All Fundamental Forces and Particles Explained Simply | Elementary particles

Summary

This script delves into the intricate composition of the human body, from organs and cells to the fundamental particles that make up our universe. It explores the standard model of particle physics, detailing the roles of quarks, leptons, and bosons, and their interactions through forces like the strong nuclear, electromagnetic, weak, and the elusive gravitational force. The narrative highlights the mass-energy equivalence, the color charge of quarks, and the significance of the Higgs boson in imparting mass to particles. It underscores the ongoing quest to unravel the mysteries of the universe at the quantum level.

Takeaways

• 🧬 Humans are made up of organs, bones, blood, nerves, and are composed of around 40 trillion cells, each containing approximately 100 trillion atoms.
• 🔬 If we zoom into a cell, we find molecules, and further into those molecules, we find atoms, which are made up of a nucleus and orbiting electrons.
• 🌌 The nucleus itself is composed of protons and neutrons, which are made of even smaller particles called quarks.
• 🚀 Elementary particles, such as quarks, are the smallest known building blocks of the universe and cannot be broken down into smaller components.
• 🌐 The standard model of particle physics classifies particles into 12 matter particles and 4 force carriers, grouped into families: quarks, leptons, and bosons.
• 🔋 Elementary particles possess three basic properties: mass, spin, and charge, which are crucial for understanding their behavior.
• 👫 Quarks come in six 'flavors' and three 'colors', and they bind together to form baryons like protons and neutrons through the strong nuclear force.
• 💥 The strong nuclear force, mediated by gluons, is the strongest force in the universe but has a very short range.
• ⚡ The electromagnetic force is responsible for the interactions between charged particles, such as electrons and protons, and is carried by virtual photons.
• 🌟 Electrons, which are leptons, orbit the nucleus and can jump between energy levels, emitting or absorbing photons in the process.
• 💫 The weak force, mediated by W and Z bosons, is responsible for processes like beta decay and is much weaker in strength and range than the strong force.

Q & A

What is the human body composed of at its most basic level?

The human body is composed of organs, bones, blood, nerves, and more, which are made up of cells, molecules, and ultimately atoms.

How many cells and atoms are estimated to be in a single human cell?

A single human cell contains approximately 100 trillion atoms, and the human body consists of around 40 trillion cells.

What are the subatomic particles found within the nucleus of an atom?

The nucleus of an atom contains protons and neutrons, which are subatomic particles.

What are elementary particles or fundamental particles?

Elementary particles, also known as fundamental particles, are the smallest known building blocks of the universe that cannot be broken down into smaller components.

What are the three families of particles in the standard model of particle physics?

The three families of particles in the standard model are quarks, leptons, and bosons.

What are the basic properties of all elementary particles?

All elementary particles have three basic properties: mass, spin, and charge.

How many quarks are there in total, and what are their charges?

There are six flavors of quarks, with up quarks carrying a charge of +⅔ and down quarks carrying a charge of -⅓.

What is the role of gluons in the context of quarks?

Gluons act as messenger particles, carrying a color charge from one quark to another and facilitating interactions between quarks, thus holding them together.

Why are protons and neutrons considered baryon particles?

Protons and neutrons are considered baryon particles because they are composed of three quarks each.

What is the strong nuclear force, and how does it relate to the structure of an atom?

The strong nuclear force is the force that binds quarks together to form protons and neutrons, and it is also responsible for holding the nucleus of an atom together.

What is the charge of an electron, and how does it interact with the nucleus of an atom?

An electron has a charge of negative 1 and interacts with the positively charged protons in the nucleus through the electromagnetic force, which causes attraction between opposite charges.

What is the significance of the weak force in particle physics?

The weak force is responsible for processes such as beta decay, which allows an unstable atom to achieve a stable state by converting a neutron into a proton or vice versa.

What is the role of the Higgs boson in the standard model?

The Higgs boson, associated with the Higgs field, is believed to be responsible for giving mass to all elementary particles and the W and Z bosons.

Why are gravitons hypothetical particles of interest in the standard model?

Gravitons are hypothetical particles that scientists are trying to add to the standard model as they are believed to be responsible for the gravitational force.

Outlines

00:00

🧬 Human Body Composition and Particle Physics

This paragraph delves into the intricate composition of the human body, starting from the macroscopic level of organs and tissues down to the atomic and subatomic levels. It explains that the human body is made up of around 40 trillion cells, each containing approximately 100 trillion atoms. The narrative zooms into the atomic structure, revealing protons, neutrons, and electrons, and further into subatomic particles like quarks and leptons. It introduces the concept of elementary particles, which are indivisible and form the fundamental building blocks of the universe. The paragraph also outlines the standard model of particle physics, which includes 12 matter particles and 4 force carriers, and explains the properties of these particles, such as mass, spin, and charge.

05:04

🚀 Exploring Quarks, Gluons, and the Strong Nuclear Force

The second paragraph focuses on the nature of quarks, which are elementary particles that come in six 'flavors' and three 'colors.' It discusses the concept of quarks binding together to form baryons, such as protons and neutrons, through the strong nuclear force mediated by gluons. The strong force is described as the most powerful force in the universe, despite its short range, and is responsible for holding atomic nuclei together. The paragraph also touches on the color charge property of quarks and how gluons facilitate the exchange of color charges, leading to the formation of colorless baryons. Additionally, it explains the phenomenon of meson formation when energy is applied to separate quarks within a baryon and how this relates to Einstein's mass-energy equivalence principle, E=mc squared.

10:09

⚛️ The Role of Electrons, Photons, and Electromagnetic Force

This paragraph explores the role of electrons and their behavior within atoms. Electrons are described as wave-like particles that occupy different energy levels around the nucleus and are responsible for the electromagnetic force through the exchange of virtual photons. The paragraph explains how the electromagnetic force arises from the interaction between charged particles and contrasts it with the strong nuclear force. It also discusses the process of electron transitions between energy levels and the emission of photons, which is the basis for the light we observe. The concept of real photons, which are detectable and carry electromagnetic fields, is introduced, and their role in the formation of atoms and the interaction between charged particles is explained.

15:10

🔬 The Weak Force, Beta Decay, and the Higgs Boson

The final paragraph delves into the weak nuclear force, which is responsible for processes such as beta decay in atoms. It describes how an unstable atom, with an imbalance between protons and neutrons, seeks stability through the conversion of a neutron into a proton or vice versa, facilitated by the emission of W and Z bosons. The paragraph explains beta-minus and beta-plus decay processes and their significance in nuclear fusion within stars and nuclear fission in atomic energy production. It also introduces the Higgs boson and the Higgs field, which are hypothesized to give mass to elementary particles. The weak force's short range and the rapid decay of W and Z bosons are highlighted, along with the ongoing quest to understand all fundamental forces, including gravity, which is not yet incorporated into the standard model.

Keywords

💡Elementary Particles

Elementary particles are the fundamental constituents of matter that cannot be broken down into smaller components. They are the smallest known building blocks of the universe and are the focus of particle physics. In the script, elementary particles such as quarks, which make up protons and neutrons, and leptons, including electrons and neutrinos, are discussed extensively. The video emphasizes their role in forming the basis of all matter.

💡Standard Model

The Standard Model is a theoretical framework in particle physics that describes three of the four known fundamental forces (excluding gravity), using 12 matter particles and 4 force carrier particles. The script mentions that these particles are classified into three families: quarks, leptons, and bosons, and it plays a central role in understanding the composition of the universe.

💡Quarks

Quarks are elementary particles and a type of fermion which combine to form protons and neutrons. The script explains that there are six 'flavors' of quarks, distinguished by their generations and charges. Quarks are never found alone in nature due to a phenomenon called color confinement, which is a key concept in quantum chromodynamics, a part of the Standard Model.

💡Gluons

Gluons are the force carrier particles for the strong nuclear force, which binds quarks together to form protons, neutrons, and other hadrons. The script describes how gluons facilitate the exchange of color charges between quarks, holding them together within particles like protons and neutrons.

💡Electrons

Electrons are elementary particles and a type of lepton with a negative electric charge. They are essential for the formation of atoms, as they orbit the nucleus, creating the electron cloud. The script discusses electrons in the context of their mass, charge, and role in the electromagnetic force.

💡Neutrinos

Neutrinos are elementary particles and neutral leptons that rarely interact with matter due to their extremely small mass and size. The script mentions that neutrinos are one of the least known particles because of their elusive nature and the difficulty in detecting them.

💡Mass-Energy Equivalence

The concept of mass-energy equivalence, represented by Einstein's equation E=mc^2, states that mass can be converted into energy and vice versa. The script uses this principle to explain how the mass of elementary particles is expressed in terms of energy and to illustrate the conversion of energy into mass during certain particle interactions.

💡Electromagnetic Force

The electromagnetic force is one of the four fundamental forces in nature, arising from the interaction between charged particles. The script explains how this force is mediated by the exchange of virtual photons and is responsible for the attraction between opposite charges and the repulsion between like charges, as well as the behavior of electrons around atomic nuclei.

💡Weak Force

The weak force is another of the four fundamental forces and is responsible for processes such as beta decay, where a neutron can transform into a proton or vice versa. The script discusses the weak force in the context of W and Z bosons, which mediate this force and are involved in the transformation of quarks.

💡Higgs Boson

The Higgs boson, often referred to as the 'God particle,' is associated with the Higgs field, which is theorized to give mass to elementary particles. The script touches on the significance of the Higgs boson in understanding why particles have mass and its role in the Standard Model.

💡Gravitational Force

Gravitational force is the fourth fundamental force in nature, which acts at an infinite range and is responsible for the attraction between masses. The script mentions the ongoing efforts to incorporate gravity into the Standard Model through a hypothetical particle called the 'graviton,' although it has not yet been discovered.

Highlights

Humans are considered the most intelligent creatures in the universe.

The human body is made up of organs, bones, blood, nerves, and is composed of around 40 trillion cells.

A single cell contains approximately 100 trillion atoms.

Atoms consist of orbiting electrons and a nucleus with protons and neutrons.

Elementary particles or fundamental particles, such as quarks, are the smallest known building blocks of the universe.

The study of elementary particles forms the foundation for classical and quantum physics.

The standard model of particle physics classifies particles into 12 matter particles and 4 force carriers.

Elementary particles have three basic properties: mass, spin, and charge.

Quarks come in six flavors and three colors, playing a role in the formation of protons and neutrons.

Gluons are massless particles that facilitate interactions between quarks and hold them together.

The strong nuclear force, mediated by gluon exchange, is the strongest force in the universe.

Protons and neutrons are baryon particles, and their mass comes from the energy of quark interactions.

Electrons are charged leptons that, along with neutrinos, form atoms through their interaction with the nucleus.

The electromagnetic force is responsible for the attraction between atoms and the repulsion between like charges.

The weak force, mediated by W and Z bosons, is responsible for processes such as beta decay.

Antiparticles have opposite charges to their corresponding particles, and lepton numbers help distinguish between neutrinos and antineutrinos.

The Higgs boson or Higgs field is believed to give mass to elementary particles and force carriers.

Gravitational force is a fundamental force with an unknown force carrier, the graviton, which is still hypothetical.

Particle physics discoveries have been awarded more than 20 Nobel Prizes, indicating the field's significance.

Understanding the universe at a quantum level is an ongoing pursuit for scientists on Earth.

Transcripts

We humans are the most intelligent creatures known  to have ever appeared in this universe.

What are humans made of?

The human body is composed  of organs, bones, blood, nerves, and more.  

Take one of the organs—the heart—

and if we zoom  into it deeply, we can see billions of cells.

But the cell isn't in its final stage.

Again, if we zoom further into the singular cell, we'll end up with molecules.

In just this one cell, there are  millions of unique complex molecules.

Take one of these molecules, zoom in even more, and—finally—we can see atoms.

To put it simply, the human body  consists of around 40 trillion cells and single cell contains approximately 100 trillion atoms.

But atoms are not the end of the story.

If we could magnify more, we would see clouds of electrons at the outer edge of the atom.

And if we magnify again, we will end up with empty spaces.  

But let’s not don't stop here,

if we could keep zooming further in, at the centre of the atom we would see the nucleus.

Yes, the orbiting electrons  and the nucleus are collectively called an atom.  

But again, the nucleus is not the end of the story.

If we zoom further into the nucleus, we  will see protons and neutrons sticking together.   

These are subatomic particles.

Let's take one of the protons and, again, zoom into it.

Inside uthe proton, we can see tiny dancing particles.  

These are quarks. These tiny particles are called  elementary particles or fundamental particles.

Quarks are elementary particles,

but there are a further total of 12 matter particles and 4 force carriers in the standard model of particle physics.

So, what classifies something as an elementary particle?

If we look at the proton, it consists of three quarks.

However, it's more precise to say,

'Quarks collectively form a proton,' rather than, 'A proton contains three quarks.'

So, protons are not elementary particles,  they are subatomic particles.  

Elementary particles don't have any sub-structures, and cannot be broken down into smaller components

Which means they aren’t made up of anything.

These are the final and smallest-known building blocks of our universe.

The study of elementary particles is called particle physics.

Studying and understanding these particles forms the  foundation for both classical and quantum physics.

So, let's return to the standard model.

There are 12 matter particles and 4 force carriers classified into 3 families:

Quarks, Leptons, and Bosons.

Quarks and leptons are together called fermions.

All elementary particles have  three basic properties: mass, spin, and charge.

If we look at the first particle,It has a mass of (2.4 MeV/c2) . 

Mass of all elementary particles is mentioned as energy.

It comes from Einstein’s mass-energy  equivalence equation E=mc squared.  

For example, if we convert 1 gram of mass into pure energy, It becomes 5.6*10^31 MeV

So, from here we can compare the mass of  this particle with 1 gram’s energy.

In the realm of particle physics, fermions are  generally characterized by half-integer spins,  

while bosons typically possess integer  spins such as 0, 1, or 2.

However, be careful: although we use the word ‘spin’,  it’s not the same as the spinning of a ball.

First, we start with quarks.

There are up quarks and down quarks, and each of them comes in three generations, 

so in total, we have discovered six  flavours of quarks.

The up quark has a charge of +⅔, while the down quark carries a charge of -⅓.

This same charge is continuous in their subsequent generations.

There is no major difference between the generations, though each generation tends to be heavier than the previous one.

We've already heard that a proton has a positive charge.

That charge is simply composed from the charges of the quarks.  

A proton is composed  of two up quarks and one down quark.

So, the combination of charges comes as +⅔+⅔-⅓,  which is a total of +1. 

Similarly, a neutron is composed of one  up quark and two down quarks,  

and the combination of charges -⅓-⅓+⅔ totals  0. So, the neutron comes with neutral charge.

The combination of three quarks  is called a baryon.

Therefore,  protons and neutrons are baryon particles.

Now, we can see that the same flavors of  quarks exist in a single baryon particle;  

for example, a proton has two up quarks.  So, how do we distinguish them?  

That's where an additional property comes into play, which is the color charge property.

And how do these three quarks bind together? It's  also related to the color charge property of quarks.   

Each flavor comes in three  colors: red, blue, and green.,  

However don't let these colors mislead you.

Quarks are much too small to be visible and thus could never have a visible property like color.  

The names were chosen because of a convenient analogy.

In a proton, there are three quarks, one of each color, and they constantly exchange colors among themselves.

But how do they exchange  colors and interact?

That's where the messenger particle or force carrier, Gluon, comes into play.

Quarks are able to change their color during their interactions. 

The gluon acts as a messenger particle,  

carries a color charge from one quark to another, and facilitates interactions between quarks.

So, gluons hold quarks together by exchanging  color charges. Since gluons are massless,  

they exchange colors between quarks  at near the speed of light. However,  

the same color cannot exist simultaneously  in two quarks. For example, in a proton,  

if one quark has a red color, the remaining  two quarks will have green and blue. If one  

quark has a green color, the other two  quarks will have red and blue. Thus,  

three quarks in a baryon particle always  have different colors by exchanging gluons.

If we combine the red, blue, and green  colors, we end up with no color. Therefore,  

the proton is a colorless particle. All baryon  particles are colorless. We've already heard  

about the strong nuclear force — that force is  simply the color charge that involves the exchange  

of gluons between quarks, binding quarks together  and creating the strongest force in the universe.

Even though it's the strongest force,  

its range is only a few femtometers.  One femtometer equals 10-15 meters.

We've already seen that protons have a positive  charge, but how do protons stick together in the  

nucleus, while the same electric charges repel  each other and opposite charges attract each  

other? This is also caused by the strong nuclear  force. The strong nuclear force can exist within  

the range of a few femtometers, while the  size of a proton is less than 1 femtometer.  

The strong force also leaks outside the  proton. This strong force overcomes the  

electromagnetic force, so two protons stick  together instead of repelling each other.

If we try to kick out a quark from a baryon, it  requires a lot of energy. Gluons are constantly  

exchanged between quarks and create a  tube-like structure. This tube is very  

strong. When providing energy to try to eliminate  one quark from a baryon, it acts like a spring  

or rubber band — the more energy given to pull  the quark, the stronger it becomes. But anyhow,  

if we provide enough energy to remove a quark,  instead of kicking it out from the baryon it  

creates a new quark and antiquark pair. This  pair is called a meson. This is how these new  

particles form, and where E=mc squared comes into  play. The energy used to expel the quark from the  

baryon is converted into mass, so the extra energy  creates a meson. However, mesons decay quickly.

The exchange of mesons between two baryons  is also responsible for same-charged protons,  

and neutrons stick together  in the nucleus. However,  

we have never found an isolated  quark or a particle with four quarks.

And another thing, if we calculate the mass  of all three quarks which exist in a proton,  

they appear to constitute only one  percent of the proton's whole mass. So,  

where does the proton get this extra mass  from? Well, gluons are massless and interact  

at nearly the speed of light. The energy between  quarks converts into mass when we measure it.

So far, we've looked at quarks, gluons, and  the strong force, which are responsible for  

creating the nucleus of the atom. However, an  atom contains both a nucleus and electrons. So,  

what is an electron? In the standard model of  particle physics, in the group of fermions,  

there is another family called leptons. This  family includes the electron, among a total of six  

particles: the electron, the neutrino, and their  next-generation particles. Electrons have a charge  

of negative 1, while neutrinos have no charge.  So, we can divide leptons into two categories:  

the charged leptons, which have a negative  charge — electrons, muons, and taus, and the  

neutral leptons, which carry no charge — electron  neutrinos, muon neutrinos, and tau neutrinos.

The electron is the only member of a  family of leptons which is involved in  

the formation of atoms. Quarks exist only  as composite particles with other quarks,  

while leptons are individual particles.

The size and mass of an electron are very  small, approximately 9*10-31 kilograms or  

0.5 mega electron volts. However, neutrinos are  extremely small, being millions of times smaller  

than electrons. That's why neutrinos rarely  interact with matter. Even though trillions of  

neutrinos pass through our bodies every second,  they are undetectable by modern methods due to  

their size. Therefore, the neutrino is one of  the least known first-generation particles.

Let's return to the topic of  electrons. Electrons orbit  

the nucleus like clouds due to their wave  behavior, but at different energy levels.

Electrons carry a negative charge, and all  charged particles have an electric field. As  

we already know, protons have a positive charge,  so protons are also charged particles. Then,  

what is the electromagnetic force? Quarks  constantly exchange gluons which are  

responsible for quarks sticking together,  generating a strong force. Similarly,  

when two charged particles come close to each  other they exchange virtual photons and create  

electromagnetic force. These are called virtual  photons because their energy cannot be detectable.

The exchange of virtual photons between charged  particles is the reason why particles of the same  

charge repel each other, and particles with  opposite charges attract each other. Unlike  

virtual photons, there are real photons  that also carry electromagnetic fields,  

which can be detectable — this is light.  We've already seen electrons orbiting nuclei  

at different energy levels. When an electron  jumps to a lower energy level, it emits a tiny  

packet of electromagnetic radiation —a photon.  It has no mass and travels at the speed of light.

But why do electrons jump between energy levels?  Electrons orbit at their own energy levels,  

but when electrons gain energy it jumps  to a higher energy level. However,  

it is always trying to remain  in its original orbit state,  

so it quickly jumps back to the normal state.  As a result, it releases its excess energy — a  

photon. Jumping between the distances or energy  levels determines the wavelength of light.

So far, we have seen quarks, leptons, and  their force carriers. The strong force is  

responsible for binding quarks together and  also for binding the nucleus. Photons act as  

a force carrier between charged particles,  creating the electromagnetic force. The  

resulting nucleus and electrons attract each  other, eventually forming a complete atom.  

The electromagnetic force is also stronger, but  it can never overcome the strong nuclear force.

The strong force needs to be strong to overcome  the electromagnetic repulsion between the  

positively -charged protons in the nucleus — if  it were weaker than the electromagnetic force,  

no atoms with more than one proton  in the nucleus would be able to form.

Now, we only have two force carriers left in the  standard model. So, what is the use of these? It's  

not very familiar to us, but it's as important  as the other forces — the weak force. In nature,  

everything seeks a stable position, so the atom  also. What is an unstable atom? In an atom,  

when the number of protons exceeds  the number of neutrons or the number  

of neutrons exceeds the number of protons,  the atom becomes unstable. This unstable  

atom will constantly try to achieve a stable  state. So, the extra neutron converts into a  

proton to maintain the stability of the  atom. But how can the neutron convert?

We've already seen that the neutron is a  combination of quarks: two down quarks and  

one up quark. And the proton is a combination  of two up quarks and one down quark. So,  

when a neutron converts into a proton, a down  quark changes into an up quark. If we look deeply,  

the down quark has a charge of -⅓ and  the up quark has a charge of +⅔. So,  

if the down quark changes into an up quark, it  needs to gain +1 charge. So, in order to do that,  

the down quark emits a W minus boson and becomes  an up quark. The W-minus boson has a charge of -1.  

So, the charge is conserved during this process.  But that boson decays very quickly into an  

electron and an antineutrino pair. An electron has  a charge of negative 1 and an antineutrino which  

has no charge. This is called beta-minus decay.  But what is an antineutrino? It's an antiparticle.

Yes, the fermion group has 12 matter particles  and also a reactionary 12 antiparticles. The main  

difference between particles and antiparticles  is their opposite charge. For example,  

electrons have a -1 charge, but antielectrons have  a +1 charge. The other name for an anti-electron  

is positron. However, neutrinos have  no charge and it remains at zero. So,  

in order to distinguish between neutrino and  antineutrino the lepton numbers come into play.

Similarly, when a proton converts into  a neutron, the up quark becomes a down  

quark. In order to gain the negative  charge, it emits a W plus boson. This  

boson quickly decays into a neutron and a  positron, which is called beta-plus decay.

Without this decay process, hydrogen atoms  cannot form helium atoms, and we can't get  

energy from this process, which means nuclear  fusion would never occur in stars. In our sun,  

hydrogen atoms turn into helium atoms. This  process provides our Earth with energy,  

which is essential for the formation and  sustenance of life and everything else.  

The same weak force is responsible  for nuclear fission. Nuclear fission  

is when large atoms split into two  atoms or release a daughter atom.

The other boson involved in the weak  interaction is the Z boson. When a particle  

and an antiparticle collide, it emits a Z boson,  and, Similar to the W boson, the Z boson decays  

very quickly, producing another particle and  antiparticle pair.The Z boson's charge is zero,  

so it only happens between a pair of particles  and antiparticles. The particle and antiparticle  

pairing together results in a zero charge.  For example, an electron has a -1 charge,  

and a positron has a +1 charge. So,  together they become zero-charged:  

the Z boson. And if we look at the meson,  it contains one quark and an antiquark,  

so it decays into a Z boson and quickly  becomes other particles. The reason why W  

and Z bosons decay quickly is because of their  mass, which is very high compared to fermions.

But why is it called a weak force? Because  its range is very, very small — smaller than  

a proton. If we look deeper, in the standard  model, only first-generation particles, gluons,  

and photons have a long life time. A  proton has a lifespan of 1034 years,  

and an electron 6.6*1028 years. On the other  hand, W and Z bosons have a lifetime of just  

10-25 seconds, and the second-generation  particle, the muon, lasts 10-6 seconds. So,  

due to their very short lifetimes, these are  only detectable in particle accelerators.

Only the first-generation particles are involved  in forming most of the matter in the universe.  

However, we can create baryon particles made up  of the second or third quarks, but these all have  

a much greater mass and decay very rapidly  into protons and neutrons. However, we don't  

yet know exactly why the remaining two generation  particles exist and quickly end their lifetimes.

And the other one that has a place in the standard  model is the Higgs boson or the higgs field, which  

is believed to be responsible for the mass of  all elementary particles and the W and Z bosons.  

That’s why it’s named “the God particle.” But  it's still a mystery. Not just the Higgs boson,  

but also all elementary things. To date, more  than 20 Nobel Prizes have been awarded in the  

field of particle physics. This means that every  discovery in particle physics is new to us.

So far, we've looked at the strong, weak, and  electromagnetic forces. However, our universe  

has four fundamental forces, the fourth one being  gravitational force. Scientists are trying to add  

an imaginary particle called ‘graviton’ to  the standard model, which may be responsible  

for gravitational force, but they are failing  because we have as yet been unable to find a  

force carrier responsible for gravitational force.  Gravitational force acts to an infinite range,  

so it’s believed that imaginary bosons will  have zero mass and be smaller than neutrinos.  

We have a long way to go to understand this.  However, scientists on the earth are becoming  

cleverer and are trying to understand how the  universe works at a quantum level. For now,  

the only way to understand the universe  is to study those point-like things. And,  

one day, we will understand everything,  before the aliens teach it to us.