Some posssible implications of anti-matter being repelled by gravity?

[halfeye]

If anti-matter is repulsed by normal matter, as seems to be suspected, surely that implies that there ought to be anti-dark-matter, which is also repelled by normal matter and normal dark matter?

I'm kind of thinking that anti-light might be light but at a different polarisation, and would anti-dark-energy make any sense?

[Lvl 2 Expert]

If anti-matter is repulsed by normal matter, as seems to be suspected, surely that implies that there ought to be anti-dark-matter, which is also repelled by normal matter and normal dark matter?

I'm kind of thinking that anti-light might be light but at a different polarisation, and would anti-dark-energy make any sense?

Anti-matter is repulsed by normal matter?

I've never heard that. Is that standard model or some side theory?

Anti-light would be anti-photons, and both normal and anti photons can occur in any polarization...

[Manga Shoggoth]

Light is always at different polarisations - polarisation is (loosely speaking) simply the relative angle of the electric/magnetic planes of particular waves. Polarising sunglasses work by cutting out light that doesn't match a specific plane of polarisation (which is why if you look through two pairs of polarising classes and rotate one of them you will reach a point where no light gets through.

There's no reason to suggest that anti-matter is repulsed by normal matter. The only difference between, for example, an electron and a positron, is that they have a different charge (and thus would attract each other) - they would have the same mass.

If I recall correctly, the idea that anti-matter would act as the reverse of normal matter goes back to the old Dirac view. It appears in some older science fiction (Lensman, in particular, has it as a minor plot point). It isn't supported by modern theories to the best of my knowledge.

EDIT: You might be interested in watching the Minute Physics video (https://www.youtube.com/watch?v=Lo8NmoDL9T8) on antimatter: Amongst the other points, there is no such thing as anti-light - photons have no charge, and therefore have no anti-particle (they don't have mass - or at least, rest mass either).

[halfeye]

Anti-matter is repulsed by normal matter?

I've never heard that. Is that standard model or some side theory?

Anti-light would be anti-photons, and both normal and anti photons can occur in any polarization...

I don't know whether it's a side theory, it's apparently currently not experimentally proven either way.

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


The gravitational interaction of antimatter with matter or antimatter has not been conclusively observed by physicists. While the consensus among physicists is that gravity will attract both matter and antimatter at the same rate that matter attracts matter, there is a strong desire to confirm this experimentally.

Antimatter's rarity and tendency to annihilate when brought into contact with matter makes its study a technically demanding task. Most methods for the creation of antimatter (specifically antihydrogen) result in high-energy particles and atoms of high kinetic energy, which are unsuitable for gravity-related study. In recent years, first ALPHA[1][2] and then ATRAP[3] have trapped antihydrogen atoms at CERN; in 2012 ALPHA used such atoms to set the first free-fall loose bounds on the gravitational interaction of antimatter with matter, measured to within ±7500% of ordinary gravity[4][citation needed], not enough for a clear scientific statement about the sign of gravity acting on antimatter. Future experiments need to be performed with higher precision, either with beams of antihydrogen (AEGIS) or with trapped antihydrogen (ALPHA or GBAR).

In addition to uncertainty regarding whether antimatter is gravitationally attracted or repulsed from other matter, it is also unknown whether the magnitude of the gravitational force is the same. Difficulties in creating quantum gravity theories have led to the idea that antimatter may react with a slightly different magnitude.[5]

Theories of gravitational attraction:

When antimatter was first discovered in 1932, physicists wondered about how it would react to gravity. Initial analysis focused on whether antimatter should react the same as matter or react oppositely. Several theoretical arguments arose which convinced physicists that antimatter would react exactly the same as normal matter. They inferred that a gravitational repulsion between matter and antimatter was implausible as it would violate CPT invariance, conservation of energy, result in vacuum instability, and result in CP violation. It was also theorized that it would be inconsistent with the results of the Eötvös test of the weak equivalence principle. Many of these early theoretical objections were later overturned.[6]

The equivalence principle

...

Morrison's argument

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Schiff's argument

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Good's argument

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Gerard 't Hooft's argument

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Theories of gravitational repulsion

As long as repulsive gravity has not been refuted experimentally, one can speculate about physical principles that would bring about such a repulsion. Thus far, three radically different theories have been published.

Kowitt's theory

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Santilli and Villata's theory

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Cabbolet's theory

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I'm saying if it was, then what? I'm not saying it is so.

[BeerMug Paladin]

You're thinking of negative matter, not antimatter.

As in, you plug in a negative mass into the F = (m1)*(m2)*G/r^2 equation to get repulsive action.

You can do that sort of thing with a lot of models out there, but typically it's understood that the reason for the wacky result in the equation is because the input range used was invalid.

Sometimes, it's called a theoretical substance. While technically true it can be called a prediction, there's still a basic question of what the intended input could even mean.

[halfeye]

Looks as if it is a bunch of side theories.

[Kato]

As has been noted, while the theory of anti matter repelling matter because it has negative mass might seem logical, there's no evidence towards it and quite some weak evidence against it.
(also, antilight is not a thing in any model I'm familiar with, annihilation between matter and antimatter results in normal photons. And I cannot begin to imagine what anti-energy might be (then again, I'm not very creative))

As for 'what if'... What are we looking for?

I tend to not worry about antimatter in my daily life (I guess I life in a pretty safe neighborhood) if it's attraction or repulsion to normal matter is a problem for you in your daily life, I think you better contact your closest particle physics faculty.

As for artificially made... Any antimatter you want to make is going to be hard to handle, but I guess it's going to fly up instead of falling down. (ignoring how it would explode)

I think the repulsion theory has come up with regard to the the imbalance between matter and antimatter and the expansion of the universe and possibly somehow removing the need for dark matter / energy if some galaxies are matter and some antimatter. But iirc none of these ideas hold up to models / calculations and one of the most obvious problems is the lack of massive bursts of energy in nowhere space between both types.

So... In what situation would you like to know what would be different?

[shawnhcorey]

Light is its own anti-matter. A photon 180° out of phase with another will cancel each other out with no residue.

Anti-matter may be anti-mass. So far, the amount of anti-matter that has been created is so small its gravity is impossible to measure.

[halfeye]

So... In what situation would you like to know what would be different?

As noted, light is its own anti-matter, so if anti-matter is repelled by gravity, under what circumstance would light be repelled by gravity?

Where would we expect to find dark-anti-matter, if it is repelled by matter (and possibly attracted by antimatter)?

Is there gravitational anti-lensing apparent in the universe?

If there is gravitationally repulsive anti-matter, does anti-dark-energy become a coherent idea?

Would an antimatter black hole be repulsive to matter (and vice versa?)?

[Bohandas]

I think he means gravitationally repulsed. Since antimatter is sometimes seen as time reversed instead of charge reversed it could mean that gravitational attraction to other matter would draw it to move closer to massive objects in the past, and therefore be further away in the future

[Douglas]

I think he means gravitationally repulsed. Since antimatter is sometimes seen as time reversed instead of charge reversed it could mean that gravitational attraction to other matter would draw it to move closer to massive objects in the past, and therefore be further away in the future
Ah, but time reversal like that doesn't actually work out to being repelled by gravity. Suppose an antimatter particle is falling towards a planet, being accelerated by its gravity, and going backwards in time during the fall. What does this look like to someone going forwards in time? The antimatter particle shoots up from the planet with high initial speed, and slows down as it gets higher, being decelerated by gravity.

It's the same trajectory, the same set of time and space coordinates, and regardless of which direction you're going in time it still behaves as gravity attracting the particle.

[shawnhcorey]

You can't go backward in time. Time is an emergent feature of our universe, not a fundamental one. Besides, speed is always positive.

[Tvtyrant]

Ah, but time reversal like that doesn't actually work out to being repelled by gravity. Suppose an antimatter particle is falling towards a planet, being accelerated by its gravity, and going backwards in time during the fall. What does this look like to someone going forwards in time? The antimatter particle shoots up from the planet with high initial speed, and slows down as it gets higher, being decelerated by gravity.

It's the same trajectory, the same set of time and space coordinates, and regardless of which direction you're going in time it still behaves as gravity attracting the particle.

If it is actually reverse gravity wouldn't the particles "fall" into wherever there was the least amount of gravity? So they would essentially roll back and forth in empty space, staying as far from each other as possible and trying to escape their own gravity wells?

They would never come near actual gravity fields, they would fly back and forth like pendulums or fly away from everything else ping-ponging until they reached empty space.

[shawnhcorey]

If it is actually reverse gravity wouldn't the particles "fall" into wherever there was the least amount of gravity? So they would essentially roll back and forth in empty space, staying as far from each other as possible and trying to escape their own gravity wells?

They would never come near actual gravity fields, they would fly back and forth like pendulums or fly away from everything else ping-ponging until they reached empty space.

No, anti-mass would be attracted to itself. Newton's gravity: F = -Gm₁m₂/r²

If both m₁<0 and m₂<0, a negative number times a negative number is a positive number, so the force would be attractive.

[Tvtyrant]

No, anti-mass would be attracted to itself. Newton's gravity: F = -Gm₁m₂/r²

If both m₁<0 and m₂<0, a negative number times a negative number is a positive number, so the force would be attractive.

So we could see an anti-galaxy full of anti-planets and anti-suns? Or would the anti-photons refuse to come close to positive-galaxies so it would be invisible to us?

[shawnhcorey]

So we could see an anti-galaxy full of anti-planets and anti-suns? Or would the anti-photons refuse to come close to positive-galaxies so it would be invisible to us?

There is a region of space where this might be happening: the Dipole Repeller (https://www.youtube.com/watch?v=NpV0GQo3P0c) (video 4½ minutes).

[Caerulea]

You can't go backward in time. Time is an emergent feature of our universe, not a fundamental one. Besides, speed is always positive.
Perhaps I am a tachyon, and traveling faster than light. If so, I would appear to be going backwards in time to any observer, which is as reasonable definition of going back in time as any. Also, you can model antimatter as normal matter that is traveling backwards in time.[citation] (https://en.wikipedia.org/wiki/Antiparticle#Feynman%E2%80%93Stueckelberg_interpre tation)



Anti-matter may be anti-mass. So far, the amount of anti-matter that has been created is so small its gravity is impossible to measure.
An antimatter particle has the same mass as a normal particle, the only difference is that the charge is reversed.

[Yora]

Light is its own anti-matter. A photon 180° out of phase with another will cancel each other out with no residue.

That would be annihilation of energy. Something must be left over.

[shawnhcorey]

Perhaps I am a tachyon, and traveling faster than light. If so, I would appear to be going backwards in time to any observer, which is as reasonable definition of going back in time as any. Also, you can model antimatter as normal matter that is traveling backwards in time.[citation] (https://en.wikipedia.org/wiki/Antiparticle#Feynman%E2%80%93Stueckelberg_interpre tation)


An antimatter particle has the same mass as a normal particle, the only difference is that the charge is reversed.

"The word is not the thing. The map is not the territory. The symbol is not the thing symbolized."
Alfred Korzybski

Just because there is a variable for time doesn't mean time is real. Time is an emergent feature of our universe. Time is the distance travelled by light. Distances are always positive. So any measure of time is positive, that is, forward.


That would be annihilation of energy. Something must be left over.

Yes, one of the quirky things that happen when quanta are considered to be only particles. So far, the best description of quanta is wave functions. And if you use wave functions it becomes impossible for photons to met exactly enough to cancel each other.

[Caerulea]

"The word is not the thing. The map is not the territory. The symbol is not the thing symbolized."
Alfred Korzybski

Just because there is a variable for time doesn't mean time is real. Time is an emergent feature of our universe. Time is the distance travelled by light. Distances are always positive. So any measure of time is positive, that is, forward.
I can quote people too! Look at these,

This quote was taken out of context

What really matters anyway is not how we define time, but how we measure it

We measure time by how far light can go. 1 day is the period between light setting off, and light reaching about 16094400000 miles away. We find that the speed of light is always the same, even if we are moving very quickly. We also see that the energy it takes to accelerate something with mass approaches infinity for any amount of mass. The speed of light is unattainable by massless particles.

So let us now imagine some friends are holding a party on one of Saturn's rings, tomorrow. If you had a rocket, or some other device that flings you into space, you could get there. You would have to go rather fast, but there is no physical reason that you can not get there on time. This event is in your future, because you can get there before it starts.

Now let us say that a different set of friends are holding a party in the galactic center of the Milky Way. They are being a bit reasonable, and told you a year in advance (through some magic telephone). Can you go to this party? No. The Galactic center is ~8000 light years away. It is reasonable to count this event as not in your future, as even if you traveled on a beam of light, you would not get to the part before it had happened.

The future is the events that you could influence, if you shone a beam of light at them. Anything that could influence you is in your past. The other events, those happening where you can not influence them and they can not influence you because of the laws of physics is the present. From this picture, it is easy to see why tachyons and other faster than light particles would travel backwards in time.

Because the events that you can influence are constrained by the speed of light, and the tachyon is not, it can travel and influence events in the present, and, if going fast enough, in the past.


(credit for explanation goes to Richard Gott, and his book Time Travel in Einsteins Universe. Credit for errors goes to me)

[Kato]

As noted, light is its own anti-matter, so if anti-matter is repelled by gravity, under what circumstance would light be repelled by gravity?

Where would we expect to find dark-anti-matter, if it is repelled by matter (and possibly attracted by antimatter)?

Is there gravitational anti-lensing apparent in the universe?

If there is gravitationally repulsive anti-matter, does anti-dark-energy become a coherent idea?

Would an antimatter black hole be repulsive to matter (and vice versa?)?
In order..

Well, if you make a new theory in which antimatter causes this... Which would be weird but I guess the mass of photons is kind of weird anyway so you might as well assume it acts however you want it to.


Dark normal matter is not much more than a theory and you're asking for (I guess) some kind of founded assumptions about dark antimatter?
What would that dark antimatter do, only repel matter and attract antimatter? Then... I guess anywhere in nowhere space that's giving a huge push to its surroundings, somewhere in the biggest gaps between galaxies / clusters / etc (?)

Not as far as I know. I feel like it would be a big deal if it happened but I'm also not sure what it would look like to us, because I think diffusion on astronomical scales would be hard to observe (I could be very wrong, I hate optics)

Not until you give any explanation what that is supposed to be, sorry. Anti energy just is not a working concept, as far as I know.

Yes, of course.



Yes, one of the quirky things that happen when quanta are considered to be only particles. So far, the best description of quanta is wave functions. And if you use wave functions it becomes impossible for photons to met exactly enough to cancel each other.

But... You were the one who started with the light canceling...
Destructive interference between light waves is not the same as annihilation between matter and antimatter. I'm really foggy on polarization but iirc, it has little to do with it either, it's just a slightly more complicated case of being out of phase (after some quick reading, though this might be off. Still, nothing to do with annihilation or antilight)

[Grey_Wolf_c]

The speed of light is unattainable by massless particles.

I’m fairly certain you have a typo there - “massy” or “only attainable” or “by anything except”.

Grey Wolf

[shawnhcorey]

But... You were the one who started with the light canceling...
Destructive interference between light waves is not the same as annihilation between matter and antimatter. I'm really foggy on polarization but iirc, it has little to do with it either, it's just a slightly more complicated case of being out of phase (after some quick reading, though this might be off. Still, nothing to do with annihilation or antilight)

Suppose you were to create an experiment where a laser beam was split in two, one of the beams was shifted to be 180° out of phase with the other and combine them back together. If you block one of the beams, the other would pass thru the experiment as expected. If you allow both beams thru, they would not reach the end of the experiment; they would bounce off the surface where they were combined.

If you do the calculation for this experiment where photons are particles, you would get the photons annihilating each other. If you calculated with photons as wave functions, you would determine that the beams would bounce of the surface where they combine.

The fact that the two beams would not cancel each other out but bounce instead makes not sense because individually they go thru the experiment as expected. Quantum mechanics can be quirky at times.

[shawnhcorey]

Because the events that you can influence are constrained by the speed of light, and the tachyon is not, it can travel and influence events in the present, and, if going fast enough, in the past.

Tachyons are speculation. There is no evidence that they exist.

Time is the distance travelled by light. When Einstein described Special Relativity, he discussed a clock on a spaceship. Here is an image of the clock.
http://homepage.physics.uiowa.edu/~rlm/mathcad/addendum%209%20notes%20on%20special%20relativity_i mages/IMG0263_579625093.PNG
Thanks to Robert Mutel (http://homepage.physics.uiowa.edu/~rlm/) for the image.

The image on the left is when the observer is stationary with respect to the clock. Time is measured by how long it takes light to bounce off the mirrors and return to its starting position and direction.

The image on the right is when the observer is moving. Again, time is how long it takes light to bounce off the mirrors and return to its starting position (relative to the mirrors) and direction. The reason why time is measured to be slower is because light has to travel a longer distance. Time is the distance travelled by light.

[Bohandas]

And also IIRC a couple of other physicists ran the numbers with how more conventional clocks and chronometers would react and came up with the same outcome, though I forget the details of that anecdote and I forget where I heard it

[Bohandas]

Just because there is a variable for time doesn't mean time is real. Time is an emergent feature of our universe.

No, it's a dimension, perpendicular to length, width, and height

[Radar]

Just because there is a variable for time doesn't mean time is real. Time is an emergent feature of our universe. Time is the distance travelled by light. Distances are always positive. So any measure of time is positive, that is, forward.
Considering that present is well defined only localy just as future and the past, time has to be as real as space. In fact they are aspects of the same thing we usually call space-time. There is really no way around this, since special relativity was well tested to work. As such, Lorentz transforms properly describe relations between frames of reference and there is no priviledged frame of reference. In short "now" is relative, so past, present and future have to all exist together, since distinctions between them are only ever defined locally.


Yes, one of the quirky things that happen when quanta are considered to be only particles. So far, the best description of quanta is wave functions. And if you use wave functions it becomes impossible for photons to met exactly enough to cancel each other.
That might be the reason for photon-photon reactions to be next to impossible, but the real solution is different. Annihilation and creation processes are in general symmetrical. This means that if annihilation of (for example) an electron and positon results in a pair of gamma photons, then a pair of photons can annihilate and create a pair of some particles provided the photon pair has enough energy. This is for example the reason for an upper limit of photon energy in the cosmic radiation: any photon energetic enough to annihilate with the background radiation photons will do so sooner or later.

There is even such a phenomenon as photon-photon scattering, but it is quite rare in everyday circumstances.

[Caerulea]

I’m fairly certain you have a typo there - “massy” or “only attainable” or “by anything except”.

Grey Wolf
Yes, thank you.

Tachyons are speculation. There is no evidence that they exist.

Yes. They are speculation that (as far as I am aware) are not ruled out by the physical laws (as we understand them) of the universe.

[shawnhcorey]

Yes. They are speculation that (as far as I am aware) are not ruled out by the physical laws (as we understand them) of the universe.

Unicorns are also not ruled out by the physical laws.

[BeerMug Paladin]

It's worthwhile to note that while time does have some connection to movement in spatial dimensions, it is not itself a spatial dimension. There's no reason I'm aware of to consider that it has "direction". It may simply be a directionless scalar in the way that period, speed, volume and other similarly basic concepts have no meaning with negative numbers.

If you want to get crazy though, consider negative energy in the equation E = 1/2*m*v^2. And suppose we have a disc made of normal matter.

Rearranging a bit, we get sqrt(E * 2/m) = v, or sqrt (negative number) = v. Imaginary spin velocity is now a prediction. What does it mean? That doesn't matter, it's a hypothetical mode of movement. All you need is a disc with negative potential kinetic energy and that's what you've got.

All you need to do is have matter that violates a fundamentally understood property of matter in order to have tachyons. I'm no expert in this field, but it strikes me as much the same thing.

[Lord Torath]

Unicorns are also not ruled out by the physical laws.And, in fact, are a real (but extinct) creature! I give you: Elasmotherium (https://dinoanimals.com/animals/giant-rhinoceros-elasmotherium-a-prehistoric-rhino/). Also available on Tee shirts (https://www.cafepress.com/orderofthestick/10861046). :smallbiggrin:

[wumpus]

Ah, but time reversal like that doesn't actually work out to being repelled by gravity. Suppose an antimatter particle is falling towards a planet, being accelerated by its gravity, and going backwards in time during the fall. What does this look like to someone going forwards in time? The antimatter particle shoots up from the planet with high initial speed, and slows down as it gets higher, being decelerated by gravity.

It's the same trajectory, the same set of time and space coordinates, and regardless of which direction you're going in time it still behaves as gravity attracting the particle.

As far as I know, entropy increases over time even with anti-matter. While [nearly?] all physics equations work forwards and backwards with time, entropy points the way of time. Anti-matter is not simply matter going in the opposite temporal direction (which would have made a nice symmetry with anti-matter going backwards in time to before the big bang).


So we could see an anti-galaxy full of anti-planets and anti-suns? Or would the anti-photons refuse to come close to positive-galaxies so it would be invisible to us?

The general argument against large amounts of anti-matter in the universe is that the boundaries between them would light up with matter-antimatter destruction. If the anti-gravity of an anti-matter galaxy was sufficiently large, it might be possible shove away the inter-galactic matter and avoid this.

The real problem would be the composition of intergalactic "stuff". Is it matter or antimatter? And are there clouds of each? If so, why aren't they colliding?

[Grey_Wolf_c]

Unicorns are also not ruled out by the physical laws.

Unicorns existed, in the same way that the half-camel half-leopards (https://en.wikipedia.org/wiki/Northern_giraffe) existed: the Greeks named creatures based on descriptions from travelers, pictures on walls, etc. The wild ox was a real animal, and just because the Greeks called it "unicorn" doesn't make it any less real.

Grey Wolf

[halfeye]

In order..

Well, if you make a new theory in which antimatter causes this... Which would be weird but I guess the mass of photons is kind of weird anyway so you might as well assume it acts however you want it to.

I don't think we know everything about the interactions between light and gravity yet.


Dark normal matter is not much more than a theory and you're asking for (I guess) some kind of founded assumptions about dark antimatter?
What would that dark antimatter do, only repel matter and attract antimatter? Then... I guess anywhere in nowhere space that's giving a huge push to its surroundings, somewhere in the biggest gaps between galaxies / clusters / etc (?)

If this theory about anti-matter repulsing ordinary matter were correct, it might mean that early on in the big bang matter and anti-matter separated out, so probably the dark-anti-matter went with the bright anti-matter, and it's out there somewhere a long way away.


Not as far as I know. I feel like it would be a big deal if it happened but I'm also not sure what it would look like to us, because I think diffusion on astronomical scales would be hard to observe (I could be very wrong, I hate optics)

I kind of like geometric optics, but have no understanding of quanta.


Not until you give any explanation what that is supposed to be, sorry.

I have no idea, it just seemed that if banging "anti-" in front of stuff worked, dark energy was a candidate for that prefix.


Anti energy just is not a working concept, as far as I know.

I'm kind of thinking potential energy versus kinetic energy.


Yes, of course.

Actually, no. I find the idea of negative gravity very attractive, however, anti-matter and black holes aren't compatible. There is no such thing as an anti-neutron, so anti-neutronium makes no sense, and without anti-neutronium there can be no anti-matter black hole. So, with quite a lot of regret, I am giving up the idea of anti-matter causing anti-gravity.

[DavidSh]

There is no such thing as an anti-neutron, so anti-neutronium makes no sense, and without anti-neutronium there can be no anti-matter black hole.

Just because the neutron has no charge, it doesn't mean that antineutrons (https://en.wikipedia.org/wiki/Antineutron) don't exist.

[Tvtyrant]

As far as I know, entropy increases over time even with anti-matter. While [nearly?] all physics equations work forwards and backwards with time, entropy points the way of time. Anti-matter is not simply matter going in the opposite temporal direction (which would have made a nice symmetry with anti-matter going backwards in time to before the big bang).



The general argument against large amounts of anti-matter in the universe is that the boundaries between them would light up with matter-antimatter destruction. If the anti-gravity of an anti-matter galaxy was sufficiently large, it might be possible shove away the inter-galactic matter and avoid this.

The real problem would be the composition of intergalactic "stuff". Is it matter or antimatter? And are there clouds of each? If so, why aren't they colliding?

But if they treat each other as repulsive then they would rarely touch right? So you could have a galaxy and an anti-galaxy whose gravities repulse each other.

[halfeye]

Just because the neutron has no charge, it doesn't mean that antineutrons (https://en.wikipedia.org/wiki/Antineutron) don't exist.

Ooh, that's interesting. What does the gravity on that one look like then? I would presume that being neutral, the gravitational direction of attraction would be much easier to determine? or has no one yet made one on purpose?

[Caerulea]

Ooh, that's interesting. What does the gravity on that one look like then? I would presume that being neutral, the gravitational direction of attraction would be much easier to determine? or has no one yet made one on purpose?
Okay, I thought it was said earlier in the thread, but, antiparticles have the same mass as the original particles, only the charge is reversed. Not negative mass, the same exact mass. Gravitational attraction works the same for all antiparticles as the normal particles. The overall interaction may be somewhat different due to the mutual annihilation producing energy, but the effect of gravity is the same.

[halfeye]

Okay, I thought it was said earlier in the thread, but, antiparticles have the same mass as the original particles, only the charge is reversed. Not negative mass, the same exact mass. Gravitational attraction works the same for all antiparticles as the normal particles. The overall interaction may be somewhat different due to the mutual annihilation producing energy, but the effect of gravity is the same.

With respect, somebody (you?) said that, that doesn't of itself necessarily make it true. It is probably true, but at this time as I understand it, it is not experimentally proven. If you can have anti-neutrons, then it's not exactly just the charge that changes.

[Lvl 2 Expert]

Unicorns existed, in the same way that the half-camel half-leopards (https://en.wikipedia.org/wiki/Northern_giraffe) existed: the Greeks named creatures based on descriptions from travelers, pictures on walls, etc. The wild ox was a real animal, and just because the Greeks called it "unicorn" doesn't make it any less real.

Grey Wolf

A real unicorn fanatic makes their own (https://i.kinja-img.com/gawker-media/image/upload/s--A2gh2AGE--/c_scale,f_auto,fl_progressive,q_80,w_800/988635472422588709.jpg).

[georgie_leech]

With respect, somebody (you?) said that, that doesn't of itself necessarily make it true. It is probably true, but at this time as I understand it, it is not experimentally proven. If you can have anti-neutrons, then it's not exactly just the charge that changes.

It is, but deeper down. An antineutron is made of the same quarks that make up a neutron, except antiquarks rather than normal quarks. Since the charges sum to 0 anyway, flipping the charges on the quarks will still make them sum to 0. Or, to put it another way, -0 = 0.

[Caerulea]

With respect, somebody (you?) said that, that doesn't of itself necessarily make it true.
Yes.

Here are some people smarter than me saying it.

"Due to CPT-theorem themasses of particles and antiparticles are equal and thus for equal values of particle momentatheir energies must be equal too." (Alexander Dolgov, Cosmological Matter-Antimatter Asymmetry and Antimatter in the Universe (https://arxiv.org/abs/hep-ph/0211260), Page 4)

"The magnitude of the proper mass cannot yet be given further than to fix an upper limit of the electron mass..." (Carl D. Anderson, The Positive Electron (https://journals.aps.org/pr/pdf/10.1103/PhysRev.43.491), Page 3)
(That they do not consider masses less than zero is telling, and they likely would have noticed had it been negative)

In any event, look at E=mc2. If you plug negative mass in, you get negative energy out, and then annihilation between antiparticles and particles should leave no energy, rather than a tremendous amount of energy.

[halfeye]

It is, but deeper down. An antineutron is made of the same quarks that make up a neutron, except antiquarks rather than normal quarks. Since the charges sum to 0 anyway, flipping the charges on the quarks will still make them sum to 0. Or, to put it another way, -0 = 0.

Yeah, but that's not a charge difference in the sense that a positron has a different charge from an electron. The point is, more or less, can a neutron star be made of negative neutrons to make an anti-matter neutron star? are antiquarks normally found making up normal matter, or are they exclusive to anti-matter? If they are exclusive to anti-matter, where do the anti-matter bits in particle accelerators come from?

[wumpus]

But if they treat each other as repulsive then they would rarely touch right? So you could have a galaxy and an anti-galaxy whose gravities repulse each other.

A lot depends on what's out there. I'd expect that plenty of dust would be moving at sufficient velocity (especially those orbiting galaxies at the outer edge) to come into contact with each other. Also any free ions between galaxies would easily overcome any gravity issues to self-annihilate. As far as I know, there aren't enough collisions for this to be true.

Gravity is really weak. It might add up enough to sweep most of the "wrong" dust away, but it wouldn't do anything to any fast moving dust that happened to come along or keep it from hitting its opposite particle once it penetrated the "wrong" galaxy.

[georgie_leech]

Yeah, but that's not a charge difference in the sense that a positron has a different charge from an electron. The point is, more or less, can a neutron star be made of negative neutrons to make an anti-matter neutron star? are antiquarks normally found making up normal matter, or are they exclusive to anti-matter? If they are exclusive to anti-matter, where do the anti-matter bits in particle accelerators come from?

In order:

It's a charge difference in the same way the charges of the quarks that make up a proton sum to 1, the antiquarks that make up an antiproton sum to -1. It's the exact same process, even if it looks different on the surface. Baryons (https://en.wikipedia.org/wiki/Baryon) like Protons and Neutrons are made up of three quarks, which have charges less than 1; remember that when scientists defined the proton/electron as the "base" charge magnitude, they weren't aware that they were made up of more fundamental particles still.

Yes, in theory you could have an antineutron star, but for reasons already elaborated on upthread, we don't believe there are (m)any large bodies of antimatter roaming around, including said antineutron stars.

Sort of yes: When you make a particle with any single quark and (not necessarily the same type) antiquark, you get a meson (https://en.wikipedia.org/wiki/Meson). They don't really make up anything we traditionally think of as matter, mostly being short-lived, unstable particles that are created in particle accelerators.

The same way we get all the different types of unstable particles in particle accelerators: the tl;dr is that when you collide particles together at relativistic velocities, the energy involved is sufficient to create new particles with mass, because E = mc2. This, incidentally, is yet more evidence that the mass of antimatter is positive rather than negative, and behaves like other massive particles in terms of gravitational effects.

[halfeye]

In order:

It's a charge difference in the same way the charges of the quarks that make up a proton sum to 1, the antiquarks that make up an antiproton sum to -1. It's the exact same process, even if it looks different on the surface. Baryons (https://en.wikipedia.org/wiki/Baryon) like Protons and Neutrons are made up of three quarks, which have charges less than 1; remember that when scientists defined the proton/electron as the "base" charge magnitude, they weren't aware that they were made up of more fundamental particles still.

I was mainly contradicting the guy/gal who said that the only difference between matter and anti-matter was the charge on the particles (by which I understood him/her to mean baryons).


Yes, in theory you could have an antineutron star, but for reasons already elaborated on upthread, we don't believe there are (m)any large bodies of antimatter roaming around, including said antineutron stars.

Sort of clearly not obviously present in the observable universe, but if it separated quickly enough after the big bang (perhaps coupled with anihilation of a lot that didn't separate), there might be an equal mass of it beyond the observability horizon, which would explain the lack of it more locally.


Sort of yes: When you make a particle with any single quark and (not necessarily the same type) antiquark, you get a meson (https://en.wikipedia.org/wiki/Meson). They don't really make up anything we traditionally think of as matter, mostly being short-lived, unstable particles that are created in particle accelerators.

Are there any baryons which contain anti-quarks? Or to put it another way, do anti-quarks exist naturally outside particle accelerators?


The same way we get all the different types of unstable particles in particle accelerators: the tl;dr is that when you collide particles together at relativistic velocities, the energy involved is sufficient to create new particles with mass, because E = mc2. This, incidentally, is yet more evidence that the mass of antimatter is positive rather than negative, and behaves like other massive particles in terms of gravitational effects.

It's evidence by inference, not observation though, and negative mass might still be mass for the energy equivalence thing.

Thanks for taking the time to answer my questions.

[Kato]

Sort of clearly not obviously present in the observable universe, but if it separated quickly enough after the big bang (perhaps coupled with anihilation of a lot that didn't separate), there might be an equal mass of it beyond the observability horizon, which would explain the lack of it more locally.



Are there any baryons which contain anti-quarks? Or to put it another way, do anti-quarks exist naturally outside particle accelerators?



It's evidence by inference, not observation though, and negative mass might still be mass for the energy equivalence thing.

Thanks for taking the time to answer my questions.

Again, in order:
Yes, possibly. But we can look pretty far. And it feels like a weird coincidence if one type was all far away, suggesting it got somehow sorted out to be on the rim of the universe or something. But I can't speak competently enough about it, my best counter argument is 'it's not a popular / widespread theory, if it was likely it would be'.

No. Normal matter doesn't contain antiquarks, because they do not 'work well' with normal quarks (i.e. they blow up)
The only kind of common antiquark is the positron which is as stable as the electron but in a world full of the latter tends to not blow up soon.

Yes, it's possible, but there is nothing to suggest that's the case. I feel like there should be something about the equation where an obvious problem arises but then if it was the case the negative mass thing would have already been dismissed entirely.

[halfeye]

Again, in order:
Yes, possibly. But we can look pretty far. And it feels like a weird coincidence if one type was all far away, suggesting it got somehow sorted out to be on the rim of the universe or something. But I can't speak competently enough about it, my best counter argument is 'it's not a popular / widespread theory, if it was likely it would be'.

It would depend on anti-matter having negative repulsive of normal matter mass (which is itself unlikely), and the anihilation of all that remained, which is expected. If 90% (number pulled from hat) of the mass from the big bang was anihilated, the remaining 10% being pure separated matter and pure separated anti-matter doesn't sound that improbable to me.


No. Normal matter doesn't contain antiquarks, because they do not 'work well' with normal quarks (i.e. they blow up)
The only kind of common antiquark is the positron which is as stable as the electron but in a world full of the latter tends to not blow up soon.

The Wikipedia page on mesons said they were involved in subatomic reactions, which sort of implied to me that anti-quarks are about, but very temporary (I assume there's an extra/missing "not" at the end of the last sentence).


Yes, it's possible, but there is nothing to suggest that's the case. I feel like there should be something about the equation where an obvious problem arises but then if it was the case the negative mass thing would have already been dismissed entirely.

It would be nice to have confirmation of either, though I suspect that anti-gravity would have fun implications.

[Caerulea]

The only kind of common antiquark is the positron which is as stable as the electron but in a world full of the latter tends to not blow up soon.
Minor nitpick, but positrons and electrons are leptons, not quarks.


I was mainly contradicting the guy/gal who said that the only difference between matter and anti-matter was the charge on the particles (by which I understood him/her to mean baryons).
Apparently I was wrong about that. Not about the negative mass statement, but that only charge differs. There are antineutrinos, which have no charge (like all neutrinos) but opposite lepton numbers and chirality.



It would be nice to have confirmation of either, though I suspect that anti-gravity would have fun implications.
Indeed it would.

[Kato]

(I assume there's an extra/missing "not" at the end of the last sentence)
...no... (I totally not corrected that just now.. I think I meant to type 'not survive for long' or so and changed my mind halfway)


Minor nitpick, but positrons and electrons are leptons, not quarks.


Ugh, I really should have the basics of the standard model memorized enough to not mix them up, thanks for pointing it out.

[Bohandas]

With respect, somebody (you?) said that, that doesn't of itself necessarily make it true. It is probably true, but at this time as I understand it, it is not experimentally proven. If you can have anti-neutrons, then it's not exactly just the charge that changes.

Aren't the anti-neutrons just anti-neutrons because they're made out of charged anti-quarks though?

[Grey_Wolf_c]

Aren't the anti-neutrons just anti-neutrons because they're made out of charged anti-quarks though?

Every time I try to follow a subatomic particle conversation, I reach a point when I look at a sentence and think "this could have been said in a Doctor Who episode that would be derided for sounding too silly and made-up".

In this conversation, it was the above sentence.

Grey Wolf

[DavidSh]

Aren't the anti-neutrons just anti-neutrons because they're made out of charged anti-quarks though?
Sure, anti-neutrons are made up out of anti-quarks. But neutrinos are elementary particles, not made up of anything smaller as far as know, and neither neutrinos nor anti-neutrinos have any charge. They do have lepton numbers.

[Mastikator]

With respect, somebody (you?) said that, that doesn't of itself necessarily make it true. It is probably true, but at this time as I understand it, it is not experimentally proven. If you can have anti-neutrons, then it's not exactly just the charge that changes.

When an antimatter particle and its counterpart matter particle come into contact they annihilate and are transformed into photons and neutrinos.

If antimatter had negative mass then there wouldn't be any photons or neutrinos.

E = m * c^2, if m = -1kg then E = -89 875 517 gigajoules.

Here's proof:

1 - 1 = 0

[Caerulea]

If antimatter had negative mass then there wouldn't be any photons or neutrinos.

Rather, they would not be produced from particle-antiparticle annihilation. They would still happen from radioactive decay, and other processes.

[Kato]

Okay, I feel I need to say this because otherwise people will misunderstand and accuse me of something else:
I'm a very firm believer that the negative mass thing is not real and that E=mc² is still very much true. (It's a cute thought experiment, still) That said...



If antimatter had negative mass then there wouldn't be any photons or neutrinos.

E = m * c^2, if m = -1kg then E = -89 875 517 gigajoules.

Here's proof:

1 - 1 = 0
This is a very poor way to phrase your argument. I'm not sure if you meant to be short and concise and went too short or if it was meant to be belittling.
It's already been stated upthread (actualy like five posts above I think) that for this negative mass thing to work, the equation would need to be modified or it doesn't work out. Or we NEED to figure out what negative energy means.

Also, what has the first statement to do with the second? What is happening in your equation? Is 1kg (500g?) of antimatter spontaneously annihilating with itself. Are you ignoring the matter half of the annihilation? Are we talking about a kg of anti-unstable-isotope that's decaying and losing 1 kg of negative mass?

And what's that proof bit? I'm going to guess you want to say we wouldn't get anything from annihilation if the positive and negative energy cancel each other out (?) which if course is right and I'm rather sure clear to everyone here, since it has been already said (I think) in clearer terms.

[halfeye]

When an antimatter particle and its counterpart matter particle come into contact they annihilate and are transformed into photons and neutrinos.

If antimatter had negative mass then there wouldn't be any photons or neutrinos.

I think "negative" is being potentially misunderstood here. Your use of it is perhaps correct, but the question is, is there another way to look at it?

As an analogy, think of blue mass and yellow mass, they are mutually repulsive and self attractive, but they are both mass (for instance, they might both have inertia). If it turns out that they are that sort of repulsive but massive, we will want new words for them, there's too much nicking ordinary words in physics as it is. Let's call them spwink mass (us) and srunque mass (antimatter)

[Mastikator]

Rather, they would not be produced from particle-antiparticle annihilation. They would still happen from radioactive decay, and other processes.

You cropped out the part that said "When an antimatter particle and its counterpart matter particle come into contact they annihilate and are transformed into photons and neutrinos." as if that had nothing to do with the next statement about those photons and neutrinos. Why?
-

Okay, I feel I need to say this because otherwise people will misunderstand and accuse me of something else:
I'm a very firm believer that the negative mass thing is not real and that E=mc² is still very much true. (It's a cute thought experiment, still) That said...


This is a very poor way to phrase your argument. I'm not sure if you meant to be short and concise and went too short or if it was meant to be belittling.
It's already been stated upthread (actualy like five posts above I think) that for this negative mass thing to work, the equation would need to be modified or it doesn't work out. Or we NEED to figure out what negative energy means.

Also, what has the first statement to do with the second? What is happening in your equation? Is 1kg (500g?) of antimatter spontaneously annihilating with itself. Are you ignoring the matter half of the annihilation? Are we talking about a kg of anti-unstable-isotope that's decaying and losing 1 kg of negative mass?

And what's that proof bit? I'm going to guess you want to say we wouldn't get anything from annihilation if the positive and negative energy cancel each other out (?) which if course is right and I'm rather sure clear to everyone here, since it has been already said (I think) in clearer terms.

I'm talking specifically about the E = mc^2 equation. If the mass has a negative sign then the energy will have a negative sign. If you have two masses, one negative and one precisely equally positive then when combined they will have a sum of exactly zero. Zero mass equals zero energy. And if anti-matter had negative mass then it would annihilate with mass to produce exactly nothing and since it doesn't it isn't.

-

I think "negative" is being potentially misunderstood here. Your use of it is perhaps correct, but the question is, is there another way to look at it?

As an analogy, think of blue mass and yellow mass, they are mutually repulsive and self attractive, but they are both mass (for instance, they might both have inertia). If it turns out that they are that sort of repulsive but massive, we will want new words for them, there's too much nicking ordinary words in physics as it is. Let's call them spwink mass (us) and srunque mass (antimatter)

Okay I get why you would use colors for mass, we use colors for strong nuclear interactions (because they have three charges).

However, anti-matter is flipped in the electromagnetic charge (which has two) and unchanged in the mass (which has only one "charge").

If you naively solve the Lorentz equation for FTL particles you will end up with energy in complex numbers, but what does that mean, why would an object with imaginary mass be repelled or attracted to an object with real mass? If you put in an imaginary number for the mass of one object in gravity then you end up with an imaginary force. How does that work?

[DavidSh]

My understanding is that current theory says that antiparticles have the same mass and opposite charge as normal particles, and that antimatter would attract normal matter gravitationally.

Furthermore, we have run enough antiparticles through particle accelerators to be sure that the ratios of charge to inertial mass for particles and antiparticles are of the same magnitude and opposite sign. Particle-antiparticle mutual annihilation, together with conservation of charge, shows that the charges are opposite. So the inertial masses are the same. Note that light has been observed to respond to gravity in a similar way to normal matter.

The issue seems to be speculation about alternative physical theories, in which having the same inertial mass doesn't mean that they respond the same gravitationally. These alternative theories would disagree with general relativity. Experiments here are harder to do.


You would get one weird implication, that equal amounts of matter and anti-matter would produce zero net attraction for an outside body, but on annihilating each other, would produce light (well, gamma rays) that would have positive attraction.

[halfeye]

Okay I get why you would use colors for mass, we use colors for strong nuclear interactions (because they have three charges).

Which is very confusing for anyone who doesn't know that you don't mean actual colours. Beside which, in physics there are no colours, colours are a biological fact about the human eye, in physics there is a whole spectrum of smoothly varying frequencies.


However, anti-matter is flipped in the electromagnetic charge (which has two) and unchanged in the mass (which has only one "charge").

This is looking like the probable truth at this point, but I am hearing that it's not theoretically certain, and certainly not experimentally proved because anti-matter hasn't survived long enough yet to be weighed.


If you naively solve the Lorentz equation for FTL particles you will end up with energy in complex numbers, but what does that mean, why would an object with imaginary mass be repelled or attracted to an object with real mass? If you put in an imaginary number for the mass of one object in gravity then you end up with an imaginary force. How does that work?

"Imaginary" in that context is another stolen word that doesn't mean in the new context what it used to mean in the old. In this case mathmaticians did it, not physicists, but it's still nicking, and it's still confusing.

[Caerulea]

You cropped out the part that said "When an antimatter particle and its counterpart matter particle come into contact they annihilate and are transformed into photons and neutrinos." as if that had nothing to do with the next statement about those photons and neutrinos. Why?
Because those statements were separated by a line break, so I interpreted them to be completely independent statements, and was only responding to the one I quoted. Did I misinterpret you?


Which is very confusing for anyone who doesn't know that you don't mean actual colours. Beside which, in physics there are no colours, colours are a biological fact about the human eye, in physics there is a whole spectrum of smoothly varying frequencies.
I believe that the correct solution here is to read a book on particle physics. Or get an introduction some other way. Yes, most people have misconceptions about the way things work, and in physics general terms have specific meaning, but I don't think it is much of a problem.



This is looking like the probable truth at this point, but I am hearing that it's not theoretically certain, and certainly not experimentally proved because anti-matter hasn't survived long enough yet to be weighed.
What do you mean by weighed? Do you mean massed? "Weight" is a measure of force, not mass, and it would be difficult to weigh any subatomic particle. Are you talking about cm3 sized chunks of antimatter? Yes, we can't make that now, nor will we be able to in the near future. What we can do, is apply our current theories, validated by mountains of data and experiment, and apply it to as of yet untested or explored ideas. When we do this, we find that the theory predicts that particles of opposite charge but otherwise identical. We then termed this antimatter. The word followed the prediction, not the other way around. You seem to be interpreting antimatter as being opposite to normal matter in every attribute, which on the face of it might seem reasonable, but is not actually true.



"Imaginary" in that context is another stolen word that doesn't mean in the new context what it used to mean in the old. In this case mathematicians did it, not physicists, but it's still nicking, and it's still confusing.
Do you have issue with terms not meaning what you expect? I feel like that is what prompted this whole conversation. (I agree that imaginary number is a poor term, and suggest using complex number as a replacement.)

[Mastikator]

Which is very confusing for anyone who doesn't know that you don't mean actual colours. Beside which, in physics there are no colours, colours are a biological fact about the human eye, in physics there is a whole spectrum of smoothly varying frequencies.



This is looking like the probable truth at this point, but I am hearing that it's not theoretically certain, and certainly not experimentally proved because anti-matter hasn't survived long enough yet to be weighed.



"Imaginary" in that context is another stolen word that doesn't mean in the new context what it used to mean in the old. In this case mathmaticians did it, not physicists, but it's still nicking, and it's still confusing.

Then what exactly do you mean by blue and yellow mass?

[halfeye]

Then what exactly do you mean by blue and yellow mass?

I mean that they are sort of opposed/complementary and different, but not exactly opposite. I got to the names by comparison with "blue and orange morality". I almost picked "green and red", but those aren't complementary in quite the same way, and "cyan and red" or "magenta and green" wouldn't have been as familiar to many people. I picked semi-random words for them "Let's call them spwink mass (us) and srunque mass (antimatter)." because I don't much like reusing words that already exist to describe new things.

[Caerulea]

What would their properties be?

[halfeye]

What would their properties be?

If they exist, which is to be determined by experiments not yet reported, then they repel each other, and the rest depends on the results of experiments. I would expect inertia, I would expect the inertia of srunque mass to be similar to that of our own spwink mass, I would expect the attraction to other matter of srunque mass to be similar to that of our own spwink mass, but experiments will tell us. It may be that experiments will tell us that antimatter has mass just like ours, in which case I wasted a few seconds coming up with admittedly poor words for null concepts.

[Caerulea]

If they exist, which is to be determined by experiments not yet reported, then they repel each other, and the rest depends on the results of experiments. I would expect inertia, I would expect the inertia of srunque mass to be similar to that of our own spwink mass, I would expect the attraction to other matter of srunque mass to be similar to that of our own spwink mass, but experiments will tell us. It may be that experiments will tell us that antimatter has mass just like ours, in which case I wasted a few seconds coming up with admittedly poor words for null concepts.

I looked about a bit more, and found some more resources on the gravitational properties of antimatter, or on the effects of negative mass.

"This serves as a confirmation of the conventional gravitational properties of antimatter without common assumptions such as, e.g., coupling of gravity to virtual particles, dynamics of distant astrophysical sources and the nature of absolute gravitational potentials." (Gravitational mass of Positron (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4962037/)) (I don't really understand their paper, but the abstract at least seems to support what I am saying).

There is also a wikipedia article (https://en.wikipedia.org/wiki/Gravitational_interaction_of_antimatter) on the subject.
What also may be of interest to you is an analysis of the effects of negative mass, like this one. (https://static1.squarespace.com/static/5852e579be659442a01f27b8/t/5873dc04d1758eea4b41c720/1483987972731/luttinger.pdf)

[wumpus]

I'm talking specifically about the E = mc^2 equation. If the mass has a negative sign then the energy will have a negative sign. If you have two masses, one negative and one precisely equally positive then when combined they will have a sum of exactly zero. Zero mass equals zero energy. And if anti-matter had negative mass then it would annihilate with mass to produce exactly nothing and since it doesn't it isn't.

If you follow Einstein's derivation of that equation, it comes directly from E**2=m**2c**4 (old school FORTRAN notation, currently available in Python). If you want to argue such a thing, you also have to include the possibility that E=+/-mc**2 as well (the plus and minus are traditionally dropped in that equation, but it can't be justified mathematically, just as an assumption of physical law).

[Lvl 2 Expert]

Physicists would certainly be happy with negative masses. Several theoretical concepts like the Alcubierre faster than light drive become a lot closer to feasible if you assume negative mass particles exist.

[BeerMug Paladin]

Physicists would certainly be happy with negative masses. Several theoretical concepts like the Alcubierre faster than light drive become a lot closer to feasible if you assume negative mass particles exist.
I feel it's worthwhile to note that the theoretical drive requires (at the most optimistic estimate) several hundred kilograms of hypothetical, never observed before negative matter to use. So, for extremely generous uses of the word 'feasible'. The earlier best estimate was a Jupiter-sized mass of hypothetical matter required, but still.

Not to mention other issues, like being exposed to temperatures hotter than the sun's core if you actually want to travel FTL instead of just very close to light speed without facing the aging problem and needing another hypothetical particle (tachyons) just to turn it on and off.

There's an awful lot of dealbreaker problems to address, so much so that if one of the issues will be addressed somehow it doesn't go very far at all.

[Lvl 2 Expert]

I feel it's worthwhile to note that the theoretical drive requires (at the most optimistic estimate) several hundred kilograms of hypothetical, never observed before negative matter to use. So, for extremely generous uses of the word 'feasible'. The earlier best estimate was a Jupiter-sized mass of hypothetical matter required, but still.

Not to mention other issues, like being exposed to temperatures hotter than the sun's core if you actually want to travel FTL instead of just very close to light speed without facing the aging problem and needing another hypothetical particle (tachyons) just to turn it on and off.

There's an awful lot of dealbreaker problems to address, so much so that if one of the issues will be addressed somehow it doesn't go very far at all.

True, true. And even after all of that you could only travel through prepared lanes because there is no way to shape the faster than light bubble from inside it. Not to mention the travel lane doubling as a death ray aimed at anything in front of it and a time machine.

Phycisists would still be happy with any sort of exotic matter with properties like these though.