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As a grad student in High-Energy Physics I worked at the XENON1T dark matter detector in Italy. I left feeling disenchanted about the search for dark matter, an
by alecst 5y ago
As a grad student in High-Energy Physics I worked at the XENON1T dark matter detector in Italy. I left feeling disenchanted about the search for dark matter, and I felt like a lot of us were just doing the best we could at the time, which was build a bigger and bigger detector to get more and more sensitivity.
One talk started with a lecture on the lamppost problem. It asked: why exactly are we looking for WIMPs? Because we know how to build a WIMP detector.
I'm not equipped to answer questions about dark matter anymore, but I will say that a lot of the knee-jerk comments in this thread underestimate how smart physicists are. Some of the most brilliant minds in science have contributed to dark matter cosmology. They are particle physicists, cosmologists, fluid dynamicists, and simulationists (reaching a little bit with the terminology here) all working together.
Science is progressing in the natural way of excluding theories from easiest to hardest. The fact that there are so many people working to exclude the "obvious" (or even "obviously wrong") theories should be evidence of how difficult this problem really is.
It may turn out that dark matter is explained by a non-particle phenomenon, or that it is matter that simply acts purely via the gravitational force and nothing else. I don't know what the implications of this would be. But none of that is obvious or easy to prove at the moment.
Nor is it easy to come up with a dark matter model which satisfies all the necessary constraints. You cannot just say, "there's some stuff out there" without collateral effects on (say) the distribution of matter in the universe.
For why we believe dark matter exists, see here: https://kids.frontiersin.org/articles/10.3389/frym.2021.576034 https://kids.frontiersin.org/articles/10.3389/frym.2021.5760...
- lil_dispaches 5y agoI know how to build a dream catcher.
- Maursault 5y agoThe reasons given for Dark Matter always begin with galaxy rotation curves (the galaxy rotation problem and the galaxy winding problem). But the problem with this "evidence" is that the observations were made of galaxies in isolation, but even galaxies are not gravitationally isolated.[1] I can not speak to the veracity of the rest of the evidence for Dark Matter, but galaxy rotation curves can no longer be counted as evidence of Dark Matter because they are more simply explained by a gravitational phenomenon caused by the out of frame mass of other nearby galaxies. [1] https://www.youtube.com/watch?v=PL0ewiwqoTw&t=4m5s https://www.youtube.com/watch?v=PL0ewiwqoTw&t=4m5s
- alecst 5y agoThere are many theories of dark matter given at conferences like this. Around that time (2013-2014) I remember hearing about axion theories too. I don't know anything about this person's presentation so I can't say how it displaces the problem of galaxy rotation curves. If the math checks out, I think it would have, but you never know. I would like to see a reaction from cosmologists. I would hesitate leaning too much on the always part. Fritz Zwicky was the first to notice the anomalous galaxy rotation curves and propose dark matter (is the story that I remember, anyway.) This is probably why it's presented first. It does not mean that it's the most important piece of evidence. I'm intentionally writing with a light touch here because I don't consider myself an expert in the field.
- pdonis 5y ago> a gravitational phenomenon caused by the out of frame mass of other nearby galaxies There have been papers published on this, but it is still speculative, so it's premature to say that this kind of alternative theory rules out dark matter.
- Maursault 5y ago> it's premature to say that this kind of alternative theory rules out dark matter No, it only eliminates the need for Dark Matter to explain galaxy rotation curves.
- russdill 5y agoExplanations always begin with Galaxy rotation curves because that's how it was first notified that something about our understanding of the universe was off. It's been a long time since then and there's been a ton more data collected about wide ranging phenomenon since.
- Melatonic 5y agoIs it possible that Dark Matter is simply not possible to observe from our frame of reference?
- wongarsu 5y agoBut we are only talking about it because we can observe it. Or rather observe how it interacts with other things, but that's just semantics: all observation happens via interactions. Dark matter could be a neighboring universe interacting with ours or something like that where the actual particle causing it is fundamentally out of reach (if it even is a particle), but just the fact that it interacts with our universe means we should in principle be able to interact with it and characterize it with experiments.
- Melatonic 5y agoThats more along the lines of what I was thinking - we can observe this specific interaction but without also observing other interactions it seems very difficult to define exactly what it is. Or maybe it is just that our current frame of reference (both physically and in terms of time) is just a bad vantage point to do so.
- russdill 5y agoAn important property of dark matter need to fit what we are seeing is that it also doesn't interact with itself. It would seem weird if it can't interact with itself because of some innate property, but we can't interact with it because we are somehow out of phase with it.
- zvrba 5y agoA naive question from a hobbyist with over-average interest in particle physics: quantum theory is based on complex numbers. Has anyone considered that mass/gravity may also have an imaginary component that manifests itself as "dark matter"? (I.e., it's not "matter" at all, just an incomplete understanding of gravity.)
- alecst 5y agoThat's exactly the kind of question a curious physics student would ask. This might be what you're looking for: https://en.wikipedia.org/wiki/Tachyonic_field https://en.wikipedia.org/wiki/Tachyonic_field > In physics, a tachyonic field, or simply tachyon, is a quantum field with an imaginary mass.
- henriquecm8 5y agoI hear the word Tachyon so much in science fiction that I was under the impression it was a sci-fi word.
- Someone 5y agoIt almost is. https://en.wikipedia.org/wiki/Tachyon#History https://en.wikipedia.org/wiki/Tachyon#History: The term tachyon was coined by Gerald Feinberg in a 1967 paper titled "Possibility of faster-than-light particles". He had been inspired by the science-fiction story "Beep" by James Blish.“ I don’t think “Beep” introduced the word, though (https://archive.org/details/galaxymagazine-1954-02 https://archive.org/details/galaxymagazine-1954-02)
- wyager 5y agoGood question. Imaginary mass -> negative 4-momentum -> momentum exceeds energy -> object is moving faster than light (backwards in time in some reference frames). There are some reasons to suspect/hope such things might not exist, such as protecting causality. In general, asking "what if <simple field type> was <more complex field type>" can actually produce super fruitful lines of inquiry. You can use "complex numbers", "quaternions", "finite fields", whatever you like. There's plenty of unexplored ground here.
- dave333 5y agoDark matter is possibly the best evidence in support of Dr. Mills' Hydrino theory https://brilliantlightpower.com/theory/ https://brilliantlightpower.com/theory/ which deserves a fair reading. There are about 20 experimental results supporting this theory that models electron orbits as spherical shells instead of probability clouds. He has machines that produce 100s of kW from small quantities of hydrogen - 200 times the energy produced by burning hydrogen. https://brilliantlightpower.com/tpv-suncell-rectanguloid-cavity-blackbody-radiator/ https://brilliantlightpower.com/tpv-suncell-rectanguloid-cav...
- tux3 5y agoIn 1999, the Nobel prize winning physicist Philip Warren Anderson said he is "sure that it's a fraud",[12] and in the same year another Nobel prize winning physicist, Steven Chu, called it "extremely unlikely".[23] The following year, a 2000 patent based on its hydrino-related technology[24][25] was later withdrawn by the United States Patent and Trademark Office (USPTO) due to contradictions with known physics laws and other concerns about the viability of the described processes, citing Park and others.[26] Source: https://en.wikipedia.org/wiki/Brilliant_Light_Power https://en.wikipedia.org/wiki/Brilliant_Light_Power Every submission you've made seems to be about this company (https://news.ycombinator.com/submitted?id=dave333 https://news.ycombinator.com/submitted?id=dave333).
- dave333 5y agoSo how do these Nobel prize winners explain dark matter? Do "known physics laws" not evolve as new discoveries are made? Wikipedia is policed by skeptics that only support the status quo. IMO that article is not a fair description of Brilliant Light Power. As for my submissions, if as I believe hydrinos turn out to be real, it will be the greatest scientific discovery since the genome, so worth harping on about.
- Epiphany21 5y ago>I left feeling disenchanted In scientific study you want and need failure. Knowing what doesn't work is as important as knowing what does. This way we can make lists of dangerous or useless things to be avoided. As long as things are documented and reproducible to the best of your abilities, you've won.
- alecst 5y agoI do not consider the search for dark matter a waste of time. But when you are working with a team of WIMP-detector-building specialists, it is (unsurprisingly) hard to have a conversation about whether we should continue building WIMP detectors. People’s egos and emotions are all wrapped up in the science, and that is the part I came away disenchanted about. Definitely don’t misinterpret my feelings to be about science in general, or about getting a negative result (the Michelson-Morley experiment comes to mind.)
- afarviral 5y agoMight dispersed matter have a higher mass than more condensed matter as an alternative hypothesis? Where the more distant and small a unit of matter is, the more curved the spacetime around it. Lonely particles longing to coalesce? These particles would reflect and scatter too little to be visible and hence be "dark matter". If this was the case, stronger attraction at either extreme of distance might be an effecient accelerator of formation of celestial bodies. This kind of wonky gravitation could also explain the accelerating expansion of the universe.