Science & Nature
1439 sites
Subcategories:
- Astronomy & Space (396)
- Chemistry (8)
- Earth Sciences (26)
- Biology (79)
- Physics (30)
- Mathematics (59)
- Weather & Climate (104)
- Amateur Radio (682)
- Electronics (47)
http://astronomical.org/
The Peoria Astronomical Society is a non-profit club for amateur astronomers in Peoria, Illinois, offering membership information, meeting schedules, constellation resources, and a newsletter archive. With links to their observatories, planetarium visits, and a learning center, this site serves as a hub for stargazers in the central Illinois community.
https://owlsp.com/stormchaseaccounts.php
OWLSP.com is a storm chaser's personal archive covering tornado and severe weather chase accounts from 2002 through 2023, with detailed entries for specific outbreaks across Oklahoma, Texas, Kansas, and beyond. The site includes chase narratives, photography, equipment info, and landscape scenes, making it a rich firsthand record of Plains storm chasing over two decades.
http://joyofpi.com/pilinks.html
A comprehensive link directory dedicated entirely to pi, curated by David Blatner, author of 'The Joy of Pi,' covering everything from basic pi facts and digit downloads to pi music, pi history, and Pi Day celebrations. Visitors will find hundreds of categorized links spanning memorizing pi, calculating digits, pi mysteries, and even wacky pi fun, making it a go-to hub for pi enthusiasts of all levels.
https://hfpropagation.com/
A continually updated reference tool for ham radio operators providing usable HF propagation frequencies and forecasts from major U.S. base cities to regions around the world. Color-coded charts, ionograms, and geomagnetic and solar data make it a practical real-time resource for planning amateur radio contacts.
http://sss-mag.com/smith01.html
SSS Online is a long-running RF and spread spectrum engineering magazine offering deep technical resources on Smith charts, S-parameters, impedance matching, Eb/N0, and link budgets. Managed by Pegasus and active since 1995, it serves RF engineers and ham radio enthusiasts with articles, software downloads, tutorials, and reference material on microwave and wireless design topics.
http://astroverde.org/
Astroverde is the official website of the Astronomers of Verde Valley, an amateur astronomy club based in Northern Arizona's Verde Valley region. Visitors can browse member astrophotography galleries, find star party schedules, access observing tools, and learn how to join the club.
https://h14s.p5r.org/2012/09/0x5f3759df.html
Christian Plesner Hansen's technical blog dives deep into the legendary fast inverse square root hack and its magic constant 0x5f3759df, tracing the algorithm's surprising history from Ardent Computer in the 1980s through SGI, 3dfx, and Quake III Arena. The post rigorously explains the underlying floating-point bit manipulation, generalizes the technique to arbitrary powers, and includes graphs and mathematical derivations that illuminate why this 'evil' hack actually works.
https://ads.harvard.edu/books
The NASA Astrophysics Data System (ADS) Virtual Library offers free online access to a curated collection of astronomy and astrophysics books, ranging from Copernicus's 1543 classic to modern astrophysics textbooks. Researchers and enthusiasts alike can browse and print foundational works on celestial mechanics, stellar astrophysics, lunar science, and solar physics from leading institutions like Harvard and the Lunar and Planetary Institute.
http://currentsky.com/
Bob Riddle's 'Qué tal in the Current Skies' is a long-running amateur astronomy site that began in the late 1980s as posts to the Big Sky Telegraph BBS and evolved over 30+ years into a web resource covering Earth and Space topics. The site now serves as a transitional landing page pointing visitors to his continuing work on Substack, with archived daytime and nighttime sky photos, calendar data, and astronomical observations.
https://tonnesoftware.com/
Tonne Software offers a catalog of free and low-cost electrical engineering programs for Windows, covering filter design, meter scale drawing, great-circle mapping, Smith charts, and more. The site also hosts technical articles and tutorials on topics like speech processing, AM demodulators, and CW bandpass filters, many published or submitted to QEX magazine.