If you look at the lengths LIGO had to go to in order to eliminate background noise to even be able to theoretically detect gravitational waves, it seems very unlikely that a comparatively crude technology from the 80s could have achieved the same things. Like modern lasers or squeezed light states, which were mostly theoretical back then. If I remember correctly, Weber's device was claimed to show a huge amount of events per year, which would indicate tons of GW sources in our neighbourhood. LIGO and the rest of modern astronomy have since disproved that.

Umm, not sure what this clumsy attempt to rewrite science history is about?

The internal nomenclature of those working within a particular approach cannot restart the clock of an entire field? Resonant bars were the first generation of gravitational wave detectors, period.

> they couldn’t work according to most physicists

That certainly requires a reference. There were several teams around the world besides Weber pursuing the approach. You make it sound as if the physics behind these bars was crackpot.

Fyi, you may be confusing physicists with astronomers. The prevailing notion in astro circles was indeed that the known pathways to gravitational waves and with calculations made using GR would be too weak to be detected.

(Incidentally astronomers were notoriously hostile to any GR research anyway. Why spend money in a high risk esoteric field if you can keep doing the same stuff over and over?)

But a new observational window can always throw a surprise. A previously unknown class of sources may hit you in the face despite your primitive instrument. Historically this happened repeatedly with x-rays, radio etc. Or the theory you use to make predictions may be deficient and not telling you the whole story...

In this respect Weber was simply unlucky. The universe is in a sense slightly more "conventional" and less exciting than it could have been.

The medium is the message. If we detected a modulated signal in gravitational waves, it would be like an Iron Age tribe receiving a 100 foot tall perfectly polished stainless steel statue with ornate inscriptions and pictograms. It would be recognizable and within our conception, but it would also be a demonstration of development and access to resources beyond our imagination. That's the upside. In a galaxy of sparse and sparingly advanced civilizations, the message might be "fear us and stay away" in a way that EM would not convey.

You can detect gravitational waves based on the strain (amplitude) directly, rather than relying on intensity like electromagnetism.

Because the amplitude is inversely proportional to the distance, but intensity is inversely proportional to the distance squared, this could allow for communication over longer distances.

Thanks for the PBS reference, interesting! As to the energy required, well, yes, I guess manipulating huge masses will be costly, but, if there is an efficient way to do this, then gravity waves are a parallel plane of communication. The analogy I heard once is about tribes communicating with smoke signals, while the air around them is filled with radio waves. Maybe we can't hear anyone out there because we're not listening to the right thing...

Maybe that is the filter. If your society hasn't figured out the tech to do it efficiently, the rest of the galaxy doesn't care about what you have to say.

The upside is that space is quite transparent for gravitational waves.

What would a gravitational wave generator look like? A machine to "wiggle" an asteroid, or say a moon? What if you made a huge array of small machines that "wiggle", say, a bowling ball, in perfect sync.

>I'm not sure I see what the advantages of communicating this way would be.

Gravitational waves might be the best way to communicate between our world and the dark matter world/dark sector?

https://en.wikipedia.org/wiki/Hidden_sector

...or maybe there is a lower noise floor for gravitational wave comms?

>The amount of energy required per bit transmitted would be astounding.

Has someone calculated this out? Or is it more of a "well we need an exceedingly sensitive instrument to detect some of the most energetic events in the universe from half-a galaxy away" gut-feel? Any reason something like a phased-array for directional comms / beam forming wouldn't work with gravitational waves?

Create tiny black holes and throw them into each other.

I'm thinking you could also create gravity waves by annihilating matter and then creating matter over and over. If you could get a bit of that wave to reflect back to you and then sync your creation/annihilation, you could build a huge wave over time

Yes, but not efficiently (it will be very slow) and will be hard to detect because of noise (the article mentions the 'cacophony' of gravity noise). This is similar to EM radiation, so, you do frequency modulation (or amplitude, but that seems harder with gravity - you'll need to modify mass...), so you have a base high frequency on top of which you add lower frequency. The substraction later gives you a clean signal (or, Gravity Radio).

I’d highly recommend it if you get the time, was an excellent tour to geek out on. Enjoy DEFCON!

Ooof missed that, thanks!

The university I studied at had a Gravitational Wave center under the Physics dept, and all the professors would joke about how LISA had been "less than a decade away" for 20 years.

> it doesn't have the same kind of predictive power that people want (i.e. too much freedom so it can be used to explain anything, not just everything).

That's the popsci version that's been disseminated, yes. It's not exactly wrong, but it's misleading.

First a bit of background. Quantum field theories like the standard model are effective theories, not fundamental ones. We know we don't know the real high-energy physics, so we treat it as a black box and loosely speaking "average it out" as a new free parameter. This is analogous to how an engineer designing a bridge can ignore the fact that iron has a crystal structure and treat it as a continuum with bulk properties like tensile strength. In reality this having a particular tensile strength is a state, not an intrinsic property, and you could end up with a different tensile strength if you melted the iron and let it resolidify (I'm not a metallurgist, substitute some other material if that's not true for iron), but we can build bridges without knowing that.

In the same way, Standard Model is a particular form of "solidified" string theory. It's true that there are many, many, many others, but they're not free parameters in the same way. You can write down perfectly reasonable looking quantum field theories that string theory can't produce, and if our best effective theory was one of them then we would have good reason to reject string theory. But it's not.

So the situation we're in is that we have some solid material, and we want to know what a single molecule of it looks like, but we can't see anything other than the bulk properties. What the "string theory is unfalsifiable" crowd is demanding is that whatever molecule we predict have only a few possible crystal structures. And maybe it does. That would be convenient. But sometimes nature inconveniences us: it might be some crazy carbon allotrope. It might be glass.

I believe they're referring to the idea of a gravitational force carrying particle, like photons for electromagnetism, W/Z bosons for the weak force, and gluons for the strong force. Typically this gets called a graviton but they've never been observed and the theories predicting them as far as I know don't predict that we can detect them in any meaningful/practical way right now which is also one of the problems for issues with a quantum theory of gravity.

I've always wondered (but not done the research/reading) on how that would mesh with black holes since you'd need gravitons to escape to mediate the curvature of space-time but that'd seemingly (to me) require them to be able to either ignore the curvature of space-time or travel faster than the speed of light in order to do so. And I believe that those two options there are actually mathematically equivalent as far as the consequences of things go.

That would suggest space is "made of" something, so what would that be? If it's made of something, how is that "carrying" the wave, causing it to distort in the presence of mass?