Astronomers sat on the discovery for nearly five months, since Sept. 14, 2015, checking back and forth to make sure it was right. They considered all sorts of Earth-bound interference or noise, examined the possibilities and eventually dismissed them.
The astronomers are so cautious that they routinely have other scientists deliberately inject false data to test their abilities. In those tests, the observatory team was able to show that the injected data wasn't real. In the case of the discovery announced Thursday, they are extra certain they are not seeing injected or hacked data because the system that allows false information to be inserted was down at the time.
In addition, the team of 1,004 scientists on the project looked over the data, and the results were then peer-reviewed by even more experts and published in the journal Physical Review Letters.
In this photo, a technician works on optics at one of the LIGO observatories.