Home
로그인
회원가입
학습 콘텐츠
Loading...
How It Works - The Atomic Bomb - Video học tiếng Anh
듣기 연습
듣기 연습
/
Video
/
The Infographics Show
/
How It Works - The Atomic Bomb
How It Works - The Atomic Bomb
학습 모드 선택:
자막 보기
단어 선택
단어 다시 쓰기
Highlight:
3000 Oxford Words
4000 IELTS Words
5000 Oxford Words
3000 Common Words
1000 TOEIC Words
5000 TOEFL Words
자막 (192)
0:00
This video is sponsored by Conflict of Nations, the free online strategy game where you get
0:04
to find out what it’s like to take control of a real country and lead it in a modern
0:08
global warfare!
0:09
You’ll take on up to 128 other players in real-time games that can take weeks to complete,
0:14
using armies filled with diverse units like powerful tanks, jet airplanes, and even nuclear
0:19
submarines.
0:20
But there’s more than just fighting on the battlefields, my favorite part of the game
0:23
is the social strategy side, forging alliances and declaring war on other real players!
0:28
It’s fully cross platform so you can play on the same account on PC and mobile.
0:32
We’ll be hosting a custom game for the first viewers that click the link in the description
0:35
with instructions on how to join at the end of this video so make sure you stick around.
0:39
Infographics Show viewers also get a special gift of 13,000 gold and one month of premium
0:44
subscription for free when they use the link.
0:47
It’s only available for 30 days so click the link, choose a country, and start fighting
0:51
your way to victory right now!
0:53
On August 6th, 1945, an American B-29 bomber flying low over the Japanese city of Hiroshima
0:59
dropped the world’s first atomic bomb on the city’s unsuspecting inhabitants, immediately
1:04
killing 80,000 innocent civilians.
1:06
3 days later, a second bomb was dropped on the city of Nagasaki, killing a further 40,000
1:11
men, women and children.
1:13
In the aftermath of the bombs’ initial explosions, tens of thousands more people would die excruciatingly
1:18
painful deaths due to radiation exposure.
1:21
While the world may be familiar with the tragic story of the first use of the atomic bomb,
1:25
we are less familiar with exactly how it works - the atomic bomb was a devastating act of
1:30
cruelty, but also a technological marvel that would forever alter the face of war.
1:36
The devastating bombing of Japan was enough to deter the use of nuclear weapons for at
1:39
least a few decades, but after World War 2, increasing tension between the U.S. and Russia
1:44
led to the Cold War, a nuclear arms race between the two world powers that saw both sides rushing
1:50
to increase their stockpile of nuclear weapons, ostensibly as a means to deter war.
1:55
People built bunkers in their backyards and stocked up on canned foods, schools ran nuclear
2:00
war drills, and the world waited with bated breath for the outbreak of nuclear war and
2:05
what felt like the imminent end of the world.
2:07
But although the existence of nuclear weapons was common knowledge, and despite the widespread
2:11
panic about nuclear war, few people truly understood just how an atomic bomb works.
2:17
To understand how the atomic bomb works, we have to take a trip back to high school physics
2:21
class to revisit the concepts of atomic structure and radioactivity.
2:25
An atom is one of the smallest units of matter, and it is made up of 3 subatomic particles.
2:30
The nucleus at the center of an atom is made up of protons, which are positively charged,
2:34
and neutrons, which have a neutral charge.
2:36
Negatively-charged electrons orbit the nucleus of an atom.
2:40
When the ratio of protons to neutrons is 1-to-1, the atom as a whole will have a neutral charge.
2:45
But, if the number of protons in an atom is changed, an entirely different element will
2:49
be created.
2:51
If the number of neutrons changes, you end up with an isotope.
2:54
For example, the Carbon atom has 3 naturally occurring isotopes - in its common, stable
2:59
form, Carbon-12 has 6 protons and 6 neutrons; Carbon-13 has 6 protons but 7 neutrons, and
3:06
while rare, is still a stable element.
3:08
Carbon-14, with its 6 protons and 8 neutrons, is both rare and unstable - or, radioactive.
3:15
Radioactive nuclei emit particles called radiation through a process called radioactive decay,
3:19
and it’s this process that scientists harnessed to create the powerful atomic bomb.
3:24
There are a few different ways to destabilize a particle, but for understanding how nuclear
3:28
bombs work, the most important processes to grasp are fission and fusion.
3:33
Fission involves splitting the nucleus of an atom in 2, which scientists can do by bombarding
3:38
it with free neutrons.
3:39
As the nucleus splits, it ejects neutrons along with bursts of electromagnetic energy
3:43
called gamma rays.
3:45
Fusion, in contrast, involves bringing together the nucleus of two atoms to form a single
3:50
larger one.
3:51
This is actually the process by which our Sun produces energy.
3:54
Through endless experimentation and a process of trial and error, scientists eventually
3:58
discovered that uranium was the element that was most cooperative in inducing a fission
4:03
reaction.
4:04
The isotope Uranium-235 is one of the few materials that can be forced to undergo fission
4:09
by bombarding its nucleus with neutrons, rather than waiting 700 million years for it to decay
4:14
naturally.
4:15
U-235’s nucleus will readily absorb the neutrons, become unstable and split, throwing
4:21
off 2 or 3 new neutrons in the process.
4:24
These new neutrons can then go on to collide with the nucleus of other U-235 atoms, starting
4:29
a fission chain reaction.
4:30
The splitting of the nucleus happens incredibly quickly - in the order of picoseconds, or
4:36
0.000000000001 seconds - yepp, that’s 11 zeros!
4:45
The scientific principles underlying the atomic bomb had been well known since Einstein’s
4:50
days, but they wouldn’t be successfully applied and weaponized until the Second World
4:53
War.
4:54
In the 1930s Italian scientist Enrico Fermi successfully bombarded elements with neutrons,
4:59
transforming them into new elements, and shortly thereafter German scientists Otto Hahn and
5:04
Fritz Strassman were the first to fission uranium by bombarding it with neutrons, producing
5:09
the radioactive barium isotope.
5:11
These breakthroughs led the scientific community to wonder if it was possible to create a fission
5:15
chain reaction that could release enormous amounts of energy that could be harnessed
5:19
and weaponized - an idea that greatly intrigued the world’s governments, who were in the
5:24
midst of fighting World War 2 at the time.
5:26
In an effort to be the first to weaponize fission - and beat the Nazis to the punch
5:30
- the U.S. government recruited the brightest minds in physics from all over the world and
5:34
launched the secretive Manhattan Project with the goal of creating the world’s first functional
5:38
atomic bomb.
5:39
In 1941, scientists at Columbia University tried to initiate a chain reaction using uranium-235,
5:46
but failed.
5:47
Shortly thereafter, Fermi, now working for the U.S. at the University of Chicago, successfully
5:51
achieved the world’s first controlled nuclear chain reaction in his lab underneath the school’s
5:56
squash courts.
5:57
Also in 1941, Berkley scientists discovered a new element - element 94 - with nuclear
6:03
fuel potential, which they named plutonium.
6:06
With these discoveries, the race to develop a nuclear bomb was on in earnest, and within
6:10
just a few short years, the world’s first nuclear bombs would be used in war.
6:15
Understanding the concept of fission was only part of the problem - figuring out how to
6:18
weaponize it and constructing devices to harness atomic power was a whole other challenge.
6:23
Critical mass is the minimum amount of material needed to sustain a chain reaction, so to
6:28
harness nuclear power, the nuclear fuel has to be kept in separate subcritical masses
6:33
that won’t support fission.
6:35
When it’s time to detonate, the subcritical masses are brought together to form a supercritical
6:40
mass, and free neutrons are introduced to jumpstart the fission process.
6:44
A small pellet made of the elements polonium and beryllium serves as the neutron generator,
6:49
and the entire reaction is confined within a dense material called a tamper, usually
6:54
made of another uranium isotope, U-238, to reflect the neutrons back into the core and
6:59
to slow the core’s expansion to ensure that as much fission as possible happens before
7:04
the bomb explodes.
7:05
Scientists developed 2 different trigger systems for the first atomic bombs.
7:09
Little Boy, the bomb dropped on Hiroshima, was a gun-triggered bomb with a 14.5 kiloton
7:14
yield, equal in power to 14,500 tons of TNT.
7:19
Little Boy was 1.5% efficient, meaning that 1.5% of the material fissioned before the
7:25
bomb exploded.
7:26
In a gun-fired nuclear weapon, a bullet of U-235 is placed in one end of a long tube
7:32
packed with explosives, which will fire the bullet down the tube where it collides with
7:36
the neutron generator, initiating fission and starting the chain reaction that will
7:41
lead to the bomb’s explosion.
7:42
In contrast, Fat Man, the bomb that was dropped on Nagasaki, was an implosion device with
7:48
a 23 kiloton yield and 17% efficiency - much more effective, but also much more complicated
7:54
to make than Little Boy.
7:56
Implosion bombs feature a sphere of radioactive U-235 as the tamper around a plutonium-239
8:02
core.
8:03
The entire sphere is surrounded by high explosives which, when detonated, create a shockwave
8:09
that compresses the core and initiates the fission chain reaction.
8:12
In the wake of World War 2, scientists recognized that fission bombs were wildly inefficient,
8:17
and turned their attention to fusion next.
8:20
Fusion bombs, also called thermonuclear or hydrogen bombs, rely on the hydrogen isotopes
8:25
deuterium and tritium as fuel, and can yield up to 10,000 kilotons, making them up to 700
8:31
times more powerful than the Little Boy fission bomb.
8:34
Hydrogen bombs combine fission and fusion to achieve a more powerful and more efficient
8:39
explosion.
8:40
Within the bomb’s casing is a tamper made of U-238, which is packed with hydrogen isotope
8:45
fuel, and surrounds a hollow rod of plutonium-239 at the core.
8:49
An implosion fission device detonates first, compressing the fuel and causing the plutonium
8:54
core to fission.
8:55
The fissioning rod in turn gives off heat and pressure, which initiates fusion in the
8:59
hydrogen isotopes and causes the bomb to explode.
9:02
The entire process takes just 600 billionths of a second.
9:07
Not only have the bombs themselves improved drastically, but the delivery methods have
9:10
come a long way since World War 2.
9:13
Philip Morrison, a former member of the Manhattan project, told Scientific American in 1995
9:17
that "All three bombs of 1945 - the [Trinity] test bomb and the two bombs dropped on Japan
9:23
- were more nearly improvised pieces of complex laboratory equipment than they were reliable
9:29
weaponry."
9:30
Today, nuclear weapons come in many forms, from ballistic missiles that can exit the
9:33
atmosphere and travel thousands of miles before reentering and detonating; to cruise missiles,
9:39
shorter range missiles with smaller warheads that are harder to detect and intercept; to
9:43
a range of tactical nuclear weapons like artillery shells and land mines that can target a smaller
9:48
area.
9:49
Nuclear weapons are terrifying because of their immense destructive power relative to
9:53
their size.
9:54
The most severe damage happens at the blast’s hypocenter, or ground zero, where everything
9:59
is immediately vaporized.
10:01
Outward from the center, most of the damage is the result of flying debris, intense heat,
10:05
a powerful shockwave and acute exposure to high radiation.
10:09
Beyond the immediate blast area, death and injury can result from heat and resulting
10:13
fires, as well as from radiation.
10:16
The physical destruction caused by a nuclear bomb is no doubt catastrophic, but the most
10:20
dangerous part of a nuclear bomb is the radiation and radioactive fallout.
10:24
After the initial explosion, clouds of fine dust made of radioactive particles are carried
10:29
away by the wind and fall back to the ground, poisoning the water supply and getting ingested
10:34
and inhaled by people even miles away from the blast.
10:38
We now know that radiation affects the cells in our body that readily divide, like hair
10:42
and gut cells, bone marrow and reproductive organs, leading to nausea, vomiting and diarrhea,
10:48
and long-term health consequences like cataracts, hair loss, loss of blood cells, and an increased
10:53
risk of leukemia, cancer, infertility and birth defects.
10:57
At the height of the cold war in the 1980s, scientists warned about the danger of a nuclear
11:01
winter.
11:02
In a worst case scenario, so many nuclear bombs could explode that great clouds of radioactive
11:06
dust could travel high into the atmosphere, blocking out sunlight and lowering surface
11:11
temperatures.
11:12
This could lead to major disruptions in the food chain and mass extinctions of species
11:16
- including humans.
11:18
The Cold War may be over, but the threat of nuclear war is by no means gone.
11:22
Countries around the world have signed treaties agreeing to limit their stockpile of nuclear
11:26
weapons and prohibiting them from using them against other countries, but still, the number
11:30
of nuclear weapons around the world continues to grow - and not all countries have agreed
11:34
to use them responsibly.
11:36
At least 9 countries currently have ballistic nuclear weapons, and 3 of those countries
11:40
- the U.S., Russia and China - have weapons powerful enough to hit any target anywhere
11:45
in the world.
11:46
Then there’s North Korea - in 2009, they tested a nuclear bomb as powerful as the bomb
11:51
dropped on Hiroshima, and the underground test explosion caused a magnitude 4.5 earthquake.
11:56
There’s no doubt that nuclear warfare still presents a huge threat to world peace - not
12:01
to mention the continuation of our species!
12:02
If you thought this video was fascinating, be sure and check out our other videos, like
12:03
this one called “Scientists Discover 2 Billion Year Old Nuclear Reactor”, or perhaps you’ll
12:04
like this other video.
12:05
Thanks again to our sponsor Conflict of Nations, the free online pvp strategy game set in a
12:09
modern global warfare!
12:10
We’ve set up a custom game for our viewers.
12:13
Click the link in the description, create an account, and enter in the game code “infographics”
12:17
and password “infographics” to join today!
