About

Difficulty level:   ★ ★ ★

Colin’s Cosmos .com is a resource for relativity and other things physics. Welcome to my little niche in the universe! Please leave your feedback in the comments, and request any topics you’d like to know about. You can email me at “colin@[this-domain.com]”.

This site is not intended to teach you relativity. The “basic” articles introduce concepts, but the best (most precise) description is in equations. To learn it thoroughly you need to do the maths/physics. Go take a university course, it is typically a 4th year maths course. Buy the course textbook and work through the assigned chapters. The “technical” section is intended as a supplement to this material, and to explore detailed topics not present in textbooks, or to better clarify themes which are.

The background image is from here, and the side panel background is the famous “Hubble deep field”.

Site layout

Layout: The left panel has articles for all ability levels, and the right panel has technical articles aimed at graduate students and researchers. NASA’s Astronomy Picture of the Day is also included.

Articles are graded by difficulty level as follows (may change):

  • 0: no science, e.g. travel diary or a discussion of science culture
  • 1: no equations, e.g. a discussion of concepts in science
  • 2: high school physics level
  • 3: university undergraduate general relativity or astrophysics course
  • 4: PhD student
  • 5: advanced or obscure/niche topic

The design is responsive, with further adaption planned. For mobile devices, I intend to make a single column format which emphasises basic articles. When displayed on a computer, I intend to make the technical articles less hidden.

Textbooks are referenced by the author(s) surname(s), followed by a book icon such as: Wald or Misner, Thorne & Wheeler aka MTW. Hover over the author text to see a tooltip with the book title and other details.

Thanks to the creators of free images used in this site, including the textbook icon.

Maps are not precise with locations.

References link to entries in the Astrophysics Data System (ADS). From there, click the “arXiv e-print” link, freely available for everyone (older articles won’t have this option). (Note arXiv is pronounced “archive”; this is some nerd humour because X looks like the Greek letter chi (χ), which has a ch sound. In fact English letter X descended from chi, whose capital form (Χ) looks just like the English!) If you have journal subscriptions, for instance student access from a university, click the “Electronic Refereed Journal Article” link for the final polished product. e.g. Link to arXiv: tethered galaxy , link to ADS: Harrison . (ADS is updating their website…)