The measurements were getting better. c is the speed of light; θ the angle the star is displaced, measured in radians (2π radians equals 360 degrees, so 1 radian is approximately 57.3 degrees). An aberration is a tiny change in the position of a star or any heavenly body by the connivance of the motion of light and the observer. In 1728, English astronomer James Bradley calculated the speed of light by observing stellar aberrations, which is their apparent change in position due to the earth's motion around the sun. By measuring the angle of this change and subtracting the speed of the earth, which he could calculate from data known at the time, Bradley came up with a much more accurate number. Another great breakthrough was conducted by James Bradley in 1728, producing the first ever quantitative experiment concerning the speed of light.
In astronomy, aberration (also referred to as astronomical aberration, stellar aberration, or velocity aberration) is a phenomenon which produces an apparent motion of celestial objects about their true positions, dependent on the velocity of the observer. In 1728 James Bradley, an English astronomer, determined the speed of light from the apparent orbital motion of stars that is produced by Earth’s orbital motion. The first measurement of c that didn't make use of the heavens was by Armand Fizeau in 1849. James Bradley FRS (1692–1762) was an English astronomer and priest who served as Astronomer Royal from 1742. The first measurement of c that didn't make use of the heavens was by Armand Fizeau in 1849. The magnitude of the aberration could be v/c? Starlight Aberration Due to the velocity of the earth, light appears to arrive at an angle. In the case of "stellar" … This is within 0.5% of the correct value. That means the deviation from the real position of a star is about 30/300000 rad =180*3600/3.14159/10000 ~20arcsecond.
In 1728 James Bradley, an English physicist, estimated the speed of light in vacuum to be around 301,000 km/s. James Bradley (1693-1762) James Bradley was an English astronomer most famous for his discovery of the aberration of starlight. Another method is to use the aberration of light, discovered and explained by James Bradley in the 18th century. Stellar aberration causes the apparent position of stars to change due to the motion of Earth around the sun. James. The finding was an important piece of evidence supporting Copernicus's theory that the Earth moved around the sun, and also provided an alternative way to estimate the velocity of light. An astronomer James Bradley, sailing on the Thames with some friends, noticed that the little pennant on top of the mast changed position each time the boat put about, even though the wind was steady. Approximately 50 years later, in 1728, the noted British astronomer James Bradley (1693-1762) made an entirely different type of astronomical observation from which he was able to calculate the speed of light.