summerinstitute?2006

Summer 2006 questions

Day 1 frequency of flashing light that triggers epilepsy

5 to 30 Hz

Day 2 glass flow

Glass doesn't flow

Paul's page on scientific myths

At room temperature for a 1 m high window 1 cm thick it would take 10^10 years to thicken by 10 angstroms (1 nm). 10^10 years, or 10 billion years, is the age of the Universe. (actually the age of the Universe is 13.7 +- 0.2 billion years.)

In the last few years the Corning Museum has revised its estimate for the viscosity of glass, it is now given the value of 10^20 poise at room temperature. Lead has a viscosity of 10^11 poise. So glass is a billion times less of a liquid than lead.

ASTM definition of a fluid

The Engineering definition for solid liquid or gas.

The ASTM (American Society for Testing and Materials) has a standard for determining whether something is a liquid. ASTM (1996) "D4359-90: Standard Test Method for Determining Whether a Material Is a Liquid or a Solid."

Here is their method: The material under test is held at 100deg.F (38deg.C) in a tightly closed can. The lid is removed and the can inverted. The flow of the material from the can is observed to determine whether it is a solid or a liquid.

They specify that the material in a 1 Liter container must flow over 2 inches in three minutes to be considered a liquid.

Under this test glass is definitely a solid.

Laser Source

A good source for pointer lasers is Z-bolt laser supply.

I now buy the slightly more expensive pointer lasers that use AAA batteries.

Since it is difficult and expensive to find the button cells for the smaller laser pointers.

I did manage to find and buy the laser button cell batteries on e-bay.

Source of Scientist biographies

Asimov's Bibliographic Encyclopedia of Science and Technology

Comparing Yellows

by Gorazd Planinsic

Using LEDs and ping pong balls.

The Physics Teacher, March 2004

http://scitation.aip.org/journals/doc/PHTEAH-ft/vol_42/iss_3/138_1.html

Gorazd also created the single water drop laser projection microscope.

Paul's Quotes

"What do you see?"

"Without a human eye and brain there is no color!"

Benjamin Franklin "About light, I am in the dark."

The number of colors in the spectrum

ROYGBIV

Isaac Newton named the colors of the spectrum,

He named 7 colors so there would be the same number of colors as there are musical notes. (At first he named 5 colors, but added two more to bring the total to 7.)

He also realized the importance of understanding perception, how the eye and brain work, while observing nature and scientific experiments. To do this he did experiments in which he inserted a knitting needle into his eye socket beside his eye ball and moved his eyeball observing the resulting changes in his perception.