‘So much science’
Last year, LIGO – Laser Interferometer Gravitational-Wave Observatory – successfully picked up gravitational waves 40 years after their search began and almost exactly 100 years after Einstein predicted the existence of the waves.
The now world-famous ‘chirp’ audio clip was also the first recorded evidence of two black holes becoming one.
The audacity of LIGO’s goal – to detect the seemingly undetectable – appealed to Reitze’s scientific spirit. He actually thought it was an impossible task: ‘When I first heard about LIGO, my reaction was that it was crazy and it would never work.’
Reitze says that a project of LIGO’s scope and duration would be unlikely to be approved of nowadays. ‘There’s pressure to do things shorter and there’s budget stress.’
He is optimistic that LIGO’s breakthrough will provide more impetus to get going with the eLISA spacecraft, which will be capable of making even more sensitive measurements in space.
Reading time: 6 minutes (1,215 words)
After lunch in the canteen flanked by a cloud of enthusiastic Faculty of Mathematics and Natural Sciences staff members, David Reitze’s next stop is the lecture hall next door. For nearly an hour, he tells the standing room only crowd about what made September 14, 2015 such a beautiful day in his life: the detection of gravitational waves at both the Louisiana and Washington locations of LIGO. ‘The phrase ‘seismic is quiet, weather is clear’ just warms my heart’, he says, quoting the message from the logbooks for that fateful day to the audience, who laughs appreciatively.
His job as the executive director of LIGO – Laser Interferometer Gravitational-Wave Observatory – doesn’t have any teaching duties attached to it at the moment, and he hasn’t actually had a chance to speak to many students during his whirlwind trip through Nijmegen, Amsterdam and Groningen (which was fortuitously scheduled weeks before the gravitational waves were detected). But his eagerness to teach shines through as he lingers in the lecture hall after his colloquium, writing out formulas on the blackboard for a handful of students.
The colloquium is geared toward a technical audience, and the crowd has come from departments with no connection to astrophysics or optics. But Reitze says that this ‘event’ – the detection of the gravitational waves generated by two black holes merging – has captured the imagination of the world, due in large part to LIGO having some pretty sweet graphics to explain it all. ‘I didn’t even use the beauty black hole graphic in the colloquium’, he says, referring to the shiny visualisation of two intertwined black holes in a starry sky, eventually consuming each other.
The now world-famous ‘chirp’ – a wavering pitch ending with a distinctive ‘bloop’, which was actually pitched up for media distribution since the original audio clip more closely resembles an ultrasound – was also the first recorded evidence of two black holes becoming one. ‘This event is the gift that keeps on giving. There’s just so much science out of this one event’, Reitze says.
LIGO first began its seemingly impossible search for evidence of the gravitational waves 40 years ago. Rainer Weiss, Kip Thorne and Ron Drever have been there from the early days, and Reitze readily credits them with getting the epic project off the ground. The methods and equipment that the two observation stations use also owe an obvious debt of gratitude to Albert Einstein, whom Reitze says actually won his Nobel prize for his least interesting work. ‘He never got the Nobel prize for general relativity or special relativity’, he muses.
Another Nobel prize-winner and namesake for the Zernike campus – Frits Zernike – also left his mark on LIGO’s breakthrough. ‘Let me tell you about Frits Zernike. The mirrors we use are exquisite mirrors’, says Reitze, a specialist in ultrafast optics and laser spectroscopy. They’re also quite large – 34 centimetres by 18 centimetres – and they are figured, meaning that the final polishing of the surface removes imperfections and changes the curve of the surface. ‘We analyse how well we polish our mirrors to within a perfect sphere using Zernike polynomials. We do the analysis and we look for higher order Zernike polynomials to see how well, or how not well, we’re polishing our mirrors.’
Will this breakthrough, which has done nothing short of giving mankind a new sense through which to perceive the universe, induct LIGO’s name among the Nobel laureates, too? ‘People like to talk about prizes, but the way I would say it is I don’t think anybody in the collaboration’ – he pauses, thinking to himself – ‘yeah, I think that’s a safe statement – really cares.’
He quickly clarifies exactly what he means: ‘I’m not trying to be flippant or dismissive. That’s just not why we do it.’ It’s about the science. What’s more, the Nobel committee does not typically award the prize recognising world-changing (if not universe-changing) scientific achievement to organisations, and LIGO has more than 1,000 researchers. ‘Sure, a Nobel prize for this would be great, but who do you give it to? There are so many people who contributed in so many meaningful ways.’
‘You’re kidding me!’
When he first heard of the research being done at LIGO, where he began working as a spokesperson in 2007, he readily admits that he never thought it would work. Trying to measure displacement that is one one-thousandth of the diameter of a proton in a four-kilometre-long vacuum tube? ‘You’re kidding me!’, he recalls now.
The task LIGO set for themselves was massive because what they were looking for was so very small. ‘Detecting a gravitational wave is in itself a challenging thing, which might have been why I got involved in LIGO. I thought, ‘This is really hard, it could be fun.’ That philosophy is what Reitze attributes to his desire to get into science in the first place. ‘For me, everything is interesting’, he says. ‘I love challenges, and in college, I said to myself, ‘What’s the hardest thing I can do as an academic career that I’m going to like?’’
And setting out to detect the constant, otherwise imperceptible waves was a challenge that took 40 years to overcome. But the possibility of getting a research project of this physical scale and, in earth terms, epic time frame approved by funding and oversight agencies would be slim nowadays. ‘LIGO would be a tough sell today’, Reitze says. ‘There’s pressure to do things shorter and there’s budget stress.’ Reitze says that a group such as the National Science Foundation may still be willing to spend a billion dollars on a project now, but they would be more eager to do so if they could ‘point to some research that comes out of it that either benefits the scientific community, but preferably the U.S. and the world through economic impact.’
It’s not as if LIGO had not contributed to science before the famed detection: the equipment they use is unique and innovative in its massiveness. Second only to the Large Hadron Collider at CERN, it’s the biggest scientific installation on earth. But over the course of the 40 years that the research was running so far, LIGO’s two observation stations – one in rural Washington and one near the swamps of Louisiana – were not online all day every day. New stations in Japan and India are planned to join the grid in the near future, but Reitze is also hoping that the high profile discovery will provide more impetus to launch eLISA: Evolved Laser Interferometer Space Antenna. That is a plan coordinated by the European Space Agency (since NASA announced it would not take part in 2011) to launch three spacecraft, each equipped to do interferometry, in order to better determine the direction that gravitational waves are traveling and hopefully expedite the search for evidence of the formation or demise of other phenomena, such as supernovae and neutron stars.
But currently, eLISA is not even scheduled, but only proposed, to launch in 2034. Reitze is optimistic that that LIGO’s detection of gravitational waves can encourage ESA to accelerate the launch date. ‘The big question – some people would say the big monkey on our backs – was, can we measure them? We knew they existed, but could we measure them? Yes, we could, and we did. So now, that monkey’s gone, and hopefully others can start getting excited about it.’
Gravity fields explained by NRC science editor Bruno van Wayenburg. Translation by Mina Solanki.