Detecting a Death Star and other gravitational wave ideas
If you follow the news, you’ll know that last Thursday (11/02) scientists detected for the first time gravitational waves – tremors in the fabric of space and time. The discovery confirmed the theories of Albert Einstein, who predicted their existence 100 years ago.
If you’re a science fiction writer, what does that mean for you?
Well, first, let’s explain gravity waves.
Imagine that space is a elastic sheet, which warps beneath planets or stars to create a gravitational well**. The larger the mass, the greater the pull of gravity around that object, and the deeper the well. The deepest wells are black holes, caused when a gigantic star collapses to an infinitesimal point.
Gravitational waves are caused when a massive event – like the collision of black holes – releases so much energy that the elastic sheet ripples and shudders.
Around 1.3 billion years ago, two enormous black holes – each about 30 times the mass of the sun – collided. The resulting shock waves in the fabric of space time travelled across the universe and washed past the Earth around five months ago. They were detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO), a gigantic instrument based in America.
Why do we care?
Detecting gravity waves allows us to see the universe in a new way. We can “listen in” to gravity waves passing through the universe, rather like using a seismograph to detect earthquakes or a radio antenna to pick up sounds.
According to theoretical physicist Michio Kaku in the Observer newspaper, we could potentially determine exactly what happened at the moment our universe was created.
“This is still speculation, but if we have space-based gravity detectors orbiting the Earth or sun, and we detect radiation from the incident of the big bang, we could run the video tape backwards and therefore get insight into what happened before the big bang. That is, what triggered the creation of the universe,” Mr Kaku told the Observer. “Of course we don’t know, but some people believe perhaps there was an umbilical cord that connected our baby universe to a mother universe. There are many theories being proposed, but they are not testable. Once we have space-based gravity wave detectors, we should be at the brink of being able to test for the impossible, that is, the world before the big bang.”
As scientists discover more about gravitational waves, some of the proposed theories in mainstream science fiction movies may begin to emerge as reality.
“A lot of the things you see in science fiction revolve around black holes, because black holes are strong enough to rip the fabric of space and time. If space is a fabric, then of course fabrics can have ripples, which we have now seen directly. But fabrics can also rip. Then the question is what happens when the fabric of space and time is ripped by a black hole? We have no way of empirically answering that question, because we know very little about black holes—but now we have a telescope. A telescope that can look at the very instant which two black holes collided and this could open up a whole new chapter because we don’t know what happens when you fall into a black hole, it’s a controversy.”
There are several theories to this controversy—including the notion that, when you fall into a black hole, you disappear—and that’s the end of the story. Another theory is that, when you fall in, information oozes out. Others believe you pass right through, like what happened in the film Interstellar.
“If you saw the movie, Interstellar, starring Matthew Mcconaughey, they actually use computers to simulate what happens if you fall into a black hole. If you just look at the math, not the physics and disregard radiation, quantum effects and stuff like that, there is another universe at the center of a black hole. The black hole is a ring—it rotates very rapidly—and if you fall into the ring it’s like going to the looking glass of Alice, so some people think the universe is like that. I work on something called String theory, and in string theory we start with membranes which can collide like beach balls or soap bubbles, and when these bubbles collide that’s the big bang, or when they peel off and bud into two bubbles, that’s the big bang. Of course this is speculation, but we hope to launch the first space-based gravity wave detectors in 2034. The European Space agency has recommended launching of their first space-based gravity detectors, so I think there’s going to be many nations setting up gravity wave detectors in space. Our gravity wave detector now is 2.5 miles long. These space-based detectors could be millions of miles across, because there is no need for shielding, no need for a tube or a vacuum chamber, space is empty up there. You could have three laser beams connecting 3 satellites in a triangle and that could be the basis of a new generation of space based gravity detectors. So a new chapter in Astronomy, as well as Theology, could be opening up.”
Space-based gravity detectors could – in theory – detect a ‘Death Star’ or ‘Starkiller Base‘ operating in another star system. To be detectable, the galactic superweapon would need to completely annihilate the planet.
“If they simply blew the planet to smithereens, the mass would still be there, just spread,” Derek van Westrum, a scientist with NOAA’s National Geodetic Survey who works on the Earth’s gravity field, told me by email. “This would make some pretty small, (currently impossible to detect) waves. But if that planet/sun were blown away into pure energy (the death star would have to be pretty far away) , the missing mass would make very large gravity waves.”
The Death Star would need good shielding against the enormous energies released and either a long range or an improbably fast getaway.
“In the real life example of the two black holes colliding, three suns worth of mass “disappeared” into waves,” van Westrum told me. ” That amount of energy was brighter than all the light in the visible universe. (if you blew up a sun this way, you’d want to be very far away!)”
One thing we can’t do – now we know Einstein was right – is ‘surf’ a spaceship on the gravity waves rippling through the universe. “The waves travel at the speed of light, and there’s no way ‘catch up to them’,” van Westrum explained.
Tiny gravity waves are created when matter (such as electrons) is created from energy (such as light). Using the powerful energies released by matter-antimatter collisions to power a gravity-wave ‘surfing’ ship is possible. The spaceship would need to create enough matter to surf across space time.
“Matter- antimatter collisions turn mass (say electron and proton to use a real life example) into energy, E=mc^2. (you get a lot of
energy for a little mass),” van Westrum explained. “Gravity waves are due to accelerating (or creating) mass. If you took pure energy and made mass out of it, you’d technically generate a tiny gravity wave, but now the equation works against you: the mass (needed to make the wave) is a tiny E/c^2. (Unfortunately, c^2 is a huge number).”
Such a spaceship would need a gigantic power source. According to van Westrum, “You’d be much better off using the energy you have to propel a ship, not make gravity waves.”
** This isn’t a correct model of spacetime, but it’s easy to visualise.
Find out more about gravitational waves
If you’re a science geek, you might want to read the Physical Review Letters paper announcing the first detection of gravitational waves. A simpler explanation can be found at PHD comics.
For a fictional alternative
Alastair Reynold’s space opera-cum-alternative-history thriller Century Rain includes a discussion of gravity waves [thanks to the Unnamed Fan for the suggestion].
Ask questions or suggest theories in the comments or on the F.L.T. Tumblr.