The Evolution of Sub-Atomic Particle Theory
I’m going to tell you
about sub-atomic
particles.
You will be
interested . . .
or else . . .
Image: pngimg.com
Written by David Ilsley
Science is the human attempt to describe and understand
the universe.
We observe lots of things in lots of situations.
We then try to find a few simple ideas which explain
everything we see.
Image: pexels.com
There are millions of different substances in the world.
About 2400 years ago, Democritus in ancient Greece
proposed that all matter was made of a few types of tiny,
indivisible particles called atoms.
(Atom is Greek for indivisible.)
Putting these atoms together
in different combinations
could make all the huge variety
of substances we see around us.
Image: commons.Wikimedia.org
By about 1890, this theory had been quite well confirmed
by experiment and about 80 different atoms were known.
These 80 atoms explained all the millions of different
substances.
Thus, millions of things were explained in terms of just a
few simple ideas.
Image: pickpik.com
Atoms were thought of as tiny spherical balls.
Image: pickpik.com
But it was to get even simpler.
By 1930, it had been shown that all atoms consist of a
nucleus made of different numbers of protons and neutrons
surrounded by a cloud of electrons.
Protons, neutrons and electrons became the new
fundamental particles that all matter is made of.
Down from 80 to 3.
Image: commons.Wikimedia.org
Starting in the 1950s, experiments were done with
particle accelerators like the Large Hadron Collider at
CERN on the border of France and Switzerland.
Image: commons.Wikimedia.org
The Large Hadron Collider uses so much power that it
can only be used in summer when people need less
electricity to heat their homes.
Image: commons.Wikimedia.org
The Large Hadron Collider should not be confused with
the Large Hadron Kaleidoscope, available in the gift shop.
Image: flickr.com
Imagefreesvg.org
The Large Hadron Collider
accelerates particles like
protons to 99.999999% of
the speed of light by
running them round and
round a 27 km circular
tunnel using
electromagnets, then
collides them with particles
coming the other way.
A cloud chamber is used to
look at new particles that
come out of the collision.
Image: en.wikipedia.org
These experiments showed that protons and neutrons are
in fact not fundamental particles, but that they are made
up of quarks – two types – up quarks and down quarks.
A proton consists of 2 up quarks and a down quark;
a neutron consists of 2 down quarks and an up quark.
Proton Neutron
Proton
Neutron
Up quarks have a charge of +2/3
Down quarks have a charge of –1/3
So, protons have a charge of +1
and neutrons have a charge of 0
So, matter is now made of up quarks, down quarks and electrons.
Still 3 things.
Image: en.wikipedia.org
As well as quarks and electrons, there
are also neutrinos.
These are not part of normal matter,
but are produced when certain nuclear
reactions take place, like radioactive
decay, fission and fusion. They then fly
off at almost the speed of light.
Neutrinos interact very little with other
particles and most will pass right
through the Earth without touching
anything.
Electrons and neutrinos are leptons.
Leptons are much lighter than quarks.
Image: commons.Wikimedia.org
Now to complicate things,
when a lot of energy is
available, like in a particle
accelerator or a supernova,
heavier versions of the
quarks and leptons can
come into existence,
though they decay back to
the lighter versions within
a tiny fraction of a second.
These heavier versions of
the particles are not part of
normal matter either.
Image: commons.Wikimedia.org
Quarks and leptons
together are called
fermions.
There are also bosons.
These produce the
fundamental forces:
the strong nuclear force
the weak nuclear force
and the
electromagnetic force.
Image: commons.Wikimedia.org
Photons produce the electromagnetic
force which causes protons and electrons
to attract and causes protons to repel
protons and electrons to repel electrons.
Gluons produce the strong nuclear force
which holds quarks together in protons
and neutrons and holds protons and
neutrons together in the nucleus,
overcoming the electromagnetic repulsion
between the protons.
Z and W bosons produce the weak nuclear
force which causes nuclear reactions like
radioactive decay, fission and fusion.
The Higgs boson gives particles their mass.
Image: commons.Wikimedia.org
Gluons pull two quarks together with a force of 8 tonnes
weight.
Quarks are so tightly bound together than no one has ever
separated them or observed a free quark. In fact, quarks
cannot be separated.
The energy required to separate them would be enough to
create more quarks which would combine with the
separated ones. So there still wouldn’t be any free quarks.
Note that the fourth force, gravity, is not included here.
The boson thought to produce gravity is the graviton,
though the quantum mechanics of gravitons is not
understood, so it is left out of theories of subatomic
particles.
Image: commons.Wikimedia.org
This set of subatomic
particles is called
‘the standard model’.
Image: commons.Wikimedia.org
There are also anti-
matter particles (anti-
particles) for most of
these particles.
Anti-particles have the
same mass as the
corresponding particle,
but opposite charge.
For example, the anti-
matter particle for an
electron is a positron.
The anti-matter particle
for a tau neutrino is a
tau anti-neutrino.
Image: commons.Wikimedia.org
Anti-matter particles
either annihilate
when they meet
their normal particle,
turning into gamma
ray energy, or they
decay after a very
short time.
So they are not part
of normal matter
either.
Image: commons.Wikimedia.org
Chemistry can still be explained in terms of protons,
neutrons and electrons.
Adding in photons and neutrinos allows us to explain most
of physics too.
If we add dark matter and dark energy, we can also explain
most of astronomy – the science of everything.
Image: wallpaperflare.com
Dark matter is thought to be made of particles, though not
any of the particles in the standard model.
So clearly, there are more particles than those in the
standard model.
Dark energy seems to be a property of space and may not
be made of particles.
Image: wallpaperflare.com
The End
Human pursuit of understanding the universe led to the concept of atoms by Democritus and further advancements in sub-atomic particle theory. From the initial idea of indivisible atoms, to the discovery of protons, neutrons, and electrons, to modern experiments with particle accelerators, the journey has been one of simplification and deeper exploration into the building blocks of matter.
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Presentation Transcript
Im going to tell you about sub-atomic particles. You will be interested . . . or else . . . Written by David Ilsley Image: pngimg.com
Image: pexels.com Science is the human attempt to describe and understand the universe. We observe lots of things in lots of situations. We then try to find a few simple ideas which explain everything we see.
There are millions of different substances in the world. About 2400 years ago, Democritus in ancient Greece proposed that all matter was made of a few types of tiny, indivisible particles called atoms. (Atom is Greek for indivisible.) Putting these atoms together in different combinations could make all the huge variety of substances we see around us. Image: commons.Wikimedia.org
By about 1890, this theory had been quite well confirmed by experiment and about 80 different atoms were known. These 80 atoms explained all the millions of different substances. Thus, millions of things were explained in terms of just a few simple ideas. Image: pickpik.com
Atoms were thought of as tiny spherical balls. Image: pickpik.com
But it was to get even simpler. By 1930, it had been shown that all atoms consist of a nucleus made of different numbers of protons and neutrons surrounded by a cloud of electrons. Protons, neutrons and electrons became the new fundamental particles that all matter is made of. Down from 80 to 3. Image: commons.Wikimedia.org
Starting in the 1950s, experiments were done with particle accelerators like the Large Hadron Collider at CERN on the border of France and Switzerland. Image: commons.Wikimedia.org
Image: commons.Wikimedia.org The Large Hadron Collider uses so much power that it can only be used in summer when people need less electricity to heat their homes.
The Large Hadron Collider should not be confused with the Large Hadron Kaleidoscope, available in the gift shop. Imagefreesvg.org Image: flickr.com
The Large Hadron Collider accelerates particles like protons to 99.999999% of the speed of light by running them round and round a 27 km circular tunnel using electromagnets, then collides them with particles coming the other way. A cloud chamber is used to look at new particles that come out of the collision. Image: en.wikipedia.org
These experiments showed that protons and neutrons are in fact not fundamental particles, but that they are made up of quarks two types up quarks and down quarks. A proton consists of 2 up quarks and a down quark; a neutron consists of 2 down quarks and an up quark. Proton Neutron
Proton Neutron Up quarks have a charge of +2/3 Down quarks have a charge of 1/3 So, protons have a charge of +1 and neutrons have a charge of 0 So, matter is now made of up quarks, down quarks and electrons. Still 3 things. Image: en.wikipedia.org
As well as quarks and electrons, there are also neutrinos. These are not part of normal matter, but are produced when certain nuclear reactions take place, like radioactive decay, fission and fusion. They then fly off at almost the speed of light. Neutrinos interact very little with other particles and most will pass right through the Earth without touching anything. Electrons and neutrinos are leptons. Leptons are much lighter than quarks. Image: commons.Wikimedia.org
Now to complicate things, when a lot of energy is available, like in a particle accelerator or a supernova, heavier versions of the quarks and leptons can come into existence, though they decay back to the lighter versions within a tiny fraction of a second. These heavier versions of the particles are not part of normal matter either. Image: commons.Wikimedia.org
Quarks and leptons together are called fermions. There are also bosons. These produce the fundamental forces: the strong nuclear force the weak nuclear force and the electromagnetic force. Image: commons.Wikimedia.org
Photons produce the electromagnetic force which causes protons and electrons to attract and causes protons to repel protons and electrons to repel electrons. Gluons produce the strong nuclear force which holds quarks together in protons and neutrons and holds protons and neutrons together in the nucleus, overcoming the electromagnetic repulsion between the protons. Z and W bosons produce the weak nuclear force which causes nuclear reactions like radioactive decay, fission and fusion. The Higgs boson gives particles their mass. Image: commons.Wikimedia.org
Gluons pull two quarks together with a force of 8 tonnes weight. Quarks are so tightly bound together than no one has ever separated them or observed a free quark. In fact, quarks cannot be separated. The energy required to separate them would be enough to create more quarks which would combine with the separated ones. So there still wouldn t be any free quarks.
Note that the fourth force, gravity, is not included here. The boson thought to produce gravity is the graviton, though the quantum mechanics of gravitons is not understood, so it is left out of theories of subatomic particles. Image: commons.Wikimedia.org
This set of subatomic particles is called the standard model . Image: commons.Wikimedia.org
There are also anti- matter particles (anti- particles) for most of these particles. Anti-particles have the same mass as the corresponding particle, but opposite charge. For example, the anti- matter particle for an electron is a positron. The anti-matter particle for a tau neutrino is a tau anti-neutrino. Image: commons.Wikimedia.org
Anti-matter particles either annihilate when they meet their normal particle, turning into gamma ray energy, or they decay after a very short time. So they are not part of normal matter either. Image: commons.Wikimedia.org
Chemistry can still be explained in terms of protons, neutrons and electrons. Adding in photons and neutrinos allows us to explain most of physics too. If we add dark matter and dark energy, we can also explain most of astronomy the science of everything. Image: wallpaperflare.com
Dark matter is thought to be made of particles, though not any of the particles in the standard model. So clearly, there are more particles than those in the standard model. Dark energy seems to be a property of space and may not be made of particles. Image: wallpaperflare.com
