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'Dark fluid' with negative mass could dominate the universe

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Re: 'Dark fluid' with negative mass could dominate the universe

#111

Post by marcosdumay »

duality wrote: post #56
raverbashing wrote: post #19

Earlier quoted context omitted.

Given there have been no detections of individual gravitons, saying it's a spin-2 gauge boson is speculation at best (though it might be what the model predicts)

If it weren't, general relativity would be wrong as well and we know that (in its domain of applicability) it's a highly accurate model. GR models gravity as fluctuations in the metric tensor of spacetime, which is a symmetric rank-2 tensor. This is all you need to know to conclude that a graviton (a quantize fluctation of that tensor) must be spin-2. https://en.wikipedia.org/wiki/Graviton mentions "[I]t can be shown…

> GR models gravity as fluctuations in the metric tensor of spacetime, which is a symmetric rank-2 tensor.

IANAP, and don't get the full picture. But isn't that definition itself derived by the fact that gravity has a single polarity?

Re: 'Dark fluid' with negative mass could dominate the universe

#112

Post by acqq »

zamalek wrote: post #96
acqq wrote: post #35

Earlier quoted context omitted.

“What’s most impressive is that the predictions of dark matter were first made in the 1970s and 1980s, and were observationally confirmed later. This is not a case of tweaking the model to fit the data; this is a case of the best kind of science you hope for: where you make predictions, make the observations, and what you see validates and confirms the predictions you had made. And yet, even 35 years later, there are…

That's putting the effect before the cause. The dark matter map can also be a map of "how wrong we are," not only "how much invisible mass is there." An incomplete periodic table of physics, if you will. We need to produce a WIMP here, on Earth, and watch it decay. That's a "thruthifiable" experiment, but it'd be enough to convince me that we've found the correct line of thinking (which the popular opinion could very…

> We need to produce a WIMP here, on Earth, and watch it decay.

No. You can't "need" something if that is simply unreachable. There’s reasonable chance that to produce the particles (which still don’t have to be the WIMPs as we imagined them, and still would be „matter“) the energies needed are simply beyond those that will ever be available to humanity. It wold not mean more than that: that we, humans, just can't repeat with our technology the extreme conditions that the Universe had/has.

The WIMPs in the form discoverable by the energies that are available to us at the moment would have been nice luck, but the existence of dark matter is not anything less certain when the dark matter is simply different from that. It would still be "matter" and not something else.

Re: 'Dark fluid' with negative mass could dominate the universe

#113

Post by starbeast »

marcosdumay wrote: post #108
starbeast wrote: post #105

Earlier quoted context omitted.

Don't you have two things that can generate gravitational fields though? As distortions in spacetime can be caused by either mass or the momentum of massless particles, such as photons. Or do I have that wrong and photons merely follow the distortions and not cause any of their own? As presumably, you could have a negative gravitational field from a photon traveling backward in time, without having any issues with ch…

> Or do I have that wrong and photons merely follow the distortions and not cause any of their own? You have that wrong in the momentum of massless particle has mass, independently of its carrier. Massless particles do not actually exist, what exist are particles with zero "mass at rest" and that are never at rest.

Ahh, I was getting a bit confused from photons distorting spacetime off their wavelength and plank's constant, given they also apparently have no mass. Thanks for that. I have to go and re-read a lot of stuff now though. ;)

Re: 'Dark fluid' with negative mass could dominate the universe

#114

Post by marcosdumay »

mklauber1 wrote: post #15

I'm curious about the idea of "allow[ing] negative masses to not only exist, but to be created continuously." Given the law (in the scientific sense) that matter/energy cannot be created or destroyed, on a scale of 1 to FTL travel, how crazy is this idea?

This is at the "would lead to FTL" level.

Re: 'Dark fluid' with negative mass could dominate the universe

#116

Post by mike741 »

tzakrajs wrote: post #63
RobertoG wrote: post #58

I'm confused. From the article: "This is explained by the Hubble-Lemaître Law, the observation that more distant galaxies are moving away at a faster rate." If we observe an accelerating universe how can be that galaxies in the past move away at a faster rate?

Because more and more negative mass fills in the space left behind by the expansion creating further expansion?

why would negative mass fill in the space rather than just "zero mass?"

Re: 'Dark fluid' with negative mass could dominate the universe

#117

Post by galadran »

walrus1066 wrote: post #89
aetherson wrote: post #10

Earlier quoted context omitted.

Is it true that every other forces besides gravity is polarised? There's a repulsive nuclear strong force and an attractive nuclear weak force? EDIT: Partial answer is that there is a three-"color" polarization for strong force. I feel like it somewhat weakens the argument of "everything else is polarized, why not gravity" if the other forces are polarized in unique ways.

Strong nuclear force is always attractive.

It most definitely isn't.

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

Re: 'Dark fluid' with negative mass could dominate the universe

#118

Post by [deleted] »

galadran wrote: post #8

Paper: https://arxiv.org/pdf/1712.07962.pdf Not a physicist, but my summary of the author's point would be: If you allow for matter with a negative mass and plug it into a n-body simulation. You seem to get what looks like dark matter from first principles. Namely, a halo of non interacting matter around galaxies in just the right "non-cuspy" shape. Their conclusion is that this is worth considering, as almost all ma…

[deleted]

Re: 'Dark fluid' with negative mass could dominate the universe

#119

Post by tonmoy »

scottmsul wrote: post #78

If you put a negative mass and positive mass side by side and release from rest, they will accelerate indefinitely and break conservation of energy. Of course science should be open to any possibility, no matter how strange. But I feel the author understates its strangeness. And requiring negative mass to be continually created makes this theory not all that much "simpler" than the standard dark matter+dark energy.

If you put two positive electrically charged particles side by side, they will accelerate in the same way

Re: 'Dark fluid' with negative mass could dominate the universe

#120

Post by SolarNet »

mklauber1 wrote: post #15

I'm curious about the idea of "allow[ing] negative masses to not only exist, but to be created continuously." Given the law (in the scientific sense) that matter/energy cannot be created or destroyed, on a scale of 1 to FTL travel, how crazy is this idea?

He points out that it's a mathematical tool and may not result in particles, e.g. matter or energy, as we currently think of it.

It could be a property of space-time, as space is always expanding everywhere, space it self could have a negative mass.

This could even be some sort of weird energy-neutral balancing mechanism (e.g. some sort of energy - my bet is on potential energy, like how gravity causes things to accelerate through the potential energy of the arrangement - is lost that accounts for the creation of negative mass particles or whatever; conservation is observational, but we don't really know what 95% of the stuff being conserved is in the first place).

Hence it can be consistent with the conservation of mass and energy.

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