LIGO Surpasses the Quantum Limit
ligo.caltech.edu
ligo.caltech.edu
This is not entirely accurate. The Heisenberg uncertainty (or Schrödinger/Robertson) uncertainty limits still work. If you somehow break those limits you disprove quantum mechanics.
Squeezing just reduces the uncertainty in one observable by increasing the uncertainty in the other observable.
> reduces the uncertainty in one observable by increasing the uncertainty in the other observable
Seems like you’re both saying the same thing with different wording
https://en.wikipedia.org/wiki/Uncertainty_principle
As you can see there is no mention of time in any of the standard inequalities (excluding the energy/time "uncertainty principle" which is not relevant here). You can not go below the limit imposed by the Heisenberg uncertainty principle for any duration of time without disproving quantum mechanics.
What LIGO does is break some metrological "limit" which is derived by combining the uncertainty principle with some assumptions about what your measurement procedure looks like and what your states are.
Unsurprisingly if you use different states you can break this "limit".
Refining the time metric in the Heisenberg limit to be couched in entropy is also common. Time is not really trusted as a fundamental quantity due to lack of observerless descriptions, and entropy and time have ultra similar properties, and indeed may be fundamentally linked. They both seem to flow in one direction and are impossible to reverse in the absolute sense.
The point of “squeezing” is to push a lot of uncertainty in one variable so that one could measure much lower variance in the other variable post-squeeze… both pre and post squeeze are Heisenberg bound, but post-squeeze uncertainty is lower than pre-squeeze and therefore “under the limit” pre-squeeze.
When I spoke to ligo for a position they were talking about amplitude / phase uncertainty trade offs.
gravitational frequencies
detected by LIGO."
Gravitational frequencies -- now that term is going into my 2023 lexicon...
(Note that I don't know what it means, just yet -- but it sounds like it could be useful in the future; it sounds like there is an interesting idea (or a series of interesting ideas) there...)
"Interesting" != "Impressive".
What would impress me however (greatly I may add!) -- is if you knew how an average experimenter with, say, $100 or less of lab equipment -- could create and test (and therefore know to be real) gravitational waves -- without relying on, or repeating any news articles or other secondhand information source...
In other words, with respect to gravitational waves, "I want to see them with my own eyes" -- to believe them...
The problem with the media today is that everybody parrots what everyone else is saying (https://en.wikipedia.org/wiki/Echo_chamber_(media) ), nobody seems to think for themselves, and it seems that very few people do actual firsthand experiments to verify media claims...
I'm not saying that gravitational waves don't exist -- far from -- but the standard of proof I require is via firsthand experiment -- rather than secondhand hearsay about someone else's experiment...
Firsthand experiments usually lead to greater understanding -- whereas secondhand hearsay usually leads to greater confusion...
So, show me a guaranteed experimental way that someone with $100 or less of lab equipment could create their own gravitational waves with (and subsequently know them to be real via their own firsthand witnessing of one)... and I'll be impressed!
Very impressed, in fact!
But humor aside, an interesting question might be:
Why is frequency -- such a fundamental component of Physics?
What is the first principle or first principles -- that gives rise to frequency?
We might step back a step, and say (and or observe) that waves and wave-like phenomena are present in many aspects of this Universe -- both seen and unseen.
So do waves give rise to frequency -- or is it the other way around, does frequency give rise to waves?
We see both phenomena present in the concept of energy -- energy of all sorts.
We also see the concept of imbalance -- over half a wave cycle, and balance (or rebalance, if you will) over a full one...
Which is in turn connected to the concept of vibration, oscillation, repetition and reversal (over a period of time, aka periodicity)...
So, frequency is not profound?
It seems to be intricately, intricately connected to a whole bunch of physical phenomena -- that are indeed profound!
But that being said (and to agree with you!) -- no it probably won't give you psi powers or expand your mind any more than the frequency of ocean waves will.
(Unless of course you somehow happen to be Aquaman! <g> :-) <g>)
I'm no physicist, but, the earth is massive so is influenced a lot more by external gravity than the specs on its surface that are people. Take the moon, it's a huge object hovering over the planet (effectively, it's slow moving, the earth rotates underneath it), its gravity pulling on seawater and causing ebb and flow. But we cannot feel its gravitational effects ourselves.
One could imagine though some configuration of many pairs of black holes, orbiting at different frequencies to interfere with one another and produce a sharp beat, perhaps with other mass configured to act as focusing lenses. Still almost certainly wouldn't exist in nature but a cool potential scifi concept.
Very exciting!
TL;DR, know your audience and cater to them if you want people to be interested.
Like with the squeezed light in LIGO there is no free lunch, but the idea in both cases is to pay for the lunch with something you have plenty of or otherwise don't care that much about, rather than your limited amount of money.
With dithering you have to filter out the noise, but if your ADC can sample faster than you require then you just oversample and average.
For LIGO they care very much about the phase accuracy but not so much the amplitude, so they pay by having worse amplitude certainty[2].
[1]: https://www.allaboutcircuits.com/technical-articles/what-is-...
But the surrounding research and advancements in all scientific fields did!
Some crazy dudes want to build a flying machine. Totally impossible, it will never happen. Just stick to horse-drawn carriages, also let’s try to squeeze a bit more efficiency from that coal-powered steam boiler over there...
And on and on and so forth. Breakthroughs and just general advances in science look like crackpot ideas or wastes of time until they aren’t. Fundamental research is almost always a good thing, no matter how out there or wildly impractical it may seem.
This expands the reach of knowledge of humanity; once made available, who knows how future humans will use these new discoveries to benefit mankind. Claude Shannon developed information theory well before networked computers were invented, but it's now critical to many disciplines and products you use every day.
Meanwhile, the actual engineering challenges overcome in the building (and refinement) of LIGO are directly applicable to development of more accurate sensors, quantum computing, and precision engineering - all of which will touch the lives of Earth's inhabitants without most of them even being aware of it.
Is it conclusive evidence? No, ultimately it's just a data point. But it's evidence.
Take another one; Einstein hypothesized that light is influenced by gravity, and came up with an experiment that didn't need super high tech instruments; observe the stars next to a solar eclipse and see if their position is different from normal. A few years later there was an eclipse, multiple people made the observations, and his hypothesis was proven correct.
Thanks to that experiment, we now have telescopes that can use gravitational lensing from galaxies to look at the farthest reaches of space.
in my opinion, the point of LIGO is no longer in detecting these gravitational events anymore tbh. Doing that is cool, and will bring us more data points about the events, but it's unlikely to ever yield "new science" like that.
Instead, LIGO (and Virgo) excel in exactly the kind of thing that we see in this article: to push the barrier of what we can do in this hyperspecific use-case, finding ways to do "new" engineering that would not make sense for other commercial projects yet and finding out how to implement cool solutions. The fairly consequent amount of funding and the extra focused goal it is aiming for will lead to new techniques and technologies that might have an impact.
Now, is there a guarantee that this new technology will have a larger impact than "better detectors"? No. Actually, there's no guarantee about anything coming out of LIGO ever, no more than out of the LHC[2] or ITER[3] or the ELT[4] will give us new science. But putting all of your eggs in the same basket is a bad solution for making more science, and there's enough room in science budgets to try a few dozen monumental projects and see what sticks.
[1] https://en.wikipedia.org/wiki/First_observation_of_gravitati...
[2] https://en.wikipedia.org/wiki/Large_Hadron_Collider
Edit: Actually you said that but consider it unlikely which I absolutely can't argue with.
1. If you have a light wave in the universe, and you "hang" a mass by each valley and trough of the light wave, and then you squash and stretch the universe, the masses stay connected to the valleys and troughs of the light wave. Said another way, when you squash and stretch space, lightwaves within that spacetime are also squashed and stretched.
2. LIGO claims to work by measuring the squashing and stretching space with light. However, as we just learned, squashing space also squashes light waves. So the LIGO arms and light waves in the arms are all compressed together.
Said another way, LIGO can't work because the ruler itself is squashing as space squashes, so you can't measure if space is compressing.
LIGO does work, but if you can't explain how it works despite this description, then you don't understand LIGO.
So uhh... how does it work in spite of that description?
No clue why GP thinks it "shouldn't work": it's an extremely difficult engineering problem, but the physics of it is relatively straightforward.
I think this misrepresents the situation, but I can't say how, so I can't dismiss it quite so quickly.
Stronger signals from some black holes depending on which way they're oriented relative to the arms. And if there were many different simultaneous signals, some could mask the others.
Clearly, we need a 3-armed, space-based LIGO. Or better, a dozen of them.
[0] https://en.m.wikipedia.org/wiki/LIGO
[1] https://en.m.wikipedia.org/wiki/Virgo_interferometer
[2] https://en.m.wikipedia.org/wiki/GEO600
[3] https://en.m.wikipedia.org/wiki/KAGRA
[4] https://en.m.wikipedia.org/wiki/Laser_Interferometer_Space_A...
Amusingly Einstein both identified gravitational waves in his then new general relativity and then changed his mind about whether they existed. Indeed he had found three different types of these waves, and two of them were simply coordinate artifacts (they could be made to travel at any speed, Eddington famously quiped that they could be made to move at the "speed of thought"). The third type however didn't have this problem (though again here Einstein would write a paper where he claimed these gravitation waves required singularities, but these turned out these were all coordinates singularities .... sort of like how late and long coordinates misbehave at the poles)
In some ways the physics of it is straightforward, in other ways....not so much.
This question is important enough that there have been papers written on it. I suggest you read https://pubs.aip.org/aapt/ajp/article-abstract/65/6/501/5300... which may strengthen your understanding.
This is a physics education journal: its papers are supposed to be interesting and accessible to undergrads, not on the frontier of the field.
What the linked paper amounts to is noticing that the sensitivity of a detector depends on the relative length scales of the arms and the waves you're trying to detect. This is true, and also one of the first things you would consider when figuring out what size your detector should be. It's a good homework problem, but not news to anyone actually working on LIGO.
> No clue why GP thinks it "shouldn't work"
It's also possible you think that this is all about laser interferometry, and aren't properly considering how it could work in the context of compressing space, since a laser interferometry system in compressed space wouldn't produce interference.
That's unfortunately true for a lot of physics. For example, there are very few good explanations available for what is electric current and it is pretty funny observing even people with lots of experience offer the same lame, false explanation.
I think the chief confusion here is that you may be thinking the light arrives at the detector in the same amount of time regardless of spacetime curvature. That is, the the ruler is itself squishing.
But what needs to be considered is the constant speed of light.
This implies that what happens is, in the presence of additional curvature, and constant speed of light, the additional distance traveled will have appeared to slow the light.
In the laser interferometer this registers as interference.
https://m.youtube.com/watch?v=ajZojAwfEbs
It is also worth noting that any claims of detection are thoroughly investigated and confirmed with other detectors.
> It is difficult for a single LIGO detector to confirm a gravitational wave signal on its own. The initial discovery of gravitational waves required that the signal be seen in both detectors (Hanford and Livingston).
I thought it made the light reduce in frequency. Or did I misunderstand?
New light that is emitted at one end of the journey while there is a stretching status will have the same frequency as normal, and just see the longer journey. In fact, the gravitational waves that LIGO is able to detect are slower than the time it takes for light to make the journey, so the stretching is effectively gradual, and the detector is basically an extremely accurate length measurement. The gravity waves aren't fast enough to make the light changing frequency a thing that needs to be worried about.
This is the thing I (as a layperson) can't really wrap my head around yet; there's gotta be so much interference from so many different sources, there's gotta be some impressive data processing going on to filter out anything not relevant to their core measurements, and then THAT data will have to be compared to that of other detectors.
This device, the LHC, space telescopes, really cool and all if you look at the published pop-sci results, but the actual data is like... individual photons captured by a worldwide network of detectors and processed / data analyzed into the first "photo" of a black hole.