To arrive at the edge of the world's knowledge, seek out the most complex and sophisticated minds, put them in a room together, and have them ask each other the questions they are asking themselves.

Interesting articles about amateur satellites.

RTL-SDR and GNU Radio with Realtek RTL2832U [Elonics E4000/Raphael Micro R820T] software defined radio receiver.

Watch the sun rise and set all over the world on this real-time, computer-generated illustration of the earth's patterns of sunlight and darkness. The clouds are updated every 3 hours with current weather satellite imagery. The site has also other interesting stuff such as hints for optimising web page load times, copies of Linux documents and manual pages and more.

Information about cardboard models of satellites (page in german, some of the links point to english sites).

Collection of experiments in electronics, magnetism and others, including esoteric subjects like "free energy" (in german).

An alternative to Wikipedia, using stricter quality control. "Our growing number of editor-approved articles are reliable and of world class quality, rivaling the best printed encyclopedias."

Abstract: This paper shows how linear algebra can be done better without determinants. The standard proof that a square matrix of complex numbers has an eigenvalue uses determinants. The simpler and clearer proof presented here provides more insight and avoids determinants. Without using determinants, this allows us to define the multiplicity of an eigenvalue and to prove that the number of eigenvalues, counting multiplicities, equals the dimension of the underlying space. Without using determinants, we can define the characteristic and minimal polynomials and then prove that they behave as expected. This leads to an easy proof that every matrix is similar to a nice upper-triangular one. Turning to inner product spaces, and still without mentioning determinants, this paper gives a simple proof of the finite-dimensional spectral theorem.

This paper was published in the American Mathematical Monthly 102 (1995), 139-154.
In 1996 this paper received the Lester R. Ford Award for expository writing from the Mathematical Association of America.

Gallery of microphotographs of animate and non-animate matter.