4 years ago by canjobear
What hypothesis is being tested here? Is there any theory that predicts that large objects won't behave like waves if they are properly isolated from the environment?
4 years ago by tooltower
Indeed, there are variations on standard quantum mechanics that postulate that large systems can spontaneously collapse their wave functions. E.g. https://en.wikipedia.org/wiki/Objective-collapse_theory
Nobody is really expecting large objects to behave differently, but somebody should still check.
4 years ago by prof-dr-ir
It appears that these theories are not relativistic and claim that energy is not conserved. Therefore they will have significant trouble explaining almost all particle physics experiments.
From the perspective of a theoretical particle physicist these theories are also awkward because they try to fiddle with non-relativistic quantum mechanics like the Schrodinger equation. But that equation merely arises in the non-relativistic limit of the more fundamental relativistic quantum mechanics, more commonly known as quantum field theory. Therefore, if you want to probe the foundations of quantum theory then quantum field theory seems like a much better place to start.
As an analogy, these attempts sound like a nineteenth-century person trying to understand gravity starting from F = m g h rather than F = - G m1 m2 / r^2.
For these reasons I would not be supportive of significant funding for theoretical or experimental research in these collapse theories.
4 years ago by krastanov
Saying that Schroedinger's equation is a non-relativistic limit is a bit misleading. The typical choice of Hilbert spaces, sure, is non-relativistic. But QFT and any other quantum theory, is basically Schroedinger's equation on a sufficiently weird Hilbert space (from second quantization, graphs, grids, or strings)
4 years ago by whatshisface
All the large objects are made up of smaller objects...
4 years ago by kordlessagain
That’s the current hypothesis, at least.
4 years ago by m-watson
There are plenty of reasons to do this that don't distill just down to do they act as expected. One reason researchers do quantum experiments in macro-objects is it is significantly easier to measure. If they can show the glass bead can be put into quantum states in space it means they can now study quantum states via a glass bead instead of atoms, which are real hard to look at.
4 years ago by andi999
One can view it as a falsification experiment to quantum mechanics. Or in other terms to see what the range of applicability is. One doesn't alway know before where new physics is, most likely it is where one hasn't looked experimentally.
4 years ago by prof-dr-ir
I often see the argument 'we should check because you never know' being used for supporting exotic science experiments. But I think it is too dogmatic.
Indeed, we have not tested experimentally whether launching andi999 into space will affect the muon g-2 anomalous magnetic moment. Although you might be very supportive of testing that hypothesis, I would sincerely doubt that it would lead to a discovery of new physics.
In the end this boils down to funding decisions for the sciences, which are invariably nuanced, difficult and political. Simply saying 'we should try because nobody else has' would convince only the most naive of funders.
4 years ago by andi999
I agree your suggested experiment shdnt be funded. I thought for the other one it is actually quite obvious. You have a quantum realm which has been confirmed by all experiments so far, and you have a classical world (objective trajectories), now it could be that there is a boundary where qm breaks down, or it could be that (when allowing for suitable coherence environments) that this never happens. I think you definitely shd try to push the (experimental) boundary on this one. Same like ppl check if Colombs law is really 1/r^2 (which is an even weaker case where one shd look).
4 years ago by bawolff
I think the big thing is many humans cant wrap their mind around qm. Lots of people are like, its ok as long as it only applies to microscopic quantities but doing a big object would force them to confront reality more head on.
4 years ago by BulgarianIdiot
> I think the big thing is many humans cant wrap their mind around qm.
Especially physicists. As the joke goes, people who think they understand QM, don't.
The fact "infinitely many universes spawned infinitely frequently" is a serious take on explaining QM suggests everyone who has a casual explanation about all of this has missed a few things.
4 years ago by nabla9
For people in this thread ask why.
The Trouble with Quantum Mechanics, Steven Weinberg JANUARY 19, 2017 ISSUE, http://quantum.phys.unm.edu/466-17/QuantumMechanicsWeinberg....
4 years ago by ThomPete
china is already fully engaged in this
https://www.scientificamerican.com/article/china-reaches-new...
4 years ago by whatshisface
Doing the double slit experiment with ever-larger particles is not related to quantum communication.
4 years ago by perihelions
Why do they need vacuum pumps at all? Do the materials of the satellite itself offgas too much?
4 years ago by mdturnerphys
Good question. They say that they need 10^-11 pascals. The pressure in low earth orbit is 10^-8 pascals [0], but the suggestion is to put it at a Langrange point (L1 or L2), where the pressure should be much below that.
[0] https://en.wikipedia.org/wiki/Orders_of_magnitude_(pressure)
4 years ago by madengr
I thought macroscopic quantum behavior had been demonstrated in a comb-like resonator? The vibrating teeth on the comb would transition from one side to the other without passing through the center.
4 years ago by whatshisface
This seems like such a bad idea, the equivalent of catapulting ever greater rocks on the moon to test Newton's laws.
4 years ago by krastanov
Funny thing is that we have been running other experiments you would find just as silly: test gravitational attraction between human-scale objects with ridiculously expensive and sensitive equipment, test whether there is a difference between gravitational and inertial mass, interfere neutrons(?) after they pass through slightly different gravitational fields on Earth. My favorite is measuring the dipole moment of the electron (like, duh, of course the electron does not have a dipole moment).
All of these tests are silly if you believe the theories of the day. The vast majority of such tests in history have simply confirmed the theory of the day. And also, there are a small handful of them that have spurred the most amazing intellectual explosion in the history of this planet (Special/General relativity and Quantum theory).
Also, the investment permits the contractors for the experiment to create an industrial base crucial for applications in the general economy.
4 years ago by evanb
The standard model of particle physics does predict the electron should have an EDM.
https://en.wikipedia.org/wiki/Electron_electric_dipole_momen...
However, a nonzero electron EDM indicates P and CP breaking; in the standard model it’s generated through loop effects from the CP violation in the CKM matrix, making it very very small (1e-38 e•cm).
The experimental results are that it’s zero with a precision of ~1e-28 e•cm. So, there’s TEN orders of magnitude between experiment and theory—-that makes it not a particularly silly thing to measure, but a particularly appealing experimental target: lots of models of new physics predict something substantially larger than 1e-38, and the small value in the standard model makes a nonzero measurement an obvious signal.
Contrast the muon g-2 measurements, for example, where a new lattice QCD calculation of standard-model effects claims to adjust the prediction in the 10th decimal, reducing the tension to 1.5 sigma. If an electron EDM is found anywhere in the next… 8 or 9 orders of magnitude, it’d be an inarguable sign of new physics.
4 years ago by krastanov
That is exactly the point I am making with my (facetious) comment. We measure it because a mismatch from the very much exected result would be monumentally important, even if improbable.
4 years ago by whatshisface
This is like spending $1B to pile up dirt to test the size of the biggest pile of dirt that can be piled with $1B. How can anyone know for sure that the laws of physics don't change when the expense of the pile crosses the $800M threshold?
Obviously, the laws of physics do not have a dirt pile expense parameter. Just because some non-absurd ideas have been called absurd does not mean that no ideas are absurd. The idea that quantum mechanics stops working when too many particles get together is likewise absurd, because just like there's no way for a particle of dirt to "tell" how much money was spent piling it up, an atom does not "know" how many other atoms are in the macroscopic crystal it lives in.
4 years ago by krastanov
The laws of physics have a lot of "dirtpile scale" parameters. When spacetime curvature (presence of mass) is measurable, Newtonian mechanics stops working. When the action integral is comparable to the Plank constant, classical probabilities do not work. When the Reynolds number goes beyond a threshold, laminar models of liquids do not work.
You are factually wrong about your quantum mechanics claims. (1) The idea that quantum mechanics stops working at some mesoscopic scale is extremely popular among (respected) sceptics of quantum computing. (2) The most well known example of a quantum thought experiment, the Schrödinger cat, is about quantum mechanics (seemingly) not working at macroscopic scale (only last year was there a good theory explanation of the paradox https://pirsa.org/20010099 ) (3) Decoherence is the thing causing fights between proponents of different formalizations of Quantum mechanics and this would be a very stringent test of that process. There are plenty more ideas that would get tested with this experiment.
Also, I think you misunderstood my examples. None of the examples I gave in last post were considered absurd, rather all of them were fine measurements that were necessary in order to believe the theory when going into a new parameter regime. With your attitude we would have never found general relativity (of course throwing a bigger rock on the moon will follow Newton's law) or quasi crystals (of course only regular repetition can make a crystal) or prions (of course proteins do not reproduce).
If you are arguing that this money right now would be better spent on global warming mitigation, then I would probably agree. But that is a relative, not an absolute statement like yours.
4 years ago by AlotOfReading
More experiments are always worthwhile, but from a practical perspective funding is a zero-sum game with a small number of finite pots. The question being raised isn't whether this proposal is worthwhile "in general", but instead whether it's a good use of finite finding vs other potential science.
Given the immense cost and the lack of serious reasons to expect otherwise, I think it's a pretty reasonable question to ask.
4 years ago by l33tman
I've heard it expressed numerous times that the zero-sum-game argument is a fallacy. There are a lot of foundations and donors that pick among projects and might just hold on to their money if a suitable project to fund is not available.
4 years ago by undefined
4 years ago by AlexCoventry
I wonder how precise the measurement of those trajectories would need to be, to detect deviations due to special/general relativity.
Daily digest email
Get a daily email with the the top stories from Hacker News. No spam, unsubscribe at any time.