LMR-086 · Gravity & Time
Frame Dragging
A spinning mass literally drags spacetime around with it.
§ A first look
§ Depths
Six ways into the same idea — from bedtime story to chalkboard. No order required.
L1 · Crayon
Told like a bedtime story.
For a curious 10-year-old. No jargon. Just a picture in your head.
Put your hand into a thick jar of honey and slowly twist your finger. The honey near your finger gets dragged around with it; the honey further away barely moves. The space around Earth behaves like honey, just a tiny tiny bit. Earth is spinning, and as it spins it actually twists the space around it along with it, by a very small amount. We've measured this with extremely careful spinning tops on a satellite, and the answer matched the prediction. The twisting is called frame dragging. The universe is sticky.
§ Strange but true
- 01A spinning mass literally drags spacetime around with it, like a spoon stirring honey.
- 02Earth does this — very slightly. Gravity Probe B measured the drag in 2011. Einstein, again, was right.
- 03Around a spinning black hole, the drag is so violent that nothing can sit still — you are forced to orbit, whether you want to or not.
§ From the field journal
Frame Dragging
"A spinning mass literally drags spacetime around with it."
— observed, sketched, not yet fully understood.
§ Nearby