We hear a lot of things about physics: only nerds and very good people goes in that domain, it is useless no possibility of job at the end because what exactly does studying in physics gives ?

The answer is a bit more complicated then for traditionnal profession as engineering, medical doctor, lawyers , teacher etc. Althought, this is true for any discipline in science, biology, chemistry, etc. The job offers are not offer specifecally for one type of person, we could even say that since there is too many options we think that there is not many.

Let’s do a quick update on why would someone go in physics ?:

1-For the fun of it! Obsviously, this is at least for me one of the most important criteria. Does resolving equation, thinking about the mechanism of the world interest me ? Am I curious about the world that surrounds us. Do I see every problem as a new challenge I am excited to try? Do I have fun resolving equation and seeing the beauty in the mathematics that surrounds us (it is quiet interesting, I shall in the future write something about it) ? Well you might not agree with all of this and be a really good physicist, but still the common denominator that you need to have I think is do you like to learn something new everyday ? Because basically that what you will do if you study in physics

2-For the possibility of it. Well, studying in research espacially in the science domain implies that you can be a part of a team that makes a big breaktrue or that is doing really specific physics for something really fondamental. There is not a lot of domain were you can explore and study the scale of the Universe from the smallest quark to the biggest cluster, it is certainly a very vast domain in which you can do mostly everything you like.

3-For the biggest human collaboration that ever existed! There is not many domains were you can have huge collaboration of 3000 people working on a single experiment ! There is certainly a diversity of people coming from different background that can give you a really different perspective of how you live.

4-For the interdisplinary of this field. The interesting I would know about physics is how many broad knowleadge you can acquire in order to build an experiment. Personnaly, I always loved to touch to many different field and learning about the specifity of each of them. Studying in physics gives me the possibility to work with engiener and depending on the project, technician, chemist, biologist, lawyer, journalist etc. For me the possibilities are mostly limitless.

5-Because there is going to be a need of even more physicist in the future. With the developpement of the technology higher formation will be more and more needed. Machine learning is a buzzer word that shows that phenomenon with the appearance of the data scientist post. A physicist that analyze the data and manage use amount of it, the formation that we acquire helps us to learn and understand anything really quickly.

Moreover, you don’t need at all to be a nerd or really good to be in physics. I want to believe that if someone is really interested and comit to study, they should be able to pass everything. From experience, I can already tell you it might be more difficult for then for the other but on the long run everything will balance itself.

That being said, we need people for all profession but I hope that this article gave you a small idea of the possibility of studying in physics and that it helped demystify some of stereotype we might have about the people studying it.

Have you ever wonder how can we exist ? It seems that everything in the Universe tends to break fall appart, every plate in a kitchen will eventually break. Cancer is develop because your cells can no longer replicate exactly the same, they makes error. It is nearly impossible to always a clean bedroom, at least for me ! All these example have a common concept,very important in physic: entropy.

What is exactly entropy ? Well really hard to define this, all I would say is that it is something that we use to measure the disorder of something. It also represent the number of states possible multiply by the Boltzam-constant. A system can never go two a system with less possible state by itself because entropy always tend to increase with time. Following that explanation then how can we exist because we are such complicated structure, how can we balance entropy ?The answer energy!

Energy is the only thing that help create a structure. Every single day, we used a gigantic amount of food to uniffenctly transfert calories in energy by what we call mitochondries, these are the factory of the body were the energy is created. This energy is used to keep the structure together. But in the end with even with this energy more entropy is still introduced in the world because of the first law.

Wait, wait so energy conserved structure okay, but is it enough to make our body hold on the ground ? What I am eating shouldn’t be enough to counter the gravity, shoudn’t we be really small structures close to the ground. The gravity is pulling the sun in the center of the solar system shouldn’t rip us appart. Actually yes probably, so why don’t we ? Because there is another force that holds the atom together. Wait ? What the hell is a force ? Well it is concept that we always talk about without really knowing what it is about: a force is a mathematical concept to explain how to give or change the trajectory of a certain particule. Instintively, you can move something using energy directed in a certain direction.

That being said, the easiest force to represent to ourself is gravity, an apple fall of a tree with a certain speed. There is also the electromagnetic force, used for example is the attraction in the magnet. It is also much more then that, it is what holds every single atom together, an atom is something really small, good comparaison would be ? To think that matter is made of many small pieces of something, a bit like a puzzle, if you take a puzzle and moves it, the friction between will make it hold but not for too long, it will eventully brake and split appart. Same case with the electromagnetic force, it holds everything together, it takes a lot of energy to break links between them. So, we hold together thank’s to the electromagnetic force.

An interesting fact with that realization is that that implies that we never touched anything, we are really close but never actually get the chance to have contact between two things. An electron which is a negative particle surrounding the nucleaus in a cloud of probability, Wait ? cloud of probability, yes yes , my friend, we into quantum mechanics, meaning that the phenomenon happening is exactly the opposite of what you would think. For example, you can’t know the position of a particle in space in quantum mechanics ? Why ? Excellent question, you simply can’t because doing a measure affects the result ?How come we can have experiment that are reproducible then ? First, if it is on a large scale, so big that we mostly ignored the laws of quantum mechanics and second if you recreate the same conditions, temperature, laser power, you will be able to reproduce the measurements.

Interested by quantum mechanics ? Well it will be my next topic since there is so much to say about it. To go back to our interesting fact, since it is a cloud of probability and that everything we see, matter, my chair, is made of electron, the electron repulse themself and do not touch at a microscopic level. How come we feel something ? The brain is made to analyse is physical environnement and will the sensor, the nerve, the dentrite are stimulate by electron. So we feel at a certain level the repulsion between the atoms !Isn’t awesome ! Ah science always surprising !

First of all, the name of that thing is called a PMT which stands for photo-multiplier and this detector is used in many experiment. It is use to convert a photon into an electron with the photo electric effect.

Okay, okay, the light, the thing that makes us see colors and the environnment as a finite speed. I know that might be weird, but you need to consider light as a particle that travel at a certain speed, 300 000 000 m/s. But how can light be everywhere if it is a particle ? it should enter in collision with many things right ? Okay, first of all, by things we mean ordinary matter (the difference will be explained in more detailed in another article) but the short answer is that light can also be a wave. Wait wait, how can something be a particle and a wave at the same time ? It is an effect we have observe since 1900. There has been many experiment proving this theory, it is what we call the Wave–particle duality. One of the important experiment that showed that light can be particle is the photoelectric effect. Here is a really quick and brief explanations of this experiment. You throw light at a metal piece and for an unknow reasons you can measure some current, in other words, electron moving towards a certain direction, the only reason for this current to exist is that the light your throw is made of particle that interact we the materiau and release an electron which creates the current. For detailed information about the experiment see :…

So we now know that light is a particle but how can it be a wave ! Let’s talk about the interference experiment ! If you throw water into a slit the water will went throw and create a maximum at a certain place (the center), okay this is normal since it is a wave (picture 1).If you do the same experiment with light the result that you should expect is the picture 2. However, we observe the result on the picture 3. Therefore, the only plausible explanation is that sometimes it is a waves and sometimes it is a particles called photon ! Depending on how your experiment is based you will observe a different state. You will then ask youself why ? why is light behaving so weirdly, I will just repat as I said, unfortunetely, we don’t really know, we just know how it is happening and this is science !

Wanna know something funny about the photon ?

The photon is massless What ? What does that mean ?How can something be massless ? We assume that since it travel as the speed of light is as not rest mass, meaning that you can never slow this particle and weight it .That being said, it is affected by gravity (see picture 4) so it is made of matter and as a tiny mass that we can’t really measure.

Okay, getting back now to are main subject. What is exactly a PMT (photo-multiplier )and why does it looks like a flower ? A photo multiplier is a detector used to detect a photon, see this was not for nothing. How it works ? Well it used a photo cathode, meaning the photo electric effect to convert the photon emitted into a electron as we as seen before. Then, the electron is acellerated by the high voltage on the small piece of metal (high voltage create a field that accelerate the particle, see picture 5). The electron has actually so many energy, as a buble of boiling water, then when he will hit the metal, it will transmit some of his energy to the electron of the metal and then if the electron have enough energy to be free of the metal, it will move and then hit the other piece of metal and etc. So at the end you have a current (bunch of electrons) that orignally came from the photon detected. Of course, the efficiency is not 1, about only 3 photon out of 10 are converted into electron with the photo electric effect. However, to also try to increase this efficency, you can reflect the light at a point you know it will work. So, you can create a certain reflector that will increase the effiency. In our case, this particular reflector as the shape of a flower.

So, just a quick wrap up, you want to detect a particle of light, so you use a photo multiplier, that will convert that photon into an electric signal using the photo electric effect.This conversion is not really efficient, so to make better, you build a reflector that looks like a flower.

Questions ? Comments ( Too long, unclear, too complicated, boring) Any feedback will be highly appreciated !

Okay let me say something clear about science just before starting, it is not something about an opinion, it is not something that you can argue, it is simply facts that have to be proven again and again by different people and at some point only then we accept this theory. It is not a matter of what you believe, it is simply about how can we explain what we see. It is not about why does the world exist, why are we alive, it answer only the how but never the why. The «why» is more link to philosophy and religion, it has to be clear science have no intention of being a religion for example you can yourself try to reproduce every experiment and argue about the method, discuss the result. However, you have to be able to explain why you would really reject the result.

Unfortunetely, it seems that people are forgetting how science is done. If this happen then you can argue every single result and maybe think that the result are not really valid and that they maybe not true or that alternative facts are real ;).

So just so that everyone is on the same page, Let’s recap what is the science method:

1- To an hypothesis that could explain a known phenomena or a effect that we still don’t fully understand.

2-Try to think about things you could measure that could test this theory.

3-Design an experiment to find these measurements.The key thing is that your experiment most be reproductible.

3-Try to thing of every background source or effect that could influence the measurements.

4-Take the data, do the analysis trying to take in account every bias of the experiment.

5-Look at your result as objectibly as possible and conclude about the result of your experiment.

6-Make a query for a publications and revise your article again, again and again, so that everything you did was perfectly clear and as objective as possible

7-After a long time of revision , publish your article

In conclusion, all this process can take a very long time and maybe your result is quite useless but it will maybe help someone in 50 years so we never know.