PB666

Suprise, suprise . . antihydrogen looks like hydrogen

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Hang on, they did colour too ?

I know of the gravity experiment - hadn't heard of the one you mentioned !

 

Edited by YNM

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6 minutes ago, YNM said:

Hang on, they did colour too ?

I know of the gravity experiment - hadn't heard of the one you mentioned !

 

I think they are probably referring to the excitation frequencies.

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So...let me just make absolutely sure...

We can tell whether distant galaxies are made of matter or antimatter, right? They don't look, you know, exactly the same in every way?

Edited by cubinator

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6 minutes ago, cubinator said:

We can tell whether distant galaxies are made of matter or antimatter, right?

Might turns to be questionable given the discovery. (though we haven't seen the annihilation if it's true, so that question is questionable as well.)

Did inflation had anything to do with this ?

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2 minutes ago, YNM said:

Might turns to be questionable given the discovery. (though we haven't seen the annihilation if it's true, so that question is questionable as well.)

Did inflation had anything to do with this ?

Well, if antimatter happens to fall up instead of down, then wouldn't the galaxies be pushed apart and we wouldn't see galaxy-sized annihilations...but if that were the case then antimatter would also probably travel backwards in time, right?

I really don't know much about antimatter, so take everything I say here with a grain of anti-salt.

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9 minutes ago, cubinator said:

Well, if antimatter happens to "fall up" instead of down...

(emphasis because they could "fall down" among itself.)

The only way to tell would be to predict what effect that would have on CMB, CNB and what have you. Then go and find it.

Edited by YNM

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3 hours ago, cubinator said:

So...let me just make absolutely sure...

We can tell whether distant galaxies are made of matter or antimatter, right? They don't look, you know, exactly the same in every way?

To quote Wikipedia (don't worry, I did check its source on this)

"Antimatter may exist in relatively large amounts in far-away galaxies due to cosmic inflation in the primordial time of the universe. Antimatter galaxies, if they exist, are expected to have the same chemistry and absorption and emission spectra as normal-matter galaxies, and their astronomical objectswould be observationally identical, making them difficult to distinguish"

 

This result just seems to add strength to that line of reasoning.

Edited by Steel

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17 minutes ago, Steel said:

This result just seems to add strength to that line of reasoning.

If there's ever an "interface" between the two component we'd see it though. And so far, we haven't identified it - so while the concept is fine the reality is unknown.

I hope we'd continue to search the truth of these things.

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6 hours ago, cubinator said:

So...let me just make absolutely sure...

We can tell whether distant galaxies are made of matter or antimatter, right? They don't look, you know, exactly the same in every way?

I think the best evidence for there not being large collection of antimatter (say an antimatter galaxy) is that it inevitably is going to come into contact with large amounts of normal matter, which would emit obvious tell-tale signs. Even the vacuum of deep space contains significant amounts of mass over large volumes and if there is a large amount of antimatter, it is unlikely to be vastly separated from the surrounding matter, so you would expect to see very visible reactions where they meet.

There is I suppose, an outside chance that there are large amounts of antimatter, but signs point to no.

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7 hours ago, p1t1o said:

it inevitably is going to come into contact with large amounts of normal matter, which would emit obvious tell-tale signs.

Unless their gravity is negative too...

Still, would be a considerable interference even with 1 atom/m^3.

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51 minutes ago, YNM said:

Unless their gravity is negative too...

We actually understand the properties of antimatter quite well - it's surprisingly easy to find, it just doesn't stick around very long, but if you know where to look you can study it's properties. It obeys the laws of gravity the same as regular matter

Edited by Steel

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2 minutes ago, Steel said:

We actually understand the properties of antimatter quite well...

Not really.

Most of them are in charged state. And being charged means you're at whim of the largest force of all - electrostatic.

Hence CERN's GBAR.

But I won't place any bet on it either way.

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3 minutes ago, YNM said:

Not really.

Most of them are in charged state. And being charged means you're at whim of the largest force of all - electrostatic.

Hence CERN's GBAR.

But I won't place any bet on it either way.

You're quite right... Clearly my particle physics is a little rusty

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GASP

 

I'm always super interested in particle physics and nuclear physics in general, but whenever I read about it, I end up forgetting most of the more complicated concepts in a few days :(

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1 hour ago, Steel said:

We actually understand the properties of antimatter quite well - it's surprisingly easy to find, it just doesn't stick around very long, but if you know where to look you can study it's properties. It obeys the laws of gravity the same as regular matter

We do understand it quite well....except for how it reacts to gravity.

This is because nobody has ever gathered enough of it to be able to measure gravity's effects on it.

How do you measure the weight of say, 100 antiprotons? Currently, we cant, so it's a total unknown.

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1 hour ago, p1t1o said:

We do understand it quite well....except for how it reacts to gravity.

This is because nobody has ever gathered enough of it to be able to measure gravity's effects on it.

How do you measure the weight of say, 100 antiprotons? Currently, we cant, so it's a total unknown.

Gravity is a reflection of Inertia. You have to think of gravity as the way inertial particles behave as the pass close to energy containing regions of space (e = mc2). Since energy and mass can be interchanged then you have conservation of gravity.

Lets not forget that antiparticles are composed of quantum elements. In a closed QM system Energy is always (always, always) conserved. Did I say always, I meant to say always.

Since antiparticles must follow conservation of energy in their creation and since gravity can be described by general relativity as a reflection of e = mc2 the there is assumption that in a closed system if a form of energy is converted to anti-particles, for energy to be conserved at every level then the gravity should remain constant.

The only way you could possibly change this is, for instance a closed systems so large that two events in the system create waves in space-time, and in that case the energy in the systems goes into space-time fluctuations itself and can only be measured external to the system. Fortunately for scientist there is no closed system that deals with that level of mass.

The issue of gravity is not whether particles choose to or not to behave in accord with warping of space-time, but how does space-time warp under the extreme variations of conditions possible in the universe, particularly in the vast emptiness of space, or underconditions with quantum scale is so small that sub-resolution behaviors apply. 

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9 hours ago, PB666 said:

Gravity is a reflection of Inertia.

... If the equvalence principle holds.

We don't know that for antimatter.

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A related question....so the past bigger decelerator gravity fall test showed anything...or the newer GBAR?  Like falling down/up? :D 

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Anti matter is not negative matter. Its a charge difference. The gravity is the same. E=MC^2. Gravity even affects photons. when matter and antimatter meet, they make high energy photons equal to their combined mass (plus neutrinos).

It still has positive mass, and as far as gravity is concerned, that mass acts like any other mass.

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1 hour ago, KerikBalm said:

Anti matter is not negative matter. Its a charge difference. The gravity is the same. E=MC^2. Gravity even affects photons. when matter and antimatter meet, they make high energy photons equal to their combined mass (plus neutrinos).

It still has positive mass, and as far as gravity is concerned, that mass acts like any other mass.

Its more than a charge difference, there are opposite quantum spins as well.

While we know antimatter has positive inertial mass, there is as yet no empirical proof that "inertial" and "gravitational" mass are identical things. 

The maths adds up, but we cannot as yet rule out some things. It is strongly expected that antimatter has the same mass properties as normal matter, but it cant yet be tested.

 

Edited by p1t1o

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10 minutes ago, p1t1o said:

Its more than a charge difference, there are opposite quantum spins as well.

While we know antimatter has positive inertial mass, there is as yet no empirical proof that "inertial" and "gravitational" mass are identical things. 

The maths adds up, but we cannot as yet rule out some things. It is strongly expected that antimatter has the same mass properties as normal matter, but it cant yet be tested.

 

Mmmm, no, here is how spin states work. First there is spin zero

Spin Zero. 0 (higgs) boson

Spin 1/2
-1/2, + 1/2 (example Leptons and quarks)

And example of this is a hydrogen molecule takes 2 s orbitals and creates 1 s-s orbital. Into that one s2 orbital we place two electrons, but QM prevents the placement of two electrons in one orbital with the same spin. So that a hydrogen molecule has an electron with spin 1/2 and spin -1/2. A helium atom has a 1s orbital and a 2s orbital (lowest energy orbitals), it has 4 electrons, we can place an electron -1/2 and 1/2 in the first orbital, then -1/2 and 1/2 in the second.
[Stanford has a course in quantum entanglement and electrodynamics online if you want to take them, its designed for retirees]

Spin 1 (Photons, Z-boson, W-boson, Gluons)
-1, 0, 1

An example of this is that most photons we encounter have a spin of zero, but many photons have circular polarization, this means the polarization is not constant but changes with distance.
https://en.wikipedia.org/wiki/Circular_polarization
Therefore a photon can either have a positive circular polarization (left handed) a negative circular polarization (right handed) or linear polarization.    

Circular polarization is the basis of circular dichroism, the study of the bulk secondary structural composition of molecules. For example CD is very good at detecting alpha-helical content in proteins.
 

Spin 3/2 (gravitinos?????)
-3/2, -1/2, 1/2, +3/2

Spin 2 (gravitons?).
-2, -1, 0, 1, 2

Spin is given as the largest positive charge but the spin can be any negative or positive as long as the absolute value of spin is not greater than the spin number as as long as it an interger variance of that spin number. 

https://en.wikipedia.org/wiki/File:Standard_Model_of_Elementary_Particles.svg

the problem with what you say is this. For energy to be conserved in a closed system, for antiparticles to have negative gravity means that energy has to be added in addition to the energy in their mass. To thing about it like this

what you experience as gravity we can do a little gedanken experiment, we are going to remove all the air from the room, now we move you to the north geographic pole, and then we lift you 1 mM above the earth. For the time it takes you to move that 1 mM you are on a suborbital trajectory your mass is following inertial motion. If the earth was a point mass you would have continued to fall and then return to its position exactly where it started.

The Hamiltionian for energy  SME = SKE - SPE is always conserved. This is the basis for planetary motion as we know it (disregard relativistic perspectives). You are technically not accelerating toward the ground, the electrostatic interactions of the earth are being forced in the direction of your shoes, preventing your shoes from falling.

As this is to point out general relativity . . . the point is that the mass of your body is not important, but the energy contained in your body and you mass. If we could keep all your energy in a container, and convert all your mass to energy it would be the same. If we were to convert all your energy to antimatter it would be the same. An excellent example of this is a black hole . . . .technically once matter falls beyond the event horizon we no longer no ifs its mass or energy, in fact we do know that most of the energy in the black-hole is gravimetric in nature, it comes from the conversion of potential energy to kinetic energy. As an object approaches the speed of light, most of its energy is not in its rest mass, but in mass added by the Lorentz variance. You can add energy to an object but at the speed of light it no longer goes into kinetic energy but into mass. But from the perspective of the viewer, he cannot tell from a sterile black hole whether its internal contents are matter, anti-matter or energy . . .a black hole is a quantum singularity.

And example of this is we could take an atom, and by focusing powerful lasers (photons have no mass) at a single atom from a very great distance and from all directions (I think it would be something like 40 light years) we could create a black hole. Probably not the easiest way of doing it, but certainly at some very great distance you could transmit enough power on a spot that the energy of the photons will create a black hole. It matters little if they are polarized left or right or linear.

If we started with a positron as the single particle, it would be the same, a black hole. The reason for this is a photon is its own antiparticle, which is also true for all bosons except the W-boson, but in a nucleus of an atom both Z and anti-Z bosons coexist, and also true for the higgs boson.

So what would happen if, in  a black box, I converted all mass to energy, all energy to antimatter of the exact opposite quality and the antimatter had anti-gravity. This would mean that I added some additional energy to the system such that there was a force being applied making it non-intertial. So lets imagine I create anti-lead from lead, the lead would sit on the bottom of the resilient black box, if it was anti-gravity lead it would adhere to the top means I would have to convert entropy to some starting energy (normal lead falls, in falling in converts potential energy to kinetic energy and kinetic energy to heat as it strikes the bottom of the container). This is a problem, because the only way I can practically do that is to reverse time. IOW in our time the lead falls to the bottom as soon as it forms, in reverse time it floats back to the top. This is not how our universe works beyond the point of QM resolution (i.e. about 1/10,000,000,000,000,000,000,000,000,000,000,000,000,000,000 th of a second) and it kind of would imply that if antimatter was also anti-gravitational that it could never persist long enough to be detected. It might be the case that we could see some very fast particles (like antigravitational neutrinos) because of time dilation.

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56 minutes ago, PB666 said:

<snikt>

Please...can you sum that up for me?

This is what I got from it:

Antimatter doesnt have exactly opposite spin values for its constituent parts, compared to normal matter, but they are different?

Something about spin deciding how it reacts to gravity?

In conclusion - antimatter has normal mass properties?

 

Am I close?

 

People seem to be leaning quite heavily on "antimatter clearly has energy, and because E=MC^2 it therefore must also have normal positive mass and therefore reacts to gravity in the expected manner."

It was my understanding that that is all well and good but empirical evidence [for antimatter's response to gravity] is for now out of our reach. I would also wager that E=MC^2 is an oversimplification in this matter...no pun intended. The formula itself is a reduction of the full mathematics of mass-energy equivalence and it is not applicable to all forms of mass or energy.

 

Id be the first to admit that this is pushing the limits of my experience, I have so far merely been regurgitating what I have seen elsewhere over time.

Edited by p1t1o

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