And now for something much happier. This is the golden age of exploration. Once, we humans could explore the universe through only one channel – light we could see with our eyes. Telescopes bent that light and let us see more, but it was still only one kind of light. Then Karl Jansky discovered, quite by accident, that we could detect another kind of light – radio waves – from the stars. We could now study the universe in a new way – and the discoveries came fast and amazing: quasars, pulsars, and radio galaxies were all identified, described, and, at least partially, understood.

Next other kinds of light – X-rays, infrared rays, ultraviolet, and gamma rays – were collected and studied by astronomers. Each one revealed new secrets. Microwaves, those bits of light so good at popping corn and warming chocolate – revealed the origin of the universe itself. X-rays showed us black holes in death struggles with other stars and ticking away in the centers of galaxies. Gamma rays revealed the most energetic events in the universe – and we still don’t know what those events are.

Here are some of the ways we use the electromagnetic spectrum to study the universe.

But all of these tools are still light, still electromagnetic waves created by jiggling electric charge. Electromagnetism is only one of the four fundamental forces in the universe (OK, five now that we know of the Higgs field). What of the others?

My favorite particle, the neutrino, is revealing the universe in another way, through the weak nuclear force. Neutrinos fill the universe – they’re incredibly easy to make and practically impossible to destroy. But their indestructibility makes them also almost impossible to detect. Almost. Neutrino telescopes all over the world – in Japan, in Canada, even in the South Pole – are revealing otherwise hidden truths of the universe.

Here’s a description of neutrino astronomy by the scientists at IceCube.

But the most exciting development in non-light astronomy was in the news again today. Scientists at LIGO (the laser interferometer gravitational observatory) announced they’ve detected a third gravitational wave event. Gravitational waves are produced whenever bodies with mass interact – in other words, all the time. But gravity is so weak (think about it, you can overcome the gravity of the entire Earth, if only for a moment, just by jumping; a small magnet can pull harder on a paperclip than the entire planet) that in order to detect these gravitational waves, we need big events.

The first indirect detection of gravitational waves happened at the Arecibo Radio Observatory in Puerto Rico. Imagine two neutron stars, revolving about one another. As they move, they create gravitational waves, carrying away some of their energy. This causes them to draw closer together, and as they do, their radio signals change. It’s much like a coin in a vortex – the kind you’ll see in museums as fund raisers. The coin starts at the top of the vortex, rolling around the edge. The sound you hear as it rolls indicates that it’s losing some energy, and sure enough, that lost energy causes the coin to drop deeper and deeper into the vortex, finally falling into the hole in the center.

In the same way, two neutron stars sending out gravitational waves have to lose energy. And observations showed the energy lost match theory (Einstein’s General Relativity Theory, in this case) precisely.

But that observation, using radio waves, was indirect evidence of gravitational waves. Now we have direct proof that these waves exist, courtesy of LIGO.

LIGO (two identical facilities in Louisiana and Washington) is shaped like a baseball diamond. Down each baseline (first and third) lasers travel precisely the same distance, bounce of mirrors, and return home. When the beams are recombined, they interfere. But if a gravitational wave passes through either baseline, the precisely-measured distance changes; the changing interference pattern is recorded, and wonders are revealed.

What has LIGO seen? Black holes, crashing together. But the surprise is that these black holes are not relatively small, like Cygnus X-1, revealed by x-ray astronomy, maybe a few times the size of the Sun. Nor are they enormous, like the million solar mass black holes we’ve found at the centers of galaxies. Instead, these black holes are of intermediate size, some tens of solar masses. Where did they come from? How did they form? How common are they in the universe? These are all questions that LIGO and other observatories can help us discover.

One last moment of wonder: the latest discovery was of two black holes of mass 19.4 solar masses and 31.2 solar masses. They merged to form a black hole of 48.7 solar masses.

Go ahead and do the math. I’ll wait.

Yes, there are 1.9 solar masses missing! Where did they go? Into gravitational waves! Just like the sound of the rolling coin signaled the loss of energy, the “sound” of the gravitational waves detected by LIGO indicates that almost two Suns worth of matter simply vanished, turned into gravitational wave energy in this astounding collision. Almost two Suns! And we got to detect it!

So, the next time you get down about politics or the state of the world, remember that this is the Golden Age of Discovery. We, right now, today, are learning things that our ancestors never could. We are exploring the universe with technologies they never even dreamed of. And we are finding wonders!

black hole merger

Artist’s impression of two black holes merging (Aurore Simonnet / LIGO)

 

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