Bizarre "Dark Fluid" with Negative Mass

December 10, 2018 3:28 PM

Our best theoretical model can only explain 5% of the universe. The remaining 95% is famously made up almost entirely of invisible, unknown material dubbed dark energy and dark matter. The two have always been treated as separate phenomena. But my new study, published in Astronomy and Astrophysics, suggests they may both be part of the same strange concept – a single, unified “dark fluid” of negative masses.
posted by MovableBookLady (30 comments total)

I think Sabine Hossenfelder has pretty strongly refuted this article. The punch line is: "like repels like, like attracts opposite" works for magnetism AND gravity. This proposal by Farbes assterts "maybe like repels like unless it's negative mass, which attracts both opposite AND like" which doesn't have a lot of great mathematical support.
posted by tclark at 3:41 PM on December 10, 2018 [5 favorites]

Used motor oil from Twin Peaks confirmed.
posted by idiopath at 3:45 PM on December 10, 2018 [6 favorites]

negative gravitational mass I can nearly understand, but negative inertial mass? gah
posted by GuyZero at 3:50 PM on December 10, 2018

Was this the stuff in Krycek's eyes?
posted by Abehammerb Lincoln at 4:15 PM on December 10, 2018 [16 favorites]

I propose a modification to Einstein’s theory of general relativity to allow negative masses to not only exist, but to be created continuously

Checking out.
posted by sjswitzer at 4:24 PM on December 10, 2018 [2 favorites]

From the Hossenfelder critique:

Furthermore, while it is okay to introduce negative gravitational masses, 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.

i.e. Farnes' theory implies that every point in the universe should always be exploding in an infinite release of energy, which seems not to be the case.
posted by justsomebodythatyouusedtoknow at 4:25 PM on December 10, 2018 [5 favorites]

Here's the paper where Farnes constructs his toy model. Note that the original version of the paper was submitted almost a year ago (18 Dec 2017) and there have been *zero* citations since then. What's happened here (once again) is that the university's PR department has gotten ahead of themselves - I think that this happens more and more as universities compete for scarce funding, and importance of questionable, or highly speculative, research is overblown for the sake of publicity. Whenever you see one of these "breakthrough" scientific findings it's good to try to find the original article and see if there are any mentions of it outside of places like slashdot, sputniknews.com, vice.com, etc... Are other scientists talking about it, and what are they saying? (In my opinion Sabine Hossenfelder is a good "voice of reason" in physics.)
posted by crazy_yeti at 4:38 PM on December 10, 2018 [7 favorites]

I ran this by a physicist friend and their critique seemed to line up pretty nicely with Hossenfelder's. It also seems to have virtually no citations. So, I think this is a lot of bad physics. That's okay, it happens.

Ask me about how much I was hoping for the EM Drive to be real.
posted by lumpenprole at 4:40 PM on December 10, 2018 [2 favorites]

Ah well, so much for my interest in science.
posted by MovableBookLady at 5:48 PM on December 10, 2018 [1 favorite]

Our best theoretical model can only explain 5% of the universe.

I always love this little factoid. This taken with the fact that we can only actually observe a bubble 28 billion miles across in a universe supposedly about 7 trillion miles across makes me wonder how anyone can claim to know anything about the universe with a straight face.
posted by Tell Me No Lies at 7:03 PM on December 10, 2018

This taken with the fact that we can only actually observe a bubble 28 billion miles across in a universe supposedly about 7 trillion miles across makes me wonder how anyone can claim to know anything about the universe with a straight face.

And once again, crappy science writing fuels anti intellectualism.
posted by mr_roboto at 7:43 PM on December 10, 2018 [12 favorites]

Huh. Years ago I made a little web toy that simulated a bunch of particles interacting with gravity. It was boring because stuff just clumped together fairly quickly and I couldn't be bothered to set up initial conditions to get orbits going on.

Then I had the idea of giving some of the particles negative mass, to see what would happen under the same F=Gm₁m₂/R² relation. No basis at all in real physics, but having negative masses repelling each other and negative masses chasing positive ones around made it more interesting. Guess I missed my true calling though.

Completely unintuitive and made before proper HTML5 animation was a thing, but here it is. Click the "-" next to "more" to add negative masses.
posted by Tad Naff at 10:18 PM on December 10, 2018 [2 favorites]

When it comes to this stuff and quantum physics, I can't help feeling that we are in a period equivalent to when astronomers were trying to explain the wacky retrograde orbits of the planets, not realizing that Earth wasn't the center of our planetary system.

As for the headline, when I read 'Bizarre "Dark Fluid" with Negative Mass', I immediately think of comedian Richard Lewis in a Starbucks.
posted by zaixfeep at 11:37 PM on December 10, 2018

I believe there's an existing mechanism that explains why galaxies don't fly apart: string theory. The universe is poorly constructed and there's a lot of string and duct tape holding things together. Also, why is the universe expanding? Obviously, because it was the wrong size as delivered.

As Walter Benjamin so nearly put it:

This is how one pictures the angel of history. His face is turned toward the past. Where we perceive a chain of events, he sees one single catastrophe which keeps piling wreckage upon wreckage and hurls it in front of his feet. The angel would like to stay, awaken the dead, and make whole what has been smashed. But a storm is blowing from Paradise; it has got caught in his wings with such violence that the angel can no longer close them. The storm irresistibly propels him into the future to which his back is turned, while the pile of debris before him grows skyward. This storm is what we call progress physics.

posted by Joe in Australia at 12:15 AM on December 11, 2018 [7 favorites]

It's funny to me how this story is spread. I can't speak to the quality of the physics, but the concept is so appealing to the certain type of nerd (like me) that thinks he's smarter than he really is. "Why not just add the ability to put a minus sign in front of mass? Look, everything magically makes sense now!" Would that it were so simple. (The Hacker News audience loved it, is what I'm saying.)
posted by Nelson at 12:49 AM on December 11, 2018 [4 favorites]

This taken with the fact that we can only actually observe a bubble 28 billion miles across in a universe supposedly about 7 trillion miles across

What.

You are aware that a light-year is about 6 trillion miles, yes?
posted by heatherlogan at 4:59 AM on December 11, 2018 [2 favorites]

The problem when you start positing things like negative mass, is that you punch that through the equations and you end up the fact that those particles must travel faster than the speed of light. In fact, to slow them down to close to the speed of light, you'd have to add energy to them. With particles travelling faster than the speed of light (and no longer obeying the arrow of time as we understand it), they're not gravitationally bound anywhere - in fact, these particles won't hang around anywhere, leaving us with a situation where we just have positive-mass particles. Now, you can do things with general relativity that means such particles can't escape, but it's really only applicable inside singularities like black holes. There are a lot of other problems when you introduce negative mass as well, and I don't think this theory can really be taken seriously.
posted by BigCalm at 5:17 AM on December 11, 2018

BigCalm - I think you're confusing tachyons with negative mass particles. Tachyons traditionally have imaginary mass (although there might be formulations where they have a real mass).
posted by edd at 7:16 AM on December 11, 2018

the fact that we can only actually observe a bubble 28 billion miles across in a universe supposedly about 7 trillion miles across

This is gibberish; even if you confused "miles" with "light years", the observable universe is about 93 billion LY in diameter. And I have no idea where the "7 trillion" figure comes from; Wikipedia gives the giddy figure of 10^{10^{10^{122}}} megaparsecs as an estimate by one theory.
posted by Halloween Jack at 7:21 AM on December 11, 2018

And once again, crappy science writing fuels anti intellectualism.

I don't think it is correct to equate skepticism with anti-intellectualism, since people have made complex arguments, for example, about the legitimacy of inductive generalizations.
posted by thelonius at 7:25 AM on December 11, 2018

The 7 trillion probably comes from this. Which if you're willing and able to dig into it probably explains how they come up with that figure with a straight face. (That's a highly reputable author list by the way, although I'd be at least cautious in how I described the result in casual conversation)
posted by edd at 7:28 AM on December 11, 2018 [1 favorite]

Being totally confused by made-up numbers is not a good standard for skepticism. Whereas getting to a point where you have no framework to even evaluate claims and give up as a result, this often leads to anti-intellectual outcomes.
posted by I-Write-Essays at 7:29 AM on December 11, 2018

Skepticism is "It's important to keep an open mind, but not so open that your brains fall out."

Anti-intellectualism is "There's huge uncertainty in the world, and I don't have a way to deal with it, so it must be impossible for anyone to know anything at all."

Skepticism challenges someone to answer, whereas Anti-intellectualism shuts down any possibility of debate.
posted by I-Write-Essays at 7:45 AM on December 11, 2018 [2 favorites]

the observable universe is about 93 billion LY in diameter

Halloween Jack, how is this possible when the universe is only 13.7 billion years old?
posted by heatherlogan at 8:00 AM on December 11, 2018

The answer is negative.
posted by Segundus at 8:02 AM on December 11, 2018

@heatherlogan:

Simply put, because space is expanding at the same time as light is travelling through it, so the space that has already been crossed grows larger before the entire journey is complete.

The speed of light is a cosmic speed limit on how fast two objects can move past each other, but the expansion of space itself doesn't count. The reason parts of the universe are inobservable is because the expansion of space is accelerating over time, so light far enough away from us will see the space between us expand faster than the speed of light before it can reach us.
posted by I-Write-Essays at 8:26 AM on December 11, 2018 [4 favorites]

The reason parts of the universe are inobservable is because the expansion of space is accelerating over time, so light far enough away from us will see the space between us expand faster than the speed of light before it can reach us.
To expand on this (sorry), there are parts of the universe that will be unobservable in the future due to space expanding at a sufficient rate, and there are parts of the universe that are unobservable now and in the past because there simply wasn't enough time for light to get here after accounting for it. Regions can of course be subject to both effects.

With accelerating expansion of the universe you can have regions that both aren't observable now and will never be observable, but it's not necessary to have that sort of accelerating expansion to have regions that are currently unobservable - indeed the accelerating expansion we have now is relatively recent and isn't that big an effect in how far we can see.

Otherwise many compliments on your comment I-Write-Essays, as it's very clear and succinct about something quite confusing!
posted by edd at 8:59 AM on December 11, 2018 [2 favorites]

Maybe what is confusing is to call the region that is now 93 billion LY in diameter the observable universe. Strictly speaking, we are not able to observe the present; we are only able to observe the past, and the past is only 13.7 billion light years long. 93 BLY is the hypothetical present size of the regions we are able to observe in our past light cone.
posted by I-Write-Essays at 9:45 AM on December 11, 2018 [2 favorites]

I'm pretty sure this idea comes up every so often, because I can remember reading a discussion around the general area of negative inertial mass, negative gravitation and so on, many many years ago. That too concluded that once you start trying to work with actual numbers in actual equations, you end up with infinities all over the place, conservation of energy completely shot and a universe that wouldn't exist in any useful form for any length of time.

To wit - not ours.

(The only things that actually seem to be continuously created are bad physics ideas like these, and Youtube videos of yet another perpetual-energy-over-unity-magnets-and-bollocks machine.)
posted by Devonian at 11:04 AM on December 11, 2018 [1 favorite]

Negative gravitation problem? This was solved over a century ago with Cavorite:

"The [spacecraft's] inner glass sphere can be air-tight, and, except for the manhole, continuous, and the steel sphere can be made in sections, each section capable of rolling up after the fashion of a roller blind. These can easily be worked by springs, and released and checked by electricity conveyed by platinum wires fused through the glass. All that is merely a question of detail. So you see, that except for the thickness of the blind rollers, the Cavorite exterior of the sphere will consist of windows or blinds, whichever you like to call them. Well, when all these windows or blinds are shut, no light, no heat, no gravitation, no radiant energy of any sort will get at the inside of the sphere, it will fly on through space in a straight line, as you say. But open a window, imagine one of the windows open. Then at once any heavy body that chances to be in that direction will attract us."

3D model, mission video, description, and journal.
posted by cenoxo at 1:33 PM on December 11, 2018 [1 favorite]