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No, negative masses have not revolutionized cosmology

backreaction.blogspot.com

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Re: No, negative masses have not revolutionized cosmology

#61

Post by acqq »

jetrink wrote: post #39
throwawaymath wrote: post #35

Earlier quoted context omitted.

> As I read that paragraph, I thought to myself that the author should read Sabine Hossenfelder's recent book Lost in Math: How Beauty Leads Physics Astray. The author is Sabine Hossenfelder :)

I realized when I reached the bottom of the post. It is odd to me to see her saying that the new theory is disqualified for not being as simple as alternatives after reading her book.

> odd to me to see her saying that the new theory is disqualified for not being as simple

No. Her main argument is, the way I read her article, is:

"Farnes in his paper instead wants negative gravitational masses to mutually repel each other. But general relativity won’t let you do this. "

The way I understand it, the author of the paper fails to be compatible with the theory that was confirmed time and again during the last 100 years. She just avoided to formulate that so bluntly.

Re: No, negative masses have not revolutionized cosmology

#62

Post by c1ccccc1 »

sgt101 wrote: post #58
khawkins wrote: post #12

Occam's razor is a heuristic used in the investigative process, not a principle. While it's fair to point out that a theory makes everything more complicated and thus might make it less likely to be sound, it's not fair to push back on the first bit of research into a theory because they haven't had the time to fully develop it. Indeed, a scientific revolution generally starts by treating as false an assumption previ…

History : Dun Scotus (really) probably invented Ockham's razor - William was his student and used it to avoid the thing that all medieval philosophers needed to avoid, namely being tied up and put on a bonfire. Why did Dun invent it (probably)… well here's the thing, Christianity has a God with three faces, son, father and holy ghost thing. Why? The answer is - don't multiply entities beyond necessity, so God has the…

I mean, we still call it Occam's razor, but I don't think that it's really even the same principle by this point, it just shares the same name. In science today, we don't really care about the number of entities. We don't reject the idea that the stars are suns like our own just because that would imply that the number of atoms in the universe is drastically larger than the number of atoms in the solar system. Instead of hypotheses with the least number of entities, we favour hypotheses with the smallest Kolmogorov complexity. [1] As a slogan for the modern version, I like the phrasing by John Von-Neumann: "With four parameters I can fit an elephant, and with five I can make him wiggle his trunk." [2]

[1] https://en.wikipedia.org/wiki/Kolmogorov_complexity [2] https://www.johndcook.com/blog/2011/06/21/how-to-fit-an-elep...

Re: No, negative masses have not revolutionized cosmology

#63

Post by acqq »

mbell wrote: post #14

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 inter…

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.

Re: No, negative masses have not revolutionized cosmology

#64

Post by garmaine »

mbell wrote: post #52
lisper wrote: post #48

Earlier quoted context omitted.

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.

> 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.

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.

Re: No, negative masses have not revolutionized cosmology

#65

Post by garmaine »

ajkjk wrote: post #24
garmaine wrote: post #19

Earlier quoted context omitted.

Also that point seemed odd. Isn't unification of two previously separate phenomenon (dark matter and dark energy) simpler in Occam terms? It's using one thing to explain two, even if the actual mathematics are more complex to state. Also there's other troubling cosmological issues that this would appear to address, such as Hubble's constant having slight variation outside of measurement tolerance, which slightly diff…

Whether it is simpler depends on the details of the unification. Two comparatively simple theories are not made simpler with a very complex unification.

The electroweak force is most certainly not easier to describe than electromagnetism and the weak force separately. But we still talk about electroweak interaction as being a simpler theory than two separate fundamental forces, because it reduces the number of things that are needed to describe the universe, even with added computational difficulty.

Re: No, negative masses have not revolutionized cosmology

#67

Post by lisper »

garmaine wrote: post #64
mbell wrote: post #52

Earlier quoted context omitted.

> 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.

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.

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.

Re: No, negative masses have not revolutionized cosmology

#68

Post by InclinedPlane »

mbell wrote: post #14

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 inter…

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.

Re: No, negative masses have not revolutionized cosmology

#69

Post by mcguire »

mbell wrote: post #23
garmaine wrote: post #20

Earlier quoted context omitted.

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

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 ha…

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

Re: No, negative masses have not revolutionized cosmology

#70

Post by comex »

c1ccccc1 wrote: post #62
sgt101 wrote: post #58

Earlier quoted context omitted.

History : Dun Scotus (really) probably invented Ockham's razor - William was his student and used it to avoid the thing that all medieval philosophers needed to avoid, namely being tied up and put on a bonfire. Why did Dun invent it (probably)… well here's the thing, Christianity has a God with three faces, son, father and holy ghost thing. Why? The answer is - don't multiply entities beyond necessity, so God has the…

I mean, we still call it Occam's razor, but I don't think that it's really even the same principle by this point, it just shares the same name. In science today, we don't really care about the number of entities. We don't reject the idea that the stars are suns like our own just because that would imply that the number of atoms in the universe is drastically larger than the number of atoms in the solar system. Instea…

Nitpick: The historical problem with stars being suns wasn't (just) the universe being larger than the solar system, but that the telescopic observations available at the time seemed to imply that every other visible star would have to be much larger than the Sun, in fact larger than the orbit of Saturn. This was because early astronomers didn't understand optical diffraction and thought the Airy disks visible around stars were the stars themselves, making their angular radius in Earth's sky seem vastly larger than the reality. [1] Both characterization of the Airy disk and observation of stellar parallax didn't occur until the 19th century, by which point religious objections wouldn't have had the same status as in Galileo's day anyway (for example, Darwin's work was published only a few decades later).

Source: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.612...

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