Gravitational-wave rumours in overdrive
What is the gossip?
Has giant LIGO experiment seen gravitational waves?
The rumours suggest that the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO), a US laboratory with detectors in Washington and Louisiana, has spotted a signal of gravitational waves. These are ripples in the fabric of space-time that, according to Einstein’s theory, are produced by cataclysmic events such as the merging of two black holes or two neutron stars.
Whispers of a possible detection were first tweeted in September by cosmologist Lawrence Krauss, at Arizona State University in Tempe. The most specific rumour now comes in a blog post by theoretical physicist Luboš Motl: it’s speculated that the two detectors, which began to collect data again last September after a $200-million upgrade, have picked up waves produced by two black holes in the act of merging. More.
Krauss? Now a credible source?
We asked physicist Rob Sheldon, who wrote back,
I think the subtitle says it all: “Physicists say they’ve heard that the LIGO observatory may have spotted the signature of merging black holes”
Which I will paraphrase “Outsiders heard a rumor that there is a hint of possible news.”
So the real question is why this is published at all? The answer is very simple- 24 years and $620M in hardware (I’m sure salaries push that over $1bn) without a signal.
It isn’t just that senior scientists are retiring without seeing any benefit from their work. It isn’t even that 4 generations of graduate students have had to write their PhD thesis on simulation results. I think more significantly, a new generation of bureaucrats have arrived in NSF who don’t think LIGO will ever return the investment. Think CERN upgrade, WIMP searches like LUX, even Gravity Probe B. These big ticket items promised the moon and the stars and provided tenure-track positions, but never delivered. The desperation is palpable.
The most recent funding of $200M upgrade was completed in Aug 2015, and that’s when the rumor started. If LIGO behaves like most big detectors, then the first year is spent getting the glitches out and writing the software to analyze the data. So to have a rumor begin in September is not a good sign, sort of like getting a pair of East German boots manufactured on the end of the month.
Nor is the type of signal discovered, a “neutron star merger event”, a good sign. Unfortunately, these events are a blip about 2 seconds long, and they don’t repeat. They have been modeled incessantly, but never observed unless one believes gamma-ray burst (GRB) events are such events. Talking to the scientists who built the Gamma-ray Burst Monitors (GBM) on the last two NASA missions, it seems unlikely that these events are indeed merging neutron stars. Nevertheless, the LIGO team optimistically uses the ~100/year GRB event rate to estimate how frequently they should see a signal. So the rumor would confirm three or four independent assumptions that are widely held to be true–which is a good sign that it is just a rumor.
Other than discovering and refining the software to remove more “artifacts” from the data, there isn’t much they can do to make the August signal any better. I would guess that if they had any confidence in this preliminary data, they would have made an announcement by now.
But many in the consortium think that the new sensitivity of the Advanced LIGO should give them a valid signal about once or twice a year, so why not wait for a real one? And of course, the real clincher would be to have the GBM see a Gamma-Ray Burst at exactly the same time and same place as LIGO. Then everyone would exhale a huge sigh of relief and break out the champagne.
What is my Bayesian probability estimate for this LIGO signal? It’ll never happen, though I will be happy to celebrate my proven fallibility.
Why? Because there are too many features of the standard model that are pure fudge–dark matter, dark energy, flatness, horizon, ahelicity, etc.
For example, if the universe had a large magnetic field, then all the support for gravity waves could be attributed to magnetic Alfven waves with far less effort. Likewise for inflation, baryonic acoustic modulations, event horizons, Lithium 7 abundances, proton decay, etc., they are all fixes to the standard models. One simple change to the metaphysics (the beginning assumptions), and the entire house of cards starts to crumble.
The standard model, despite what you may have heard, is extremely fragile, and that is yet another reason that billions of dollars has been spent at CERN, at LIGO, at LUX, trying hard to shore up the foundations of the initial physics assumptions. And yet, to quote the New Year’s predictions of famous physicists (published in Edge), the big news of 2015 is the lack of news in 2015.
All of this make me believe that is 2016 announcement is akin to the pronouncement of physicists of 1890, who never suspecting the Quantum revolution, said “the superstructure of physics is complete, all that is needed is to tidy up some loose ends…”
See also: Gravitational wave detection could be a false alarm (Guardian)
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