Modern Physics

We do not Know It All!!

General Relativity• Einstein’s merging of Special

Relativity with Gravity, Space and Time.

• The math involved is super difficult!!

• Solved the problem with the orbit of Mercury, which Newtonian Mechanics never described with complete accuracy.

• All observations have confirmed the theory thus far.

Basic Ideas of General Relativity• Space and time are merged into a single

“fabric” called space-time.• Gravity is caused by objects warping the fabric

of space-time.• Where there is more gravity, time is slower.

Where there is less gravity, time is faster.• Light is warped by gravity. This is used in

gravitational lensing.

Gravity and Time

Gravity and Time

Gravity and Time

Gravity as Warping of Space-Time

Gravitational Lensing

Quarks • Physicists now know protons and neutrons are not fundamental particles.

• Protons and neutrons are made of quarks, namely the up and down quarks.

• Six quarks are known to exist and each have an antiquark.

Proton

Quark Confinement• Quarks have never been observed in isolation,

which caused their existence to be doubted for a long time.

• Quarks either exist as a triplet (baryon) or a meson (quark/anti-quark pair).

• Latest calculations indicate a force of about 16 tons hold the quarks in a meson together.

The “Color” of Quarks

• Do not confuse this with color in the traditional sense, it is a quantum state.

• There are eight known colors of quarks but most common are red, green, and blue.

• These colors combine so that anything made of quarks is “colorless”.

Asymptotic Freedom

• It is the idea that the further apart quarks get from one another, the strong nuclear force gets even stronger.

• Quarks which are close to one another actually have some freedom to move about.

• In the 1970s these calculations saved to Standard Model of Particle Physics.

Leptons• Leptons include the very familiar electron, the muon, and the tau.

• μ and τ leptons are similar to electrons but heavier.

• Each has a corresponding neutrino, which are specific.

• νe

• νμ

• ντ

Fermions• Fermions are particles which have a “spin” of ½.

• Namely Fermions are quarks and leptons.

• The Force Carriers, or Bosons, have a “spin” of 1.

• Do not confuse this “spin” with the traditional idea of spin.

More on Bosons• Photons, γ, carry electromagnetic

interactions, such as light.• The W and Z bosons are involved in weak

interactions, most familiar is nuclear radiation.• Gluons are involved in strong nuclear

interactions and have “color”. The study of gluons is a part of Quantum Chromodynamics (QCD).

No Gravity??• As of yet there is no

quantum definition of gravity.

• Gravity is so weak at the particle level it seems to be insignificant.

• Unification is the goal of combining General Relativity with Quantum Physics.

• The graviton boson has been proposed but there is no evidence.

Mesons• Mesons most simply are a quark

and anti-quark pair.• Combined they are “colorless”.• They are involved in strong force

interactions.• They mediate interactions

between baryons and leptons.

Baryons• Baryons are structures composed of three

quarks.• A Baryon is “colorless”.• There have been hundreds of these

discovered, most of which decay quickly.• Protons and Neutrons are Baryons.• Mesons and Baryons together are known as Hadrons.

Higgs Boson?

The End?