Getting Wibbly-Wobbly with Space-Time: LIGO Detects a Second Gravitational Wave Pulse

Image: LIGO, Axel Mellinger The colored lines show an approximation of where the signal came from in space. They are 90% certain it came from the purple area. As the colors proceed inward, the certainty is less, but it's a decent way of making a prediction where the black holes collided.

Image: LIGO, Axel Mellinger

The colored lines show an approximation of where the signal came from in space. They are 90% certain it came from the purple area. As the colors proceed inward, the certainty is less, but it's a decent way of making a prediction where the black holes collided.

Remember in February, when LIGO (Laser Inferometer Gravitational-Wave Observatory) announced they had observed ripples in space-time called gravitational waves? Well, they’ve done it again!

This time, the waves were detected on December 26th by LIGO’s two gravitational wave detectors in Hanford, Washington and Livingston, Louisiana. The signal they received was the final burst of energy caused by two black holes that were closely orbiting each other and then ultimately colliding, about 1.4 billion light years away. Why are we only seeing the news about this now? Well, it takes a while to absolutely confirm that what the equipment saw was true. The scientists don’t want to release the news only to have to retract it a couple months later because of a computer glitch.

Everyone is really excited about the discovery of gravitational waves, and with good reason. This is a major scientific discovery, one of the biggest we’ve made in a long time. People have been cheering this discovery on social media and asking, “Does this mean we’re closer to building a Tardis?” “What cool things will we be able to do now?” “Can we go the speed of light?”

Well…not exactly.

This discovery is a potential game changer, but not for reasons that seem—on the surface—as exciting as what people are saying. No, we can’t fold space yet, and time is still as wibbly wobbly as ever. But, imagine this:

You are Dorothy, living in Kansas with Aunt Em and Uncle Henry and Toto. Your entire world exists in shades of gray. This is normal to you. You’ve never known anything else. You’ve never even known anything else exists. The sky is gray, your food is gray. The flowers are gray. Then one day, you step out into the world, and you are in the land of Oz. Color EVERYWHERE. Everything has its own color. It’s gorgeous, and it takes a while for it to sink in. After a while, you notice that not only is everything beautiful, and you can tell things apart more easily, but you can make other judgments about things as well. You develop preferences for certain colors, and other colors turn you off. You can see that foods that are a certain color taste a certain way sometimes, and other times, colors can warn you about things that are poisonous. Eventually, you realize you can use color as a system of communication. Red means stop, yellow caution, green means go.

Color, and the rest of the sense of sight, changes everything we perceive in the world, and the difference our perception changes our behavior. So does that of sound and smell.

Image: LIGO This is a diagram of the gravitational wave detectors in Washington and Louisiana, for those of you who are more technical. Figure A shows the time difference between signal detection in the two locations (there are multiple locations to have more reliable data--the more observations of an event, the more likely it is to have happened vs just being a glitch). The time difference is how long it took the energy to travel from one point to the next. Just like if you had two posts in your yard, one several feet behind the other. If you shoot water from the hose at them, you'd hit one and then seconds later, the water would hit the next.

Image: LIGO

This is a diagram of the gravitational wave detectors in Washington and Louisiana, for those of you who are more technical. Figure A shows the time difference between signal detection in the two locations (there are multiple locations to have more reliable data--the more observations of an event, the more likely it is to have happened vs just being a glitch). The time difference is how long it took the energy to travel from one point to the next. Just like if you had two posts in your yard, one several feet behind the other. If you shoot water from the hose at them, you'd hit one and then seconds later, the water would hit the next.

Going back to astronomy, when radio astronomy was developed, we could “see” the universe in terms of sound. We could hear pulsars far better than we could see them and make better observations about them. When infrared astronomy was developed, we could “see” even more. In fact, most of the astronomy we do these days is all based on things we can’t see with our eyes. Electromagnetic radiation allows us to experience the universe in a new way, and we can observe things that never would have been possible if we were only able to use our eyes. Gravitational waves are potentially another way we can make observations of the universe around us, just like light waves/particles and sound waves. They have the potential to allow us to observe things we’ve never thought possible, and to learn more about things we already THINK we know everything about.

Now, like with basically anything on the internet, there are some (including myself, to a small extent, until we got this second observation) who are being a bit cautionary about this news, and even poo-pooing it. Why, you might ask? Well, science in the last hundred or so years has gotten tricky. We’ve moved away from things that we can see and touch and experience directly, and are moving toward observing things second hand. We know there are planets around other stars than our own. How do we know this? Not because we’ve ever seen one. We have never seen a planet outside of our solar system with our eyes. Not even our biggest or best telescope could do this right now. We can tell there are planets by observing blips in the amount of electromagnetic radiation that stars put out. When suddenly there is a drop in the amount of observable radiation of a star, we believe that could be because a planet passed in front of it. But we have no direct evidence of these planets. We’ve never seen them, we’ve only seen their effects on other bodies. The same with the case for dark matter. We don’t exactly know that dark matter exists, but we can make a strong case for it by observing other things. This is where it gets kind of hairy.

In the past hundred years, there have been cases where things have been suggested as theory in order to explain some phenomena. Dark matter, superstrings, things like that. We see something happen that we can explain, and so we say, “Hey, you know what could make this happen? BAGELTRONS.” And then we work backwards to prove that bageltrons are indeed the cause of the effects we see.

This is what happened with Einstein in 1915.

In 1915, Einstein predicted gravitational waves as part of his general theory of relativity. According to his theory, two black holes (which hadn’t been truly discovered yet at that point, but only theorized) can orbit each other, much like stars can orbit each other in a binary system, or how the Moon orbits the Earth (though the gravity of the Moon isn’t strong enough to make the Earth orbit it in turn—it only tugs on us, causing the ocean tides to occur). As these black holes orbit each other, they would shed energy in the form of gravitational waves, and as they lose this gravity, they slowly approach each other over billions of years, until they get really close to each other. At that point, in the last few minutes, the speed at which they approach increases rapidly, as does the amount of energy they emit (gravitational waves), until they smash into each other at a speed of about one half the speed of light. At this point, they form one huge black hole, and in the process, a portion of the black holes’ mass is transferred to energy, emitted as a huge burst of—you guessed it—gravitational waves. Basically, if we were to explain this all in letters, numbers, and symbols, it would be E=mc2. And that’s what Einstein did. He said that the energy emitted from the collision would be equal to the mass lost in the collision times the square of the speed of light.

But—until now—all of this was a prediction. We couldn’t prove anything, we could just look at some numbers on paper and say, “This is what should happen.”

Image: LIGO These graphs are a way of showing what the gravitational wave detectors measured. The top diagram has a picture of spheres (representing the black holes) over a graph. Don't worry about if you don't know what the words and numbers mean. See how the red/gray waves get skinnier, taller, and closer together? That's the representation of the big pulses of gravitational waves as the black holes collided (as you can see the spheres doing). The bottom graph shows the measurements recorded--as the distance between the black holes decreased (the black line), the velocity or speed of their approached increased until they collided. Looking at the two graphs together, you can see that once they collided, the red waves hit their peak.

Image: LIGO

These graphs are a way of showing what the gravitational wave detectors measured. The top diagram has a picture of spheres (representing the black holes) over a graph. Don't worry about if you don't know what the words and numbers mean. See how the red/gray waves get skinnier, taller, and closer together? That's the representation of the big pulses of gravitational waves as the black holes collided (as you can see the spheres doing). The bottom graph shows the measurements recorded--as the distance between the black holes decreased (the black line), the velocity or speed of their approached increased until they collided. Looking at the two graphs together, you can see that once they collided, the red waves hit their peak.

So what happened with the two (and a possible third) detections of gravitational waves currently is this: Because gravity is a weakish force, our equipment isn’t able to detect the normal emissions of gravitational waves from the black holes as they orbit each other. But at the point of their collisions, such a huge burst is released that we CAN observe it with special equipment—and we can see that it is working as Einstein predicted it would. This is our first successful test where we can see his theory in action, and is one step toward proving the theory of general relativity is true (my old quantum mechanics professor must be gnashing his teeth).

What’s exciting about this second observation is that it shows that the first observation was not a fluke. This means that space-time really DOES bend into gravity wells, just as Einstein said it would, and it gives us a whole new way of looking at the universe, a whole new way of making measurements, and a whole new way of explaining phenomena that have been inexplicable until now.

“With this discovery, we humans are embarking on a marvelous new quest: the quest to explore the warped side of the universe—objects and phenomena that are made from warped space-time,” says renowned physicist (and executive producer/consultant for the movie Interstellar) Kip Thorne. “Colliding black holes and gravitational waves are our first beautiful examples.”

Do you have a science question? Is there a science topic you've always wanted to learn more about, whether it's got to do with space, the ocean, dinosaurs, or anything between? Let us know in the comments!

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Melanie R. Meadors is the author of fantasy and science fiction stories where heroes don’t always carry swords and knights in shining armor often lose to nerds who study their weaknesses. She’s been known to befriend wandering garden gnomes, do battle with metal-eating squirrels, and has been called a superhero on more than one occasion. Her work has been published in several magazines, and she was a finalist in the 2014 Jim Baen Memorial Science Fiction Contest. Melanie is also a freelance author publicist and publicity/marketing coordinator for both Ragnarok Publications and Mechanical Muse, an independent gaming company. She blogs regularly for GeekMom and The Once and Future Podcast. Her short story “A Whole-Hearted Halfling” is in the anthology Champions of Aetaltis, available now on Amazon. Follow Melanie on Facebook and on Twitter as @MelanieRMeadors.