Physicists believe that our universe is
made up of indivisible particles.
Everything.
Galaxies,
planets,
animals,
cells,
atoms,
nuclei.
These particles are minuscule
– at least a billion times smaller than an atom –
but they’re amazingly interesting.
They’re called leptons, quarks, gauge bosons
...and then there is the Higgs boson.
My bit of the Universe is made up of four particles.
Two of them are really tiny,
but they are extraordinarily cute.
They are called Ondřej and František
...and then there is my wife Jana.
This is where my day as a particle physicist begins:
among heaps of toy cars and stuffed animals!
Come with me to experience the excitement
that drives thousands of particle physicists to overcome the impossible
on their road to discovery.
Our trip starts with ...particles. What else?!
Even in ancient times,
people probably asked themselves,
“Can an object be broken down into ever smaller and smaller pieces,
or are there some pieces that can’t be broken down any more?”
In their attempts to find an answer, two people in ancient times
may have taken some stones and thrown them at each other.
I mean stone against stone, not stone against people.
Unfortunately throwing stones at other people
has been a much more common experiment since ancient times!
When the stone breaks,
the experiment continues with the pieces.
And when the pieces stop breaking,
does that mean that they can’t be broken down any more?
Perhaps you will say
“What would happen if they were thrown against each other with even greater force?”
But then what would happen after you had invited
the two greatest strongmen in ancient times to take part in the experiment?
The ancient philosopher Democritus thought that matter cannot be broken down endlessly.
He introduced the term “atomos” for the smallest particle.
Atomos simply means indivisible.
Democritus’s concept of an atom corresponds more to what is nowadays called a molecule.
In the 19th century, the concept of “atomos” was used
for the basic structural elements of molecules,
that is to say atoms.
However, this was premature,
because it soon turned out that atoms are tremendously divisible.
Despite the fact that it is minutely small in size
a typical atom is ten to the power of minus ten metres,
or one tenth of a millionth of a millimetre.
Surprisingly, atoms and their components are still
being investigated in the same way as in ancient times –
by smashing them against each other.
For example, at the beginning of the 20th century,
the famous physicist from New Zealand, Ernest Rutherford,
carried out an experiment in which he irradiated
a very thin gold foil with alpha radiation,
that is, with nuclei of the element helium.
He had thought that all the alpha particles would pass through the foil
without changing their direction of flight.
But what happened?
Some of them even turned right round after striking the foil!
Rutherford concluded that the gold atoms must contain
a very heavy nucleus that alpha-particles bounce back from.
This is the same thing as if you throw a tennis ball at a medicine ball –
the tennis ball will bounce back at you,
while the medicine ball will scarcely move.
However, if you throw the tennis ball at a ping-pong ball,
the tennis ball will not even notice
that something has come into its path,
and will continue in its original direction.
It is the same thing when an alpha particle strikes
electrons from the electron envelope of an atom of gold.
Most of Rutherford’s alpha particles passed
through the gold foil without changing direction.
Just a very few of them turned right round.
From this, Rutherford concluded that the nucleus
must be very, very small.
And it really was tiny:
ten to the power of minus fourteen metres
which is ten thousand times smaller than a typical atom.
Experiments of the ancient type,
or, if you like,
experiments of the Rutherford type,
are still being performed today.
The main idea is as follows:
if we want to investigate something very small,
we need to send something towards it that moves very fast.
Or, more precisely, something with high energy.
Quantum theory teaches us
that every particle can be used for microscoping;
the greater its energy,
the better its spatial differentiating ability.
This “simple” principle was used for example in the 1960s
in an experiment that proved the existence of quarks –
the particles from which protons and neutrons are composed.
However, the energy of the particles that were used
was ten thousand times greater than the energy
that had been available to Rutherford.
The Large Hadron Collider,
or LHC accelerator experiment
in the international laboratory at CERN in Switzerland
is also a Rutherford-type experiment.
It is the best microscope that has ever been constructed,
and is capable of investigating objects with dimensions
of ten to the power of minus nineteen metres –
that is to say,
objects ten thousand times smaller than a proton.
It achieves this fantastic spatial differentiation thanks to the huge energy
with which it accelerates the particles that it uses as projectiles.
An important task for the LHC is to determine
whether particles which are currently regarded as indivisible
are nevertheless composed of even smaller particles.
From the present-day viewpoint,
the basic particles that cannot be further subdivided
are the electron, the muon, the tau,
neutrinos, quarks, gluons, photons,
W and Z bosons, and the Higgs boson.
Is it not fascinating
that nature in all its enormous variety
is composed of these particles?
Is it not fantastic
that people have been able to reach this conclusion
by throwing stones against each other?
I live in Prague,
the capital city of the Czech Republic.
I work 45 minutes away from my home.
I take the underground and a bus.
The bus line ends at Prague ZOO,
and it’s nice to travel with kids looking forward to seeing the animals.
I’m arriving at my university.
It’s the Charles University,
which is about 700 years old.
Well, not this building of course!
The university is spread all over Prague.
Here in Troja, we just do physics.
Besides Charles University,
Troja is also home to part of the Czech Technical University.
The buildings are full of
microscopes,
cryogenics,
plasma devices,
there’s a nuclear reactor,
a particle accelerator
and plenty of other stuff.
The site was built in the communist era,
and the spectacular thing is that students had to help to build it.
These were difficult times for everybody,
and the life of a physicist must have been very different than it is nowadays.
There is an urban legend about a physicist
who topped up his income by driving a bus
during the communist era.
One day he was driving a group of foreign physicists
who were in Prague for a conference.
Two of them sitting near the driver’s seat
were talking about theoretical physics.
He interrupted them and explained what they were discussing.
They were shocked!
In Czechoslovakia even bus drivers had an in-depth understanding of physics theory…
Hi, Martin. - Hi, Vojta. - How are things with you?
Not so bad, thanks,
but I’ve just received twelve pages of comments
on my three-page paper.
Wow!
This is what happens if these three thousand colleagues here all send in their comments, doesn’t it? - You’re right!
I see that I have about twenty unread e-mails from yesterday.
Then I have a meeting at ten with colleagues from ATLAS.
And it’ll go on like that until the evening. - Yes. I know.
When they hear the word “experiment”,
people mostly imagine a person heating up some strange liquid
which ends up exploding
or a person working on an instrument full of wheels and wires.
They do not usually imagine an experiment
that is as high as an eight-floor building
and as long as a swimming pool.
However, these are the dimensions of the ATLAS experiment at CERN,
and of similar huge experiments based on the LHC accelerator,
short for Large Hadron Collider.
These are detectors of the smallest known particles,
and it does seem a bit strange that the devices need to be so gigantic.
The ATLAS experiment is a kind of outsized camera.
The aim is to take photographs of the most high-energy particles
that humanity has been able to create.
The LHC is used for accelerating and smashing.
A large part of ATLAS functions on the same principle as the silicon chip in your camera.
ATLAS even has the same number of pixels
as the biggest and best smartphone camera.
One ATLAS photo is several megabytes in size.
A camera can produce an image like that.
However, you cannot order an ATLAS online for 2 000 dollars,
and you certainly would not be able to get it into your pocket!
There are certain differences between ATLAS and a camera.
ATLAS can take 40 million pictures in one second.
You will not find anything like that online.
ATLAS has to withstand many years of being exposed to huge doses of radiation.
It has to function in an extremely strong magnetic field.
It has to absorb high-energy radiation, or particles,
and keep track of their properties,
such as their energy and their velocity.
To absorb an ordinary proton, born in a collision at LHC,
ATLAS needs two-metre thick layers of iron.
And that would not exactly fit into your pocket.
ATLAS would not fit into that pocket either -
it weights 7000 tonnes.
It is incredible that the people who constructed a device
the size of an eight-floor building
know the position of each wire with the accuracy of a single hair’s breadth.
ATLAS was planned and built over a period of almost 15 years,
and has currently been in operation for seven years.
Data concerning billions of collisions of particles have been
under absolutely incredibly thorough investigation by physicists for years.
The numbers of scientists collaborating on ATLAS have not exactly been small.
The ATLAS collaboration has over 3 000 members!
Nobody at ATLAS has an overview of all the parts and all the functions of the device.
For this reason, specialists need to share information constantly.
Each member of the ATLAS collaboration receives several dozen e-mails every day,
and takes part in several meetings with colleagues every week.
Within the ATLAS collaboration,
there are about 400 registered meetings per week,
and many more informal meetings of two or three scientists.
For these reasons, the coffee bars are some of the busiest places at CERN.
From morning until evening,
every coffee bar buzzes like a beehive,
and scientists go from table to table
and hold discussions over litres and litres of coffee.
This helps them to keep going all day,
and to carry on far into the night.
If you have not experienced it for yourself,
you will not be able to imagine the tension
among 3000 scientists over a detailed investigation
of every sensor, every part, and every byte of valuable data.
Any meeting could turn out to be the key meeting.
Any e-mail might lead to a major step forwards,
and in any hour a decisive idea might occur to you.
You are investigating data
that has reached the Earth for the first time in history,
and any graph that you prepare could contain some shocking information.
The results of complicated measurements
are carefully compared with theoretical predictions.
On the day when there was no longer any doubt
that measurements confirmed the theory about the existence of the Higgs boson,
there was massive excitement at CERN!
If you aren't based at CERN, meetings with your colleagues are held
via a videoconferencing application.
“Good morning everybody and welcome
to our weekly analysis group meeting.
We don’t have any general announcement today
but we have a very full agenda.
So I would suggest we directly go ahead with the first presentation
which is an update on the BDT-based tagger of VH events.
Vojtech, if you are ready, please, go ahead.”
“Good morning,
as you all know, we are aiming at measuring a new process
which is the production of the Higgs boson
in association with a hadronically decaying vector boson.
We are trying to separate these events from background
with the use of a multivariate technique,
the Boosted Decision Tree.”
Boosted Decision Tree, Likelihood Ratio,
Neural Networks, Fisher discriminant –
these are all names of various methods
that are referred to together as artificial intelligence.
In simple terms, it can be said
that artificial intelligence is any kind of computer algorithm
that appears from the outside to make decisions about something
or to recognize something.
But we should not be deceived.
It is always an algorithm that is just a calculation, or formula.
It has nothing at all to do with intelligence.
Unless, of course, we have in mind the intelligence
of the creator of the algorithm, which may be considerable!
Artificial intelligence is always pleasing
when it recognizes a pet dog in a photo,
or the face of our best friend.
It helps us to translate into a foreign language,
it can talk with us as a virtual assistant,
and it can even drive a car.
It helps us to make an online search.
It plays the role of the bad guy against us in computer games,
it deals on the stock exchange,
and it protects us against cyberattacks.
Particle physicists love it.
They use it mainly for something similar to recognizing pet dogs in photos.
Experiments in particle physics are rather like big cameras
that capture the worst moments in the lives of elementary particles –
the moment when they smash together and disintegrate.
For each “photo”,
we need to ascertain what particles are in the image,
what energy they have,
and where they are flying to.
And artificial intelligence is happy to provide assistance.
In the distant past, particle physicists with standard cameras
used to photograph a certain substance
in which elementary particles leave a visible trace.
Large quantities of these photos were acquired,
and universities employed whole teams of assistants,
whose job was to inspect each photo
and assess the evidence in it about all the paths of the particles.
These assistants were not skilled physicists.
They had only been trained to recognize a line of a certain thickness
and bent in a certain way,
and to identify it, for example,
as a proton with energy of 2.54 megaelectronvolts.
They did not need to have any idea
of what a proton or a megaelectronvolt actually is.
Today, the principle is basically the same.
However, digital images emerge from the experiments,
and they are examined by artificial intelligence.
And, just like the assistants in the early history of particle physics,
artificial intelligence is trained to recognize types of particles and their energy.
Each artificial intelligence algorithm has undergone a training phase,
in which it was shown digital records from simulations of experiments,
and was informed what was in them.
A well-trained algorithm recognizes
that such and such a combination of data from a digital image
was a proton with energy of 2.54 megaelectronvolts.
Besides being a student of physics,
Hedvika is also an excellent dancer.
She always comes to meetings on her thesis like this.
How much progress have you been making?
I’ve been trying to calculate the Fake Factor as a function of pT and eta,
but I seem to have got stuck on the grid.
A lot of jobs are broken, and some haven’t even started.
Well, there are going to be a few problems with the grid these days.
A huge Monte Carlo simulation began last Friday,
and the grid is terribly overloaded.
We’ll just have to show some patience.
It’s a long time since people used their eyes
to scan the data from experiments in particle physics.
In those days, the data consisted of ordinary photographs.
Now a physicist sits at a computer and writes a long program that scans the data.
The data consists of digital images, in incredible amounts.
The experiments on the LHC accelerator at CERN
spat out as many as 88,000 terabytes of data in 2018 alone.
Stored on CDs, the data would form a 150-kilometre high column.
And if you decided to scan the data using your desktop computer,
you would have to wait at least a hundred years for your results.
Fortunately, the physicists at CERN have a lot more
than their desktop computers available
for storing and processing the data from the experiments on the LHC accelerator.
A vast network of around one hundred and seventy computing centres
in more than 40 countries has been created to meet their needs.
It is called the LHC Computing Grid.
The grid as a whole acts like a single, massive computer
that has a million terabytes of storage space
and a million computer cores.
Every day, about two million computer tasks are processed.
The data flowing from the LHC experiments
are stored in the main computing centre,
which is located directly at CERN.
Since they are in a very raw state,
the data first need to be pre-processed.
The results proceed to further tiers of the grid,
where they are processed and filtered again.
Imagine that you are a physicist,
and you have just for the tenth time tuned your image-filtering program
to a few collisions that interest you,
from among all the billions.
You press Enter to send your program to the grid
to go through maybe five hundred terabytes of data.
The calculation is automatically divided
into several tens of thousands of smaller calculations,
which are referred to as jobs.
These are distributed to computing centres all over the world.
There they join the queues of jobs submitted by your colleagues,
and wait until their turn comes round.
After a week, most of your jobs will have gone through,
but many are still waiting to be released.
However, it is worth the wait:
you never know whether you may be rewarded with something beautiful,
like this graph,
with which CERN won a Nobel prize for Higgs and Englert.
Finally, it’s lunchtime.
Today’s conversation is led by Daniel,
who has a passion for free diving.
Have you been doing any interesting diving recently, Dan?
Yes, plenty!
I was in the Philippines not long ago. On a diving trip.
We had some fantastic times there.
We saw some whale sharks,
and we went swimming with them.
Great! - Yes. it was fantastic.
One of the really interesting places there was a small island.
Well, the Philippines are made up of a whole lot of islands.
It was a small island, with a freshwater lake in the middle of it.
The water in the lake was about 28 degrees,
but when you dived down a bit deeper, there was a sudden thermocline.
That’s to say, a boundary between two different types of water,
and the water below is at 38 degrees.
When you swim into it,
it’s just as if you’d suddenly swum into a heated swimming pool.
It’s quite an unpleasant feeling.
And another interesting thing is that the water below,
the hot water, is saltwater.
In fact, that is why the hot water is below.
The salt fights against the heat.
The salt wins, so the salt water is below.
And normally when you dive down there,
you can actually see the boundary between the two types of water,
and it is just a fascinating thing to experience.
Daniel does free diving.
His record is 50 metres under water on one breath.
Gentlemen, I should have been in my lab class five minutes ago!
In the labs students learn how to operate simple experiments,
how to detect radiation
and how to evaluate and present results in a scientific manner.
On the way, they find out some pretty amazing facts.
That they would have to eat 10 million bananas
for an immediate fatal dose of radiation from potassium-40.
That almost every household used to own a small particle accelerator -
a Cathode-Ray Tube TV.
Or that the Earth is constantly being bombarded by particles
coming from our galaxy and beyond
with much higher energy than the most powerful accelerators ever built can achieve.
Students are often surprised to find out
that there is a huge and kind of scary labyrinth of corridors
underneath the building where the labs are
when they try to activate samples as part of their experiment
using the neutron source hidden in the basement.
Education is one of the key responsibilities of every physicist.
The future of the whole field of study and investigation depends on
passing knowledge and experience down to younger generations.
Every great discovery in particle physics
has its roots firmly in studies
carried out by past generations of physicists.
Even the greatest discoverer adds only a small part
to the whole of human knowledge.
Another pillar of particle physics is the exchange of information
and the building of personal links among scientists.
Countless meetings, consultations, congresses and conferences
are organized for this very purpose.
The participants present their results to their colleagues,
and in the breaks they can meet each other,
start a longer conversation,
or just agree to collaborate straight away.
Particle physics faces the opposite problem
to the one faced in many engineering and military applications.
In particle physics,
it is necessary to disseminate the progress and the results
of all research to as many people as possible.
It is therefore natural that the most important instrument of all
for transferring information from person to person
was born at CERN:
the WorldWideWeb.
Time passes quickly!
It’s 4 o’clock already!
After the labs you answer emails,
edit a piece of code of your computer program,
perhaps attend one more meeting.
My family’s waiting for me!
I'm heading home, walking over our favourite bridge,
joined by my colleague Daniel.
“Vojtech, people often ask me
what are the benefits of particle physics for society.
What would be your answer?”
When Anderson discovered anti-matter in 1932,
he surely never thought that,
within a hundred years, his discovery would form the basis
for ordinary equipment that can be found in any major hospital.
However, this is what has happened –
Positron Emission Tomography is an expensive
but widely-used method in medicine
for displaying the organs in the human body.
An accelerator produces a radioactive element
that is introduced into the patient’s body.
There it breaks down into anti-particles to the electron,
and each of them immediately annihilates with an electron.
From each annihilation, two particles of light emerge
that pass through the body
and are detected by a device that is similar to the ATLAS experiment.
All the components of experimental particle physics
at the disposal of medicine!
The most widely-used invention to have emerged from CERN
is without doubt the WorldWideWeb.
Everybody knows the initials WWW,
but just for the sake of completeness:
it is the way to share documents, or web pages, on the internet,
and to link text elegantly with references to other pages.
This excellent idea, which rapidly changed the lives of people across the planet,
was dreamed up and created by Tim Berners-Lee at CERN in 1989.
He is the author of HTTP –
short for HyperText Transfer Protocol,
the means by which computers on the internet transfer web pages
of HyperText Markup Language, or HTML
in which the pages are programed,
and the WorldWideWeb – the first web browser, or program,
which displays text in unreadable HTML language
as a beautiful web page.
A small plaque in honour of Berners-Lee’s world-changing invention
hangs in a permanent display dedicated to him
near his former office at CERN.
There is exceptional competition among inventors at CERN.
If each of them were to have been awarded a statue,
there would no longer be any space left for anything else.
“Wow, that’s a good answer!
And what fascinates you about the particle physics itself?”
Particle physics takes years of hard work
before anyone can achieve any results.
However, the feeling of working
at the cutting edge of human knowledge and understanding,
of studying data that no-one else on earth has ever seen,
and that I could at any moment find in them something revolutionary –
that is what drives me.
Not only me, but you and thousands of our colleagues.
Most of them keep working long into the night,
because they have this passion deep inside themselves,
and there is nothing that can stop them.
We carry our work around with us constantly,
and we think about it all the time.
To be a part of the experiment that discovered the Higgs boson,
and to investigate the data within which it was discovered –
that is just fantastic!
HERE, ADD ACKNOWLEDGEMENT TO YOURSELF FOR THE TRANSLATION! YOUR NAME, AFFILIATION AND ANY ADDITIONAL INFORMATION YOU WOULD LIKE TO BE MENTIONED YOU CAN ALSO MENTION IPPOG SOMEHOW BECAUSE THE TRANSLATION IS MOSTLY DONE BY IPPOG PEOPLE, IN GENERAL