[mbell]

I'm not a physicist, just an interested bystander but some of these arguments don't seem to hold water to me:

> There’s a more general point to be made here. The primary reason that we use dark matter and dark energy to explain cosmological observations is that they are simple.

> A creation term is basically a magic fix by which you can explain everything and anything.

Dark matter is an unknown 'substance' that interacts only through gravity (weakly) and must have a very specific and complex distribution in the universe to 'work'. That strikes me as neither 'simple' nor much different than tossing a constant into an equation to make it work. Similarly Dark Energy is an unknown form of energy that in uniformly distributed through the universe, which to me is just a fancy way of saying "we added a constant to make it work". In both cases I don't see how either are implicitly better than adding a 'creation term'.

[rwilson4]

I believe the author's argument is: however simple or complicated dark matter and energy are, negative (inertial) mass just makes things even more complicated, without offering any new (testable) insights. The author herself points out that she (and the GR community) may be wrong about a lot of this stuff (e.g. that gravity is mediated by a spin-2 field), but absent a testable hypothesis, negative masses don't actually move the field forward at all.

Seemingly "crazy" ideas sometimes turn out to be correct! But in science, we demand radical ideas at least make testable hypotheses.

[kjeetgill]

That's the thing, I think it's exciting because that researcher does believe it to be testable. My comment from the last negative mass thread:

My favorite bit from the author on Twitter: https://threadreaderapp.com/thread/1070302359325151233.html > The next-generation radio telescope - the Square Kilometre Array @SKA_telescope will be able to test this theory, and directly confirm or invalidate its predictions. 13/17 It is rather surprising that the model predicts the properties of a LambdaCDM universe.

As a casual observer this is is what gets me excited! We'll get our answers one way or another

[guitarbill]

> "it’s highly problematic to introduce negative inertial masses because this means the vacuum becomes unstable. If you do this, you can produce particle pairs from a net energy of zero in infinitely large amounts. This fits badly with our observations."

Basically, if you mess the the equation, you have to be very sure you aren't simulating something silly. Which is easy to do, unfortunately I've done it often.

I still need to read the original paper in detail to confirm, but if the post is correct, the N-body simulation might have some issues.

[Izkata]

Waaait a minute, isn't that describing something we've already observed - spontaneous creation of virtual particle pairs in a vacuum?

[aroberge]

We have definitely not observed spontaneous creation of virtual pairs in a vacuum. I do not blame you for thinking so as it is often described this way.

Almost no computation in Quantum Field Theory can be done exactly. What physicists do is using perturbation theory which is very similar to doing Taylor series in introductory calculus. Feynman, in a genius inspiration, found a way to represent the various mathematical terms that occur in these types of calculations as pictures which could be described in words. In this pictorial language, one would say things like "this term correspond to the creation of a virtual pair of particles", etc." The perturbation expansion is a mathematical "trick" done so that we can do obtain approximate results. Each individual term in that expansion has no physical meaning - in spite of the pictorial language used.

[kgwgk]

In infinitely large amounts?

[InclinedPlane]

Dark matter is a weakly interacting massive particle which hasn't been detected directly yet. This is not a terribly controversial theory because we already know of other particles with very similar behavior (neutrinos) and we also know for a fact that our theories of particle physics are incomplete. Moreover, the most straightforward "improvements" of our current theories of particle physics (supersymmetry, for example) would all necessarily involve the existence of previously undiscovered particles. Additionally, the conditions by which such "new" particles would be created (high energy densities) are precisely the conditions which would occur during the early Big Bang, leading to a very natural process of formation of a "cosmic dark matter background" (just as there exists a cosmic neutrino background and a cosmic microwave background) as a relic of the Big Bang, which unlike the other background relics would evolve in structure significantly after the Big Bang, responding to the evolution of baryonic matter (into clumps which became galaxies and galaxy clusters). In short, it's not very far of a leap from everything we already know about physics and cosmological history, and it matches the observational evidence remarkably well, which is why it is the accepted theory in astronomy and cosmology.

Dark energy is less well studied but the idea of vacuum energy is not a new one. We don't understand why vacuum energy is not zero but instead a very tiny number, but it's only a little surprising. It is, after all, fundamentally a theory that is a century old, dating back to Einstein's work with the cosmological constant.

[simonh]

I don’t know about dark matter, but the case for dark energy or something like it is pretty compelling. The expansion of the universe is accelerating. Things don’t generally accelerate unless there is something pushing them. So what is it that’s pushing everything in the universe apart?

Maybe it isn’t a ‘thing’ doing it, who knows, but there must be a reason.

[gnulinux]

As an extension of this argument. What caused the initial acceleration of the Big Bang? Isn't it possible the current acceleration of the universe is an extension of this force?

[garmaine]

Dark energy is the cosmological constant introduced by Einstein. So that criticism is rather ironic.

[mbell]

Maybe? We don't know, also Einstein wasn't a fan:

> Einstein originally introduced the concept in 1917 [2] to counterbalance the effects of gravity and achieve a static universe, a notion which was the accepted view at the time. Einstein abandoned the concept in 1931 after Hubble's discovery of the expanding universe.

> Einstein reportedly referred to his failure to accept the validation of his equations—when they had predicted the expansion of the universe in theory, before it was demonstrated in observation of the cosmological red shift—as his "biggest blunder".

[lisper]

It was actually a double-blunder. Einstein missed the opportunity to predict the expanding universe (and, as a corollary, the big bang). And then, when it turned out the universe was expanding, he retracted the CC despite the fact that it actually turned out that there is a (non-zero) CC, the expanding universe notwithstanding. He got the right answer, but he abandoned it because he got it for the wrong reason.

[mbell]

> he retracted the CC despite the fact that it actually turned out that there is a (non-zero) CC

Dark Energy being the CC is just _one possible explanation_, it hasn't been tested.

[garmaine]

I think you have that backwards. Physics doesn’t arise from mathematics; reality just is and the math describes it. The universe is expanding, and the cosmological constant simply describes this relationship between space and the matter inhabiting it.

[lisper]

Exactly right. Einstein had no idea what the physical mechanism behind the CC might be (and we still don't). It was just something he threw into the equations because he believed the universe was static, and the only way to make GR support a static universe is with a non-zero CC.

[mcguire]

It turns out that, when he thought he was wrong, he was mistaken.

[danharaj]

Actually, a cosmological constant is derivable from the Standard Model. But it's off by a very remarkable amount. Dark energy is the observation that that the Standard Model mispredicts the cosmological constant, so there must be something wrong with it.

[zwkrt]

Also known as the Vacuum Catastrophe, "the largest discrepancy between theory and experiment in all of science".

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

[acqq]

> cosmological constant is derivable from the Standard Model.

Well.. not really directly "derivable."

To be more specific, the "problem" is: when using the the "Standard Model of particle physics" (which is confirmed time and again for anything we do with the particles, and which, of course, we anyway know that is still inconsistent with the General Relativity model) to calculate the "renormalized value of the zero-point vacuum energy density" as the contribution to the cosmological constant, the number is calculated that, to our present understanding of the factors involved, can't match our cosmological measurements. Note that that "renormalization" process is a method used otherwise to "extract" the finite answer from the divergent expression (i.e. one that would involve infinities). Applying such method in this derivations gets the "wrong" number.

It's much less surprising when it is stated precisely. Attempting specific derivations in which the "infinities" are "avoided" by using a specific approach which for some other cases works, we discover that in these derivations the mentioned approach "doesn't work", that is, that something is missing in an attempt to compare two theories for which we anyway know that they aren't consistent when they have to be applied together.

https://arxiv.org/abs/1205.3365

Luckily, these inconsistencies aren't something that prevents us to use both General Relativity and the Standard Model independently to great success. Using them together is needed only to model very extreme conditions like writing the equations for some point inside of the black hole or something like that. And that doesn't disprove black holes in any way: we measured even their collisions(!) using the predictions of the models.

And we can claim already:

http://www.preposterousuniverse.com/blog/2010/09/29/seriousl...

"The Laws Underlying The Physics of Everyday Life Are Completely Understood"

[acqq]

It's not an "argument." The first sentence you quote is a statement of the fact. The theory containing dark matter and dark energy is the simplest that we have and to appreciate/understand that statement you would have to be able to actually write the formulas for different approaches and compare.

The author of the article actually did that: she provably wrote many, many papers filled with formulas attempting different approaches: it's her profession, she does that for living, and her statements represent something that she really knows.

Other (pseudo)arguments of yours are also the consequence of the lack of understanding of the basics of the topic which you attempt to comment.