Testing quantum mechanics in space

https://www.nature.com/articles/d41586-021-02091-8

by pseudolus • 5 years ago

73 52 5 years ago

This seems like such a bad idea, the equivalent of catapulting ever greater rocks on the moon to test Newton's laws.

I wonder how precise the measurement of those trajectories would need to be, to detect deviations due to special/general relativity.

krastanov9• 5 years ago

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.

AlotOfReading• 5 years ago

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.

evanb• 5 years ago

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.

whatshisface11• 5 years ago

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.

perihelions• 5 years ago

Why do they need vacuum pumps at all? Do the materials of the satellite itself offgas too much?

mdturnerphys• 5 years ago

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)

canjobear• 5 years ago

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?

tooltower• 5 years ago

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.

whatshisface11• 5 years ago

All the large objects are made up of smaller objects...

prof-dr-ir3• 5 years ago

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.

bawolff• 5 years ago

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.

BulgarianIdiot6• 5 years ago

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.

andi9992• 5 years ago

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.

prof-dr-ir3• 5 years ago

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.

BulgarianIdiot6• 5 years ago

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?

We can probably devise some interesting experiments when we have conscious human observers within the apparent independent wave function.

Chris20482• 5 years ago

Are you pushing "quantum conscious" here?

dekhn3• 5 years ago

BTW, these fringe theories have no real place in modern QM. Nobody has demonstrated anything even remotely relevant to quantum mechanics in consciousness.

m-watson• 5 years ago

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.

ThomPete• 5 years ago

china is already fully engaged in this

https://www.scientificamerican.com/article/china-reaches-new...

whatshisface11• 5 years ago

Doing the double slit experiment with ever-larger particles is not related to quantum communication.

nabla9• 5 years ago

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....

Testing quantum mechanics in space

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