"Is there anything like LIGO outside of the USA?"
Yes! First, let me establish that there are 2 LIGO observatories in the United States.
Why are there 2 LIGO's?
Detectors like LIGO, gravitational wave interferometers, are sensitive to gravitational waves coming from nearly any place in the sky, including the sky that's above the other side of the planet. The fact that gravitational waves can travel through matter and come out the other side unchanged is a huge advantage over doing astronomy using different forms of light and allows LIGO to have this amazing sensitivity. It does have the downside that, given only a single detector, we cannot tell where a detected gravitational wave came from on the sky. So, we built 2 detectors in the United States to ensure that, even if no other countries built gravitational wave detectors, we would be able to narrow down the location of any detections.
|LIGO Livingston's sensitivity to sources coming directly above locations on Earth. Red is the highest sensitivity and blue is the lowest. Since this is a flat map of a spherical object, sizes are distorted. CLICK TO SEE DETAIL.|
Another reason to have at least 2 detectors is eliminate the possibility that a local vibration is mistaken for a real gravitational wave. LIGO is very sensitive to vibrations from our environment. It is possible for a passing truck or a dropped hammer near the detector to make the mirrors inside vibrate in such a way that it "looks" like a gravitational wave. In order to avoid making mistakes like this, we do not believe that anything is a gravitational wave unless we see the same signal in both detectors within the time it would take it to travel between detectors. Therefore, we only consider a candidate detection if we see the same signal within +/- 0.01 seconds of when the signal is seen in one of the detectors.
Now, back to the original question:
Is there anything like LIGO outside of the USA?There are several other gravitational wave interferometers in other countries. The Virgo detector is located outside of Pisa, Italy, the GEO600 detector is located in Hannover, Germany, and the TAMA300 and the future KAGRA (formerly known as the LCGT) is located in Japan. LIGO collaborates extensively with all of these detectors so that any time detectors are collecting data at the same time, that data is shared. We also share technology so that all of the detectors are as sensitive as they can be. The more observatories that see the same gravitational wave, the better we can localize it and the more we can know about it.