Page 392 - 89 history of astronomy_opt

from the sun is to measure the velocity of
the earth’s orbital motion, giving the cir-
cumference traversed in a year, and so the
radius of the orbit. This has been done
by comparing observation and experiment.
The aberration of light is an angle 20” 48,
giving the ratio of the earth’s velocity to
the velocity of light. The velocity of light is
186,000 miles a second; whence the distance
392