If a particle had negative mass where would it go?

[PRDan4th]

If an oblect or sub atomic particle had negative mass, would it "fall" up? And if so where would it go? If the universe is infinite the particle would find a place as far away from all other positive mass objests as possible and we would never see it or know it existed at all! It could agglomerate with other negative mass particles and as such create another universe of anti matter.

Any thoughts along this line of thinking?

Pete

 

[ZapperZ]

Why is there suddenly a rush of questions on "negative mass" all of the sudden? Was there a TV show on this, or did some webpage started doing something?

Anyway, please continue this in an already existing thread.

https://www.physicsforums.com/showthread.php?t=127166

Zz.

 

[rbj]

I think this is a slightly different twist than that other thread, Z.

From a POV of gravitation, and using the Equivalence Principle (which implies, for this case, that gravitational mass is the same thing as inertial mass), what you get with the concept of negative mass is contradiction.

A positive mass, M, will attract another mass, m, positive or negative. For the negative mass, m, the gravitational force from M, will be in the opposite direction than if m were positive. But then when using Newton's 2^nd law, if its mass is negative, it will move in the opposite direction of the force applied to it. Two negatives means it will still fall.

But the problem is that a negative mass M will always repel the other object m whether positive or negative mass.

You can set up a curious situation with two masses M and m of equal magnitude but opposite sign. Do they move toward each other or away from each other? It seems that the negative mass will move toward the positive mass, but the positive mass will move away. Kinda like a dumb thing I remember seeing in high-school where a cute (and popular) girl is being followed around by a less cute (and less popular) guy that is in love with her.

I think if we had two masses of equal magnitude and opposite sign (and no electric charge), we could construct a perpetual motion machine out of it.

 

[Danger]

I think if we had two masses of equal magnitude and opposite sign (and no electric charge), we could construct a perpetual motion machine out of it.

I remember a couple of decades ago Dr. Robert Forward proposed just such a situation for a space drive system in an Omni article.

 

[WhyIsItSo]

Pardon my towering ignorance, but doesn't the current state of Physics "know" that matter and antimatter will attract each other and suffer mutual annihilation?

 

[rbj]

Pardon my towering ignorance, but doesn't the current state of Physics "know" that matter and antimatter will attract each other and suffer mutual annihilation?

i don't think that antimatter is negaive mass, is it?

 

[WhyIsItSo]

i don't think that antimatter is negaive mass, is it?

I suppose not, I just thought that must be what he meant.

Reason being, I thought mass was always a positive number (0,\infty ).

Guess I'll just quietly go away

 

[rbj]

I suppose not, I just thought that must be what he meant.

Reason being, I thought mass was always a positive number (0,\infty ).

Guess I'll just quietly go away

it's a reasonable assumption. i just don't think that's what they say it is.

 

[Andrew Mason]

i don't think that antimatter is negaive mass, is it?

It is not clear whether an anti-particle has negative mass or an opposite charge (opposite to its normal counterpart). It may not be possible to tell the difference. It may be that the laws of physics are the same whether you think of charge or mass as the quantity having positive and negative attributes. I have not yet seen any test that would distinguish the two possibilities.

Positive and negative mass seems a bit contrived. But when you think about it, so does positive and negative charge.

When you consider that the collision of a particle with its anti-particle causes matter annihilation, negative mass may be a better model.

AM

 

[Rach3]

You can set up a curious situation with two masses M and m of equal magnitude but opposite sign. Do they move toward each other or away from each other? It seems that the negative mass will move toward the positive mass, but the positive mass will move away. ...

I think if we had two masses of equal magnitude and opposite sign (and no electric charge), we could construct a perpetual motion machine out of it.

No, they would both accelerate away from each other.

 

[Rach3]

The classical physics of negative mass is consistent. For instance, air bubbles in water.

 

[rbj]

No, they would both accelerate away from each other.

it's not what the math says. if inertial mass is the same as gravitational mass (sometimes gravitational mass is differentiated as "passive" and "active" gravitational mass, but I'm not doing that), then a positive mass attacts both negative and positive masses and a negative mass repels both negative and positive masses if we stay consistent with the signs. if you want to hear it from a physicist a lot bigger and more authorative than me, check out

http://groups.google.com/group/sci.physics.research/msg/306fc58690ff8a19

The classical physics of negative mass is consistent. For instance, air bubbles in water.

non sequitur. we're not talking about air bubbles in water.

 

[rbj]

When you consider that the collision of a particle with its anti-particle causes matter annihilation, negative mass may be a better model.

matter is maybe annihilated, but there's some energy left. wouldn't the energy equivalent of a negative mass particle be negative energy?

 

[yaminohohenheim]

i'll try to spare the mumbo-jumbo and make it quick and simple:
physicists define mass as always positive, negative mass is nonexistent.

this is unless you get into theoretical physics involving hypothetical particles such as tachyons.

 

[yaminohohenheim]

and it's not an arbitrary definition by the way, there are many formulas that, when derived properly, prove that mass is a constantly positive quantity, such as the classic equation E=mc^2 when it is manipulated in a more complex manner.

 

[ZapperZ]

matter is maybe annihilated, but there's some energy left. wouldn't the energy equivalent of a negative mass particle be negative energy?

But look at the Dirac equation. What are the "energies" of the "positive electrons"?

Zz.

 

[Hurkyl]

It is not clear whether an anti-particle has negative mass or an opposite charge (opposite to its normal counterpart).

I thought it was rather straightforward -- look at the electric field the anti-particle generates.

I have not yet seen any test that would distinguish the two possibilities.

Again, I thought it straightforward! A particular charge may be either attracted or repelled to other charges. A particular mass may only be attracted to other masses.

 

[Andrew Mason]

I thought it was rather straightforward -- look at the electric field the anti-particle generates.

The field of the antiparticle is measured by the force it exerts. If negative mass accelerates in a direction opposite to the force, a negative mass with the same charge behaves the same as a positive mass with an opposite charge. How do you distinguish the two?

Again, I thought it straightforward! A particular charge may be either attracted or repelled to other charges. A particular mass may only be attracted to other masses.

If it is attracted to another charge is it because it has opposite charge or because it has negative mass (same charge) and accelerates in the opposite direction to the force?

AM

 

[Andrew Mason]

matter is maybe annihilated, but there's some energy left. wouldn't the energy equivalent of a negative mass particle be negative energy?

I don't see why that should follow. Negative matter would have inertia - it would require energy to change its speed. It is just that the direction of the acceleration is opposite to the direction of the force.

So the annihilation of normal matter or negative matter causes loss of inertia to occur. If energy is a measure of the inertia of an object, the loss of negative mass should result in energy being released.

AM

 

[Hurkyl]

The field of the antiparticle is measured by the force it exerts. If negative mass accelerates in a direction opposite to the force, a negative mass with the same charge behaves the same as a positive mass with an opposite charge.

So? I use the same test-charge to measure the electric field generated by my particle and its antiparticle. If the test-charge reacts in the same way to each field, then the particle and its antiparticle have the same charge. If the test-charge reacts in opposite ways, then they have opposite charges.

Even more explicitly:

If Z repels the test charge, and anti-Z attracts the test charge, they must have opposite charges.
If Z repels the test charge, and anti-Z repels the test charge, they must have the same charge.
If Z attracts the test charge, and anti-Z repels the test charge, they must have opposite charges.
If Z attracts the test charge, and anti-Z attracts the test charge, they must have the same charge.

If it is attracted to another charge is it because it has opposite charge or because it has negative mass (same charge) and accelerates in the opposite direction to the force?

Observational evidence shows that electric forces can either repel or attract, and gravitational forces can only attract. Furthermore, any particular charge can be observed to be attracted by some charges and repelled by other charges.

How you are going to get this behavior (what happens, happens, and what doesn't happen, doesn't happen) using only positive charges and both positive and negative masses?

 

[rbj]

matter is maybe annihilated, but there's some energy left. wouldn't the energy equivalent of a negative mass particle be negative energy?

I don't see why that should follow.

only from

E = m c^2 .

since c^2 is decidedly positive, then if m < 0 so also must E < 0.

just a simple thought.

nonetheless, I'm still pretty confident (as was John Baez in first informing me about it) that a negative mass object repels everything (gravitationally) and a postive mass object attracts everything. a small negative mass falls to the Earth at an acceleration of 9.8 m/s² just like any other amount of mass. it's not a step function (like the sgn() function) where the acceleration is -9.8 m/s² and suddenly becomes +9.8 m/s² when the small mass crosses over from positive to negative.

and two masses of equal size and opposite sign can be put together to make a perpetual motion machine. the negative mass will keep chasing the positive mass which will keep moving away from it. i think they would even accelerate along the axial line that connects the two masses.

 

[WhyIsItSo]

nonetheless, I'm still pretty confident (as was John Baez in first informing me about it) that a negative mass object repels everything (gravitationally) and a postive mass object attracts everything. a small negative mass falls to the Earth at an acceleration of 9.8 m/s² just like any other amount of mass. it's not a step function (like the sgn() function) where the acceleration is -9.8 m/s² and suddenly becomes +9.8 m/s² when the small mass crosses over from positive to negative.

Could explain why there isn't any negative mass known.

If negative mass repels itself gravitationally, it would never coalesce into larger forms (clouds or bodies). Since the expansion of positive matter from origin is slowed due to gravitational attraction, and expansion of negative matter would be increased from origin, it follows that negative matter, if it exists, would be the farthest material from origin and in atomic form. Such would make it virtually impossible to detect from here.

 

[rbj]

If negative mass repels itself gravitationally, it would never coalesce into larger forms (clouds or bodies).

yeah, but it's attracted to positive mass (just like anything else is attracted to positive mass). that's where this is so self-contradictory (which i think bodes poorly for the existence of the stuff).

if there is a lot more positive mass in the universe (or in some local region) than there is negative mass, the attraction of the positive mass will exceed the repulsion of the negative mass and the negative mass will fall inward along with the positive, although the positive mass would feel a small repelling force from the negative mass.

the big contradiction happens in the hypothetical situation of two masses of equal size and opposite sign separated by some not very large distance. such a scenario would have pretty impossible consequences.

 

[robphy]

interesting reading:

http://link.aip.org/link/?AJPIAS/61/216/1

American Journal of Physics
March 1993 -- Volume 61, Issue 3, pp. 216-217

Negative mass can be positively amusing
Richard H. Price

 

[rbj]

interesting reading

but not for the price they want. and i can't find the paper for free online anywhere.

 

[Rade]

...You can set up a curious situation with two masses M and m of equal magnitude but opposite sign. Do they move toward each other or away from each other? It seems that the negative mass will move toward the positive mass, but the positive mass will move away...

Question. What would be predicted if the two masses had "unequal" mass magnitude and opposite sign ? Would not the two move toward each other ?

 

[Andrew Mason]

Question. What would be predicted if the two masses had "unequal" mass magnitude and opposite sign ? Would not the two move toward each other ?

I think it would depend on which mass was greater (ie. absolute value of the masses).

The negative mass would create a gravitational force directed awayfrom the positive mass and would accelerate in the direction opposite to the force so the negative mass accelerates toward the positive mass.

The positive mass feels an equal but opposite force, directed awayfrom the negative mass. So it accelerates away from the negative mass.

So, if the absolute value of the magnitude of the negative mass is less than that of the positive mass, the negative mass accelerates faster and the distance between the two masses decreases. If the negative mass is greater, the positive mass moves faster and the separation increases.

AM

 

[Rade]

I think it would depend on which mass was greater (ie. absolute value of the masses)...So, if the absolute value of the magnitude of the negative mass is less than that of the positive mass, the negative mass accelerates faster and the distance between the two masses decreases.

OK, seems clear. But what happens when they meet ? Would these types of asymmetrical positive mass and negative mass structures be predicted to form a type of stable superposition ?

 

[Andrew Mason]

OK, seems clear. But what happens when they meet ? Would these types of asymmetrical positive mass and negative mass structures be predicted to form a type of stable superposition ?

I don't know. It is hard to say know how negative mass, if it existed, would differ physically from positive mass.

It may be, after all, that negative mass exists all around us. It may be that negative mass only exists, if it exists at all, in anti-particles.

It is interesting to consider the possibility that electrons have positive charge and negative mass (which, as far as I can tell is consistent with physical evidence). Electrons would be attracted to the nucleus but the nucleus would be repelled by the electron. Interesting...

AM

 

[NoTime]

and it's not an arbitrary definition by the way, there are many formulas that, when derived properly, prove that mass is a constantly positive quantity, such as the classic equation E=mc^2 when it is manipulated in a more complex manner.

There are some some pretty sharp math people using negative mass. So the equations don't prove mass is a positive quantity.

Until they construct an Etovos experiment using antimater it's an unresolved question.

 

[Rade]

...It may be, after all, that negative mass exists all around us. It may be that negative mass only exists, if it exists at all, in anti-particles. It is interesting to consider the possibility that electrons have positive charge and negative mass (which, as far as I can tell is consistent with physical evidence)...

Would not the "positron" (e.g., the antimatter conjugate of the "negatron" [old term for electron]) fit this possibility ? Also, you may be interested to know that there is a model of the atomic nucleus that predicts such existence of negative mass (as antimatter) within beta stable isotopes (it builds on the nucleon cluster idea of the Linus Pauling Close-Packed Spheron Model of the mid 1960's)--however to mention it here would violate forum rules--so send me an email if you want more information. Also, it is my understanding that the experiments on antimatter to begin at CERN in 2007 will shed light on possibility that anti-particles have negative mass--so I think all is speculation until experiments are conducted.

 

[Rade]

There are some some pretty sharp math people using negative mass. So the equations don't prove mass is a positive quantity. Until they construct an Etovos experiment using antimater it's an unresolved question.

Could you please provide some references to peer reviewed mathematical equations using "negative mass". Thank you.

 

[NoTime]

Could you please provide some references to peer reviewed mathematical equations using "negative mass". Thank you.

How about Alcubierre's warp drive, R. L. Forward has been mentioned in this thread, anything to do with worm holes. I'm not real good with vol and page# unless it's something I'm working on.

 

[NoTime]

only from

E = m c^2 .

since c^2 is decidedly positive, then if m < 0 so also must E < 0.

just a simple thought.

nonetheless, I'm still pretty confident (as was John Baez in first informing me about it) that a negative mass object repels everything (gravitationally) and a postive mass object attracts everything. a small negative mass falls to the Earth at an acceleration of 9.8 m/s² just like any other amount of mass. it's not a step function (like the sgn() function) where the acceleration is -9.8 m/s² and suddenly becomes +9.8 m/s² when the small mass crosses over from positive to negative.

This would be my understanding of how it should work.

 

[WhyIsItSo]

only from

E = m c^2 .

since c^2 is decidedly positive, then if m < 0 so also must E < 0.

just a simple thought.

Perhaps your "simple" thought is rather profound. The result of your thinking may mean the famous equation gets rewritten:

E = m(\pm c^2)

Just my simple thought

 

[Farsight]

My latex doesn't work. I think it's something to do with my Internet permissions.

And I understand negative mass as much as I understand negative colour. Which is not a lot. So if anybody could help I'd be grateful.

 

[rbj]

This would be my understanding of how it should work.

then, if you can assemble two mass of identical size but one is negative and the other positive, then you have a perpetual motion machine. patent that and you solved forever the energy resource problem of modern humanity.

still think that negative mass is for real?

 

[rbj]

Perhaps your "simple" thought is rather profound. The result of your thinking may mean the famous equation gets rewritten:

E = m(\pm c^2)

Just my simple thought

i s'pose you're being facetious. (i can't always tell.)

 

[WhyIsItSo]

i s'pose you're being facetious. (i can't always tell.)

Me either

 

[NoTime]

then, if you can assemble two mass of identical size but one is negative and the other positive, then you have a perpetual motion machine. patent that and you solved forever the energy resource problem of modern humanity.

still think that negative mass is for real?

You might have noticed that I cut that part from your original post.
For perfectly matched masses, nothing will happen.
The attraction of one would balance the repulsion of the other. Net effect is 0.

I'll wait to when (or if) they can get anti H to form and can run an experiment with it.
Until then this is just speculation.

Edit: Just a clarification. The concept that one mass would run away from the other is based on negative mass also having negative inertia. I don't see an absolute reason why this should be so.

 

[WhyIsItSo]

Not wanting rbj to think I am always facetious, here is my serious thinking.

Premise​

All mass is a postive measure, or perhaps mathematically more accurate would be to say it is an unsigned value. All matter, whether normal, negative, or anti, has inertia. It takes some force to accelerate it. Therefore it has mass, and that is mathematically taken as a positive value.

Arguments Supporting Premise​

Whether matter is normal-, negative-, or anti-matter, it requires some force to accelerate it. To illustrate that mass cannot be viewed as a negative quantity, consider:

We use F=ma to express force. Hypothesizing that, for example, negative mass might be repelled by forces that would attract normal mass has no bearing. This merely reverses the vector of the Force. In a free body diagram, you would reverse the arrow. If you arbitrarily chose to instead reverse the sign of F, then you have reversed the sign of acceleration, ie., -F=m(-a). The "positive" or "negative" respresentation has no bearing on mass. Mass is a magnitude only.

Also, again since all matter has inertia, it therefore has mass. No matter how small the magnitude, some force is required to accelerate it. Only by converting mass to energy can you remove this value.

Therefore, m>0 is always true, since it must be represented mathematically as a positive value, and to be 0 it must be converted to energy, hence is no longer matter.

E=mc^2 is safe. It is not contradicted by, nor is there any conondrum because of the concept of negative-matter. Since c^2 is decidedly postive, and m is shown to be positive, E is therefore always positive, as it must be. For similar logical reasons, E is a magnitude/rate, but has no vector. It is meaningless to apply a sign to this value. Do not confuse this with a rate of change, which would introduce a sign, since it now has a vector (we must note the direction of change).

Next I will debunk any perpetual motion hpothesis.

 

[WhyIsItSo]

The hypothesis from some has been that perpetual motion may be possible with negative matter.

Premise​

1. Perpetual motion is impossible. Specifically, the arguments in this thread on the subject are both in violation of logic, and are fundamentally flawed in their premise regarding behavior.

2. Normal Matter and Negative matter will attract on the macroscopic level (ie, gravity). I make no prediction at for quantum level, but will show this is irrelevant to the issue of perpetual motion.

Arguments Supporting Premise​

Argument 1
To produce a perpetual motion machine, some sustained net force is required. This has variously been argued by suggested differences in how negative matter would respond to normal matter, and comparing that to how normal matter would respond to negative matter.

Seperating these behaviors is necessarily a gross error in logic. Whatever the natures of the two types of matter, they wll either attract, or repel. There will be some net force that acts upon this system, and the system will move towards equilibrium.

Have you ever encountered the story of 3 brothers who bought a radio? The radio they want costs $30. They put in $10 each, and give it to a young lad to run to town and buy the radio. The store owner decides to give the brothers a $5 discount, so the lad returns with the radio and $5. Along the way, he realizes he can't readily divide 5 by 3, so when he gets back, he gives each brother $1, and keeps $2 for himself. This now means each brother paid $9. $9 x 3 = $27, and the boy has $2. $27 + $2 equals $29. Where is the missing $1?

Such is the nature of the above perpetual argument. It is pure and simply a mixing of two unrelated equations in such a manner as to make them appear related.

Argument 2
What about the question of whether or not the type of matter will attract or repel? I assert they will attract macroscopically, that is, gravitationally speaking.

First, recall that many "wrong" ideas can still be used in everyday context. A centrifuge works on the "idea" of centrifugal force. Though we know there is no such force, it is often convenient to overlook that fact. How about weight? Because we mostly use this on the face of this planet, we freely exchange the terms weight with mass. But mass has no vector, weight does. They do not even have the same units of measure. Remember that weight is really mass times g, and g is the "downward" accleration we take as 9.8m/s^2. Most of the time, we can get away with ignoring this fact, but when delving into issues where this matters, we must return to more formal concepts.

In like manner, we must remember here that treating gravity as a force is convenient, but not accurate. I would be interested to know if anyone can offer any other "force" that we cannot feel unless there is some opposing force. Please omit any forces that, due to their magnitude, are impercetable to us. Gravity is decidedly strong enough that we feel its effects, but only while some force opposes it, and only to the magnitude of that opposing force. Logically, therefore, while standing on the ground, the only force you feel is the ground accelerating you in an "upwards" direction at 9.8m/s^2 or thereabouts. We hold a concept that the peculiar nature of gravity is such that it affects all parts of our body simultaneously, whilst the ground presses back at only the contact area of our feet.

If gravity is not a force, then we must throw out the Newtonian concept that for every force there is an equal an opposite force, otherwise we would be launched skywards. Yet we remain firmly planted on the ground. So there must be a force to balance... and around we go to conclude gravity is a force.

Just like we conclude that a centrifuge operates by centrifugal force, until our understanding reveals the truth.

I do not profess to know the explanation for space-time bending due to a mass, but this concept can be used to satisfy the apparent contradiction above.

If you accept that, then consider this. If gravity is not a force, I suggest it has no vector. Where I traveling in space and approaching the gravity well of Earth closely enough to be "attracted" to it, I will feel no acceleration; because there isn't any. From my perspective, I continue to travel in a straight line, at a constant speed. My velocity does not change. Hence, if my path nevertheless "seems" to deviate towards Earth, then it must follow that the light reaching my eyes is not as affected by the bending as is my body. Since mass is a magnitude only, this bending is a magnitude only, and its magnitude is a function of the magnitude of the mass causing it. In this scenario, the Earth's mass is constant, so the difference I perceive is between the mass of the light, and my mass. I too am bending space-time, just not very much compared to the Earth. Better to say, I probably am bending it just as much, just in a much smaller region; a smaller scale if you will. I suspect "mapping" this bending would not be entirely disimilar to how we represent magnetic fields. Not the same, but there would be "curves" which "tighten" in close proximity to the mass.

That is conjecture on my part. What matters is that the bending of space-time is a magnitude only. There is no "negative bending" is you will.

Therefore, negative matter, having mass (which is a positive value), will also bend space-time around itself.

More important to this discussion, there is no acceleration involved. Hence, there is no force involved. Hence, any consideration of repulsion or attraction (being necessarily vectors) is irrelevant. The Earth is bending space-time, so all matter, having inertia, will continue on in the direction, and with the speed, it started with, but this "straight line" is altered by the gravity well of Earth, so the negative matter will "fall" towards Earth.

Note that the gravity well of Earth has nothing to do with a reaction on the negative matter. It is a phenomenon of space-time. Space-time is bent, and that's that. Matter, of any form, will simply follow its "straight" path along this well. The only thing that affects the actual path is the mass of the matter; how much is it bending space time?

The interactions, therefore, are expressed only in terms of the magnitude of space-time bending; there is no issue of "sign". From the perspective of an observer (whose perceptions are based on light, and the path that takes), will simply be that the greater mass has the greater influence. Observing our moon in orbit, the observer may notice that the Earth appears to wobble as a result of the Moon's influence. But remember that the visual perception (light-based) and the actual event (dependent on the mass of the objects observed) will not be the same, because light is not nearly as affected by a gravity well as, for example, something with as much density of mass as the Moon or Earth.

Finally, and briefly, there is the level at which issues such as electrostatic forces and whatnot become significant. Please don't get bent out of shape by my clumsy naming or lack of understanding of such issues. Detailed knowledge of such may be required to calculate net forces, but one need not be a quantum physicist in order to predict there will be some net force. Why normal matter and negative matter might attract or repel, is not at issue. That they will do one or the other, and that will result in some net force, which will move towards equilibrium, is all that is important to this discussion.

Unfortunately for those hoping for a perpetual motion device, "equilibrium" negates such a possibility.

 

[NoTime]

Premise​

All mass is a postive measure, or perhaps mathematically more accurate would be to say it is an unsigned value. All matter, whether normal, negative, or anti, has inertia. It takes some force to accelerate it. Therefore it has mass, and that is mathematically taken as a positive value.

Mass has two properties.
One is inertia the other is spacetime curvature otherwise known as gravity.
Generally the only way we have of measuring mass is by measuring its inertia.
Its easy enough to imagine that the curvature of antimatter could be opposite that of normal matter and still have positive inertia.

So a small amount of antimatter might still "fall down"
as it is constrained to follow the geodesic set by a large amount of normal matter.
OTOH two masses of antimatter would repel each other.

AFAIK there is no way to eliminate this possibility short of doing an Etovos experiment with antimatter.

 

[Andrew Mason]

We use F=ma to express force. Hypothesizing that, for example, negative mass might be repelled by forces that would attract normal mass has no bearing. This merely reverses the vector of the Force. In a free body diagram, you would reverse the arrow. If you arbitrarily chose to instead reverse the sign of F, then you have reversed the sign of acceleration, ie., -F=m(-a). The "positive" or "negative" respresentation has no bearing on mass. Mass is a magnitude only.

But the distinctive quality of negative mass, if it exists, is that it accelerates in the opposite direction to force:

F \propto -a so:

-F = ma \ne m(-a)

You cannot use logic to eliminate the possibility of negative mass. You need evidence.

AM

 

[WhyIsItSo]

Mass has two properties.
One is inertia the other is spacetime curvature otherwise known as gravity.
Generally the only way we have of measuring mass is by measuring its inertia.
Its easy enough to imagine that the curvature of antimatter could be opposite (1)that of normal matter and still have positive inertia.

So a small amount of antimatter might still "fall down"
as it is constrained to follow the geodesic set by a large amount of normal matter.
(2)OTOH two masses of antimatter would repel each other.

AFAIK there is no way to eliminate this possibility short of doing an Etovos experiment with antimatter.

1. For that to hold, you must show mass as having a negative value. So you need to argue against my reasoning for stating mass is also a positive. I am curious to see what you offer.

2. Since the context is space-time bending, this statement is also dependent on (1).

An important tenet of my argument is that gravity is not a force, yet it appears to me your concept remains embedded in notions of vector. My explanation of space-time is such that no acceleration occurs, therefore the path an object takes in the presence of gravity has no direct connection with inertia.

Since there is a relationship between gravity and mass, and there is a relationship between mass and inertia, it seems logical that a relationship between gravity and inertia could be expressed.

But keep in mind that inertia has a vector (possibly undefined as 0), whilst gravity and mass do not. Also, a 0 inertia vector is a relative concept. To an object itself, it's inertia vecotr is 0, it can consider itself stationary, and all observed motion means those objects are moving. But to one of those "moving" objects, the original observer is moving, hence it has some vector to its inertia. We are dealing with issues of relativity, so you must be careful how you form your concepts

 

[WhyIsItSo]

But the distinctive quality of negative mass, if it exists, is that (1)it accelerates in the opposite direction to force:

F \propto -a so:

(2)-F = ma \ne m(-a)

You cannot use logic to eliminate the possibility of negative mass. (3)You need evidence.

AM

I would answer your statement (1) with your own assertion (3).

2. That is not the equation I presented. Neither, at any point, did I attempt to "eliminate the possibility of negative mass".

 

[blackwizard]

Just a simple suggestion. I heard tachyons, negative mass, are supposed 2 travel backward in time. If that meant that some of the logic used here would have 2b completely reversed if ye were assumin they travel in the normal time direction. Like it repeling a positive mass (backward in time) but when viewed by us it would look like its attracting it, like all other mass?

 

[Andrew Mason]

That is not the equation I presented. Neither, at any point, did I attempt to "eliminate the possibility of negative mass".

I guess I misunderstood your statement:

Therefore, m > 0 is always true,

AM

 

[rbj]

But the distinctive quality of negative mass, if it exists, is that it accelerates in the opposite direction to force:

F \propto -a so:

-F = ma \ne m(-a)

did you not mean:

F = ma \ne m(-a)

or more specifically

\vec{F} = \frac{d \vec{p}}{dt} = m \vec{a}

if we can assume the mass is constant.

You cannot use logic to eliminate the possibility of negative mass. You need evidence.

can we use logic to eliminate the possibility of a perpetual motion machine? if not, what evidence is sufficient? we can't look everywhere in the universe to verify that no perpetual motion machine lives there.

i think we can use existing knowledge of physical behavior, analytical extension of that physical behavior (with the minus signs), and logic to conclude that two balls of mass with equal magnitude and opposite sign makes a system that accelerates indefinitely.

i've seen some posters here deny that, but they are not saying why.

 

[rbj]

So a small amount of antimatter might still "fall down"
as it is constrained to follow the geodesic set by a large amount of normal matter.
OTOH two masses of antimatter would repel each other.

AFAIK there is no way to eliminate this possibility short of doing an Etovos experiment with antimatter.

this is not about antimatter. it's about negative mass and, as best as i can read about it, the two are different.

is not "antimatter" this stuff where electrons are replaced by positron and protons are replaced by antiprotons? i just looked these two antiparticles up and they believed to have positive mass. antiparticles have the same (positive) mass as their normal counterparts and the opposite electric charge.

if there was no gravity, the motion of such might be indistiguishable from having the same electric charge and opposite mass (in an electrostatic context, the particle motion would be the same).

but this thread is about negative mass and its motion in the context of gravity. and that's where you can tell the difference.

negative mass means perpetual motion machines, the end of conservation of energy, and the solution to humankind's energy shortage forever.

so may i suggest that we don't use the term "antimatter" to mean matter with negative mass?

and may i suggest to those who say that equal and oppositely massed objects (also uncharged, electrically) will either just attract each other or just repel each other (because of gravity), to show what the justification they have for such a belief?