  In the well-known EPR paper, Einstein et al. called the nonlocal correlation
in quantum entanglement as `spooky action at a distance'. If the spooky action
does exist, what is its speed? All previous experiments along this direction
have locality loopholes and thus can be explained without having to invoke any
`spooky action' at all. Here, we strictly closed the locality loopholes by
observing a 12-hour continuous violation of Bell inequality and concluded that
the lower bound speed of `spooky action' was four orders of magnitude of the
speed of light if the Earth's speed in any inertial reference frame was less
than 10^(-3) times of the speed of light.
