James Bradley

James Bradley:
the Discovery of Stellar Aberration


Stellar Aberration

" In 1728 James Bradley made another estimate by observing stellar aberration: The apparent displacement of stars due to the motion of the Earth around the Sun. He observed the star Draconis and found that its apparent position changed during the year. All stellar positions are affected equally in this way. This distinguishes the effect from parallax which affects nearby stars more noticeably. A useful analogy to help understand aberration is to imagine the effect of motion on the angle at which rain falls. If you stand still in the rain when there is no wind it comes down vertically on your head. If you run through the rain it appears to come at you from an angle and hit you on the front. Bradley measured this angle for starlight. Knowing the speed of the Earth around the Sun he found a value for the speed of light of 301,000 km/s. "
(source: Relativity FAQ by Philip Gibbs www.public.iastate.edu/~physics/sci.physics/faq/measure_c.html)

Read more: James N. Douglas lecture excerpt

P Bickers at U of Idaho has some relevant notes with the following nice image.

www.phys.uidaho.edu/~pbickers/Courses/310/Notes/book/node136.html (excerpt)


Take one 24 foot vertical telecope ...

This method requires more astronomical expertise, namely the ability to accurately measure ecliptic coordinates. Maybe we could enlist the help of the Connecticut SAS chapter, they have a super telescope facility.