Introduction
On 28 September 2023, ABC science reporter Belinda Smith reported on an experiment at the CERN particle accelerator facility on anti-hydrogen that took many physicists investigating the nature of our universe by surprise. (See https://www.abc.net.au/news/science/2023-09-28/antimatter-gravity-graviational-repulsion-experiment-physics/102900592 ).
The aim of the experiment carried out at the ALPHA-g device was to ascertain how anti-hydrogen (the antimatter companion of normal hydrogen), behaved in the earth’s gravitational field. The result of the experiment, published in Nature journal (see https://www.nature.com/articles/s41586-023-06527-1 ) showed that antihydrogen falls under earth’s gravity just as hydrogen does, revealing antimatter is attracted by a gravitational field just as matter is. This was extremely puzzling to many physicists who have been trying to explain why our universe is made up predominantly of matter (with only a sprinkling of antimatter found under specific conditions).
Why the puzzle?
To understand the Big Bang theory, physicists appeal to the Standard Model of particle physics, and assume that equal amounts of matter and antimatter were produced at the moment of the Big Bang. According to this model, the matter and antimatter that was formed should have recombined to yield pure energy again (see, e.g. the ABC Science report by Bernie Hobbs at
https://www.abc.net.au/news/science/2016-06-23/antimatter-explainer/7487354 )
A possible explanation for the matter-antimatter asymmetry was that antimatter was repelled by matter (and thus escaped the known universe) after the moment of creation.
Therefore, there was an expectation that antihydrogen would not fall towards the earth, but be pushed upwards, away from it, when it was released in the ALPHA-g experiment. It did not. And so the mystery of the missing antimatter in the universe remains unsolved.
There are several serious issues with the Standard Model. Perhaps the most serious is that it does not include gravitation. So it does not (and cannot) explain how the gravitational force (one of the two long-range forces out of the four fundamental forces of nature), works. Neither does it say anything about the existence of dark matter (which is needed to account for 85% of the gravitational force within the universe), or dark energy (which explains why the universe is expanding at a faster and faster rate).
Despite these serious limitations, this model is still used to provide the theoretical basis for the scientific research to explain mysteries such as the matter-antimatter asymmetry. There are four approaches being investigated, the most promising being the violation of CP symmetry in matter-energy processes.
A new insight
There is clearly a need for a more encompassing theory/model to account for the mystery surrounding the asymmetry and dark matter/energy issues. Such a theory must start by establishing a conceptual framework that includes the gravitational force as a first requirement.
Insights into such an approach is provided in the book Concepts and the Foundations of Physics, published by AIP Publishing in 2021
(see https://pubs.aip.org/books/monograph/37/Concepts-and-the-Foundations-of-Physics ).
In Chapter 7, it points out that the energy-mass transformation equation E = mc2 derived by Einstein should be accorded a central role, and treated as a foundational pillar, of physics and cosmology. Such a Fundamental Energy-Mass Transformation (FEMT) Model is used to reveal insights into the nature of the matter-energy duality that has seemingly not been explored before. One revelation of the model is that there could be more than one type of “antimatter” that contributes to a more holistic picture of the universe. And we could be looking at the wrong one!
What is FEMT?
The Fundamental Energy-Mass Transformation (FEMT) model is a model that provides a common conceptual framework for energy-mass transformations for the forces of nature. When applied to the gravitational force, it reveals an obvious difference between the two long-range forces, with possibly far-reaching consequences.
The model begins by stating as a postulate, the (observed) formation of e- e+ pairs (i.e. matter-antimatter particles) when an e/m wave (quantised as photons) passes through the strong electric force field Fe of a nucleus, and the requirements of the equality of the masses of the pair and the “equal and opposite” nature of their electric charges. This is labelled as the First Form of the model.
It next generalises this to the case where the force includes all the other three forces, i.e. postulates that energy can transform into “particle/antiparticle pairs” in the presence of the other forces as well, with properties that are similar to those of the massive particles in the First Form of the model. The primary motivation for the formulation of this model is to compare the results for the two long-range forces, i.e. the e/m and the gravitational force (Fe and Fg).
Note that the FEMT model postulates that the mass of the antiparticle formed in the case of each force is the same as (i.e. equal in magnitude to) that of its particle counterpart. This implies that the antiparticles produced by both long-range forces of nature should be attracted to gravitational fields just as the particles are. This result derives directly from the definition of antimatter as elaborated by Dirac, Stueckelberg and others, and leads to the equivalence of their inertial and gravitational masses as stated by Einstein and others.
FEMT and Matter- Antimatter Asymmetry
As the FEMT model considers a broader perspective for pair production than the case involving the e/m interaction only, it presents a larger concept set for the conceptualisation of the asymmetry problem.
According to the FEMT model, as there is more than one type of fundamental force of nature, there should be several types of “antimatter” possible. Thus at the beginning of the Big Bang timeline (around the Planck Era), it is possible that the antimatter that was formed was not of the e/m variety.
In the case where the force is the gravitational force, and the e/m wave (which carries the photon) is replaced by a gravitational wave, the new antimatter formed (which may be labelled as antimass) is postulated to repel its matter counterpart. If pair production was of this gravitational type during the Planck Era, this reveals the possibility of the antimatter component of the early universe being separated from the matter component at the earliest instance, leaving behind a universe where the massive bodies are made predominantly of matter particles as observed.
Alpha-g, Einstein and Dark Energy
The equivalence principle, which provided the inspiration for Einstein in his development of the General Theory of Relativity, states that gravitational mass and inertial mass are equivalent. Although antiparticles were unknown in 1915, it may be inferred that the same equivalence applies to them as well, and therefore one expects that they behave in the same way in a gravitational field as ordinary matter does. This was confirmed by the Alpha-g experiment at CERN in September this year. Thus to explain the asymmetry issue, a new antimatter candidate needs to be found which is repelled by the source of a gravity field. We saw above that antimass satisfies such a criterion.
This same source provides a likely candidate for Dark Energy as well. Thus it may be possible for mass-antimass pair production to occur as gravitational waves pass through the strong gravitational fields of black holes in the universe. The antimass produced would be repelled from all matter (which consists predominantly of mass), being forced to accrete into isolated regions, and provide the repulsive force necessary to account for the observed accelerating expansion of the universe.
In conclusion, it is interesting to summarise and note that
- Early physicists noted the equivalence of the inertial and gravitational mass
- Einstein went further to “interpret” it (i.e. thought about it asked why does this happen) and used the result as the stepping stone for the development of the General Theory of Relativity
- It may also be interpreted from this early thinking and that of Dirac and Stueckelgerg, that antimatter should fall in the earth’s gravitational field, which implies the equivalence of antimatter mass with inertial mass
- The ALPHA-g experiment has just confirmed this
- We can postulate that all types of mass are equivalent with inertial mass
- And finally conclude that the mass of antimass is equivalent with inertial mass.
The oldest concept prevails over the rest, and the ideas of Newton and other early physicists still rule!
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