se dwarfs us.
But let me add something here, because it's beautiful.
Black holes spin. They have to; they form from stars that explode (usually), and these stars are spinning. When the stellar core collapses the spin is magnified for the same reason that an ice skater's spin increases rapidly when they draw their arms in. This is called "conservation of angular momentum," and basically says that when something is spinning, that spin rate will go up if the size of the object shrinks.
Both of the black holes that merged were spinning. But they were also in orbit around one another. Now, here's an amazing thing: If the two black holes were spinning in the same direction as they orbited each other (say, they both spun clockwise looking down from above, and their orbit around each other was also clockwise), then their merging will be a bit slower. It's tougher to slough off the angular momentum they have, so the merger is sluggish.
However, if one or both of their spins are not aligned with their orbital spin, the merger happens more quickly. This spin-orbit alignment (or lack thereof) is reflected in the signal we detect here on Earth; the speed of the merger tells us this. And in this case, although it's not rock-solid, it appears as though the spins were not aligned.
That's interesting. If these two stars formed together as a pair of normal but ridiculously massive stars orbiting each other, then their mutual gravity would align their spins over their brief lifetimes. The signal we saw seems to weigh against that.
Instead, it may be they formed separately in a dense cluster of stars. They exploded as supernovae separately (though, again, see my previous post about that), and over time their gravitational interaction with other stars in the cluster dropped them to the cluster center. It was there that they matched up, eventually becoming bound to each other, circling in a dance that would, after several billion years, result in the catastrophic merging and explosion of energy we detected billions of years after that.
All this inferred from the timing of a signal so weak that it moved a set of mirrors less than the size of a subatomic particle.
This is science. This is what we humans do. We can plumb the depths of the Universe without ever leaving home, but instead explore by patiently waiting and cleverly listening in ways our ancestors couldn’t even have imagined.
And yet, despite all this, we're just getting started. In the case of gravitational waves this is literally true; we’ve been listening for decades but detected the first signal less than two years ago. Even today, a whole new field of observational physics is still possible to be opened.
What awaits us ahead? What new and amazing things have we yet to learn, yet to imagine?
It's a big Universe, and it whispers its existence to us constantly. With science, we can hear what it has to say.
Image Credit: LIGO/Caltech/MIT/Sonoma State (Aurore Simonnet)