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The 3 Strongest Lasers in the World (For Now) - Video học tiếng Anh
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The 3 Strongest Lasers in the World (For Now)
The 3 Strongest Lasers in the World (For Now)
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Phụ đề (257)
0:00
You know, I miss when we used to answer Patreon questions on Scishow.
0:04
In fact, I have a list of them.
0:06
I’m gonna just take out my phone and I’m going to pick one at random.
0:09
“Dear Mr. SciShow, I just got promoted to
0:12
head-henchperson (cool) for an aspiring supervillain.
0:16
The department heads just got out of their weekly Evil Pitch Meeting
0:20
and my boss would like to hold the world ransom with the world’s biggest laser.
0:25
I need the plans on his desk by Friday.
0:28
Please help. Love, H.”
0:30
Well, H, this definitely wasn’t an invented bit.
0:33
Let’s see what SciShow can do for you.
0:35
Here are a few candidates for the worlds strongest lasers.
0:39
This is exciting, I can’t wait to find out more.
0:42
[♪ INTRO]
0:45
Now we have to figure out what a laser even is.
0:48
Your boss might be looking to Hollywood for examples,
0:50
where the word might be used to refer to any beam of energy,
0:54
like what Superman shoots from his eyes.
0:56
Or cyclops, but everybody knows that’s just “punch energy”
0:59
from the Punch Dimension — it’s not a laser.
1:01
The word laser is a technical term for a specific thing.
1:04
In fact, the word is an acronym:
1:06
Light Amplification by Stimulated Emission of Radiation.
1:09
And that tells us that lasers are a kind of light.
1:12
Often, the same electromagnetic waves that we use to see the world.
1:16
But there are also light waves humans can’t see,
1:18
like infrared radiation and x-rays.
1:20
And we can make lasers emit that kind of light, too.
1:23
That’s right, we can make X-ray lasers!
1:25
Sounds very dangerous!
1:26
The rest of the acronym tells us how lasers produce light.
1:30
Specifically, by forcing atoms to emit light much more readily than they usually do,
1:35
hence words like ‘amplified’, and ‘stimulated’.
1:38
And that light is emitted in a very particular way,
1:41
using the laws of quantum mechanics to
1:42
ensure that only one wavelength of light…one color…comes out.
1:46
Lasers can also be super concentrated, only travelling in one narrow beam.
1:50
That’s why the beam of your laser pointer is invisible from the side,
1:53
unless someone has recently clapped two chalkboard erasers together to fill the
1:57
room with a bunch of teeny particles for bits of the laser beam to bounce off of.
2:00
Ultimately, lasers produce light that you can
2:02
tune to flow down one precise channel.
2:06
You can also control its exact color and the amount of energy the beam carries.
2:10
Easy to see how this could be useful in lots of circumstances…
2:13
even if you are not an aspiring supervillain.
2:16
Since they were invented in 1960, lasers have found uses in everything from
2:20
barcode scanners, to eye-repair surgery to fundamental physics research.
2:23
So with that background out of the way,
2:25
because we actually want to be talking about lasers
2:26
when we’re talking about lasers,
2:28
let’s talk about what the current strongest lasers in the world are.
2:32
We’ll start with the most powerful laser.
2:34
And that’s actually a technical term.
2:36
In physics, power refers to energy per unit time,
2:40
usually measured in the unit watts.
2:42
One watt is a joule of energy that’s used or released over one second.
2:47
And one joule is roughly the energy you need to pick up a small laptop.
2:51
The “per unit time” bit is also important.
2:53
A laser can be made more powerful by emitting
2:56
the same amount of energy in a shorter amount of time.
2:59
A typical laser pointer will emit a few milliwatts of light, one-thousandth of a watt.
3:04
The most powerful lasers you could plausibly buy emit kilowatts,
3:07
thousands of watts, so about a million times more power,
3:11
and those lasers are used in industry for welding metals together.
3:14
You are not gonna get them on Amazon.
3:16
Also be careful, we do not condone the purchase of dangerous lasers.
3:21
Cause yes, even supervillains should follow lab safety protocols.
3:24
So here we should stress that even low-power lasers can be super dangerous.
3:29
One would never, for example, point them in someone’s eye.
3:32
So the question becomes, how powerful can lasers get?
3:36
To go more powerful than the kilowatt scale,
3:38
you need to go to a pretty advanced physics lab.
3:41
But it turns out that the most powerful lasers
3:43
in these labs don’t fire continuous beams.
3:46
Instead, they emit laser light in short bursts, called pulses.
3:50
And by “short” I mean, well, some labs can achieve pulses
3:53
that last a few quintillionths of a second, which are called attoseconds.
3:57
These attosecond pulses are hugely important for modern physics,
4:01
and won their developers a Nobel Prize in 2023.
4:04
Because the pulses are so brief, such a laser works like a high frame rate camera.
4:09
A like super duper high frame rate camera:
4:12
it can even let researchers see electrons moving around inside atoms!
4:17
This trick works by using the rules of quantum mechanics
4:20
to combine laser beams at multiple different frequencies.
4:24
So unlike with a laser pointer, if you could see the light
4:26
from these ultra-short pulses (which you couldn’t, but if you could)
4:29
it wouldn’t appear to be any particular color.
4:31
Supposedly, the current record holder for highest power in a laser pulse
4:35
is located at the Extreme Light Infrastructure facility in Romania.
4:39
Although, we should point out this record is disputed by other labs
4:42
who have staked their own claim to the superlative.
4:44
We’ll be getting to one of those lasers, later.
4:47
A laser at the ELI can produce ten petawatts of power.
4:51
That’s one trillion kilowatts, and one quadrillion joules per second.
4:56
It’s quite the punch, although no one’s using it to hold the world hostage.
5:00
Over the years, hundreds of different experiments
5:03
have been done with this laser, in a number of scientific fields.
5:06
Like, researchers have tested biological sources’ exposure to radiation
5:09
for cancer research, studied fundamental nuclear physics,
5:13
and re-created extreme astrophysical scenarios for cosmology research.
5:17
But because their pulses only last for tiny amounts of time…
5:20
just a few thousand attoseconds…each pulse only emits a few joules of energy.
5:25
So as powerful as these kinds of petawatt lasers are,
5:28
your evil boss is going to be disappointed.
5:30
They’re not especially energetic.
5:32
But there is a laser out there that emits way more energy,
5:36
even if it’s also over a relatively short amount of time.
5:39
And we’re gonna tell you all about that, after this break.
5:42
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5:59
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6:03
So lots of people trust them.
6:05
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6:08
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6:30
In the small California town of Livermore,
6:33
a research facility is trying to harness the power of the Sun.
6:36
The National Ignition Facility, or NIF, is a prominent figure in humanity’s race
6:41
to produce a commercially-viable form of nuclear fusion.
6:45
It’s basically the opposite of nuclear fission,
6:47
which is how modern nuclear power plants source all of their energy.
6:51
But pound-for-pound…or since this is SciShow, kilo for kilo…
6:54
fusion releases way more energy than fission.
6:57
And depending on the kind of fusion that you do, it doesn’t leave you with much,
7:01
if any, harmful nuclear waste.
7:03
So it would be great if we could figure out a way to make nuclear fusion
7:07
work that isn’t just “let the Sun do it’s thing and then use solar panels
7:11
to absorb a tiny fraction of the energy that eventually reaches Earth”.
7:14
Unfortunately, achieving any amount of nuclear fusion,
7:17
let alone doing it in such a way that you can get
7:20
more energy out than you have put in, is ludicrously difficult in practice.
7:25
People have been trying for decades with no success.
7:28
It requires you to pump an unbelievable amount of energy
7:31
into incredibly tiny spaces, to push particles extremely close together.
7:36
While scientists around the world have tested a variety of techniques,
7:39
NIF achieves this extreme energy density by shooting
7:42
ultra-powerful laser beams at tiny pellets of nuclear fuel.
7:45
It takes a single ultraviolet laser beam and splits it into 192 smaller ones,
7:50
each of which is then separately amplified up to monster energies.
7:54
Those beams then hit the pellet from all sides,
7:57
squeezing the fuel particles together.
7:59
Like the laser at the ELI, the NIF lasers only emit light in super-short pulses.
8:04
Though here, we’re talking about nanoseconds:
8:06
about a billion times longer than before.
8:09
But the real difference between these two setups is in the energy scale.
8:12
A typical pulse at the ELI emits a few joules of energy,
8:16
but a typical NIF pulse emits millions of joules.
8:20
In fact, there’s a joke that NIF scientists like to
8:22
tell about how much more energetic the NIF laser is compared to its peers.
8:26
And it goes like this: “What’s the strongest laser in the world?
8:29
The NIF laser. What’s the second strongest laser in the world?
8:32
The reflection of the NIF laser.”
8:34
Cool folks over there — not nerds at all!
8:37
Which is to say, any random stray laser light bouncing around inside of
8:41
the laser chamber is still far more energetic than any other laser in the world.
8:46
And yeah, that is what passes for humor among nuclear physicists…
8:49
It also gets brought up by NIF tour guides.
8:52
In 2022, NIF reached a key milestone in nuclear fusion research called ignition,
8:57
where the fusing material emits more energy
9:00
than it absorbs: three megajoules out for two megajoules in.
9:04
However, there’s a super important caveat, here:
9:06
that “two megajoules” is only the energy that went directly into the fusion pellet.
9:12
It does not account for all the energy needed
9:14
in the laser chamber, which can be hundreds of times greater.
9:17
So humanity is still a long way off from building
9:19
a proper nuclear fusion power plant.
9:22
And I would personally recommend to any supervillains with a giant laser
9:26
at their disposal to help conduct nuclear fusion research that everyone
9:30
can benefit from, rather than holding the world hostage.
9:33
If NIF’s ultra-high energy laser doesn’t impress your boss,
9:37
then here’s a nice backup plan: the highest intensity laser in the world.
9:42
See, one factor we haven’t mentioned yet is how focused the laser beams are.
9:46
Each of the lasers so far has been able to dump its energy over
9:50
a very short period of time, but each can also
9:53
dump the energy into a very tiny area.
9:55
This is the intensity: how much energy is emitted, per unit time, per unit area.
10:01
It’s usually measured in watts per square centimeter.
10:04
Basically, it tells you how concentrated the laser energy is.
10:08
And once again, we’ve got some pretty big numbers to consider here.
10:11
In 2021, a milestone breakthrough was achieved at
10:14
the Center for Relativistic Laser Science in Gwangju, South Korea.
10:18
Like other cutting-edge lasers around the world,
10:20
this one achieved a few petawatts of power.
10:23
But by focusing that wattage onto just a few square micrometers…
10:27
an area roughly the size of a bacterial cell…
10:30
the laser achieved a record-breaking intensity
10:33
of 10^23 watts per square centimeter.
10:37
That’s roughly 100 zettawatts per square centimeter, if you want the fancy jargon.
10:42
And this wasn’t just to break a record, of course.
10:44
Not that scientists don’t like breaking records.
10:47
In lots of fundamental physics research,
10:49
energy density is the name of the game.
10:51
Some strange phenomena only happen when
10:54
you pack enough energy into a really small area.
10:57
For instance, if the laser’s intensity is high enough,
11:00
an electron within the beam’s path can absorb multiple light particles at once.
11:05
And then, that electron can emit a single
11:07
light particle with hundreds of times as much energy.
11:11
The hope is that those super energetic light particles can
11:14
mimic the effects we see in extreme astrophysical situations,
11:18
like the magnetic fields around black holes.
11:20
It’s also thought that at even higher intensities,
11:22
we might be able to see different properties of the vacuum,
11:26
of empty space itself, because empty space isn’t actually empty.
11:31
But we’re not quite there, yet.
11:33
In the years since 2021, other laser facilities have claimed they too can go past
11:37
10^23 watts per square centimeter.
11:40
So the fight for the title of “Most Intense Laser” continues.
11:43
But maybe that boss of yours doesn’t like any of the options available right now.
11:47
Maybe they’re the patient sort.
11:48
So what lasers might be available in the next several years or so?
11:52
Well there are a few facilities under construction around the world
11:54
that intend to utterly blow the current record holders out of the water.
11:59
In the UK, there’s the Central Laser Facility’s Vulcan laser,
12:03
which is currently getting a major upgrade called Vulcan 20-20.
12:07
That’s due to go online in 2029.
12:09
The 20-20 name comes from their two main goals:
12:12
to upgrade the beam from one petawatt to a record-breaking
12:15
20 petawatts of power, and to produce beams with 20 kilojoules of energy.
12:20
It’s not because they thought they were going to be done in 2020…
12:22
which would be funny but it’s not.
12:24
But the’re not going to be able to do those 2 things at the same time.
12:26
The 20 petawatt beams would have about 400 joules of energy,
12:30
and the higher-energy beams would have less power.
12:32
Vulcan 20-20 also hopes to reach an intensity of
12:35
10^23 watts per square centimeter, to test the
12:38
Unexplored physics at those energy densities.
12:41
But as ambitious as Vulcan is, it’s nothing compared to
12:45
what they’re building in China.
12:46
At the Shanghai Superintense Ultrafast Laser Facility,
12:49
(Super intense and ultrafast?!) researchers have already claimed to
12:53
hold the current power record, and are building something even bigger.
12:57
The new facility, which is called the Shanghai Station of Extreme Light,
13:00
is intended to house a 100 petawatt laser in the next few years,
13:05
which would be the undisputed king when completed.
13:08
With ultra-short pulse times, and super high intensities,
13:12
this thing could rip the vacuum apart, creating cascades of subatomic particles
13:17
in never-before-seen ways, mimicking the highest-energy
13:21
astrophysical events and unlocking untold new physics.
13:25
And we will just have to wait and see what actually happens.
13:28
We definitely will cover it, I promise.
13:30
As cool as these super lasers are, none of them work as some kind of death laser
13:34
that would help an aspiring supervillain take over the world.
13:38
But there’s also clearly a market for building bigger,
13:41
better, fundamental physics-understanding lasers.
13:43
So if the head-henching ever seems to not be working out,
13:46
I have a great alternate career path for you to consider.
13:50
Just something to think about.
13:52
[♪ OUTRO]
