2012, Week 20
Audio (MP3, 57Mb)
Neptune and Vulcan: Dark Matter in the Solar System
Dr. Rob Knop
Professor of Physics, Quest University, Canada
The cosmological Dark Matter is one example of a more general thing that we might call “dark matter” with lowercase letters– that is, something that has not been observed directly, but whose existence we infer because of its gravitational effects. In the 19th century, there was dark matter in the Solar System: Uranus was showing deviations in its orbit that could not be explained by the action of the Sun and the other known planets. That led to the discovery of Neptune. Similarly, deviations in the orbit of Mercury led to the postulated planet Vulcan inside Mercury’s orbit. However, it turned out that Vulcan didn’t exist at all, and that the answer to the question of Mercury’s orbit was a modification of our theory of gravity.
First presented in Second Life in April, 2009.
Questions and comments can be posted on the discussion thread on Starship Asterisk; Dr. Knop will answer a selection of questions posted by May 20, 2012.
PDF of slides (PDF, <1Mb)
Files also available here: http://www.mica-vw.org/wiki/index.php/Neptune_and_Vulcan