Slashdot Mirror
Cosmologists Show Negative Mass Could Exist In Our Universe
KentuckyFC (1144503) writes The idea of negative mass has fascinated scientists since it was first used in the 16th century to explain why metals gain weight when they are oxidized. Since then, theoretical physicists have shown how it could be used to create exotic objects such as wormholes and the Alcubierre warp drive. But cosmologists' attempts to include negative matter in any reasonable model of the cosmos have always run into trouble because negative mass violates the energy conditions required to make realistic universes with Einstein's theory of general relativity. Now a pair of cosmologists have found a way around this. By treating negative mass as a perfect fluid rather than a solid point-like object, they've shown that negative mass does not violate the energy conditions as had been thought, and so it must be allowed in our universe. That has important consequences. If positive and negative mass particles were created in the early universe, they would form a kind of plasma that absorbs gravitational waves. Having built a number of gravitational wave observatories that have to see a single gravitational wave, astronomers might soon need to explain the absence of observations. Negative mass would then come in extremely handy.
The summary makes mention that we haven't noted any substantial signs of this material, but how is that any different from, say, antimatter, which we know can exist?
The summary makes mention that we haven't noted any substantial signs of this material, but how is that any different from, say, antimatter, which we know can exist?
Not too long ago, I think we even created an anti-hydrogen atom.
Negative mass? Not so much (yet).
Anyone else sick of these fantasies? What ever happened to Occam's Razor?
wrong
Negative mass is very diferent from antimatter. Antimatter is opposite to normal matter in charge and quantum numbers (such as baryon number, etc.), but still has positive mass.
Negative mass reacts oppositely to both gravity and intertia. Oddly, that means that negative mass still falls down in a gravitational field: The gravitational force is opposite, but negative mass responds negatively to force (a=F/m, where both F and m are negative). So negative mass particles repel each other gravitationally, but are attracted to positive mass objects.
This has peculiar consequences. One consequence is that, for objects of negative mass, gravity and electrostatic charge switch. For normal mass objects, gravity is attractive, but like electrical charges repel. For negative matter, gravity is repulsive, but like electrical charges attract.
I wrote about this once, in the AIAA Journal of Propulsion and Power-- not a journal that physicists usually read, I'm afraid. If you have access to AIAA online, it's here: http://arc.aiaa.org/doi/pdf/10...
http://www.geoffreylandis.com
A goal for all those zero sized models and weight loss fanatics to aim for!
What ever happened to Occam's Razor?
It competes with the totalitarian principle, "everything that is not forbidden is compulsory."
http://www.geoffreylandis.com
"Not even wrong."
This kind of subject always leads to a cascade of stupid questions in my head that I can't answer, leaving me feeling even dumber than usual. Does negative mass necessarily imply negative weight? What about momentum and kinetic energy? If a lump of matter with negative mass hit something, would it actually absorb energy from it rather than imparting energy to it? Would a negative-mass planet have an anti-gravity field? Is it even meaningful to talk about matter with negative mass, or is some physicist going to pop up and explain to me that negative mass is a property of some sort of field, and not something that could actually be expressed by anything that I would recognise as matter?
Oh no... it's the future.
If they must see that same single gravitational wave over and over again, why do we need to keep building more of them? Why don't we build some to see OTHER gravitational waves?
It's Sylphs not Pixies.
Why did my brain read that headline as "Cosmetologists"?!
It was used by William of Ockham in the late middle ages to argue against the species theory of perception -- the idea that everything you can see constantly emanate images of themselves in every direction. It states (in scholastic Latin) "Do not multiply entities beyond necessity."
It was then stripped of its context somewhere halfway through the previous century, became a rallying cry of pretty much every self-proclaimed skeptic, and erroneously believed to say "the simplest explanation is usually right"
That is what happened to Ockham's razor, and I wish it had stayed in the 13th century, along with all the other idiotic arguments for and against realism about universals.
Before I read the article, I'd have been predisposed to agree with the poster who called this "The crackpot cosmology theory Du Jour". However the article does note that not only does negative matter possibly explain the current lack of detection of gravitation waves but (presumably unlike many other phenomena) predicts that if there is negative matter, we WOULD be able to detect gravitational waves but only above a certain frequency:
"the evidence that could back it up would be the discovery of the threshold frequency above which the waves do propagate"
If anyone who can read and understand the actual paper could tell us non-cosmologists when our improving technology might be able to detect gravitational waves above the cut-off frequency I would appreciate it. I mean is it technology that is (very roughly) 10 years away, 25 years, a century or basically only when we have god-like powers. I seem to remember that NASA was going to launch a space based interferometer with "arms" (free floating platforms) in a triangle 5 million km on a side. Would that be able to detect them? The whole point now isn't just to prove the existence of gravity waves but also negative matter (and the possibility of warp drives, yay!).
Actually, since (if I am reading the article correctly) they are looking for "higher frequencies", doesn't that mean the detectors should be smaller? ("arm" length shorter?) Shouldn't they be increasing the sensitivity instead? Or is the sensitivity increased by making the detector larger? I'm so confused!
Balloons have positive mass, but they float because the surrounding air has a bigger positive mass than the balloon. This can happen one of two ways. In a hot air balloon or thermal airship, the air is heated to push most of it out. Otherwise, the air is replaced with a lighter lifting gas, such as hydrogen, helium, methane, or steam.
The NASO/ESA interferometer was LISA, but NASA pulled out.
http://en.wikipedia.org/wiki/L...
If negative mass and positive mass collide, what would happen?
...
They are supposed to be opposites, and let's presume they cancel each other out
What could they cancel out into? You still have to conserve the energy.
High energy photons can create particles with mass if they strike matter, what kind of photons would the negative mass particles be related to?
Even positive and negative mass don't cancel out, would having a lot of positive mass and negative mass in the same area cancel out gravity?
What role does the Higgs play in negative mass?
I'm no particle physicist, but negative mass seems to integrate very poorly into the system here.
And presumably negative mass would have particles of some sort, some sort of unusual electrons or quarks or protons or maybe none of those --- but all mass as we know it interact with photons (neutrinos excluded?), so presumably negative mass would need to reflect light or absorb it.
Priest: "Universe from nothing, no laws of physics, sped up time"+ huge discrepancies. Creationism? No. Big Bang Theory
As I understand it (could certainly be wrong) the whole hypothesis for "dark energy" was created to explain the reason why the Universe's rate of inflation is increasing. Also, I believe we have, so far, been unable to prove its existence except through this increasing speed of inflation.
Wouldn't negative gravity obviate the need for dark energy?
Someone on Wikipedia put together a nice image showing frequency and sensitivity of a couple different kinds of detectors and upcoming upgrades to them. There are some high frequency microwave interferometers not shown on there that could measure in the GHz range, with sensitivities to much smaller characteristic strains than on that chart. (You kind of need to multiply the strain by frequency to get something more comparable to say amplitude of EM waves, which is part of why higher frequency is more sensitive on that scale).
The Doctor: "Yeah, it's fine, we're just entering conceptual space. Imagine a banana, or anything curved; actually don't, because it's not curved or like a banana. Forget the banana!"
find a way to make them in the lab. I want my anti-grav car.
The Kruger Dunning explains most post on
I feel dumb for posting this but could this also be another explanation for the new science buzz word "dark matter"?
Is this similar to, unrelated to, part of, dissimilar, orthogonal, integral, or in any way linked to Dark Matter?
It's unrelated to dark matter (which has positive mass- that's how we know it's there), but dark energy is gravitationally negative (it causes expansion to accelerate: it's gravitationally repulsive)
Because I (and probably most of us) don't understand that either.
You're in good company! If you did understand it, you could publish, and you should be getting a phone call from Stockholm soon.
http://www.geoffreylandis.com
That type of interferometer would be for detecting low frequency gravity waves. I think you would need some high frequency oscillating or vibrating mass in close proximity to a smaller detector in order to look for a physical threshold for the propagation of high frequency gravity waves.
have yet to see?
I'm seriously asking....I assume thats the typo?
What am I missing?
Nothing. Negative mass is weird.
What you're pointing out -- that a positive mass and a negative mass would chase each other-- was pointed out in 1957 in Bondi's paper about negative mass, "Negative Mass in General Relativity". Rev. Mod. Phys. 29 (3). Robert Forward, in 1990, then extended that analysis even further and pointed out that negative mass is even weirder than that.
A negative mass chasing a positive mass accelerates forever... but it doesn't violate conservation of energy, because the faster a negative mass moves, the more negative the kinetic energy, so the positive kinetic energy and the negative kinetic energy cancel out, leaving energy conserved.
There are weirder things than that, too.
If you think this is so weird that bulk negative mass can't exist... well, that's what Einstein thought (the "positive energy condition").
http://www.geoffreylandis.com
Dark matter conerns the "missing" (i.e. never observed directly) mass in the universe, which has despite its "invisibility" been observed indirectly; for example look up Bullet Cluster on Wikipedia.
Dark energy concerns what it is that is causing the expansion of space-time (and consequently) the universe itself.
HAND.
Ruh roh!
In C++, your friends can see your privates.
while the negative mass proponents go do more math
If only they could do some experiments...
Why would a bunch of people doing makeup care about the mass in the Universe?
that the President's brain is made from negative mass.
As mentioned above by Geoffrey.landis, negative mass matter has a number of very interesting properties.
Among them are that if you were to balance a matter spaceship with an equal (negative) mass of anti-mass
matter, then it takes essentially no energy to accelerate the combined craft to very high speeds.
Balancing them, however, might be a problem. If you apply a force to an anti-mass, it accelerates the 'wrong'
direction.
It's not at all clear that a mixture of mass and anti-mass would not be self-separating.
Negative mass?! That would have a gravitationally REPULSIVE effect, and nothing seems to be repeling on a large scale!
Oh wait......
This has a couple of connotations in science (that have also existed in sci-fi previously)
The obvious one would be antigravity. What gravity attracts, it would repel. So there's your Marty McFly hoverboard. There are further connotations for other things though, such as achieving orbit or space-travel (getting too close to a gravity well at the wrong angle=not good in most cases). Depending on whether such anti-mass would be created/harvested in quantity, it could be used to cancel out mass of vehicles being sent to space, or used in propulsion.
Similarly, anti-inertia has a lot of interesting using. The old trek "inertial dampers" come to mind.
tom swift jr can finally create his repelatron!-)
TFA grossly misrepresents the state of gravitational wave detection. Previous attempts were not expected to succeed, they were tests of the functionality of the systems.
Gravitational wave have already detected by indirect means -- their influence on celestial bodies nearby the event that produced them. We have just not yet *directly* measured gravitational waves.
Gravitational waves decrease in amplitude following the inverse square law. So the farther away an event, the smaller the wave is when it hits the earth.
The sensitivity of the detector dictates the area within which measurable events are observable. Higher sensitivity means a larger "visible area."
Measurable events occur within a given area at a given probability over time. The bigger the area, the higher the probability that an event will occur in that area within a window of time.
Detectors to date have had a visible area within which the probability of a detectable event was one in twenty five years. Observation windows have only been one to two years at a time. So the likelihood of actually making a detection has been very low, and not expected -- past "science runs" have been efforts to verify that the science and engineering works -- "dress rehearsals" so to speak. The instruments have a lot of bleeding edge science and engineering involved.
Upgrades to the detectors coming online in the next couple of years will have 10x sensitivity == 1000x large area == 1000x higher probability of a measurable event, which means likelihood of an event occurring will be on the order of one per week. It's quite likely that a successful detection will happen in the next few years.
Frequency range of the detectors depends on a variety of variables -- design limitations of the system, terrestrial noise, and models of the events that they are looking for. Any system design has given set of constraints.
Don't expect TFA to give a good understanding of that. Look at what LIGO, VIRGO, and KAGRA and doing. I'd start with this nice layperson accessible article at http://archive.ncsa.illinois.edu/Cyberia/NumRel/GravWaves.html
He's my negative mass brother!
But there probably is less than a pound of it!
They filled up the Dark X meme, so now are switching to the Negative X meme to explain oddities. We'll get Negative Matter, Negative Energy, Negative Gravity, Negative Particles (prior art?), Negative Universes, and probably Negative Feedback.
-5
Table-ized A.I.
Math doesn't take as much funding, but with enough math, you can hope to get a mite of funding.
I think we've pushed this "anyone can grow up to be president" thing too far.
Ah, the
Pauli exclusion
principle. IANA physicist, but I've never been happy with this here thingy.
Fortunately, your happiness is not relevant to whether physics works.
...
Oh, BTW - this is just one of many examples where science does, in fact, depend on pure faith.
No, this is one of the many examples where science depends on pure observation. The Pauli exclusion principle was first arrived at from observations, and only somewhat later was the theoretical basis-- the spin-statistics theorem-- worked out.
http://www.geoffreylandis.com
Wouldn't that be a Black Sabbath?
Not so fast! Let me quote the GP:
Negative mass reacts oppositely to both gravity and intertia. Oddly, that means that negative mass still falls down in a gravitational field: The gravitational force is opposite, but negative mass responds negatively to force (a=F/m, where both F and m are negative). So negative mass particles repel each other gravitationally, but are attracted to positive mass objects.
Right
In other words, unlike normal matter, negative mass matter can never lump together under influence of gravitational force,
Right
but it will nevertheless attract normal matter.
You'd think, if it behaved like ordinary matter, that if it is attracted to positive matter, than it would conversely also attract positive matter. But no.
Negative matter particles attract each other, as you say, but repel normal matter. (They're attracted to it... but they repel it.)
The equations are: F = ma
and F = G mM/r^2
http://www.geoffreylandis.com
When can I have my flying car. The one with no wings.
My boss' brain
I might be made fun of for this but I'll ask anyway: If negative mass could be practically harnessef, would it allow for the antigravity/repulsorlift/mass effect technology of science fiction to be real?
Well, if you load your positive-mass vehicle up with an amount of negative mass, it will still fall downward, but it will have less overall mass and less weight. So it will only take a little amount of force to lift it or move it around.
The "if negative mass could be practically harnessed" is a big "if," though. Even aside from the fact that you have to figure out how to make negative mass.
http://www.geoffreylandis.com
Fascinating. Thanks for answering.