Proton

Along with neutrons, protons make up the nucleus, held together by the strong force. The proton is a baryon and is considered to be composed of two up quarks and one down quark.
It has long been considered to be a stable particle, but recent developments of grand unification models have suggested that it might decay with a half-life of about 10³² years. Experiments are underway to see if such decays can be detected. Decay of the proton would violate the conservation of baryon number, and in doing so would be the only known process in nature which does so.
When we say that a proton is made up of two up quarks and a down, we mean that its net appearance or net set of quantum numbers match that picture. The nature of quark confinement suggests that the quarks are surrounded by a cloud of gluons, and within the tiny volume of the proton other quark-antiquark pairs can be produced and then annihilated without changing the net external appearance of the proton.

Constituents of an Atom

The electrons, protons and neutrons which make up an atom have definite charges and masses. If they are modeled as hard spheres with the same density, they would have the relative sizes shown. While that model should not be taken as reality, it gives us a convenient object to which to attach the definite properties of the particles.
While the charges and masses are precisely known, the sizing is just fun and games. Our best information about the proton and neutron indicates that they are constituent particles, made up of three quarks each. They do however seem to have an effective density which is roughly characteristic of all nuclei, and we can attribute to them a radius of about 1.2 x 10^-15 meters. The electron is a fundamental particle, classified as a lepton, which is apparently not made out of any constituent particles. Down to scales of a thousand times smaller than the proton radius quoted above, they have no apparent structure.

The Size of an Atom

The size of atoms can be estimated with the use of Avogadro's number along with the atomic mass and bulk density of a solid material. From these, the volume per atom can be determined.


The cube root of the volume is an estimate of the diameter of the atom. For carbon, the molar mass is exactly 12, and the density is about 2 gm/cm^3. The estimated volume is then


and the estimate of the carbon atomic diameter is the cube root of that.


This estimate is a bit small. It can be refined somewhat by considering the atoms to be spheres and packing them in different ways. Carbon in diamond form has a different density than graphite because of its atomic lattice structure. But this estimate at least establishes the kind of atomic sizes expected. A typical atomic diameter is 0.3 nm.

Sooo Funny

Question:

Upon entering a laboratory, you see an experiment. How do you know which class it belongs to?

Answer:

If it's green and wiggles, it's biology.

If it stinks, it's chemistry.

If it doesn't work, it's physics.

Particle Physics

particles inside protons and neutrons (in the left) and new sub-particles after a reaction between neutron-neutron and proton-proton (in the right)

Wind power

Wind power is the conversion of wind energy into more useful forms, such as electricity, using wind turbines.

At the end of 2006, worldwide capacity of wind-powered generators was 73.9 gigawatts; although it currently produces just over 1% of world-wide electricity use, it accounts for approximately 20% of electricity use in Denmark, 9% in Spain, and 7% in Germany.Globally, wind power generation more than quadrupled between 2000 and 2006. Most modern wind power is generated in the form of electricity by converting the rotation of turbine blades into electrical current by means of an electrical generator.
In windmills (a much older technology), wind energy is used to turn mechanical machinery to do physical work, such as crushing grain or pumping water. Wind power is used in large scale wind farms for national electrical grids as well as in small individual turbines for providing electricity to rural residences or grid-isolated locations.

Wind energy is plentiful, renewable, widely distributed, clean, and reduces toxic atmospheric and greenhouse gas emissions if used to replace fossil-fuel-derived electricity. 

The average output of one megawatt of wind power is equivalent to the average electricity consumption of about 250 American households.

Physics Joke 1:
When a third grader was asked to cite Newton's first law, she said, "Bodies in motion remain in motion, and bodies at rest stay in bed unless their mothers call them to get up."