Graph Interpretation of Gravitational Waves In the image is the data recorded by the LIGO's 2 observatories in USA. What is its interpretation? I mean what does the zig zag lines represent? Similarly, what does the blond red and blue lines (that seem like exponentially increasing up) represent? Could you please clarify? (Note: I am a highschool student so please make sure a high schooler like me too understands it.)
 A: LIGO works essentially by monitoring the separation of two large mirrors.
The zig-zag lines could be thought of as by how much the separation of the mirrors changes over the course of the 0.2 seconds represented along the x-axis. The separation oscillates in response to the passage of the gravitational wave. Confusingly, there are no indications of the size of this signal on the y-axis (the frequency numbers refer to the other plot, see below).
If you look carefully at these zig-zag lines you will see that the oscillation appears to grow in strength (the amount by which the signal oscillates) and in frequency (the peaks are getting closer together in time) before dying away at the end of the data sequence. This is the classic "chirp" signature of the merger of a binary black hole system.
The coloured plots show how the frequency of the oscillation (the numbers on the y-axis) increases with time, whilst the intensity of the colour of the signal represents the growing strength of the signal.
A: This is showing what is called a black hole merger. It is two black holes that are orbiting each other, and after time, they get closer to each other and then finally combine.
These graphs show the frequency spectrum versus time of the gravitational wave signal (each graph is from each detector of the LIGO). As time passes, the  frequency of the signal increases, corresponding to what is described as a "chirping" noise.
This black hole merger happened because orbiting black holes rotated around each other at increasing frequency and energy (corresponding to the oscillatory pattern on the graphs), coming closer together after each revolution, where finally at the end they merge forming one black hole.
As all of this is happening, the binary black hole system releases a massive burst of gravitational waves in its final instants before merging. Also as this happens, the binary system radiates gravitational waves, which are waves in spacetime, and this is what the LIGO is detecting.
