Physics keeps life going-物理 依据 生命

Δευτέρα, 29 Ιουλίου 2013

Κυριακή, 28 Ιουλίου 2013

Teaching Feynman Diagrams with Technology

Interesting technological  prosedure for teaching Feynman Diagrams is the following program as you  can see in the video:  

interaction e-e

 the interaction of two photons,
known as pair production γ +γ ➝ e- + e+. (One of
those photons is normally part of a strong static field
that interacts with a high energy passing photon.)                   

the procedure can be seen in the following video:

This procedure is based on the article :

Teaching Electron—Positron—Photon Interactions with Hands-on Feynman Diagrams,  The Physics Teacher -- April 2013 -- Volume 51, Issue 4, pp. 232, George Kontokostas and George Kalkanis.

More details you can find at the page

Τρίτη, 23 Ιουλίου 2013

The Maribo Meteorite and IPHO

The Maribo Meteorite...........

and the theorical problem of olimpiad.

A meteoroid is a small particle (typically smaller than 1 m) from a comet or an asteroid. A
meteoroid that impacts the ground is called a meteorite.
On the night of 17 January 2009 many people near the Baltic Sea saw the glowing trail or fireball of
a meteoroid falling through the atmosphere of the Earth. In Sweden a surveillance camera recorded
a video of the event, see Fig. 1.1(a). From these pictures and eyewitness accounts it was possible to
narrow down the impact area, and six weeks later a meteorite with the mass 0.025 kg was found in
the vicinity of the town Maribo in southern Denmark. Measurements on the meteorite, now named
Maribo, and its orbit in the sky showed interesting results. Its speed when entering the atmosphere
had been exceptionally high. Its age, year, shows that it had been formed shortly after
the birth of the solar system. The Maribo meteorite is possibly a part of Comet Encke.
The speed of Maribo
The fireball was moving in westerly direction, heading 285 relative to north, toward the location
where the meteorite was subsequently found, as sketched in Fig. 1.1. The meteorite was found at a
distance 195 km from the surveillance camera in the direction 230 relative to north.