Scale of the Universe



"By convention there is color, by convention sweetness, by convention bitterness, but in reality there are atoms and space."

Democrtitus, the laughing philospher ~400BC

"The division of natural things has a limit; an indivisible something exists. The division of natural things attains the smallest and last parts which are not perceptible by the aid of human instruments."

A view at odds with the church

Giordano Bruno ~1600

"though they may not be primary Concretions of the most minute Particles of matter, but confessedly mixt Bodies, are able to concurre plentifully in the composition of several very differing bodies without losing their own Nature or Texture, or having their cohesion violated by the divorce of their associated parts or ingredients."

Robert Boyle 1661

M. et Mlle. Lavoisier
Charles-Augustin de Coulomb


John Dalton


Joseph Louis Gay-Lussac
Amedeo Avogadro
Dmitri Mendeleev
"At first there were very few who believed in the existence of these bodies smaller than atoms. I was even told long afterwards by a distinguished physicist who had been present at my [1897] lecture at the Royal Institution that he thought I had been `pulling their legs.' "
J J Thomson

Conclusions from these quantitative experiments led to an Atomic Theory



Their are five known forces

  • Gravity F=G(m1m2)/r2
  • Electromagnetism F=k(q1q2)/r2
  • Strong: attraction among quarks and between neutrons and protons
  • Weak: radioactive decay
  • Dark Energy

above picture of sun taken by Wellesley student. A more dynamic

DM and DE

Dark Matter

Dark Matters from PHD Comics on Vimeo.



Tom Lehrer words

We are Star Dust



Following the Big Bang, the universe is mostly protons (Hydrogen), neutrons and electrons. As gravity pulls clumps of matter together gaseous clouds form. At first electromagnetic repulsion limits this condensation, but if the mass is large enough gravity overcomes the repulsion of the protons. The cloud collapses until the strong force begins to fuse the hydrogen into helium and a star is born.

An equilibrium between the gravitational attraction and the kinetic energy released from the fusion of hydrogen keeps the star from further contraction. As hydrogen is used up in the core, the core again collapses from gravity until the helium begins to fuse. This process repeats creating an onion like series of shells undergoing a series of fusion reactions.

For large stars, this continues until the core has become iron, which can no longer fuse. The star rapidly collapses on itself and the resulting rebound is known as a supernova. The various elements are formed from these fusion reactions and the reactions occurring during the supernova explosion.

 A more detailed and coherent, well illustrated, explanation can be found at this U. Va. Astro site.






Physics Chantuse  

Structure and Periodicity

Build an atom from quarks

Scattering Experiment



Changing Ideas of Atomic Structure

The NY Times had a special issue on the Best of the Millennium. Oliver Sacks wrote this piece on the Best invention of the millennium

Make your own Bohr atom


Bohr Atom

Interference Debroglie Atom
light absorption and energy levels

periodicity in atom size

Atomic Radii decrease across the periodic table and increase down the table


university of akron periodic trends





What is Science? Feynman


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