While the news about detecting gravitational waves is amazing, let me note that there was a previous occasion when they were “detected,” only for the scientists involved to retract the claim later on (according to this morning’s Wall Street Journal). So, based on everything I’ve read (including this) and heard (I went to a talk today by two of the one thousand people involved), here’s what has happened. An event was detected in two out of three rigs for detecting gravitational waves. The third one is not yet ready. In fact, the first two weren’t quite ready when they detected this event, nearly, but not quite simultaneously. A query was sent to everyone in the project to see if someone had done this to test the system, and no one admitted doing so. Then a longer investigation was done to see if this was nothing but a prank, and that turned out to be negative (apparently, things are so complicated that it would have taken a large team to have pulled off such a prank). After a lot of analysis, they concluded that this event was caused by two black holes crashing into one another and that the two rigs had detected gravitational waves.
Now comes my little bit of skepticism. The link says that the source is 1.3 billion light years away (they use megaparsecs rather than light years), and it seems that they base this on a red shift that was calculated from the data. Ok. But so far they don’t seem to have linked this event with any particular part of the sky or, more important, with any other astronomical observations. Was there anything other than this event that was detected at the same time? A brightening in some distant galaxy? Lots of static in a radio telescope? Gamma ray bursts aplenty? Anything other than this event?
I asked one of the researchers about this, and she said that astronomers were alerted the next day after the event, and they will issue a separate report, although she doesn’t know what they have to say. Things will get better once the third rig is up to speed because then it will be easier to pinpoint what part of the sky an event is coming from. Anyway, I assert that this event will be better confirmed if it correlates with something else. Right now, they assume they are right because the particular signal correlates closely with what is predicted from theory.
By the way, the event has been given the complicated name GW150914, but all this means is “gravitational wave of September 14, 2015.”
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