Really? Gravitational Waves

Yesterday there was some announcement about some proof of gravitational waves predicted by Einstein.  It is amusing to see the jubilation about the discovery as being far more encompassing than it is.

Of all the ways gravitational waves are proposed to be generated, this study focused on just one: waves created during the first infinitesimal moments after the big bang.   During this time, nothing of known physics existed.  Nothing except, apparently, gravity that could ripple at a time when the universe was on the scale of sub-atomic particles, a scale where gravity is essentially irrelevant today.

Physics was very very different during these first moments, so different it defies logic to explain it.  So logic defying that it permits contradictions such as the presence of gravity that can ripple but no mass to produce the gravity.

I’ll grant that scientists have all this figured out and there is no contradiction, that gravity could exist in a form to be rippled by the big bang.  I’m not motivated enough to study to figure it out for myself.  I’m just amused by the spectacle.

More interesting gravitational waves coming from supernovas, coalescing black holes or whatever are still waiting for their discovery.

Another curious thing is about the way the discovery is described as a kind of optics experiment where the waves are deduced from the use of polarizers or other optical equipment.  But the optical equipment are massive structures of the universe itself, far beyond the ability of humans to move around, rotate, or remove from the path of the source.  We can’t even move the source with respect to this optical equipment.

The findings are announced in analogy to optical light experiments.  I recall performing optical light experiments on optical tables in college labs.  We can test ideas by controlling the light source, its direction, its frequency distribution (if white) or frequency (if coherent).   We can turn the light on or off.  In the path of the light, we can place mirrors, prisms, splitters, diffraction gratings, refraction plates, polarized plates, filters.  We can manipulate these obstacles by removing them, rearranging them, adjusting their orientation etc.   Through this laboratory we can separate the physics of the light from the physics of the rest of the world allowing us to understand light as something that has a distinct existence.  Complementing that conclusion is the identification of properties unique to the physics of light.

This gravitational wave discovery is on par with this kind of rigor?   The light table and all its fixtures is the universe itself far beyond the control of the scientist and effectively frozen in place in terms of human time scales.

Gravitational waves are predicted by theory, they are product of the application other other science.  They are like dark matter or dark energy until they can become subjects of science.

What this announcement addresses is not gravitational waves but something else entirely: measurable gravitational waves with the emphasis more on the measurable.  

From popular reporting of this discovery, there is the further claim that they can see actual ripples of the wave: the crests and valleys of the wave like a waves from a pebble thrown into a still pond.  This doesn’t make sense to me to think that the big bang is analogous to a pebble thrown into a still pond.  The contents of the entire universe is the big bang, the big bang is both the pebble and the pond and the pebble was a monstrous boulder and the pond was experiencing a tempest.   In this chaos, there would emerge a sweet tone?  The event should have produced something analogous to white light.  The wave nature of light could not really be studied until we could create coherent, single frequency light from scratch.  Coherent light provides stable peaks and valleys that can be measured with interference patterns that are not possible with incoherent or white light.   It is very difficult to extract coherent light from white light, it is far easier to create it from scratch in a very controlled manner. 


This is a gravitational wave discovery is not about the physics of the universe.  I grant that there is great care in setting up the data collection apparatus to be sure that the measurements and their interpretation can only be explained by an intrinsic property of the universe.  They universe doesn’t provide a laboratory where we can control the experiment, we are just using metadata about one fixed experimental arrangement provided by the universe itself.  

This discovery is more analogous to a big-data type of discovery than an experimental physics discovery.   Like big data, there is no way to replicate the experiment (the universe isn’t going to rearrange itself or rerun the big bang).  At best, the data can be collected again and studied by another team.  But in the end it is a data project, not a physics project.

It is an interesting discovery, just like some statistical result about the habits of some demographic inferred by algorithms run on some company’s big data.   But just like the business intelligence data, the results don’t really expose some intrinsic property about that demographic, at best it may support a business decision which may or may not pay off.   But it doesn’t enlighten us about the science of that entity.   There is no decision-making to be done with big-bang gravitational waves, so it is even less interesting. 


2 thoughts on “Really? Gravitational Waves

  1. An update to this story is that later analysis shows that most of the signal is due to interstellar dust.

    But in a statement today, scientists with the European Space Agency said that data from the agency’s Planck space observatory has revealed that interstellar dust caused more than half of the signal detected by the Antarctica-based BICEP2 experiment.

    and as a result

    When the dust is accounted for, the signal identified by BICEP2 becomes too faint to be considered significant.

    This is not the argument I made about concluding something from just one historical observation (there can be only one big bang). In fact, they are continuing to search for this sole possible observation:

    “The gravitational wave signal could still be there, and the search is definitely on,” said Brendan Crill, a leading member of both the Planck and BICEP2 teams from NASA’s Jet Propulsion Laboratory in Pasadena, California.

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