Testing quantised inertia on Proxima Centauri

68 points by ilove_banh_mi 1 year ago | 40 comments
  • georgeburdell 1 year ago
    Only read the first few pages, but as a non-physicist, but who went through grad school, it appears the author is advertising their own prior work quite a bit. I generally associate this behavior with a) cranks b) stubborn people who lost an ideological turf battle
    • pdonis 1 year ago
      > it appears the author is advertising their own prior work quite a bit

      Not only that, but it's prior work that is based on a false premise. The author's proposed "solution" is based on Unruh radiation, but Unruh radiation is zero for an object in a free-fall orbit. To get nonzero Unruh radiation, you need proper acceleration, i.e., some non-gravitational force has to be acting on the object. Unless the author is claiming that Proxima Centauri has a rocket attached to it, his model fails at step one. I believe other physicists have pointed this out but the author prefers not to mention or address this criticism.

    • yongjik 1 year ago
      I'm not a physicist, but a massive Wikipedia article on Alpha Centauri says nothing about the system not being gravitationally bound, and at least one scholarly article says they are gravitationally bound:

      https://www.aanda.org/articles/aa/abs/2017/02/aa29930-16/aa2...

      > ... the question as to whether they actually form a single gravitationally bound triple system has been open since the discovery of Proxima one century ago. Owing to HARPS high-precision absolute radial velocity measurements and the recent revision of the parameters of the α Cen pair, we show that Proxima and α Cen are gravitationally bound with a high degree of confidence. The orbital period of Proxima is ≈ 550 000 yr.

      • alfiopuglisi 1 year ago
        > the fast orbit of Proxima implies it is gravitationally unbound given the visible mass of A and B

        Since when? For example these measurements from 2016 say the opposite: https://www.aanda.org/articles/aa/full_html/2017/02/aa29930-...

        • avsteele 1 year ago
          I wish he spent a bit more time on the section regarding magnitude of the effect for different accelerations.

          If indeed there is a minimum acceleration I wonder if it might not be measurable with some atomic physics experiment (atomic clock, etc..) in space a bit away from earth.

          • dvh 1 year ago
            Really interesting paper, however:

            >The Alpha Centauri system is ideal for testing quantised inertia since it is close to us and well-observed.

            Yet they're using 1994 estimate for AB mass, have nobody measured alpha centaury AB mass since 1994?

          • Iolaum 1 year ago
            > All three stars are co-moving with similar chemistry, which implies they are bound

            This is a weak assumption IMO. It is also possible that the stars "just" have a common origin and move at similar enough trajectories without being gravitationally bound.

            • myrmidon 1 year ago
              Not a physicist, but I never heard of this before and looks quite interesting at first glance.

              Google indicates that mainstream physics regards it sceptically ("pseudoscience"), but it was difficult for me to find out why.

              I found a single paper containing criticism from an actual physicist ("A sceptical analysis of quantized inertia" by Michele Renda: https://academic.oup.com/mnras/article/489/1/881/5545603), but that did not make the theory sound that bad, and it even mentions "absence of arbitrary tunable parameters", which sounds very promising to me...

              I'd be very curious on why this is so controversial from an actual physicist (e.g. compared to MoND). Hopefully Hossenfelder will cover this at some point on youtube, those videos are always quite merciless with overhyped results...

              • btilly 1 year ago
                My first criticism is this. The scale on which quantization works is the https://en.wikipedia.org/wiki/Planck_constant. We should not expect quantization to be a visible effect at the scale of stars.

                And if quantization was a visible effect at the scale of stars, it should be very visible in our own solar system. But no, our solar system operates classically to a crazy number of decimal places, and the deviations follow general relativity - with no evidence of quantization.

                • chc4 1 year ago
                  The main reason, as far as I'm aware, is because McCulloch then went on to claim to invent several thrusters (EmDrive, most notably) derived from the effect that break normal conservation of momentum.
                  • cwillu 1 year ago
                    In what sense does McCulloch claim to have invented the EmDrive? The only citation about him on the EmDrive wikipedia article isn't even talking about anything relevant to the purported mechanism of action of the drive.
                    • chc4 1 year ago
                      The theory behind EmDrive is based on his quantized inertia theory. I was under the impression he was the original proposer of the idea. It looks like it was instead proposed by someone else in 2006; however McCulloch submitted a paper in 2013 supporting it (https://arxiv.org/abs/1302.2775) and publically advertises about how his theory allows for "an electric rocket" on his twitter https://twitter.com/memcculloch
                  • pdonis 1 year ago
                    See my response to georgeburdell upthread. Tl/dr: Unruh radiation, on which the proposed model relies, is zero for an object in a free-fall orbit.
                  • delichon 1 year ago
                    > All three stars are co-moving with similar chemistry, which implies they are bound ...

                    I am not an orbital mechanic, but the word "chemistry" is jarring to me here. Is it just a strained metaphor or is there some sense it which it fits? Maybe the romantic chemistry of mutually attracting bodies?

                    • lopuhin 1 year ago
                      I think they mean "chemical composition", e.g. how much hydrogen / helium / other elements there are in the star, deduced from their spectra
                      • delichon 1 year ago
                        What could the chemical composition of the planets have to do with observations of their inertia? How could that matter other than by their mass?
                        • jessriedel 1 year ago
                          I think the idea is that if they have the same chemical composition this is good evidence that they formed from the same primordial gas cloud. If they just happened to be passing by each other, there would be no reason for the composition to be so similar.
                    • andrewflnr 1 year ago
                      So, not a physicist, but the claims in the PDF about how GR has "never predicted a single galaxy rotation curve" are overblown, right? Aren't there a handful of galaxies where the rotation curve lines up pretty close with the predictions from the visible mass? Any new physics has to explain those, too.

                      Anyway, I think I can see why QI is so appealing. The paper contains a very short and sweet explanation.

                      • ilove_banh_mi 1 year ago
                        I'm not aware of any match between GR theory and observations when it comes to galaxy rotation curves. The wikipedia entry provides a decent description of the issue.

                        https://en.wikipedia.org/wiki/Galaxy_rotation_curve

                        • basil-rash 1 year ago
                          > The discrepancy between the two curves can be accounted for by adding a dark matter halo surrounding the galaxy.

                          Funny. “This discrepancy can be accounted for by accounting for the discrepancy using the number fudging we developed specifically to account for the discrepancy.”

                          Discrepancy’s been accounted for, boss!

                          • btilly 1 year ago
                            I don't know why this got downvoted.

                            The top theory is exactly that - most of the mass in a galaxy is in the form of dark matter of some kind that can't fit our current theories of physics. The second top theory is that gravity behaves differently at long distances than at short distances. The third theory that is proposed every so often is general relativity, but those who know it best universally agree that it is too small an effect by several orders of magnitude. Every other theory that I've encountered is generally labeled a crank theory.

                            The reality is that we don't actually know what's going on with the galaxy curves. But we do know that it involves physics that we do not yet understand. And the leading two theories involve weird fudge factors.

                          • andrewflnr 1 year ago
                            For instance: https://en.wikipedia.org/wiki/NGC_1277 Citation trail leads to https://www.aanda.org/articles/aa/full_html/2023/07/aa46291-... I vaguely recall there being a few more such instances, but can't find them with a casual googling. The paper is from 2023. Perhaps the Galaxy Rotation Curve wiki article is out of date.
                          • pdonis 1 year ago
                            > The paper contains a very short and sweet explanation.

                            As the saying goes, all complex questions have simple, easy to understand wrong answers. This is an example. See my response to georgeburdell upthread.

                            As for galaxy rotation curves, yes, the paper's claim is overblown.

                            • andrewflnr 1 year ago
                              Haha, yes, I remain skeptical at best of QI. I know just enough physics that I probably should have thought of the issue you mentioned up there, too. Still, the idea remains pretty enough that it's tempting to try to salvage it, like even if it's not technically Unruh radiation, maybe there's a reference frame or other perspective where the math works anyway... But that only makes sense if the real life numbers work out, and I'm not going to take this guy's word for it.
                              • pdonis 1 year ago
                                > even if it's not technically Unruh radiation, maybe there's a reference frame or other perspective where the math works anyway

                                There can't be, by Lorentz invariance. If a free-falling observer sees zero radiation in one frame, they must see zero radiation in any frame.