Humanity is anticipating a spectacular performance. Two black holes will merge in a galaxy in the constellation Bootes. Scientists ensure that these occurrences will not be disastrous.
A tremendous gravitational wave will arrive as a result of such an event, as well as a flash in the sky. A gravitational wave is a space-time distortion. That is, time begins to slow or reverse, and space "pulsates." Nobody knows how it looks in reality because this has never happened before.
Gravitational waves arrive on Earth on occasion, but they are quite faint.
The relevant galaxy is 1 billion light-years away. This is beneficial because the phenomenon will not be disastrous.
Two black holes revolve around each other in the heart of this faraway galaxy. Their combined mass is around 800 million times that of the Sun, yet they are minuscule by cosmic standards, smaller than the radius of the Earth's orbit. Black holes approach and then recede. There is a little flash as they approach.
Astronomers have been following these lights for a long time, and they have discovered that the frequency of the flashes is increasing.
Until recently, such an outbreak occurred once a year. It is now done once a month. This signifies that the smaller black hole is closing in on the larger one.
When will it occur? It's difficult to say. Some astronomers believe it will take a thousand days to complete the merger. That is, it will occur either this year or next.
Taking into consideration the many millions of years these black holes have likely been orbiting each other, NASA's Jet Propulsion Laboratory in California believes that they are now more than 99 percent of the way to colliding. In practise, this means a collision 10,000 years from today.
Earthlings will notice a faint flash in the sky (normally this galaxy is not visible to the naked eye). One can only conjecture on the potential repercussions. The union of black holes is the most powerful catastrophe that can only be expected in our universe.