Antimatter And Gravity

[sanctus]

A few weeks back I read some interview with some guy at CERN, and he said something which surprised me a lot: that antimatter could have anti-gravity. I never heard about something like that before and it seems to come from a serious source.

Anyone knows what the theory behind for such a claim could be?

 

I mean take GR, it is mass that gives rise to the gravity effects and an electron orbiting a proton has about the same mass as a positron orbiting an anti-proton...

Or if one considers QE, how does it work with gravitons?

 

What is cool though, is that it could explain where all the anti-matter went.

[Rade]

Hi,

 

As an introduction to the topic to begin some discussion for this exciting thread, see this 1962 paper by Robert Forward...it was one of the first attempts to link antigravity to Einstein relativity. There is much science fiction concerning antigravity, this information comes from a journal that I assume was peer reviewed. Forward suggested propulsion engines that used antigravity:

 

http://u2.lege.net/culture.zapto.org_82_20080124/passed_shows/Om%20nya%20energik%E4llor/Energy%20papers%20%20%20%20Mina%20dokument/antigravidity/Robert%20L.Forward%20-%20Guidelines%20to%20Antigravity.pdf

 

==

 

This physicist, Dr. Hajdukovic, at CERN works in the area of antigravity...perhaps who you read about ?:

 

http://arxiv.org/ftp/arxiv/papers/1106/1106.1260.pdf

 

==

 

And see these theory papers by Villata on antimatter and predicted antigravity as relates to time (read in order given):

 

http://iopscience.iop.org/0295-5075/94/2/20001/pdf/0295-5075_94_2_20001.pdf

 

http://arxiv.org/pdf/1109.1201v2.pdf

Edited October 1, 2014 by Rade

[sanctus]

Thanks Rade,

 

I'll post here when I read some of the links.

[HydrogenBond]

The term anti-matter is very misleading and needs to be clarified to avoid confusion. 

 

In beta-decay, if a nucleus has too many protons, it can give off a positron, which is called anti-matter, and a negative neutrino, which has no charge, without an electron needing to be formed.

 

The positron was originally a stable part of matter, co-existing in the nucleus as part of a proton because it is matter. Anti-matter is just matter in less stable arrangements not a mirror image. 

 

The universe is composed of matter primarily of combinations of protons, neutrons and electrons, instead of positrons and negative protons, because protons and electrons are the most stable arrangements. Positive charge has more stability when combined with larger mass than does negative charge, thereby resulting in the universe having mostly protons instead of positrons. 

 

Where I would guess the confusion arrises can be seen with an analogy. If we react chemicals, such as hydrogen and oxygen, at very high temperature, instead of making water, what tends to form are radicals which are unstable intermediate states between hydrogen and oxygen. These radials may be the rule when everything is very hot enough. But if we continue to cool toward room temperature, these excited states begin to disappear until the most stable or water is the last things standing. In the case of high energy going to lower energy, matter is the last one standing, due to stability. Having too many protons in a nucleus is high energy state. 

 

The positron and electron will annihilate each other, but the electron and proton will not. The reason is the positive charge is stabilized within the higher mass of the proton, making the reaction with the electron far more difficult. The positron is analogous to a positively charge radical state, given the positive charge more reactivity. But it is all matter. 

 

 

[Rade]

The term anti-matter is very misleading and needs to be clarified to avoid confusion. 

 

In beta-decay, if a nucleus has too many protons, it can give off a positron, which is called anti-matter, and a negative neutrino, which has no charge, without an electron needing to be formed.

 

The positron was originally a stable part of matter, co-existing in the nucleus as part of a proton because it is matter. Anti-matter is just matter in less stable arrangements not a mirror image. 

 

The universe is composed of matter primarily of combinations of protons, neutrons and electrons, instead of positrons and negative protons, because protons and electrons are the most stable arrangements. Positive charge has more stability when combined with larger mass than does negative charge, thereby resulting in the universe having mostly protons instead of positrons. 

 

Where I would guess the confusion arises can be seen with an analogy. If we react chemicals, such as hydrogen and oxygen, at very high temperature, instead of making water, what tends to form are radicals which are unstable intermediate states between hydrogen and oxygen. These radials may be the rule when everything is very hot enough. But if we continue to cool toward room temperature, these excited states begin to disappear until the most stable or water is the last things standing. In the case of high energy going to lower energy, matter is the last one standing, due to stability. Having too many protons in a nucleus is high energy state. 

 

The positron and electron will annihilate each other, but the electron and proton will not. The reason is the positive charge is stabilized within the higher mass of the proton, making the reaction with the electron far more difficult. The positron is analogous to a positively charge radical state, given the positive charge more reactivity. But it is all matter. 

I find that your discussion is misleading.  

 

First, the matter proton with positive charge is not more stable than the antimatter proton with negative charge. 

 

Next, it is not true that "the positron was originally a stable part of matter, coexisting in the nucleus as part of a proton..."   Also originally (as you mean it) was the antineutron, which can beta+ decay into a positron (e+) + antiproton + neutrino.   So, your hypothesis that the e+ is only a stable part of matter is false, it is equally a stable part of antimatter within your meaning of these terms. 

Edited October 8, 2014 by Rade

[sanctus]

Rade, got to the second article, both are really cool. The idea of a cyclic matter-antimatter universe is quite fascinating and it even would get rid of infaltion :-).

[HydrogenBond]

First, the matter proton with positive charge is not more stable than the antimatter proton with negative charge. 

 

Can you show me any other example, in nature, where the final stuff standing (persisting) at lowest background energy, after millions or billions of years, can be one of two random alternatives that are mutually exclusive?

 

The protons and electrons is what persists because these are at lowest free energy. One can see radial matter, which is coined as anti-matter, out in space, but it will not persist if given enough time because it has higher free energy; radial matter is more reactive. 

 

We can see ozone or O3 high in the atmosphere, but O2 is at the lowest energy state and this is what will persists in the long term at lowest energy.

 

 

[Rade]

HB...There is no evidence that the hyperfine energy levels of hydrogen differ from antihydrogen....if you have a peer reviewed article to share, please post a link.   

 

This graph shows how the energy levels of matter hydrogen (white background) and antimatter hydrogen (dark background) are predicted to have exactly the same hyperfine structure based on four different models.  

 

 

Also, you suggest that somewhere in the history of physics a paper was published where the term 'antimatter' was shown to be what you call 'radial matter that has a higher free energy' than matter.  Please post the link to this interesting publication, I would like to read it. 

[HydrogenBond]

Free energy is a combination of enthalpy and entropy; G=H-TS, where G is free energy, H is enthalpy, T is temperature and S is entropy. 

 

Enthalpy is a defined thermodynamic potential, designated by the letter "H", that consists of the internal energy of the system (U) plus the product of pressure (p) and volume (V) of the system:^[1]

 

 

If matter is more stable than anti-matter, as inferred by there being net matter in the universe, and if we employ the second law, then matter could be stabilized by being in a higher internal state of entropy. Anti-matter would be at lower entropy, and therefore have a higher internal potential to change.  

 

The free energy can be the same, for both matter and anti-matter, as shown in your diagram, but since free energy is the internal energy (+PV) minus the entropy, the higher entropy of matter, would require that matter have a higher internal energy U. 

 

The value of a higher internal energy within matter, over anti-matter, is matter fusion burns stronger, with the higher entropy nucleons having better stability during the burn. In this explanation, anti-matter would burn not as hot as matter, since it has lower internal energy. This lower internal energy release of anti-matter fusion may be low to compensate for the lower internal entropy. However, mass burn may be too hot, for antimatter and can trigger an entropy increase, into matter/energy. 

 

Have anyone ever seen antimatter helium? 

Edited October 9, 2014 by HydrogenBond

[sanctus]

HB, if you consider my question in the opening post what you infer can be completely wrong...if anti-matter has indeed a gravitationally repulsive interaction with matter, then the fact that we only measure/infer net matter in the VISIBLE universe has nothing to say about the the stability of each. It would just mean mean that all anti-mater has long gone out of the visible universe...

[Rade]

Have anyone ever seen antimatter helium?

Yes. Antihelium-3 isotope was produced in 1970s, and more recently antihelium-4 (the anti alpha)...see this link for the latter:

http://newscenter.lbl.gov/2011/04/24/antihelium/

[CraigD]

5 years ago in this thread, we had some discussion of whether the gravitational mass of antimatter is positive, like ordinary matter, or negative – that is, whether antimatter is gravitationally attracted or repelled by ordinary matter.

 

As mentioned in the papers Rade linked to in post #2, a direct, definitive experiment to answer this question, AEGIS (Antimatter experiment: Gravity, interferometry, spectroscopy) has been underway at CERN since 2007. While conceptually a simple experiment – make some electrically neutral antimatter (such as antihydrogen), toss it horizontally, and see if it falls down or up – doing this is technically challenging, so so far, the AEGIS collaborative has published some papers and done work on the apperatus needed for the experiment, but not actually assembled and done the experiment.

 

I'd hoped AEGIS would be done years ago, but things are going slowly. The main difficulties are that it’s hard to make neutral antimatter, cool it enough to “toss”, then toss it. Charged antimatter (such as positrons and antiprotons) can be “handled” fairly easily with magnets, but because the electromagnetic force is so much stronger (about 10³⁶ times!) than the gravitational, it’s practically impossible to measure the effect of gravity on charged matter or antimatter (such as ions or anti-ions).

 

From what I’ve been able to gather over the years I’ve been following them, the AEGIS folk expect to find that the gravitational mass of antimatter is positive. What they don’t know to expect, is whether the more massive antimatter particles (such as the antiproton) have precisely the same gravitational mass as their ordinary matter counterparts. So AEGIS is being designed not just to see if “antimatter falls up or down”, but if antimatter falls slightly slower than matter.

 

It makes sense (via my semi-classical interpretation of quantum particle physic) to expect the gravitational mass of an antiprotons or antineutron to be slightly less than that of a proton or neutron, because these are composite particles, consisting of quarks or antiquarks and force-carrying bosons (mostly, by mass, gluons). Quarks, antiquarks and gluons have very small or zero rest masses – most (about 98.7%) of the mass of a proton or neutron is due to the “relativistic mass” of the zero or very small rest mass gluons. If antiquarks have negative gravitational mass, while the mass-dilated gluons that bind them have positive (it’s hard to imagine how relativistic mass cannot), we can expect AEGIS to find that antihydrogen weighs about 97.4% what hydrogen weighs.

[HydrogenBond]

A simpler experiment one can do is to weigh a given mass of Magnesium-23 going to Sodium-23, via beta decay, where a positron (anti-matter) is given off. If anti-matter has negative gravity, the Sodium-23 will become heavier than the Magnesium-23. If it gets lighter than the positron is matter. 

 

 

 

I used the concept of free energy, which can be the same for matter and anti-matter and therefore will measure the same. But since free energy is composed of two distinct parameters; enthalpy (internal energy) and entropy (disorder), matter and anti-matter, although equal in free energy, can still be unequal at another level.

 

Entropy is an odd duck, because once the genie of randomness is let out of the bottle, it is not as easy to put it back in with a simple reversal. Enthalpy can be reversed by simply adding or taking away energy. But with entropy you can't just unroll the dice in an exact reverse fashion as easy as roll the dice. 

 

With entropy having to increase in the universe, this reflects the net direction of genie out versus genie in. Matter already has the genie out, while anti-matter has the genie in. So anti-matter has a much easy path to disruption; genie out. 

 

Entropy is the closet concept to the concept of time, in the sense that both net move in one direction; to the future. Putting the Genie in the bottle could be done if we could play time backwards. This would allow us to pack the genie in the same way it unpacked. But since time only moves in one direction this path is not possible. Enthalpy does not have this reversible problem.

 

If we try to put the genie back by reversing entropy, we will need to take another path due to the mono-directional vector of time. The second law says this cannot 100% efficient, requiring a slight addition of more energy for the entropy; waste heat. This time asymmetry favors matter. 

Edited October 12, 2014 by HydrogenBond

[CraigD]

A simpler experiment one can do is to weigh a given mass of Magnesium-23 going to Sodium-23, via beta decay, where a positron (anti-matter) is given off. If anti-matter has negative gravity, the Sodium-23 will become heavier than the Magnesium-23. If it gets lighter than the positron is matter.

That’s a clever idea, but I’m pretty sure it can’t work, for a couple or reasons:

 

First, and most important, in QCD and QED, the best theories explaining the mass (and, assuming inertial and gravitation mass are equivalent, the main question of this thread, the weight) of atomic matter, don’t allow you to calculate the mass of atoms by just adding the mass of their separate constituent particles, or particles emitted when atoms on one element decay into another.

 

Second, even ignoring quantum physics, the experimentally measured masses of the atoms and particles you mention don’t add up correctly for the effect you propose.

An atom of ²³Mg (12 protons, 11 neutrons) has a mass of 22.9941237(14) AMU,

an atom of ²³Na (11 protons, 12 neutrons) has a mass of 22.9897692809(29) AMU,

which differ by about .0043544191 AMU.

A positron has a mass of 0.0005485798868(12) AMU,

which is about 8 times too small to account for the difference in mass of the two atoms.

 

A couple of key informal, intuitive QCD ideas help one to understand the mass of atoms:

One, that most (nearly 99%) of the mass of nucleons – protons and neutrons – comes not from the particles that carry their electric charge – quarks – but from the virtual particles that bind quarks and nucleons together – gluons. Electrons contribute even a smaller fraction of the mass of atoms than quarks do. A hydrogen atom has a mass of about 1000 MeV/c², it’s quarks about 10, its electron about 0.5.

 

Two, the reason we can’t determine the mass of a given atom’s nucleus simply by multiplying the number or protons in it by the mass of a single proton and adding this to the number of its neutrons times the mass of a free neutron is that the mass contributed by gluons depends not just on the way they bind the 3 quarks within each proton and neutron, but also by the way they bind the protons and neutrons together. These interactions are very complicated, and can’t be described as a collection of classical physical interactions. This is an example of what we mean when we describe quantum physics as “weird”.

[JMJones0424]

Can you show me any other example, in nature, where the final stuff standing (persisting) at lowest background energy, after millions or billions of years, can be one of two random alternatives that are mutually exclusive?

 

The protons and electrons is what persists because these are at lowest free energy. One can see radial matter, which is coined as anti-matter, out in space, but it will not persist if given enough time because it has higher free energy; radial matter is more reactive. 

 

We can see ozone or O3 high in the atmosphere, but O2 is at the lowest energy state and this is what will persists in the long term at lowest energy.

I'm sorry to jump in to the middle of the conversation, but i can't resist the urge to call into question the validity of this post of yours.  Either I'm fundamentally failing to understand what you are saying or you are spewing nonsense.

[HydrogenBond]

In a later post, the data of the parallel energy states of matter and anti-matter, caused me to remembered that free energy is the sum of internal energy minus entropy; G= H -TS, where G is free energy, H is enthalpy (internal energy plus PV), T is temperature and S is entropy. Matter and anti-matter have the same G, but are opposites in terms of H and TS; sums add to the same free energy. 

 

Since these are equal and opposite, that would imply matter has higher enthalpy and higher entropy and anti-matter has lower enthalpy and lower entropy; both add to the same free energy. The lower entropy of anti-matter gives it a greater potential to change, while matter will persist without second law violation for longer periods. We ended up with a matter universe. 

 

When a positron becomes part of a nucleus, its enthalpy and entropy go up into that of the matter phase, so it can last for eons. But if it is released, such as in positron emission, its entropy lowers, so it will not last as long before there is a need for an entropy increase that changes its state. 

 

Gravity causes pressure to increase and volume to decrease. This impacts the enthalpy term (nternal energy plus PV), increasing the free energy. This is helpful for the activation energy of fusion. The pressure also restricts movement causing the entropy to fall. One would expect anti-matter to form more frequently within fusion cores, than on the surface, but it may not persist due to its interaction with matter. 

 

As far as Magnesium 23  to Sodium 23 the mass does go down, but like you said one needs to account for other things. One part is connected to the change of enthalpy and entropy, going to anti-matter, with a lowering of entropy and enthalpy, exothermic. 

[Pmb]

This sounds like the subject at http://newscenter.berkeley.edu/2013/04/30/is-antimatter-anti-gravity/

 

The trouble I have with this is that there is no unique way to determine which particles are particles and which are antiparticles. The choice is arbitrary. When you choose one particle to be "particle" then its antimatter particle or "antiparticle" is determined. Of course there is always the situation where testing its antigravity properties tells you which is "really"  the antiparticle, i.e. the choice is no longer arbitrary.