# 1729 Aberration of light

## Aberration of light

James Bradley used the apparent slant of starlight to show that the speed of light is finite, and to calculate its speed to be 10,210 times faster than Earth in its orbit.

## It’s not where it seems

Hans discovered that the light rain that slanted toward him
when he moved with the light wind slanted away from him
when he stood still.

Starlight moves; Earth moves in a frame of reference that feels motionless, which is why, it seems, rain that falls hits us in the face and telescopes pointed at a star slant toward the way we orbit.

## Aberration of sight

My brain fills in for my blind spot. Two faces become a candlestick. A distant lake disappears as I approach. A mote flies in my eye. I blink and then it isn’t there.

Aberration is not parallax, which Friedrich Bessel used in 1838 to calculate the distance to a star. Parallax is the apparent movement of an object relative to a more distant object, and depends on the movement of the observer and the distance of the object from the observer. Aberration of light is the apparent displacement of an object and depends only on the speed of light and the movement of the observer. Both aberration and parallax, however, support the Copernican theory that the earth revolves around the sun.

See also in The book of science:

Readings in wikipedia: