WHAT IS THIS UNIVERSE WE LIVE IN?

SATURDAYS WITH PHYSICS – PART 1

Dr. Larry Curtis

Distinguished University ProfessorDepartment of Physics and Astronomy

University of Toledo

THE NATURE OF MATTER_________________________________________________________

All matter consists of little bits of positive and negative electricity:in perpetual motion;attract each other at short distances;repel each other when pressed too close together.

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The most important discovery ever made.If all other scientific information we know were lost in some

cataclysmic event, and only this information survived, all could be rediscovered in a very short time.

  - Richard P. Feynman

Matter: microscopic constituency - atoms

Atoms near each other attract by mutually induced electric dipoles

net attraction (1/r6)

Atoms squeezed together repel by Pauli fermion exclusion

net repulsion (1/r12)

M+ 2000 m-

Einstein's Explanation of Brownian Motion

ATOMS: Democritus ~450 BC Unproven conjecture until 1905

Brownian Motion (pollen grains in water) Robert Brown 1827

Atomic size deduced from Brownian Motion Albert Einstein 1905

ATOMS became FACT, not THEORY

Iron atoms positioned on a carbon surface

700 keV Li+ beam (v=4.4 mm/ns) incident on a thin (3 g/cm2) carbon foil.

The blue light is H-like 4f-5g in Li2+ (4500Å, =3 ns, x=1.3 cm). The green light is He-like 2s 3S-2p 3P in Li+ (5485Å, =44 ns, x=19 cm).

Successive Doubling:

1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024Ten doublings (or halvings) increases (or decreases) the size by a thousand-fold !

79 halvings of one mole takes you to the last atom!

79 doublings of one meter takes you to the next galaxy!

Interactive Comet Animation

Does watching something change what it does?

If the sun were electromagnetically dark, butgravitational massive, would orbits be the same?

Where does the pendulum spend the most time? The least time?

Dwell time:

High: many / slow

Low: Few / fast

Time exposure

Equal time insideNo time outside

Most time at end points Least time at center

Most time at aphelion and perihelion

Kepler Planetary Orbits

Trojan asteroids

Position of electrons in an atom

Laplacian Determinacy – A Certain Mistake

Pierre Simon Laplace - 1776: “An intelligence that knows all of the relations of the entities of the universe at one instant could state theirpositions, motions, and general effects any instant in the past of future.

Henri Poincare – 1903: “Small differences in the initial conditions can produce very great ones in the final phenomena – prediction Then becomes impossible (1st recognition of chaos).

Werner Heisenberg – 1924: There is a fundamental limit on the accuracy to which position and velocity can be determined.

Stephen Hawking –1988: In the cosmology of the Big Bang and BlackHoles, space and time themselves break down at short distances.

ACTION-AT-A-DISTANCEExchange of a “gauge boson”

Exchanging a particle can produce both attractive and repulsive interactions.

Interactions between any two particles involves all the particles in the universe.

Electron-positron pair production

PET scan: Ingest sugar with tagged positron-emitting Fluorine-18 (110 min. halflife).

Sugar concentrates at high metabolism. On decay, positrons encounter electrons.

 

Ragnar Hellborg

Lund University

Positron Emission Tomography (PET) Scan

Electron-Positron PairCreation and Annihilation

Once created, e+ and e- are stable until annihilated

Past

Future

Here-Now

Are they all reallythe same electron?

time

space

Backward, turn backward, O time in your flight.Make me a child again,just for tonight. - Elizabeth Akers Allen

The “dressed electron” is like the parable of the blind men and the elephant. It has many seemingly separate aspects, but it is nonetheless a single thing.

Cambridge University Press