Mini Gravitational-Wave Detector Could Probe Dark Matter (scientificamerican.com) 34
A miniature gravitational wave detector under development would measure higher-frequency waves than LIGO. From a report: Within one second of the big bang, the first newborn black holes may have announced their formation with gravitational waves that stretched and squeezed the fabric of existence as they rippled outward into the expanding universe. Now researchers at Northwestern University have begun planning a tabletop-size sensor that could detect these primordial howls for the first time. The gigantic $1-billion Laser Interferometer Gravitational-Wave Observatory (LIGO) first measured the spacetime ripples known as gravitational waves in 2016; these phenomena came from the collision and merging of distant supermassive black holes. Since then, massive detectors have also recorded gravitational waves from merging neutron stars. Northwestern's proposed mini detector, which received an influx of funding in July, could measure higher-frequency waves from objects that have never been measured before -- such as black holes in the earliest universe.
Current gravitational-wave detectors such as U.S.-based LIGO and Europe's Virgo use a sprawling system of mirrors and laser "arms" that stretch for kilometers to measure tiny changes in distance caused by passing gravitational waves. Northwestern's Levitated Sensor Detector would use lasers to suspend a glass bead inside a vacuum chamber, creating an extremely force-sensitive sensor with arms just a meter long. It would listen for echoes from the formation of primordial black holes and the activity of theoretical particles called axions, both of which are candidates for mysterious dark matter -- hidden materials that may constitute much of the universe's mass and are invisible except for their gravitational presence.
Current gravitational-wave detectors such as U.S.-based LIGO and Europe's Virgo use a sprawling system of mirrors and laser "arms" that stretch for kilometers to measure tiny changes in distance caused by passing gravitational waves. Northwestern's Levitated Sensor Detector would use lasers to suspend a glass bead inside a vacuum chamber, creating an extremely force-sensitive sensor with arms just a meter long. It would listen for echoes from the formation of primordial black holes and the activity of theoretical particles called axions, both of which are candidates for mysterious dark matter -- hidden materials that may constitute much of the universe's mass and are invisible except for their gravitational presence.
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Re:Spacetime and mass (Score:4, Interesting)
Can someone answer the following question - Does matter reside within space-time, or does it displace it?
Matter, according to quantum mechanics, is simply composed of energy in fields that permeate all space. On large scales however, matter and energy curve spacetime. Both of these stem from theories where the evidence is so insurmountable, no theory will ever prove them wrong, but simply refine them around the edges.
We don't really know how this breaks down at the microscopic scale because we don't quite know how gravity works there. It's a small step to guess empty space isn't really even possible as Hisenburg uncertainty creates a froth of "virtual" particles that tend to cancel each other but we really have a poor understanding as the calculated value from theory and the measured value are off by over a hundred orders of magnitude.
Tl;dr matter definitely resides within spacetime but also curves spacetime so the answer is both, but we understand this poorly and is part of ongoing research.
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Matter, according to quantum mechanics, is simply composed of energy in fields that permeate all space.
That's Quantum field theory (QFT) which combines classical field theory, special relativity, and quantum mechanics
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More to the point, no one knows the answer to the question. However, it strikes me that the question doesn't really make sense since it assumes matter and space-time have some sort of inverse relationship.
We do not have particle punishers of sufficient energy to probe down to the Plank length scale and it appears we never will since the energy jump required is on the order of 10^12 short. There are physical "theories" purporting to explain energy and matter at the Plank scale but some aren't even known to b
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Yes.
lolz.
We don't have a theory that combines the space-time warping of matter with the quantum nature we know matter has. A theory of quantum gravity (if gravity is even quantized, unknown) has been sought for decades.
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A little bad a-priori reasoning (Score:2)
So, dark matter makes up far more of the universe than all detectable matter, and we have no idea what it contains or how complex the structures within that may be...
I suppose it is nice that Dawkins and Tyson told you already what kinds of things it definitely -does not- contain, though. Big time saver.
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Nothing a-priori about building detectors to see if there is experimental evidence that supports a theory, or to refine a theory based on observations That's how particle physics is done.
Modern tech and medicine partially is a result of particle detectors to verify theories and models of particle physics. Seems there has been some success in such endeavors.
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Oh, agreed. It's assumptions before the scientific determinations are made (insofar as they can be made) that's problematic to me.
And, hypothetically, I'm sure I'd see it the same if my consciousness was mostly opaque to scientific analysis among all the other dark matter, as well.
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"Assumptions before the determinations are made"
Eh, that's why the detectors are built, to see if assumptions or hypothesis are valid. There is nothing wrong with a model of the early universe that has early primordial black holes, for example. Yes, that is the result of several assumptions, BUT it is a testable and verifiable part of a model.
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Re:A little bad a-priori reasoning (Score:4, Interesting)
Or maybe not. [arxiv.org]
You link to a 4-year old report of a preliminary observation, but work since then has shown that the original interpretation was wrong. Dark matter still appears only to interact by gravity alone.
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"Whilst we do not find an offset between mass and light (suggestive of self-interacting dark matter) as previously reported, the numerical simulations that have been performed to calibrate Abell 3827 indicate that offsets and asymmetry are still worth looking for in collisions with particular geometries."
"Still appears". Fair enough.
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dark matter isn't matter so much as a catch all for "how come that galaxy doesn't fly apart". The intellectual jump required is, gravity is the only force we know that can hold a galaxy together, hence there must be some source of gravity we cannot see, let's call it dark matter.
It is a logical inference, not a scientifically proved substance.
I'm a dummy. (Score:1)
I always wonder how this type of shit works. I'm sure it does because they are way smarter than me, but seems like there are a billion different things that could trigger such a system. It's like if you setup a super-sensitive tripwire in the jungle and somehow determine, for every disturbance of the wire, what breed of mosquito tripped it (vs a piece of dust or debris falling on it), the sex of the mosquito, and how much blood it just drank, and also the type of animal it drank from all based on the the mo
Re:I'm a dummy. (Score:5, Insightful)
Not a dumb question - that is exactly why experiments like this are difficult. There is an old saying that its easy to build something that measures everything, the trick is to measure the thing you want to measure.
For conventional gravity wave detectors, decades of work has gone into isolating them from all other known sources of noise. It helps that there were specific types of signals that they were looking for (black hole in spirals) and there were not a lot of other things that would mimic that signal. For these detectors we would need to know what the expected signal looks like. If its just white noise, it could be very tricky to be sure they found the right thing. (but this is a lot of what experimental scientists do - so they may have a plan)
Will it be "mini" enough for a mobile phone? (Score:3)
So please, make them really "mini".
Maybe, but it wouldn't work (Score:2)
The device measures really tiny forces exerted on a glass bead. While that part in itself could (probably) be made quite small the problem is to first shield all the other, much larger forces, or at least control and counteract them to a precision that still allows for those tiny forces to be measured.
Gravity is an extremely weak force, only because we sit on a chunk of matter the size of the earth it is so noticeable. So i don't think using gravity waves for information transfer is a good option.
Also i don
Not likely (Score:3)
Politicians (Score:2)
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Nah, that's not empty space. If it were, there'd be virtual particles popping in an out of existence and it wouldn't be considered empty. Rather, I look to Idaho and their potatoes for an answer. Politicians brains are filled with smashed potatoes. It explains their affinity for gravy trains.
Too late to observe (Score:2)
The gravitational waves created by the formation of the first black holes would have gone past us already.
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remember that we are *inside* the big bang, so all the radiation it generated is all around us. Maybe there is a cosmologist here? I thought gravitational radiation from the big bang would have red shifted to very long wavelengths by now. This is probably some other mechanism.
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Not a fan of universe expansion I see. The far side of the universe has expanded so far that it is only now gravity waves generated over there have made it over here.
And what have we given in return? Reruns of "I Love Lucy"....a rather poor exchange if you ask me.
likelihood vs cost (Score:2)
Putting limits on things like high frequency intense gravity waves has some value - but that of course depends on some guess as to how likely they are to exist and how expensive it will be to do the experiment. (since there are always more science experiment ideas than there is money).
The article doesn't talk much about the expected sources.
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The project is finances with $1 million from the W. M. Keck Foundation and additional resources from the Norhwestern University, both private entities so you'll have to take the issue of prioritization to their respective boards. Although I doubt they will get more than a boilerplate answer unless you've made a sizable donation.
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Or are working on projects which they also fund.
I don't have an opinion on whether or not this makes sense, just interested in the scientific justification.