Scientists observe Einstein's gravity in the quantum world

Blocked? No. Greatly attenuated and restricted in what modes can be accommodated? Yes.

More critically though the study gets into how they used a reference wave packet to establish a stationary baseline for the interferometer. Assuming the experiment is sufficiently isolated to reduce noise below the necessary threshold this can work in principle.

https://www.science.org/doi/10.1126/sciadv.aec8045

They can't exactly occupy the same space due to the Pauli exclusion principle. IIRC that's believed to be the final "barrier" that prevents neutron stars from collapsing into black holes. But this is also getting into the tricky parts of wave particle duality, so the precise details are a bit difficult for me too.

It's not a stupid question at all, here's the answer:

Electrons (as an example) experience Coulomb pressure (charge repulsion), but also a quantum statistical pressure called Fermi Degeneracy pressure related to their kinetic energy, AND ultimately the Pauli Exclusion Principle (Identical Fermions cannot occupy the same state, but higher momentum states take more energy to reach naturally so this creates resistance to collapse). If you want to learn more about this you can get a lot of mileage out of some reading on Fermi-Dirac statistics, the Pauli Exclusion Principle, and degeneracy pressure. Now this is just using electrons as a model, but ultimately all of the above can be overcome by gravity. When it does you still can't have electrons disobeying the rules, but the potential energy barrier to merge electrons and protons into neutrons is overcome. THEN you have neutron degeneracy pressure, and in theory after that you have a black hole (spacetime singularity surrounded by an event horizon.

However... that may not be the case. It is true that observation has confirmed the existence of objects that are so dense and massive they must have an event horizon, but beyond that we have no way of direct observation, right now (even in principle). A lot of people believe this indicates that a singularity doesn't really exist; it's the usual lesson when a singularity appears in your math: your math is wrong. In the end maybe there's another sort of degeneracy pressure from quarks or something even more fundamental like strings that ultimately prevents final collapse to a true singularity.

ed: typos

Thanks! We'll put that link in the toptext as well.

Any explanation by Roger Penrose is bound to be good

The article says that this proves that Einstein's equivalence principle (resulting in relativity) holds in this test of a falling quantum particle (where gravity results in a phase shift in the quantum state).

It doesn't show/prove how general relativity and quantum mechanics interact.

NOTE: The Dirac equation and Quantum Electro Dynamics (QED) unify quantum mechanics and special relativity (non-accelerating frames of reference).

So the remaining piece is either to extend QED/QCD to accelerating frames of reference or to quantize general relativity. That would likely predict the phase shift observed in this experiment.

From the article: "The result does not unite quantum mechanics and gravity, nor does it show that gravity itself is quantum".

I must say, it's actually quite refreshing to read an article about a science topic that conveys the caveats and limitations of the study. Far too many of these studies get filtered through the news outlet hype-machine

By "every particle" do you mean like, every type of particle?

If you mean individual particles, fundamental particles don't really have distinct individual identities (as shown by fermi and bose statistics).

As for types of particles: Well, photons surely move at the speed photons move at.

Special relativity is derived from the assumption/observation that light travels at the same speed in all inertial reference frames, and generally that the laws of physics work the same in any inertial reference frame.

What you are proposing sounds pretty vague and unclear to me, but, is what you are trying to say compatible with this?

Probably no, because according to quantum mechanics, photons are indistinguishable in a way that affects experiments.

What measurable predictions does this hypothesis make that would differ from the existing models?

> Please don't use Hacker News for political or ideological battle. It tramples curiosity.

https://news.ycombinator.com/newsguidelines.html