Lecture 34
Astronomy/Origins 2B03
“The Big Questions”
Lecture #34
What makes a particle “elementary” ?
• A particle is elementary if it has no inner structure (i.e not “made” of some even smaller entities).
Quarks and leptons are the most elementary particles we know about at this time. They are no larger than 10-18 [cm]
The Standard Model
• Quarks and leptons are the most fundamental particles of nature that we know about.
• Up & down quarks and electrons make up ordinary matter.
• The other quarks and leptons can be produced in cosmic ray showers or in high energy particle accelerators.
Matter
Hadrons
Baryons
Mesons
Leptons
Charged
Neutrinos
Quarks
Anti-Quarks
Baryons (baryonic matter) - all normal ‘stuff’ made of protons and neutrons (you, me, stars, planets, etc)
W IMP dark matter would be “non-baryonic” MACHOS would be baryonic
The Four Fundamental Forces
Weaker
1. Gravity
2. Weak Force
Stronger
3. Electromagnetic force
4. Strong Force
All other forces you know about can be attributed to one of these!
The New Concept of
Force
In the 1960’s, a new theory of interactions was developed.
At the heart of it is the concept that:
Richard Feynman, 1918 -1988
1965 Nobel Prize in Physics
Forces are the result of the exchange of
“force carriers” between the two particles involved in the interaction.
The force carrier of the electromagnetic force is the
photon
Unification of the forces
Two BIG questions:
1. W hen does gravity unify?
2. What breaks the
Electroweak force?
• Grand unified theories (GUTs) try to explain three of the forces in terms of a single consistent set of physical laws
• A “theory of everything” (TOEs) would explain all four forces
• TOEs suggest that all four physical forces were equivalent just after the Big Bang
Antimatter = Same mass but opposite charge
We can make anti-matter
• And so can nature
– Cosmic Ray shower
• PET Scans
“The Big Questions”
Lecture #34
What makes a particle “elementary” ?
• A particle is elementary if it has no inner structure (i.e not “made” of some even smaller entities).
Quarks and leptons are the most elementary particles we know about at this time. They are no larger than 10-18 [cm]
The Standard Model
• Quarks and leptons are the most fundamental particles of nature that we know about.
• Up & down quarks and electrons make up ordinary matter.
• The other quarks and leptons can be produced in cosmic ray showers or in high energy particle accelerators.
Matter
Hadrons
Baryons
Mesons
Leptons
Charged
Neutrinos
Quarks
Anti-Quarks
Baryons (baryonic matter) - all normal ‘stuff’ made of protons and neutrons (you, me, stars, planets, etc)
W IMP dark matter would be “non-baryonic” MACHOS would be baryonic
The Four Fundamental Forces
Weaker
1. Gravity
2. Weak Force
Stronger
3. Electromagnetic force
4. Strong Force
All other forces you know about can be attributed to one of these!
The New Concept of
Force
In the 1960’s, a new theory of interactions was developed.
At the heart of it is the concept that:
Richard Feynman, 1918 -1988
1965 Nobel Prize in Physics
Forces are the result of the exchange of
“force carriers” between the two particles involved in the interaction.
The force carrier of the electromagnetic force is the
photon
Unification of the forces
Two BIG questions:
1. W hen does gravity unify?
2. What breaks the
Electroweak force?
• Grand unified theories (GUTs) try to explain three of the forces in terms of a single consistent set of physical laws
• A “theory of everything” (TOEs) would explain all four forces
• TOEs suggest that all four physical forces were equivalent just after the Big Bang
Antimatter = Same mass but opposite charge
We can make anti-matter
• And so can nature
– Cosmic Ray shower
• PET Scans