What if we find gravitational waves and what if we don’t?

On May 14, 2012, Sergei gave a talk at Theoretical Physics Seminar, University of Central Lancashire: “What if we find gravitational waves and what if we don’t?”. Some interest to this subject, the following week discussions, and Andrei’s (our host) suggestion led us to the idea to post and considerably extend the introduction to it. Here is the beginning.

Prelude

A title of the talk, given at UCLan (May 14, 2012), imitates another one from the World Leaders Forum, Columbia University (April 18, 2012) [1]: “What if we find the Higgs particle? And what if we don’t?”. We found that such a title is universal, we substituted Higgs by gravitational waves, but equally well one can use supersymmetry, strings, extra dimensions, violation of Lorentz symmetry, … dark matter, dark energy, likely coming soon “dark forces” that will completely drag us into dark ages of Physics.

Any theoretical prediction without experimental confirmation is a subject of scepticism. If it is not feasible to carry out an experiment for a long time, then such predictions have tendency to become a conventional wisdom. When the experiment is finally (after many years) performed and it does not immediately confirm the expected results, then the question “what if we don’t?” raises again.

The question about existence of the Higgs boson is one of such examples due to recent results (or rather absence of expected results yet) from LHC. It becomes a subject of discussion of the World Leaders and starts to attract widespread attention of general public leading to some surprising outcomes.

Two days before the talk, we entered UK at the Manchester airport and were immediately surprised by questions at the passport control (we in recent years crossed only Canada/U.S. border and expected similar questions). The custom officer:
“What is the purpose of your visit?”
“To give seminars”, we replied.
“What is the subject?”, “Theoretical Physics”.
Next and absolutely unexpected: “Do you believe in Higgs?” …
On some borders, especially with heavy Russian accent and Sergei’s non-standard hair cut, it is not a good idea to think about your answer (it makes officers suspicious) and we immediately answered “No”. It turned out to be a right guess (a password), stamps appeared in our passports accompanied (with a smile): “Welcome to United Kingdom!”

The conclusion of the World Leaders in the case “what if we don’t?” (we, to be consistent with our answer on the border, will stick with “No Higgs”) is not new – “back to a drawing board” – which is a poetic rephrase of well-known interplay between theory and experiment that we have learnt in first lessons about Physics (in our case – it was grade six at secondary school, this was when study of Physics began in former Soviet Union, it wasn’t just “science” and was a mandatory course for all school students).

The most recent example of this interplay is the short story about discovery of superluminous neutrinos which also illustrates specific of theoretical versus experimental components of Physics. The discovery lived for a few months and the story ended by resignation of the head of experiment [2] . But even in such a short period of time, a few theoretical papers, explaining the observation, were published (e.g.  [3] ). Who are the editors of these journals, did they also resign, publish errata, corrections?

In the case of superluminous neutrinos, the experimental results were quickly proven to be wrong (theories explaining this phenomenon are not), but this is rather an exceptional case. Very often even possibility to perform experiment to check some models or their predictions has to wait for decades, e.g. supersymmetry and Higgs (30-40 years without experimental confirmation), in such cases models can undergo a phase transition and become new branches of physics, new textbooks are written, meetings are called, new journals are open, articles are published, etc.

In the case of gravitational waves (GW) in General Relativity (GR) almost 50 years passed before first attempts were made to detect them, and another sort of predictions start to appear – about the time of observation.

Here is a “brief history” of predictions:

1967 Wheeler [4]: “gravitational waves, … , are going to be one of the big discoveries of the next ten years. One will detect them for the first time. That is one great prediction of Einstein’s theory”.

1999 (a doctoral school on “Gravitational waves….” [5]) contribution of Schutz and Ricci, in conclusion (p. 80): “In a few years, perhaps as little as two, perhaps as many as eight, we will start to make observations of gravitational radiation from astrophysical sources”.

Today is 2012 and even counting from the time of publication (published in 2001 by IOP) and taking the most pessimistic estimate (eight years), this prediction was expired in 2009.

More recent – April 9, 2012 [6]: “The first direct detection of gravitational waves will likely come no later than the centennial anniversary of Einstein’s 1916 paper on general relativity, or at least by the anniversary of his 1918 paper on gravitational waves…”.

The last prediction reminds us again (as our first acquaintance with Physics) our childhood. Living in Soviet Union, we used to expect something good (or presented as good) exactly at anniversaries of revolution, birthdays of former rulers, or just general meetings of the Communist party.

The above few quotations are only a tip of an iceberg of the long chain of such predictions. Old ones are safely forgotten (after reaching an expiry date) and substituted by new ones (we are lucky that such practice, to change an expiry date, is not used in grocery stores). “Insanity is doing the same thing, over and over again, but expecting different results”; this phrase is often attributed to Einstein but always without a reference.

In the case of Higgs, we are waiting for already scheduled announcement (the date is set for the U.S. Independence Day). There are now new and serious speculations about the place (!?) of announcement (seems to be very important question for Physics World [7]) .

The idea of GW is much younger for humanity (even if we trace it back to Poincare and Laplace) than, e.g. the end of days, but even in this business predictors eventually resigned [8] :

“Harold Camping is an eccentric American pastor and a serial predictor of the end of days. He previously announced that the Rapture would take place on 21 May 1988, then again on 7 September 1994. His most recent prediction, 21 May 2011, came and went, so he “reinterpreted” his prophecy and Judgment Day was re-scheduled for 21 October 2011. The fact that you are reading this now is evidence enough of the need for a further re-scheduling. Apparently an “invisible judgment day” took place last May, so invisible that it took the pastor two days to realise it has happened. Harold Camping later apologised for the whole eschatological mess and resigned from ministry.”

The only prediction about GW that was somewhat realised is the oldest one due to Wheeler – in 1969 (even less than in cautious “of the next 10 years”) Weber claimed the first observation of GW [9]. His second and less known observation of GW from SN1987A was reported in 1994 [10]. Until today he remains the only person on the Earth who “saw” gravitational waves…

Here are only a few extractions from recent reports of the most powerful collaboration of the GW hunters, LIGO/VIRgo:

February 26, 2010 [11] : “We report no signal detection from any of the targets…”

December 16, 2011 [12] : “No gravitational-wave signals were detected …”

May 10, 2012 [13] : “We find no evidence for gravitational wave…”

Let us compare the number of people/institutions involved in search of GW with similar numbers for Higgs (ATLAS). Some statistics was provided in introduction of [1] by Professor M. Tuts, U.S. ATLAS operation program manager at the LHC, and for LIGO/VIRgo collaboration we used only data from  [13]:
experiment               Higgs (Atlas)            GW (LIGO/VIRgo)
scientists                   3000                        808
countries                   38                             17
institutions               175                            95
U.S. institutions       43                             42

The numbers are of the same order, even though in the case of GW, data were taken only from one report. The level of funding can also be compared, but according to [14] (p. 119), i.e. till 2007: “…LIGO is the most expensive project ever funded by the National Science Foundation”, and taking into account financial difficulties and cutting funding for science, it likely remains unbeaten.

Hermann Bondi, who had attended the Berne conference in 1955, later recalled that on this conference there were several discussions concerning whether gravitational waves existed – “A subject not widely pursued at the time because we could not compete with the big battalions” [14] (p. 125). Today there are legions of GW hunters, and skeptics (if any) are doomed to be defeated.

We actually applaud LIGO/VIRgo collaborators for so clear and unambiguous statements quoted above, despite temptation to find the results expected for a long time, possible pressure from granting agencies and anticipated difficulties to secure further funding, not to mention that no one can possibly check their results.

Using the Maxwell/Einstein analogy, so popular in the GW textbooks , Marconi’s experiment can be repeated today by almost anyone who wants to do this without need for “discovery grant” – the term used by the Canadian granting agency, NSERC, for their support of basic research, probably to assure the general public that money is spent wisely and given to scientists only if they promise not less than discovery. Where is a waterfall (like Canadian Niagara) of Nobel prices in Canada? Who can possibly separate the search for a devious path to the truth (not without dead ends) from the roadmap to discovery? Maybe, anyone now can find on the Googlemap the way to discovery and the shortest one.

Inability to perform experiment, and especially when experiment began, but no experimental confirmation, is the reason to questioning and skepticism. The examples are the search for Higgs and supersymmetry that become possible only recently, but almost immediately questions and skepticism are on the rise. Contrary, the unsuccessful search for GW continues for almost 50 years (the first experiment was performed by Weber in 1962) preceding by 50 years of pure theoretical debates whether Einstein’s theory really has predicted the existence of gravitational radiation, but skepticism is not on the rise.

Why is the idea/hypothesis of GW in General Relativity so special? Why is, unlike in all other predictions, the second part of the question: “what if we don’t?”, absent, despite the stream of negative experimental results during the last 50 years?
To be continued…


1. http://news.columbia.edu/higgs
2. http://www.bbc.co.uk/news/science-environment-17560379
3. http://arxiv.org/pdf/1110.0889v1.pdf
4. J.A. Wheeler, “Physics in Transition: Dialogues with Wheeler and Dicke”, Scientific Research, 2 (1967) 50-56
5. Gravitational waves, Eds. I.Ciufolini, V. Gorini, U. Moscella and P. Fre, IOP Press, 2001
6. http://arxiv.org/pdf/1204.2000v1.pdf
7. http://physicsworld.com/blog/2012/06/cern_calls_press_conference_fo.html
8. http://www.bbc.co.uk/news/uk-northern-ireland-16305083
9. J. Weber, Evidence for Discovery of Gravitational Radiation”, Physical Review Letters 22 (1969), 1320-1324
10. J. Weber in: Experimental Gravitation: Proceedings of the International Symposium on Experimental Gravitation, eds. M. Karim, A. Qadir, IOP Press (1994), 251-260
11. http://arxiv.org/pdf/0909.3583v4.pdf
12. http://arxiv.org/pdf/1111.7314v3.pdf
13. http://arxiv.org/pdf/1205.2216v1.pdf
14. D. Kennefick, Traveling at the Speed of Thoughts, Einstein and the Quest for Gravitational Waves, Princeton University Press, 2007

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About Natalia Kiriushcheva

I am a theoretical and computational physicist.
This entry was posted in Public and tagged . Bookmark the permalink.

5 Responses to What if we find gravitational waves and what if we don’t?

  1. Pingback: Our replies | Gravity attraction

  2. s.vik says:

    Well what if the are no GW. Does that mean that GR needs to be modified?
    Can GR be changed with “new geometry” are still match currents results??

  3. It seems now, the second part of the question is obsolete, isn’t it? But can you comment on the first one now, as GW have been experimentally reported?

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