# Meaning of Gravitaional Shear?

1. Oct 20, 2009

### beech

Is there more than one meaning for "gravitational shear". It seems to refer to focusing of light beams.

When I calculate the difference in velocity, of earth's side closest and farthest from the sun: the difference is about one meter/second. Is that gravitational shear?

Calculation

Orbital velocity is 2 times pi times the distance to the sun, divided by time, in this case the number of seconds in a year.

Velocity of Earth
v1 =2 * pi * 1.5 * 10^8 / ( 365.25 * 24 * 60 * 60 )
= 29.8653 km/sec.

v2 =(2 * pi * 1.5 * 10^8 - radiusEarth) / ( 365.25 * 24 * 60 * 60 )

Subrtact v1 - v2

The Radius of Earth is 6378 km.
The orbit is inclined to have a different velocity, at the sides nearest and farthest from the sun. This difference is, 1.27 meters/sec.

2. Oct 21, 2009

### AstroRoyale

Usually, gravitational shear is mentioned in relation to gravitational lensing, mainly weak lensing. The shear causes background galaxies in relation to a foreground cluster to become elongated, and also curved towards the center of the cluster. Look up "weak gravitational lensing". . .