
millions, probably even billions of dollars trying to invent this because whoever has
one of these will rule the world, basically. So, anyway, once fusion bombs, well, fission
fusion bombs are started, they get larger and more powerful because you don’t need as
much material. 1961, the Tsar bomb in Russia was the equivalent
of 50 million tons of TNT. That’s about 3,333 times as strong as the
bomb on Hiroshima was. So, the bombs we have now are far more powerful
than the bombs we used to have. We have enough bombs on Earth now to destroy
Earth thousands of times over. OK. So, we talked about how bombs destroy. Let’s talk about how many bombs there are
in the world. Which country do you think has the most nuclear
bombs? Well, it’s actually Russia. Russia has 7,500. America has 7,200. France has 300. China has 250. The U.K. has 215. Pakistan 100. India 100. Israel 80. And North Korea, we don’t know, but probably
about 10. That’s a lot of countries that have nuclear
bombs of course. So why do they have them? Why do all these countries have nuclear bombs? Well, of course, the idea is mutually assured
destruction. What does that mean? Mutually assured destruction means if you
have a gun, I get a gun. If you shoot me, I’m going to shoot you. So, you won’t shoot me because you know I
would shoot you. If you have a nuclear bomb and I get a nuclear
bomb, you won’t launch your bomb because you know I will launch my bomb and I won’t launch
my bomb because I know you will launch your bomb. Mutually assured destruction means we won’t
launch our own weapons because we don’t want to be destroyed. Ok? So, this is the basic idea. Now, this works as long as governments … as
long as regular governments stay in power, as long as they can control their military. What happens of course though, with terrorism
or civil war? What happens in the future? Because these bombs
are getting smaller and more powerful, what happens if a terrorist organization can
get their hands on a bomb? The manufacturing … the plans of these bombs
are kept very classified because they don’t want people to make them. It’s very difficult to make a bomb. To get your hands on this uranium. However, when countries collapse, like the
USSR collapsed in the 1990s, when countries collapse, they lose track of some of their
missiles. Some of Russia’s nuclear bombs have actually
disappeared. They don’t know where they are. So, if terrorists managed to get their hands
on one of these bombs, which I’m sure is the goal for many terrorist organizations, what
would stop them using them? The end of the world could happen not because
of mutually assured destruction but because of one group just deciding to launch it. Now, currently nuclear bombs are the most
powerful weapons we have on the Earth. However, humankind is always looking for more
powerful and deadlier bombs so who knows what we’re going to have in the future. However, to finish, from the Manhattan Project
there … one of the scientists was called J Robert Oppenheimer. I think he was in charge of the project. And, when the first nuclear bomb was tested,
he quoted an Indian poet, and he said, “I am become Death, the Destroyer of Worlds.” Which is very true. He had created the first weapon that could
destroy a world not just a few people. So, now we have planet destroying weapons. What’s going to happen in the future? I have no idea. Hopefully, the world will see sense and we
will start to cut back on nuclear weapons. But, it doesn’t seem to be happening. Anyway, thank you for listening. That was nuclear bombs. I hope you understood it. It was a little bit difficult to explain. Now you’ve finished listening to the talk,
try the questions. If you click on the link below here in the
description box you can find questions for this talk. You can find essay questions, multiple choice
questions, you can find simple answers. You can also find the transcript, so you can
read it and you can download the MP3 if you want. If you practice your English, if you write
and if you listen and if you read and if you talk, your English will get better. Keep trying. Do your best. Thank you for listening. If you liked this click “like”. If you want to share it click “Share”. If you want to subscribe, that button’s over
here somewhere, looks like my head. Thank you for listening. Have a great week. I will try and be back next week. Bye.

1 thought on “(#40) Nuclear Bombs – English listening with subtitles, script, questions, answers

  1. Halo sir, my name is is mahdi
    I'm really like your education video sir! I waiting for your next video video sir! Well may i get your email addres??

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