1. The Lense-Thirring Effect Alex Robson

2. General Relativity Albert Einstein (1879-1955) Einstein realised the Newtonian theory of gravity did not account for events over large distances. Space is not just an empty place where things happen, but, combined with time, is a kind of fabric.

3. Space-Time Fabric The properties of this space-time fabric dictate how things move within it. If a heavy spherical mass were placed on a rubber sheet, it would deform this sheet. In the same way mass- energy in space-time warps the area accordingly.

4. The Lense-Thirring Effect In 1918, Joseph Lense and Hans Thirring predicted frame dragging. Any object with mass warps space-time around itself. If this object is spinning, it will induce a second distortion as it twists space-time around itself. If the space around this first mass is being dragged, then objects in or near this space should also affected.

5. Detecting the Lense-Thirring Effect Two satellites, LAGEOS and LAGEOS 2 have been used to detect the Lense-Thirring effect over 11 years. Each satellite is a highly reflective sphere. Laser signals are bounced off these satellites, and then analysed. The result from this is 99% of the predicted value (from Einstein’s general theory of relativity), with a 10% error margin. Another satellite, Gravity Probe B, is intended to measure the Lense-Thirring Effect.

6. Summary Any object with mass warps space-time. If this mass spins, it will induce a second distortion around itself, as it drags the space-time fabric. Objects within this region of space should be affected by it. The Lense-Thirring effect has been confirmed with the LAGEOS and LAGEOS 2 satellites. Gravity Probe B is also to measure the Lense-Thirring Effect.