The problem with "dark matter" is that people use the term to mean three different things. 🧵

https://twitter.com/elonmusk/status/1680669208932241408?s=20

1) In the original meaning dark matter was a simple hypothesis (some kind of energy density) that explained a lot of data, hence an excellent idea

People in the foundations of physics had pretty much given up wanting true progress when I entered the field 20 years ago. Only thing most of them really seem to want is tenure and appreciation by their peers. It's a meaningless insider game.

https://twitter.com/EricRWeinstein/status/1667195003914035200?s=20

A few comments. First, note I carefully wrote "most of them". Of course there are exception. And now each of you can believe they are the exception... 2/

The wave-function in quantum mechanics is necessary to describe observations. It's useful to that end and therefore a good scientific hypothesis. Postulating the existence of universes that we don't observe does nothing to describe the universe we do observe. It's not scientific. If someone tells you that you need to believe in the existence of other universes because we accept the wave-function as scientific, that's a non-sequitur. We do have observational evidence for the wave-function. We have no observational evidence for something we can't observe.

I guess I should be kind of flattered that the phrase "some don't like the concept of the multiverse" is a link to one of my videos, unfortunately, that's not what the video says. What I like or don't like is beside the point.

phys.org/news/2023-03-m… The point of the video is to explain why the multiverse hypothesis is not scientific, and it addresses all the commonly-made strange claims by physicists that try to convince people otherwise.

We have a new paper, that is Tobias Mistele, @DudeDarkmatter & me. It's about superfluid dark matter but highlights what I believe is a general problem of hybrid approaches.

arxiv.org/abs/2303.08560 The issue is roughly speaking this. You introduce a new field that reproduces modified gravity in some regime and CDM in some other regime. Question is, do you couple it to photons or not.

I've been doing my weekly Science News for about 4 months now. I have literally read thousands of press releases to that end. The major insight that I have taken away from this is to never, ever, trust a press release. I kind of knew this already in the sense that in cases when I've traced down the origin of a bad headline most often it came from a press release. But I usually don't read press releases right from the bottle, so to speak, I've only started doing this last year.

Yes, I've seen the headlines saying that black holes may be dark energy. I think that's extremely implausible. A brief 🧵 1/

theguardian.com/science/2023/f… First of all, the statement is immediately contradictory because what we mean by "dark energy" is defined by having a particular equation of state. A collection of black holes does not have the right equation of state, so it can't be dark energy. 2/

"The strongest hint we have of the unity of nature comes from particle physics. At high enough energies, the fundamental forces — gravity, electromagnetism and the strong and weak nuclear forces — seem to become equal."

factually untrue

nytimes.com/2023/01/24/sci… What she is probably referring to is the idea of gauge coupling unification in certain supersymmetric extensions of the standard model. Three problems with that 2/

Physicists fumble together a dark matter model with the explicitly stated purpose of being able to claim it's detectable. Paper gets published, no one even questions the methodology.

news.umich.edu/a-new-model-fo… From the press release: "The challenge for a suitable model: If dark matter interacts too strongly with normal matter, its (precisely known) amount formed in the early universe would be too small, contradicting astrophysical observations." 2/

I don't know why everyone wants me to comment on the nuclear fusion news. It's all well and fine and a great experimental achievement and all, but as I've said before, that's energy in and out of the reaction, not the entire system. Great science, but far from application. I watched the press announcement and I thought it was really well done. They were very clear on this point and they also stressed that commercialization is likely decades away, which is also my current estimate.

No they didn't create a wormhole. It's a bullshit headline that deliberately misinforms the reader and I think you should unfollow and unsubscribe from every outlet that promotes this nonsense.

https://twitter.com/QuantaMagazine/status/1597984021522178048?s=20&t=FxmVQ4NSc6QauWmFkFtQFw

Lots of people have asked me to comment on this, but I have talked about this dozens of times before. I even made a joke about how the "wormhole" nonsense made it into a document of the US government in my Quantum Hype video

(at around 10:30 mins)

According to a 2014 analysis by @Nature nature.com/news/the-top-1… , the most cited physics paper falls in the subfield of condensed matter physics and was published in PRB in 1988 the paper is here journals.aps.org/prb/abstract/1…

Ah, what would twitter be without quality comments from my fellow physicists.

https://twitter.com/MMylova/status/1596792055795449858?s=20&t=kqEesBYzrOdnl-YmMPM3CA

So, after looking up "malarkey" in the dictionary, let me just say this is an incredibly ill-informed comment. Superdeterministic hidden variables models are the only known way to complete quantum mechanics while respecting locality.

Since everyone has a hot take on the future of twitter, I don't want to withhold mine because it's what you're here for, right? 🧵 1/ First of all I'm afraid I care very little about twitter. I have some friends here who I'd like to stay in touch with, but certainly this can be done on another platform. Social media platforms come and go, the only constant is change, etc. 2/

Extremely common misconception, so worth a brief comment: While the word "quantum" has its origin in discrete chunks (of energy) that does not mean everything quantum is discretized.

https://twitter.com/Kyochi_Myogo/status/1590929959480340486?s=20&t=PeYmNIMfRPhYvaXzh9HILg

The best example is indeed the position of a quantum particle -- it remains continuous in quantum mechanics. For the same reason, if gravity was quantized this doesn't mean space (and/or time) would be made up of discrete units.

I've changed my mind about whether gravity must be quantized back and forth several times. There are good arguments both for and against it. In the end, we need to find an experiment to test it, so I think that's what research should focus on.

https://twitter.com/RiffelBruce/status/1590786266177499136?s=20&t=2MN9iER0XrR4UIpCoOPJpA

I've worked on this question, how to find experimental evidence for quantum gravity, for about 10 years after my PhD. Eventually stopped simply because I couldn't get funding for it. The usual problem with academia.

Since I see people constantly stumble over this in science communication: There isn't just one Nature journal, there's THE Nature journal, and then there are 32 others called Nature Somethingsomething (Nature Physics, Nature Communications, etc) Each time you look there's a few more of those

This article is well worth mentioning because it explains the consequences of Bell's theorem reasonably correctly (though it remains unclear why the author thinks it has anything to do with "free will").

theconversation.com/four-common-mi… Though I should add, I know of course why the author adds the not about "free will" -- because physicists in the past have linked Bell's theorem (or rather a specific assumption to Bell's theorem) to free will. And then argued that this assumption cannot be discarded.

Oh dear, there are so many mistakes in this one paragraph, where to even begin!
phys.org/news/2022-10-b… For starters, one doesn't experimentally "prove theorems". In fact one can't experimentally "prove" anything. Bell's theorem is a mathematically proven consequence of certain assumptions.

And guess what, they didn't find it.

phys.org/news/2022-10-q… I am afraid that a lot of people who follow me on twitter today don't understand why I'm making jokes about such searchers for "new physics". I get often called cynical or dismissive. So here's another attempt to explain myself

Nooooo, she said, in despair. You are STILL confusing the measurement update (aka "spooky action") with entanglement (a correlation: not spooky, no action). @overbye

nytimes.com/2022/10/10/sci… Entanglement is just a correlation between properties of particles. It is locally created. It becomes non-local if you move the particles apart. Do you know these friendship bracelets with two parts that fit together? That's a non-local correlation!