Somewhere very far away, a long time ago, two black holes smashed into each other.
One was around 36 times more massive than the Sun, and the other 29 times more massive.
So devastatingly powerful was this event that it did something that might not even be obvious to most of us: it sent a sort of ‘quake’ through the fabric of spacetime.
The power radiated by the combining of the black holes is estimated to be more than the combined light power of all the stars and galaxies in the observable universe.
This ripple event is something known as a ‘gravitational wave’ and we’ve known about them for a very long time ~ sort of.
Einstein predicted their existence long ago as a consequence of the theory of general relativity, but up until now we’ve never had a direct observation of them.
A team of researchers from an international collaboration known as LIGO (Laser Interferometry Gravitational-Wave Observatory) seems to have been the first to observe.
Using lasers, LIGO found a subtle stretching and squeezing of spacetime itself was going on. How this happened is actually a remarkably simple concept:
First they shot a laser beam into a tunnel, that got split into two directions:
Here’s an ‘L’ shape to help you imagine the two tunnels it split into.
Next, once both lasers reached the end of their respective tunnels, they bounced back towards the spot where they split so that they could recombine.
A way to think about this is both lasers racing towards the lower-left corner of the ‘L’ again.
Here’s the rub:
Light can be thought of as a wave, with ripples and peaks etc. The waveform of these two laser beams, when combined add into each other.
If the two laser beams have the same wavelength (as they should if there’s no gravitational waves disturbing spacetime) the two split beams will recombine again into the original beam. It looks like this:
If the two laser beams get somehow disturbed and the waves peak on one as the other crests, the resulting combined beam will be that they simply cancel out:
So in the end, if the LIGO researchers detect alterations to their laser when the two beams recombine, they can tell if spacetime’s subtle ripples have morphed the lasers.
The consequences of this discovery are profound.
It, in a sense, opens up the universe to an entire new branch of physics: the universe of gravity.
Ever hear of dark matter? How about dark energy?
These two things are bound to get close scrutiny now as they’re both a part of what’s known as the ‘dark universe’ - basically neither phenomena interact with light (meaning one can’t see them), making it tough to learn much about them.
Yet much of the universe seems to be comprised of these ‘unseeable’ things.
If this discovery holds up, there’s almost certainly a Nobel Prize in the works.
Why? They may have - and I do mean maybe, not did - well…
The folks at LIGO may have just illuminated the 96% of the universe that’s been invisible to our senses for so long. We’ll have to wait and see.
(Image credit: NASA, NSF/LIGO and Brews Ohare respectively)