# LIGO event - energies involved?

So, we have two Black Holes merging shortly after LIGO turns on after the upgrade. Some questions:

a) How lucky was it to see this event? What are the expected rate of occurrence?

b) Was this event energetic enough to be seen on the original LIGO?

c) How close to the event would you have to be to actually feel the gravitation wave physically?

• see this blog discussion motls.blogspot.gr/2016/02/… – anna v Feb 12 '16 at 16:47
• – Keith McClary Feb 12 '16 at 23:42
• – Rob Jeffries Apr 5 '16 at 7:22
• – Rob Jeffries Apr 5 '16 at 7:26
• I think this question suffered from having an obscure title and asking three (good) quedtions, rather than one. As it is, this seems to be well covered by other, sometimes later, questions and answers. – Rob Jeffries Apr 5 '16 at 7:33

The occurance rate expected in the Universe is about 4 times per hour, of which, LIGO thinks we can detect 4 or so per year. So it was probably lucky to see the event a few days after turning the detector on, but not too good to be true. The event would not have been seen in the original LIGO, The strain peaks at $10^{-21}$ which is detectable by pre-advanced LIGO, but the rest of the shape of the wave would not have been. The energy of the event has a lot of uncertainty, but about 3 solar masses emitted in gravitational wave energy.